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Content Benchmark L.8.A.1
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Life Science
Heredity
  L.8.A.1
  L.8.A.2
  L.8.A.3
  L.8.A.4
Structure of Life
Organisms and Their Environment
Diversity of Life
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Nature of Science (NOS)
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Students know heredity is the passage of genetic instructions from one generation to the next generation. E/S

Inside almost every cell of every living thing is the blueprint for building that organism. This blueprint contains information on all of the organism’s inherited characteristics. The blueprint is deoxyribonucleic acid, or DNA. Much like a blueprint, DNA provides step by step instructions for building each part of the final product. The final product would be an organism. DNA accomplishes this by providing the instructions to make all of an organism’s proteins. In humans for example, this blueprint gives the instructions for making a protein called melanin, which will determine how dark or light a person’s skin will be. In plants, DNA gives the instructions for proteins that influence traits like plant height and flower color. Where does the DNA and the information it holds come from? It is inherited from an organism’s parents through reproduction. During sexual reproduction, each parent donates half of its genetic material to the offspring. So, each parent gives half of the blueprint, and when they are put together, they form a complete blueprint from which the offspring can be made. Heredity is the reason organisms can look similar to their parents, yet also look unique. A thorough understanding of heredity requires at least a basic understanding of DNA, RNA, proteins synthesis, cell division, reproduction and genetics principles.


DNA Structure
Just a little less than a century ago, scientists were still trying to figure out what molecule held genetic information. In the early 1990s they knew cells were made of nucleic acids, proteins, lipids, and carbohydrates; but they did not know which of these was passed from parent to offspring. During this time, people thought DNA was too simple of a molecule to code for the variety of traits found in most organisms. Scientists believed proteins were more likely the genetic material because there were a greater variety of proteins known. Many experiments were done to find out which molecule contained the genetic material, but none definitively showed it was DNA until the 1950s. Alfred Hershey and Martha Chase proved that DNA, not protein was the genetic material in viruses. This experiment led most scientists to believe DNA was the genetic material for all life.

Soon after Hershey and Chase’s discovery, two scientists named James Watson and Francis Crick proposed the first accurate model of DNA’s structure. They used research done by other scientists such as Erwin Chargaff, Rosalind Franklin, and Maurice Wilkins to decipher the molecular structure of DNA. Watson and Crick’s model showed that DNA is a double helix (shown on the right side of Figure 1) and is composed of nucleotides (shown in the bottom left of Figure 1). Nucleotides are made of a sugar, phosphate, and a nitrogenous base (these components are also shown in Figure 1).The nitrogenous bases are adenine (A), thymine (T), cytosine (C), and guanine (G). Notice that if adenine is on one side, thymine is opposite and if cytosine is on one side, guanine is opposite. These are considered complimentary base pairs and they always pair together in DNA.

Figure 1. The Structure of DNA.
(From http://www.accessexcellence.org/RC/VL/GG/dna2.html)

For more information on DNA history, go to
http://nobelprize.org/educational_games/
medicine/dna_double_helix/readmore.html

For detailed information and an animation of DNA, go to
http://www.johnkyrk.com/DNAanatomy.html


DNA, RNA, and Protein Synthesis
The nitrogenous bases of DNA – A, T, C, and G provide the basis for DNA to code for genetic characteristics. There can be hundreds to billions of nucleotides on just one side of the DNA strand, depending on the organism. The order of the nitrogenous bases on the nucleotides is called the base sequence. The base sequence is comprised of all the codes for each gene that an organism has. A gene is a specific nucleotide sequence on the DNA that codes, or contains the genetic instructions, for one protein. To discover how these genes are turned into proteins, we must take a closer look at RNA.

While DNA holds the genetic instructions for making proteins, it is ribonucleic acid, or RNA, that must read and translate them. Protein synthesis involves two parts, transcription and translation. It also involves 3 kinds of RNA- messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA). A summary of the process is pictured in Figure 2 and explained below it.

