REVIEW answers Genetics 1 (ch 14ish)
1 A couple who are both carriers for the gene for cystic fibrosis have two children who have cystic fibrosis. What is the probability that their next child will have cystic fibrosis? 25%
2 A couple who are both carriers for the gene for cystic fibrosis have two children who have cystic fibrosis. What is the probability that their next child will be phenotypically normal? 75%
3 What is a genetic cross between a homozygous recessive individual and one of an unknown genotype? a test-cross
4 In crossing a homozygous recessive with a heterozygote, what is the chance of getting a homozygous recessive phenotype in the F1 generation? 50
5 In snapdragons, heterozygotes have pink flowers, whereas homozygotes have either red or white flowers. When plants with red flowers are crossed with plants with white flowers, what proportion of the offspring will have pink flowers? 100%
6 Black fur in mice (B) is dominant to brown fur (b). Short tails (T) is dominant to long tails (t). What proportion of the progeny of the cross BbTt x BBtt will have black fur and long tails? 8/16 \
7 Feather color in budgies is determined by two different genes that affect the pigmentation of the outer feather and its core. Y_B_ is green; yyB_ is blue; Y_bb is yellow; and yybb is white. A green budgie is crossed to a blue budgie. Which of the following results is not possible? all green offspring -all blue offspring - all white offspring - all yellow offspring
8 What was the most significant conclusion that Gregor Mendel drew from his research? Traits are inherited in discrete units, one from each parent.
9 A couple has three children, all of whom have brown eyes and blond hair. Both parents are homozygous for brown eyes (BB), but one is a blond (rr) and the other is a redhead (Rr). What is the probability that the next child will be a brown-eyed redhead? 1/2
Use the information below to answer the following question(s).
A woman and her husband both show the normal phenotype for pigmentation, but both had one parent who was an albino. Albinism is an autosomal recessive trait.
10 What is the probability that their first child will be an albino? 25%
11 If their first two children have normal pigmentation, what is the chance that their third child will be an albino? 25%
12 What is the chance that their fourth child will have a homozygous genotype? 50
13 Sickle-cell anemia is the result of a single recessive gene in thehomozygous state (ss), yet this disease has a complex set of symptoms affecting many parts of the body. Which term is most applicable to this example?pleiotropy
14The advantage of chorionic villi sampling over amniocentesis is that CVS: can give results much earlier in the pregnancy than amniocentesis.
Use the information given below to answer the following question(s).
A woman who belongs to blood group A and is Rh positive has a daughter who is O positive and a son who is B negative. Rh positive is a simple dominant over Rh negative.
15 Which of the following is a possible genotype for the son? IBirr
16 Which of the following is a possible genotype for the mother? IAiRr
17 Which of the following is a possible phenotype for the father? B positive
18 Given the parents AABBCc x AabbCc, assume simple dominance and independent assortment. What proportion of the progeny will be expected to phenotypically resemble the first parent 3/4
19 The fact that all seven of the garden pea traits studied by Mendel obeyed the pri seven pairs of alleles determining these traits are on the same pair of homologous chromosomes.seven pairs of alleles determining these traits behave as if they are on different chromosomes. A A sexually reproducing animal has two unlinked genes, one for head shape and one for tail length. Its genotype is HhTt. Which of the following genotypes is possible in a gamete from this organism? HT E Which of the following is an example of polygenic inheritance? skin pigmentation in humans
20 Two true-breeding stocks of garden peas are crossed. One parent had red, axial flowers, and the other had white, terminal flowers; all F1 individuals had red, axial flowers. If 1,000 F2 offspring resulted from the cross, how many of them would you expect to have red, terminal flowers? (Assume no linkage.)190
Refer to the terms shown below to answer the following question(s). Each term may be used once, more than once, or not at all.
1. incomplete dominance 2. multiple alleles 3. pleiotropy 4. epistasis 5. penetrance
21 The ability of a single gene to have multiple phenotype effects.3
22 One example is the ABO blood group system. 2
23 The phenotype of the heterozygote differs from the phenotypes of both homozygotes. 1
Use the following information to answer the question(s). Albinism (lack of skin pigmentation) is caused by a recessive autosomal allele. A man and woman, both normally pigmented, have an albino child together.
24 For this trait, what is the genotype of the albino child? homozygous recessive
25 The couple decides to have a second child. What is the probability that this child will be albino? 1/4
26 The mother is now pregnant for a third time, and her doctor tells her she is carrying fraternal twins. What is the probability that both children will have normal pigmentation? 9/16
27 A 9:3:3:1 phenotypic ratio is characteristic of the F2 generation of a dihybrid cross
28 A 1:2:1 phenotypic ratio in the F2 generation of a monohybrid cross is a sign of intermediate inheritance
29 How many unique gametes could be produced through independent assortment by an individual with the genotype Aa Bb CC Dd EE? 8
30 In cattle, roan coat color (mixed red and white hairs) occurs in the heterozygous (Rr) offspring of red (RR) and white (rr) homozygous. When two roan cattle are crossed, the phenotypes of the progeny are found to be in the ratio of 1 red:2 roan:1 white. Which of the following crosses could produce the highest percentage of roan cattle? red x white
31 Roan color in cattle is the result of absence of dominance between red and white color genes. How would one produce a herd of pure-breeding roan-colored cattle? It cannot be done.
32 Three babies were recently mixed up in a hospital. After consideration of the data below, which of the following represents the correct baby/parent combinations?
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_ Couple # _ I _ II _ III _
_ Blood groups _ A and A _ A and B _ B and O _
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_ Baby # _ 1 _ 2 _ 3 _
_ Blood groups _ B _ O _ AB _
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(A) I-3, II-1, III-2 (B) I-1, II-3, III-2 (C) . I-2, II-3, III-1 (D) I-2, II-1, III-3 (E) I-3, II-2, III-1
(process of elimination...figure it out!)
33 Tallness (T) is dominant to dwarfness (t), while red flower color is due to gene (R) and white is its allele (r). The heterozygous condition results in pink (Rr) flower color. A dwarf red snapdragon is crossed with a plant homozygous for tallness and white flowers. What are the genotype and phenotype of the F1 individuals? TtRr--tall and pink
34 What do all males inherit from their mother? mitochondrial DNA and X chromosome
35 What does independent assortment refer to? . the random arrangement of chromosomal tetrads at metaphase I