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Unit #7 GENETICS VOCABULARY

1. alleles

2. carrier

3. codominance

4. complete dominance

5. dominant allele

6. epistasis

7. F1 and F2 generation

8. genotype

9. heterozygous

10. homozygous

11. incomplete dominance

12. law of independent assortment

13. law of segregation

14. monohybrid

15. P generation

16. pedigree

17. phenotype

18. pleiotropy

19. polygenic inheritance

20. testcross

21. true-breeding/ pure-breeding

22. crossing over

23. deletion

24. duplication

25. genetic recombination

26. inversion

27. linkage map

28. linked genes

29. map unit

30. nondisjunction

31. polyploidy

32. recombinant

33. translocation

34. wild type

Ms. Gaynor/ AP Biology Name _________________________

Mendel and the Gene Idea Reading Guide Worksheets

1. Who was Gregor Johan Mendel?

2. What is the difference between “self fertilization” and “cross fertilization” in flowers?

3. List a few advantages of using pea plants in Mendel’s experiments.

4. How did Mendel carry out his experiments (what were his procedures)?

5. Sketch what Mendel saw below when he crossed a true breeding pure flower plant with a true breeding white flower plant. Be sure to use the correct colors. Label the P, F1, and F2 generations. THEN make notes on what Mendel saw (his results).

6. What is Mendel’s Law of Segregation?

7. What is the Law of Independent Assortment?

8. When does segregation of alleles occur during meiosis? ____________________________

9. What is an allele? How is it connected to DNA?

10. How do you determine the gametes that a parent will make if the genotype is HtTt? List all DIFFERENT possibilities.

11. Define the Rules of Multiplication and the Rules of Addition.

12. What is the purpose of a test cross?

13. If you cross 2 heterozygotes in the following crosses what are the expected PHENOTYPE ratios?

a. MONOHYBRID (Hh x Hh) : __________________________________________________

b. DiHYBRID (HhTt x HhTt) : ________________________________________________________________________

________________________________________________________________________

14. What is the difference between codominance and incomplete dominance?

15. Fill in the tables below on human blood types.

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16. How are blood types an example of multiple alleles?

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17. What is a pedigree?

18.

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19.

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20.

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21.

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22. Describe the following inherited disorders:

a. Tay Sachs

b. Cystic Fibrosis

c. Sickle cell disease

d. Achondroplasia

e. Huntington’s disease

23. What is nondisjunction?

24. When in meiosis can nondisjunction occur? _________________________ or ___________________

25. What are the gamete outcome/results (“n” numbers) if a cell undergoes nondisjunction?

26. Define the following terms: Aneuploidy, Monosomic, and Polyploidy.

27. What is the difference between amniocentesis and chorionic villus sampling?

Chromosomal Basis of Inheritance Reading Guide Worksheets

28. What does wild type mean? __________________________________________________________

29. What does it mean when genes are linked?

30. In what step of meiosis, would recombinants form? _________________________________

31. What is the SRY gene and why is it important?

32. What is a sex-linked gene? ____________________________________________________________

33. What is X inactivation?

34. What are Barr bodies?

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More Genetics Practice Problems

Problems Involving One Gene (MONOHYBRIDS)

1. In humans the allele for albinism is recessive to the allele for normal skin pigmentation. If two heterozygotes have children, what is the chance that a child will have normal skin pigment? What is the chance that a child will be albino?

2. In cats, long hair is recessive to short hair. A true-breeding (homozygous) short-haired male is mated to a long-haired female. What will their kittens look like?

3. Two cats are mated. One of the parent cats is long-haired (recessive allele). The litter which results contains two short-haired and three long-haired kittens. What does the second parent look like and what is its genotype?

4. Mrs. And Mr. Smith both have widow’s peaks (dominant). Their first child also has a widow’s peak, but their second child doesn’t. Mr. Smith accuses Mrs. Smith of being unfaithful to him. Is he necessarily justified? Why or why not?

5. Mr. and Mrs. Jones have six children. Three of them have attached earlobes (recessive) like their father, and the other three have free earlobes like their mother. What are the genotypes of Mr. and Mrs. Jones and of their numerous offspring?

6. Two plants having red flowers are mated. When their F1 offspring are studied, it is found that 95 have red flowers and 31 have white flowers. What is the genotype of the parents and diagram a cross to support your answer.

7. In purple people eaters, one-horn is dominant and no horns is recessive. Show the cross of a purple people eater that is heterozygous for horns with a purple people eater that does not have horns. Write the genotypes & phenotypes of the possible offspring.

8. In humans, the brown-eye (B) allele is dominant to the blue-eye allele (b). If two heterozygotes mate, what will be the likely genotype and phenotype ratios of the offspring?

9. In seals, the gene for the length of the whiskers has two alleles. The dominant allele (W) codes long whiskers & the recessive allele (w) codes for short whiskers.

a. What percentage of offspring would be expected to have short whiskers from the cross of two long-whiskered seals? one that is homozygous dominant and one that is heterozygous?

b. What percentage of offspring would be expected to have short whiskers from the cross of one that is homozygous dominant and one that is heterozygous?