Figure 2. Protein Synthesis
(From http://www.accessexcellence.org/RC/VL/GG/protein_synthesis.html)

In transcription (#1 on Figure 2), mRNA transcribes, or copies down a gene from DNA. An enzyme called RNA polymerase opens the necessary gene in the DNA and begins adding complimentary nucleotides to “copy” the gene base sequence. RNA does not contain thymine; instead, it contains uracil (U). Therefore, as mRNA copies the gene from DNA, it pairs adenine with uracil, thymine with adenine, guanine with cytosine and cytosine with guanine. Once the gene base sequence has been copied, the mRNA leaves the nucleus to travel to the ribosome where the protein will be made.

Translation occurs in the cytoplasm (#2 on Figure 2). In translation, the mRNA first binds to a ribosome. Ribosomes are made of rRNA and provide the environment for protein synthesis. The mRNA molecule is read 3 bases at a time. These 3 base sequences are called codons. Each codon codes for a specific amino acid. Amino acids are the building blocks of proteins. The amino acids are brought to the ribosome one at a time by tRNA. Once all the codons are read and all the amino acids have bonded to form a protein, the mRNA and ribosome release the protein. The protein goes on to perform its function.

Although middle school students are not responsible for protein synthesis, it is necessary background information for teachers to understand heredity.

For an animated simulation of protein synthesis and further explanation, go to
http://www.lewport.wnyric.org/JWANAMAKER/animations
/Protein%20Synthesis%20-%20long.html
and,
http://www.wisc-online.com/objects/index_tj.asp?objID=AP1302

For information on how mutations affect the expression of DNA, see MS TIPS Benchmark L.8.A.2


Meiosis and Gamete Formation
In eukaryotic organisms, DNA strands can be incredibly long due to the fact that it takes hundreds or thousands of nucleotides to code for one protein. For example, the DNA in just one human cell can be over 2 meters long from end-to-end! How does all of that DNA fit into a cell? The DNA coils tightly around itself and special proteins to form chromosomes. Human DNA has 46 chromosomes as shown in Figure 3, which is a human karyotype. A karyotype is a picture of an organisms chromosomes, lined up next to their homologues. Homologous chromosomes, or homologues, are chromosomes that are the same size, the same shape, and have the same genes. These homologous chromosomes may not have the same base sequences for the genes. For example, a gene that codes eye color would be located on the same spot in two homologous chromosomes; but one of the genes may code for blue eyes on one chromosome while the other codes for brown eyes on the other chromosome. These different forms of a gene are called alleles. Each parent donates one chromosome to the homologous pair. In order for this to be possible, each parent of any organism would need to produce a cell with half the total number of chromosomes for that organism. Or, in other words, a cell with only one homologue would be produced. This cell, used for sexual reproduction, would be called a gamete and is produced through the process of meiosis.

Figure 3. Human Karyotype and Chromosome Structure.
(From http://www.accessexcellence.org/RC/VL/GG/human.html)

Figure 4 depicts a simplified summary of meiosis. The figure shows 4 chromosomes, or 2 homologous pairs. In prophase 1, the chromosomes duplicate themselves, which is what gives them the X-shape. In metaphase 1, the homologues line up next to each other in the middle of the cell. Two events happen at this step that creates genetic variation among the gametes produced. The first is independent assortment. The homologues will line up and be separated randomly. In the figure, two chromosomes of the original four come from the mother and two come from the father. When the chromosomes are pulled to each side of the cell to create two new cells, (as seen in Anaphase 1 and Telophase 1), the daughter cells of the first cell division may end up with two chromosomes from the same parent or they may end up with one chromosome from each parent cell. The second event is crossing over. When homologues line up next to each other, parts of the chromosome may be swapped. This results in the daughter cells of the first division having different chromosomes than the parent cell. After two daughter cells are produced by the first division in meiosis, a second division occurs. In this division, each of the chromosomes are split in half. Notice the four daughter cells that result after Telophase 2 have half the number of chromosomes as the parent cells. These daughter cells would be considered gametes.

