Download Genetics Review

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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.
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
Mother
Baby
Bartender
Guy at the club
Cabdriver
Flight Attendant
Blood Type
Type AB
Type AB
Type O
Type AB
Type A
Type B