Problems Involving Two Genes (DIHYBRIDS)

10. In horses, black is a dominant trait (B), chestnut is recessive (b). The trotting gait is dominant (T), pacing is recessive (t).

a. If a homozygous black pacer is mated to a homozygous chestnut trotter, what will be the appearance of the F1 generation?

b. If two F1 individuals were mated, what types of offspring could they have and in what ratios?

11. In garden peas, axial flower position is dominant and terminal flower position is recessive, tall vine is dominant and short vine is recessive. A plant known to be purebred for tall vine and axial flowers is crossed with a plant having short vines and bearing terminal flowers

a. What is the phenotype of the offspring? _________________________________________

b. What is the genotype of the offspring? __________________________________________

c. Predict the types of offspring (their phenotypes) that would appear in the F2 generation and their ratios.

12. Elizabeth is married to John, and they have four children. Elizabeth has a straight nose (recessive) and is able to roll her tongue (dominant). John is also able to roll his tongue, but he has a convex (Roman) nose (dominant). Of their four children, Ellen is just like her father, and Dan is just like his mother. The other children—Anne, who has a convex nose, and Peter, who has a straight nose—are unable to roll their tongues. Please answer the following questions about this family.

a. What are the genotypes of Elizabeth and John?

b. Elizabeth’s father was a straight-nosed roller, while her mother was a convex-nosed non-roller. What can you figure out about their genotypes?

c. John’s father was a straight-nosed roller, while his mother was a convex-nosed roller. What can you determine about their genotypes?

d. Diagram the three described generations of this family in accepted pedigree form, including the phenotypes for these two traits.

13. In horses, one which runs best in water (or in wet conditions) is called “water” and one which runs best in dry conditions is called “dry”. “Water” is recessive to “dry.” A horse can also be either a trotter, which is called “gait” or a pacer, which is called “pacer.” “Pacer” is recessive to “gait.” We have mated two horses, a stallion named Halter-Man and a mare named Erlich-Mane. Halter-Man is a water, pacer horse while Erlich-mane is a dry, gait horse. One of Erlich-Mane’s parents was a water, pacer horse.

a. What are the chances of Erlich-Mane and Halter-Man producing a water, gait foal (that’s a baby horse, in case you didn’t know)? SHOW YOUR WORK!

14. In garden peas, long stems are dominant to short stems, and yellow seeds are dominant to green seeds. 100 long/yellow pea plants, all of which had one short/green parent, are interbred (bred to each other). 1600 progeny result. Please answer the following questions about these progeny.

a. Assuming that these two genes are unlinked, about how many long/green pea plants would you expect to find among the offspring?

b. What ratio of yellow to green seed color would you expect among the offspring?

c. What would you expect the overall phenotypic ratio among the 1600 offspring to be (taking into consideration both traits)?

MendAliens are from the plant LaneTechius. In MendAliens, black eyes are dominant to orange eyes. They usually have green skin, which is dominant but they can have white skin. Some MendAliens are 4 feet tall, which is dominant to being 2 feet tall. Four eyes is dominant to having 2 eyes and straight horns are dominant to curly horns.

15. Sam, a MendAlien with black eyes and green skin, has a parent with orange eyes and white skin. Carole is MendAlien with orange eyes and white skin. If Sam and Carole were to mate, what are the phenotype probabilities of their offspring?

16. Graham is a MendAlien with four, black eyes but his father has two, orange eyes. Graham meets Stella at the LaneTechius bowling alley and falls in love with both her black eyes. Stella is bowling with her sister, Sarah, who has four, orange eyes. Graham only like black eyes. If Stella and Graham were to mate, what are the phenotype probabilities of their offspring?

17. Matthew the MendAlien is heterozygous for horn shape and height. He marries and mates with Mandy, who is also heterozygous horn shape and height.

a. What is the possibility that their offspring will be tall with curly horns?

b. What is the possibility that their offspring will be tall with straight horns?

c. What is the possibility that their offspring will be short with curly horns?

d. What is the possibility that their offspring will be short with straight horns?

e. What is the possibility that their offspring will have the same genotype as the parents?

f. What is the possibility that their offspring will have a recessive genotype for horn shape but be heterozygous for height?

18. Determine the results of a cross between two dolphins.  One is heterozygous dominant for skin color and tail length and the other is heterozygous for both traits.  Grey skin (G) is dominant to white skin (g) and long tails (T) are dominant over short tails (t).  List all phenotype ratios for the F1 generation.

Problems Involving Incomplete dominance

19. In certain cats, tail length is determined by a gene that demonstrates incomplete dominance. The allele that causes a long tail (T) is not completely dominant over the allele that causes no tail (t). If a cat is heterozygous for this trait (Tt), then the cat will have a short tail. What is the probability that the offspring will be manx cats (no tail) if a short – tailed cat is bred with a manx cat (no tail)?

20. Incomplete dominance is seen in snapdragons flowers. The allele that causes red flowers (F) is not completely dominant over the allele that causes white flowers (f). When a plant is heterozygous for the trait of flower color (Ff), pink flowers result. Cross two pink snapdragons, and provide the genotype and phenotype of all offspring.