Figure 4. Meiosis Overview.
(From http://www.accessexcellence.org/RC/VL/GG/meiosis.html)

Gamete formation is also where mutations can happen, for more information,
see MS TIPS Benchmark L.8.A.2

For meiosis animated simulations, go to
http://www.lewport.wnyric.org/jwanamaker/animations.htm and,
http://www.sumanasinc.com/webcontent/anisamples/majorsbiology/ and,
http://www.cellsalive.com/meiosis.htm

For a meiosis tutorial, see
http://www.biology.arizona.edu/CELL_BIO/tutorials/meiosis/main.html


Genetics
Now that we have seen how gametes form, let’s take a look at how hereditary information is passed through these gametes. First, we will need some background information on genetics. Long before scientists knew that DNA was the genetic material, a monk named Gregor Mendel studied genetics in pea plants. His experiments led to the discovery of several important genetic principles. Mendel discovered that some alleles for genetic traits are dominant and some traits are recessive. Alleles are alternate forms of genes. When the dominant allele for a gene is present, it will mask the appearance of the recessive allele. For example, in his pea plants, Mendel discovered that green pea pods were dominant over yellow pea pods. The parent pea plants will each give one allele for pea pod color to their offspring. If one parent gave the allele for green pea pods and the other parent gave the allele for yellow pea pods, then the offspring would have green pea pods. This passing down of alleles is related to the previously discussed concept of meiosis. At the end of meiosis, each gamete contains one homologue of each chromosome for the given organism. This means the gamete also contains one allele for each trait on that chromosome. Each parent donates one allele to the offspring for each gene.

For more information on Gregor Mendel, go to
http://www.mendelweb.org/MWtoc.html and,
http://www2.edc.org/weblabs/Mendel/mendel.html

Genetic traits are often symbolized by letters. Dominant alleles are often symbolized by capital letters, like ‘G’ for green pea pods. Recessive alleles are often symbolized by lower case letters, like ‘g’ for yellow pea pods. So the offspring from the previous example would have the genotype Gg and a phenotype of green pea pods. Genotype is the genetic makeup, while phenotype is the physical appearance of an organism. This genotype is called heterozygous, because there is one dominant and one recessive allele. Genotypes that have two of the same allele, such as GG or gg would be considered homozygous dominant and homozygous recessive, respectively.

When the genotype of parents is known, Punnett Squares can be used to determine the possible genotypes of the offspring. For example, the allele for being tall (T) in pea plants is dominant over the allele for being short, so if we breed a heterozygous plant (Tt) with a homozygous recessive plant (tt). The possible offspring genotypes are shown in Figure 5. Punnett squares can also help us determine the probability that offspring will turn out a certain way. Figure 5 shows that there is a 50% chance that an offspring of these parent plants would be tall and a 50% chance that it would be short. Punnett Squares shows the possible gamete combinations that would be made by parents during meiosis. So, in this example, for the Tt parent, meiosis would produce a gamete with the T allele in it 50% of the time and a gamete with t in it 50% of the time. The tt parent would only produce gametes with t in them. This Punnett square is an example of a monohybrid cross, which mean it only contains one inherited trait. Punnett squares can be much larger when they are used for dihybrid or trihybrid crosses.

Figure 5. Punnett Square for Tt and tt Pea Plant Cross
(From http://users.adelphia.net/~lubehawk/BioHELP!/psquare.htm)

For step by step instructions on making Punnett squares, go to
http://users.adelphia.net/~lubehawk/BioHELP!/psquare.htm

For an online animated tutorial of making Punnett square and how they relate to breeding and probability, go to http://www.usoe.k12.ut.us/CURR/Science/sciber00/7th/genetics/sciber/intro.htm

For a Punnett square calculator (shows you the Punnett square if you type the genotypes), go to http://www.changbioscience.com/genetics/punnett.html

For more information on selective breeding, see MS TIPS Benchmark L.8.A.3.

