Genetics Review - Higley Unified School District



Genetics Review

I. Know the definitions and UNDERSTAND the following terms:

1. homozygous

2. heterozygous

3. dominant

4. recessive

5. hybrid

6. purebred

7. genotype

8. phenotype

9. genetics

10. alleles

11. Punnett square

12. mutation

13. cross-pollination

14. self-pollination

15. gene

II. Who was Gregor Mendel?

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

IV. What information can be determined from a pedigree? What do the different symbols indicate?

V. Practice Problems

a. Marge is heterozygous for blue hair and Homer has (had) yellow hair. (use B for blue hair and b for yellow hair)

What will be the genotypes of their offspring?

What will be the phenotypes of their offspring?

What is the genotypic ratio for their offspring?

What is the phenotypic ratio for their offspring?

b. If one-fourth of the offspring between two sea sponges are round, what are genotypes and phenotypes of the parents? (use S for square and s for round)

c. Fuzzy wuzzy is homozygous fuzzy and heterozygous brown. If he mates with a bear that is not fuzzy and heterozygous for brown color, what are the possible genotypes and phenotypes for their cubs? What is the genotypic ratio? What is the phenotypic ratio? (Use F for fuzzy, f for not fuzzy and B for brown, b for white)

d. In some chickens, the gene for feather color is controlled by codominance. The allele for black is B and the allele for white is W. The heterozygous phenotype is known as erminette (black and white spotted). What is the genotype for black chickens, white chickens, and erminette chickens?

e. If an erminette chicken was crossed with a white chicken, what is the probability that: they would have a black chick? A white chick? An erminette chick?

f. A black, heterozygous long-legged (dom) chicken is crossed with a white, short-legged (rec) chicken. What is the genotypic and phenotypic ratio’s for this cross?

g. Brown eyes are dominant over blue eyes. This is NOT a sex-linked trait. Cross a brown-eyed colorblind male (whose mother had blue eyes) with a normal, blue-eyed female (whose father was colorblind). What is the probability of getting a: blue-eyed carrier female? Blue-eyed offspring? Blue-eyed, colorblind male? Brown-eyed, carrier female? Blue-eyed, normal male? Colorblind offspring?

h. A normal woman, who is a carrier for colorblindness marries a normal man. What types of offspring would you expect?

i. In Andalusion fowl, black individuals (BB) and white individuals (bb) are homozygous. Heterozygotes in Andalusion fowls are a bluish-gray. What results would be expected if a black individual is crossed with a bluish-gray individual?

j. If two bluish-gray Andalusion fowls were crossed, what would be the ratios for both the phenotype and genotype of the offspring?

k. Two wavy haired people marry and have 8 children. Of these eight, how many would you expect to be curly haired? How many wavy haired? How many straight haired? (Assume the family follows the expected statistically predicted patterns.)

l. Mrs. Smith has type A blood, Mr. Smith has type B. Their first child has blood type AB. Their second child has type O. Could these children truly be Mr. Smith’s? Explain.

m. In certain portions of the Jewish population, there is a genetic disease called Tay Sachs disease, which is fatal to infants within the first five years of life. This disease is caused by a recessive allele of a single gene. Why does this disease persist, even though it is invariably fatal long before the afflicted individual reaches reproductive age? In other words, why doesn’t the allele for Tay Sachs disease simply disappear?

n. The pedigree seen below is for colorblindness. Shaded individuals are colorblind. First, determine the probable genotype of persons 1-15; then answer the questions below the table.

[pic]

1. How did you determine the genotype of #3?

2. Number 8 was colorblind just like his father. Where did #8 get his allele for colorblindness?

3. Neither #1 or #2 were colorblind, How did they have a colorblind son?

4. What must be the genotypes of the parens of a colorblind daughter? Explain.

5. If #13 marries a normal man, what is the probability that their sons will be colorblind?

o. Based on the information in this table, which man could NOT be the father of the baby? Justify your answer with a Punnett square.

|Name |Blood Type |

|Mother |Type AB |

|Baby |Type AB |

|Bartender |Type O |

|Guy at the club |Type AB |

|Cabdriver |Type A |

|Flight Attendant |Type B |

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