Problems Involving Codominance

21. A black cat breeds with a tan cat and their kittens are all black-and-tan tabby (striped or mottled) cats. Set up a Punnet square that shows how this could happen. Why is this an example of co-dominance?

22. If two black-and-tan tabby cats, with genotypes that are like the kittens in problem #21, are bred, what are the odds of any one of their kittens being:

a. tabby? _____________

b. All black? ___________

c. All tan? _____________

23. Certain breeds of cattle show incomplete dominance in coat color. When pure breeding red cows are bred with pure breeding white cows, the offspring are roan (a pinkish coat color). Summarize the genotypes & phenotypes of the possible offspring when a roan cow is mated with a roan bull.

Problems Involving Blood Types (multiple alleles)

NOTE: The ABO blood type gene has three alleles. IA and IB are codominant; i (for Type O) is recessive to both.

24. In a particular family, one parent has Type A blood, the other has Type B. They have four children. One has Type A, one has Type B, one has Type AB, and the last has Type O. What are the genotypes of all six people in this family?

25. In a recent case in Spokane, Washington, a young woman accused a soldier of being the father of her child. The soldier, of course, denied it. The soldier’s lawyer demanded that blood types be taken to prove the innocence of his client. The following results were obtained: Alleged father, Type O. Mother, Type A. Child, Type AB. The court found the soldier guilty on the basis of the woman’s remarkable memory for dates and details that apparently eliminated all other possible fathers.

a. What are the possible genotypes for these three people?

b. Do you agree with the court’s decision? Why or why not?

26. It was suspected that two babies had been exchanged in a hospital. Mr. and Mrs. Jones received baby #1 and Mr. and Mrs. Simon received baby #2. Blood typing tests on the parents and the babies showed the following:

|Mr. Jones: Type A |Mr. Simon: Type AB |

|Mrs. Jones: Type O |Mrs. Simons: Type O |

|Baby #1: Type A |Baby #2 Type O |

a. Were the babies switched? How do you know whether they were or they weren’t?

27. A man with type O blood marries a woman with Type AB blood.

a. Among their children, what proportion would you expect to have blood types like one or the other of these parents?

b. What proportion would have expect to have blood types different from both parents? Explain.

28. A woman has a daughter. There are three men whom she claims might have been the father of the child. The judge in the paternity court orders that all three men, the child, and the mother have blood tests. The results are: mother, Type A; Daughter, Type O; Man #1, Type AB; Man #2, Type B; Man #3, Type O. The mother claims that this proves that Man #3 must be the little girl’s father.

a. Is the mother correct? Why or why not?

b. The judge isn’t satisfied, so he asks for the medical records of the people involved. He discovers that the little girl is colorblind. Men #’s 1 and 2 are also colorblind; Man #3 has normal color vision, as does the mother. (NOTE: Colorblindness is X-linked and recessive.) Assuming that one of these three men must be the father, can you now determine which of the three it is?

29. Another woman has the same problem. Her blood type is A, her child’s is B. She again has three candidates for fatherhood. Their blood types are: Man #1, B; Man #2, AB; Man #3, O. Based on blood types, the mother says it must have been #1.

i. Do you agree? Why or why not?

ii. This child, a son this time, is also colorblind. The only one of the men in question to share this characteristic is #2. The mother is not colorblind. Can you now determine who the father of the little boy is, assuming it must be one of these men? Explain your answer.

Problems Involving Sex Linkage

30. In Drosophila (fruit flies), the gene for red eyes (R) is dominant to the gene for white eyes (r).  This trait is x-linked.  Determine the genotypic and phenotypic ratios expected from a cross between the following parents: (hint: remember to write the alleles X-X- and X-Y)

a. a heterozygous female and a red-eyed male?

b. a heterozygous female and a white-eyed male

31. Colorblindness is an X-linked trait, and the normal allele is dominant to the colorblindness allele. Ethan is colorblind. His wife, Edna, is homozygous for the normal color vision allele. If they have eight children, how many of them would you expect to be colorblind?

32. Marian’s father is colorblind, as is her maternal grandfather (her mother’s father). Marian herself has normal color vision. Marian and her husband, Martin, who is also colorblind, have just had their first child, a son they have named Mickey. Please answer the following questions about this small family.

a. What is the probability that this child will be colorblind?

b. Three sources of the colorblindness allele are mentioned in this family. If Mickey is colorblind, from which of these three men (Marian’s grandfather, Marian’s father, or Martin) did he inherit the allele?

c. Using proper pedigree format, diagram the available information about the four generations of this family described, assuming that Mickey is colorblind.

33. In humans, the gene for normal blood clotting (H) is dominant to the gene for hemophilia (h).  The gene for this trait is found on the X chromosome.  A woman and a man, both with the ability to clot blood normally, have a normal son, a hemophiliac son, and two normal daughters.  What is the probable genotype of each family member?

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Please SHOW ALL YOUR WORK and write your answers under each question.

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