Now let’s take a look at a human trait that is often passed down through generations. The trait is thumb straightness. In human, as discussed in previous sections, there are 46 chromosomes. When meiosis occurs and gametes are formed, the resulting cells have 23 chromosomes, which means one homologue and one allele for each gene. In humans, the allele for hitchhikers thumb (h) is recessive, while the allele for a straight thumb (H) is dominant. These thumb types are pictured in Figure 6. Each person has two alleles for this trait. A genotype of HH or Hh would result in a straight thumb, while hh would result in hitchhikers thumb.

Hitchhiker's Thumb
Regular Thumb

Figure 6. Hitchhiker Thumb Compared to a Straight Thumb
(From http://www.ncrtec.org/tl/camp/gene/thumbs.htm)

Now let’s take two parents, a male with hitchhikers thumb and a female with a homozygous straight thumb (hh and HH respectively). When their gametes are formed through meiosis, the male will produce gametes with the h allele. The female will produce gametes with the H allele. When the gametes fuse together to form a zygote during fertilization, the zygote would receive the genotype Hh and therefore have a straight thumb. Let’s say the offspring of this child was a female who has children with a male who has the genotype Hh. Both parents will have straight thumbs, but it will be possible for them to have a hitchhiker thumbed child. Each parent will form some gametes with the H allele and some with the h allele. As demonstrated in the Punnett Square in Figure 7, there is a 25% chance that they will have a child with hitchhiker’s thumb and a 75% chance they will have a child with straight thumbs. This example illustrates how a recessive trait can be passed through generations and stay hidden or unseen in some individuals. These individuals carry the allele for the recessive trait, but do not express it.

H
H
H
HH
Hh
h
Hh
Hh

Figure 7. Punnett Square of a heterozygous cross for hitchhikers thumb

Heredity is often not as simple as monohybrid crosses. Most human characteristics are polygenic, which means they are controlled by many genes. Eye color, for example, is controlled by at least three genes and there may be more. Many human traits are also complex characters, which means the environment plays a role in the phenotype. Skin color, for example, can be influenced not only by several genes, but by the amount of sunlight a person’s skin receives. Some traits are incompletely dominant. This means that in heterozygous individuals, the phenotype is somewhere in between the phenotypes of the homozygous individuals. For example, if a curly haired Caucasian and a straight hair Caucasian have children, the child will have wavy hair. Some traits are controlled by multiple alleles, such as the ABO blood types in humans. The three alleles for blood typing are A (IA), B (IB), and O (i). The IA and IB alleles are also codominant, which means that if a person has both alleles, they are both expressed as the phenotype and that person would have AB blood. The type O (i) allele is recessive to A (IA) and B (IB) allele. In order to have type O blood, an individual must inherit a recessive allele (i) from each parent. If an individual inherits an A allele (IA) from one parent and an O allele (i) from another parent, then the individual will have type A blood (IA i) because the A allele is dominant to the O allele.

For more information on blood typing and inheritance see http://www.biology.arizona.edu/Human_bio/problem_sets/blood_types/Intro.html

Some traits are sex-linked, which means they are found on the sex chromosomes. These traits, such as colorblindness, are usually located on the X chromosome and are more prevalent in men. For colorblindness, women would only be colorblind if the colorblind allele were on both X chromosomes; but in men, the allele only needs to be on their one X chromosome. Some traits are sex-influenced, which means males and females will show different phenotypes when they have the same genotype. Pattern baldness is an example of a sex-influenced trait, as it is dominant in males but recessive in females. Many genetic traits found in organisms, especially in humans, are not controlled by two alleles where one allele is dominant and one is recessive; but that kind of trait is the simplest way to explain heredity.

For more information on the genetic and environmental influences on organisms see
MS TIPS Benchmark L.8.A.4.

For an animated tutorial on the basics of genetics, go to
http://learn.genetics.utah.edu/units/basics/tour/

For a guide to understanding genetic conditions, go to
http://ghr.nlm.nih.gov/

For an overview of heredity concepts and genetics, see
http://library.thinkquest.org/20465/info.html

For several links to other DNA and genetics websites, go to
http://sciencespot.net/Pages/kdzbiogen.html


Asexual Reproduction
Asexual Reproduction is a process that involves only one organism. This process does not involve meiosis. Offspring in asexual reproduction are usually exact copies of the parents, unless mutations occur. Asexual reproduction mainly occurs in single-celled organisms, though it does also occur in some multicellular organisms.

Many types of bacteria reproduce asexually in a process known as binary fission. This process is pictured in Figure 7 below.

Figure 7. Binary Fission
(From http://www.uic.edu/classes/bios/
bios100/lecturesf04am/lect06.htm
)

Some fungi, such as yeast also reproduce asexually. Yeast use a process called budding in which the offspring “buds” off the parent. Budding of yeast is pictures in Figure 8 below.

Figure 8. Budding of Yeast
(From http://mpf.biol.vt.edu/research/budding_yeast_model/pp/intro.php)


Some species of star fish can also reproduce asexually. The parent star fish body splits in half and each “daughter” regenerates the other half of its body to form two separate star fish.

For more information and examples on asexual reproduction, visit
http://regentsprep.org/Regents/biology/units/reproduction/asexual.cfm and,
http://www.ucmp.berkeley.edu/glossary/gloss6/asexual.html

For more information on asexual reproduction in plants, visit
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/A/AsexualReproduction.html

For more information on asexual reproduction in animals, visit
http://biology.about.com/library/weekly/aa090700a.htm

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Content Benchmark L.8.A.1

Students know heredity is the passage of genetic instructions from one generation to the next generation. E/S


Common misconceptions associated with this benchmark

1. Students incorrectly believe that if no one else in the family is affected, the condition is not inherited.

Students often believe that if they do not see a characteristic such as in their family, then it must not be inherited. For example, if a student had a hitchhikers thumb, but their parents and possibly grandparents did not, then the student may believe something happened to their thumb to make it bend back. This is especially common with genetic disorders, like colorblindness, which often skip generations. Drawing Punnett Squares and pedigrees can help students visualize that some traits or genetic disorders tend to skip generations. The first resource below explains how to create pedigrees, or family trees.

For information on this and other misconceptions as well as information about why this misconception is not true, go to
http://genetics.kaiser.org/home/genetics101highlights.htm

For more information on the inheritance of genetic disorders, go to http://www.mdausa.org/publications/gen_inhr.html


2. Students inaccurately believe that traits are inherited from only one of their parents.

Some students believe girls inherit most of their characteristics from their mothers and boys inherit most of their characteristics from their fathers. Some students may also believe their mothers give them more genetic material because they were carried in their mothers as fetuses. Students may tend to believe they look more like one parent and therefore they received most of their genetic material from that parent. In reality, each parent contributes half of their genetic material to their offspring. One parent may pass more dominant traits to their offspring, which would result in that offspring looking more like that parent. These misconceptions can be overcome by discussing the processes of meiosis and fertilization.

For information on this and other misconceptions, go to
http://www.project2061.org/publications/bsl/online/ch15/findings.htm

For information on meiosis and fertilization, see
http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=cooper.section.2484


3. Students have difficulty with the relationship between genetics, DNA, genes, and chromosomes.

Students may realize that physical appearances are inherited, but they may not make the connection that these characteristics have underlying biochemical processes, such as the production of proteins. As a result they may also not realize genes on DNA are responsible for these biochemical processes. Chromosomes are passed from parent to offspring. They are made of DNA, which has genes on it that code for proteins. These proteins cause our characteristics.

For information on this and other misconceptions, go to
http://www.project2061.org/publications/bsl/online/ch15/findings.htm, and
http://www.genetics.org/cgi/rapidpdf/genetics.107.084194v1 (page 15), and
http://homepage.mac.com/vtalsma/syllabi/2943/handouts/misconcept.html#top

For more information on the link between genetics, DNA, genes, and chromosomes, go to
http://learn.genetics.utah.edu/units/basics/tour/


4. Students have difficulty distinguishing the difference between acquired and inherited characteristics.

While many of our characteristics come directly from out genetics, that is not the case for all of our characteristics. Genetics plays a role in some behaviors and diseases, but the majority of these are the result of one’s environment. Talent is something that can be inherited, but skills must be practiced in order for talent to develop. This misconception can be overcome by looking at several examples of inherited characteristics and several examples of acquired characteristics.

For information and research about this misconception, go to
http://www.msu.edu/~ostrow22/sciencelessonplan.htm

For information on this and other misconceptions as well as lesson plans to overcome it, visit http://public.doe.k12.ga.us/DMGetDocument.aspx/Fifth%20Grade%20
Frameworks%2020Genetics.pdf?p=6CC6799F8C1371F61DE930EB
A3265FC8133CC6DC95D97C 40022D61E56BBE1C86&Type=D
, and
http://www.uen.org/Lessonplan/preview.cgi?LPid=69

For activities and information on learned versus inherited behavior, go to
http://utahscience.oremjr.alpine.k12.ut.us/Sciber01/7th/cells/html/inhvsacq.htm, and
http://www.sciencenetlinks.com/lessons.cfm?BenchmarkID=6&DocID=461, and http://www.computerladyonline.com/PDF%20Instructions%20for%20Activities
/Session%206/635--6029en--Inherited%20Versus%20Learned.pdf


5. Students inaccurately believe that one gene controls one trait and all genetics show Mendelian patterns of inheritance

When teaching genetics, it is important to emphasize that there are non-Mendelian patterns of inheritance. Most traits in humans are not monogenic (controlled by one gene). Monogenic traits are the first examples that we teach, so students assume that all traits are governed by one gene. Examples should be given for other patterns of inheritance, such as polygenic inheritance or linked genes, which will not show Mendelian patterns.

For information on this and other misconceptions as well ideas on how to overcome it, go to http://www.genetics.org/cgi/rapidpdf/genetics.107.084194v1

For information on non-Mendelian inheritance, go to
http://geneticsmodules.duhs.duke.edu/
Design/MainMenu.asp?CourseNum=2
, and
http://en.wikipedia.org/wiki/Non-Mendelian_inheritance

For information on polygenic inheritance, go to
http://staff.jccc.net/pdecell/evolution/polygen.html, and
http://waynesword.palomar.edu/lmexer5.htm

For information on linked genes, go to
http://biology.clc.uc.edu/Courses/bio105/sex-link.htm

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Content Benchmark L.8.A.1

Students know heredity is the passage of genetic instructions from one generation to the next generation. E/S


Sample Test Questions

1st Item Specification: Know reproduction of organisms includes cell division, transfer of genetic information, and the probability of certain characteristics passed from one generation to the next

Depth of Knowledge Level 1

  1. What molecule allows hereditary information to be passed from generation to generation?
    1. DNA
    2. ATP
    3. Lipids
    4. Proteins
  1. Which of the following is a TRUE statement about human reproduction?
    1. Each parent contributes an equal number of chromosomes to their offspring.
    2. Mothers contribute a higher number of chromosomes to daughters than sons.
    3. Fathers contribute a higher number of chromosomes to sons than daughters.
    4. Mothers contribute a higher number of chromosomes to sons and daughters.

Depth of Knowledge Level 2

  1. Having a hitchhiker's thumb is a recessive trait to having a straight-thumb. When a straight-thumbed homozygous person has offspring with a hitchhiker's thumbed homozygous person, the offspring will
    1. have a 50% chance of having hitchhikers thumb.
    2. have a 50% chance of having straight thumb.
    3. all be heterozygous with a straight thumb.
    4. all be heterozygous with a hitchhikers thumb.
  1. In human blood types, type A and type B are codominant over the allele for type O blood. If a female with type O blood and a male with type AB blood have children, which of the following statements will be TRUE?
    1. 50% of their offspring will have type O blood.
    2. 50% of their offspring will have AB blood.
    3. 50% of their offspring will have type A blood and 50% will have type B blood.
    4. 50% of their offspring will have type A blood and 50% will have type AB blood.

2nd Item Specification: Differentiate between asexual and sexual reproduction

Depth of Knowledge Level 1

  1. A process that involves two parent cells fusing to form the first cell of a new organism is known as
    1. sexual reproduction.
    2. asexual reproduction.
    3. meiosis.
    4. mitosis.
  1. A process in which one organism produces genetically identical offspring, by itself, is known as
    1. sexual reproduction.
    2. asexual reproduction.
    3. meiosis.
    4. mitosis.
  1. A form of asexual reproduction in single-celled organisms, in which one cell duplicates its DNA and then divides into 2 cells, is known as
    1. binary fission.
    2. translation.
    3. transformation.
    4. conjugation.
  1. A form of asexual reproduction in which a part of the parent organism “pinches off” to form a new organism is known as
    1. transcription.
    2. budding.
    3. transformation.
    4. conjugation.

Depth of Knowledge Level 2

  1. A colony of E. Coli bacteria asexually reproduce every 20 minutes. If the colony begins with 10 individuals, how many individuals will be in the colony after 1 hour?
    1. 20
    2. 40
    3. 60
    4. 80
  1. A difference between sexual and asexual reproduction is that the offspring of
    1. asexual reproduction have fewer chromosomes than their parents, while offspring of sexual reproduction have the same number of chromosomes.
    2. sexual reproduction have fewer chromosomes than their parents, while offspring of asexual reproduction have the same number of chromosomes.
    3. asexual reproductions are clones of their parents, while offspring of sexual reproduction are genetically different from their parents.
    4. sexual reproduction are clones of their parents, while offspring of asexual reproduction are genetically different from their parents.

Constructed Response L.8.A.1

  1. Mr. and Mrs. Smith recently had a baby. The nurses at the hospital were not careful and mixed up the name tags of 3 babies (A, B, and C), one of which belongs to the Smiths. Baby A has type O blood and freckles. Baby B has type A blood, and no freckles. Baby C has type B blood, and freckles. Use this and the following information to determine which baby belongs to the Smiths. Be sure to justify your answer with both an explanation and by drawing the Punnett squares for each trait.

    1. Freckles (F) are dominant over no freckles (f). Mr. Smith is homozygous dominant for freckles, while Mrs. Smith has no freckles.
    2. Type A and B blood are codominant to type O blood. Mr. Smith is heterozygous type A blood, while Mrs. Smith has type AB blood.

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Content Benchmark L.8.A.1

Students know heredity is the passage of genetic instructions from one generation to the next generation.

Answers to Sample Test Questions

  1. A, DOK level 1
  2. A, DOK level 1
  3. C, DOK level 2
  4. C, DOK level 2
  5. A, DOK level 1
  6. B, DOK level 1
  7. A, DOK level 1
  8. B, DOK level 1
  9. D, DOK level 2
  10. C, DOK level 2

Constructed Response L.8.A.1 Score Rubric:

 

3 points

 

 Response addresses all parts of the question clearly and correctly.

Both Punnett Squares are drawn and completed correctly. Note that the letters may be different for freckles as long as the capitalization is the same. For blood type, the letters must be the same. The Punnett squares show that Mr. and Mrs. Smith can only have children with freckles, so baby B cannot be theirs because it does not have freckles. The Punnett squares also show that Mr. and Mrs. Smith can only have babies with the blood types A, B, or AB. Baby A has type O blood and cannot be theirs. Therefore, by the process of elimination, Baby C is their baby.

Freckles

 

F

F

f

Ff

Ff

f

Ff

Ff

 

 

Blood type

 

A

O

A

AA

AO

B

AB

BO

2 points

 Response addresses all parts of the question and includes only minor errors.

1 point

 Response does not address all parts of the question.

0 points

 Response is totally incorrect or no response provided.



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Content Benchmark L.8.A.1

Students know heredity is the passage of genetic instructions from one generation to the next generation. E/S


Intervention Strategies and Resources

The following is a list of intervention strategies and resources that will facilitate student understanding of this benchmark.


1.Reproduction and Heredity

This website was created by the Utah State Office of Education. It contains worksheets, quizzes, animations, and descriptions related to the basics of genetics. It also provides ideas for labs and projects. This website was created for a seventh grade class and has many fun activities.

To access this information, go to
http://www.usoe.k12.ut.us/CURR/Science/sciber00/7th/genetics/sciber/intro.htm


2.Mendelian Genetics Problems

This website was created through “The Biology Project” at the University of Arizona. There are several links on the page that allow students to view genetics problems. There are individual problem sets for monohybrid, dihybrid, and sex-linked crosses. The greatest part about the web site is that incorrect answers are linked with tutorial to help the students find the correct answers.

To access these problem sets, go to
http://www.biology.arizona.edu/mendelian_genetics/mendelian_genetics.html


3.Genetics Tutorial

This tutorial was created by GlaxoSmithKline. It is a tutorial designed especially for kids on DNA, genes, and heredity. It also has education games for kids to play, such as “Build DNA”, “Build a Protein”, or “Punnetts and Pedigree.” The website also has great animated explanations for the adults.

To access the general public tutorial, go to
http://www.genetics.gsk.com/generalpublic_flash.htm

To access the student tutorial, go to
http://www.genetics.gsk.com/kids/index_kids.htm


4.From Jeans to Genes

This website gives a fun lesson plan for introducing students to genes and chromosomes. In this activity, students use pieces of clothing to simulate chromosomes. It also teaches students to demonstrate genotypes, phenotypes, and use Punnett Squares. The website where this lesson comes from is by Joell Marchese at Pine Valley Middle School. There are also other great lesson plans available on this site.

To access this activity, go to
http://www.cccoe.net/tdf/Marchese/jtg/index.html

To access the general website for other lesson plans and information, go to
http://www.cccoe.net/genetics/student.html


5.Crack the Code

This website is the official site of the Nobel Foundation. It gives a brief tutorial on how DNA is changed into proteins. The tutorial provides excellent pictures and a couple animations. At the end of the brief tutorial, students can learn more about protein synthesis and DNA. There is also a game called “Crack the Code,” in which the students must quickly decipher codons into amino acids.

To access this tutorial and game, go to
http://nobelprize.org/educational_games/medicine/gene-code/index.html


6.The Basics and Beyond

This web site is by The University of Utah, Genetic Science Learning Center. This web site provides great tutorials on the basics of DNA. Students can build a DNA model, transcribe and translate a gene, and discover how proteins function. There is also an excellent tutorial which takes students through protein synthesis to determine how fireflies glow.

For the Basics and Beyond website, go to
http://learn.genetics.utah.edu/units/basics/

For the direct link to “What makes a Firefly glow?” go to
http://learn.genetics.utah.edu/units/basics/firefly/


7.Mitosis, Meiosis, and Fertilization

Models of chromosomes made from pairs of socks are used to illustrate the principles of mitosis, meiosis, and fertilization in this activity. Students will see how chromosomes divide in meiosis and mitosis, as well as how they come back together during fertilization. The activity is by Dr. R. Scott Poethig, Dr. Ingrid Waldron, and Jennifer Doherty of the Department of Biology, University of Pennsylvania. The site gives both the student worksheets and a teacher preparation guide.

For information on meiosis and fertilization and student activities, go to
http://serendip.brynmawr.edu/sci_edu/waldron/#mitosis

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Gene
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Genetic
Heredity
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