The Genetics of Sex Practice Test
Review the following concepts if needed:
- Sex-Determining Mechanisms for Genetics
- Sex-Linked Inheritance for Genetics
- Variations of Sex Linkage for Genetics
The Genetics of Sex Practice Test
For each of the following definitions, give the appropriate term and spell it correctly. Terms are single words unless indicated otherwise.
- A form of reproduction involving the union of haploid gametes to form a diploid zygote.
- An animal that has both male and female reproductive organs.
- A flower having female but no male reproductive parts.
- An adjective applicable to the sex that produces gametes bearing structurally different sex chromosomes (e.g., half X-bearing and half Y-bearing).
- The two symbols that represent the sex chromosomes of female chickens, corresponding respectively to the X and Y chromosomes of mammals.
- The mode of sex determination for Drosophila. (Two words.)
- The mode of sex determination for bees.
- An adjective applied to genes on the differential (nonhomologous) segment of the Y chromosome.
- A class of traits governed by autosomal alleles whose dominance relationships are reversed in the two sexes as a consequence of sex hormone differences.
- A class of autosomal traits having phenotypic variability in a population in only one sex; the other sex exhibits a single phenotype regardless of its genotype.
Choose the one best answer.
- In an animal with the XO method of sex determination, which of the following could be the normal number of chromosomes in its somatic cells? (a) 26 in males (b) 17 in females (c) 33 in females (d) 13 in males (e) more than one of the above
- Suppose that in bees the dominant gene b+ produces wild-type (brown) eyes, and its recessive allele b produces pink eye color. If a pink-eyed queen mates with a brown-eyed drone, their offspring would most likely be (a) only wild-type progeny (b) wild-type workers and pink-eyed drones (c) only pink-eyed progeny (d) workers = 2 wild : 2 pink-eye; all drones wild type (e) insufficient information to allow a definitive answer
- In the guinea pig pedigree shown below, supposedly involving sex-linked inheritance: (a) III could exhibit the dominant trait (b) both I1 and II2 must be carriers of the gene responsible for the trait shown by II1 (c) the probability that the next offspring of II2 ×II3 has the same phenotype as III1 is 0.5 (d) if II1 is crossed to a female genetically like his sister, 75% of his offspring is expected to be phenotypically like their aunt (e) this pedigree is incompatible with a sex-linked explanation
- The presence of horns in the Dorset breed of sheep is due to a sex-influenced locus with horns dominant in males and recessive in females. Polled (hornless) males are mated to horned females. The fraction of the F2 expected to be polled is (a) 1/4 (b) 1/2 (c) 3/4 (d) 3/8 (e) none of the above
- In the clover butterfly, all males are yellow, but females may be yellow if they are homozygous (cc) or white if they possess the dominant allele (C-). Matings between heterozygotes are expected to produce an F1 generation containing (a) 1/2 yellow: 1/2 white (b) 3/4 white : 1/4 yellow (c) 3/8 white : 5/8 yellow (d) 9/16 yellow: 7/16 white (e) none of the above
- If sex determination in a species (2n = 14) is determined by genic balance (as it is in Drosophila), then an intersex could have (a) 10 autosomes + 2X (b) 14 chromosomes + 2X (c) six pairs of autosomes + XY (d) 21 autosomes + 2X (e) none of the above
- The presence of tusks is governed by a holandric gene in a certain mammalian species. When a tusked male is mated to nontusked females, among 100 of their F2 progeny we would expect to find (a) 50 tusked males, 50 nontusked females (b) 25 tusked males, 25 tusked females, 25 nontusked males, 25 nontusked females (c) 50 nontusked females, 25 tusked males, 25 nontusked males (d) 50 nontusked males, 25 tusked females, 25 nontusked females (e) none of the above
- In a bird species, blue beak is a sex-linked recessive trait; red beak is the alternative dominant trait. If a red-beaked male is mated to blue-beaked females, we would expect to find in theF1 (a) all progeny red-beaked (b) all males red-beaked, all females blue beaked (c) all males blue-beaked, all females red-beaked (d) all females red-beaked, 1/2 of males red-beaked, 1/2 of males blue-beaked (e) none of the above
- Suppose that the testes of a male (in a species with an XO sex-determination mechanism) experiences a primary sex reversal and begins to produce only eggs. Long tail is a dominant sex-linked trait; short tail is its recessive alternative. If a long-tailed male undergoes a primary sex reversal (to function as a female) and is mated to a short-tailed male, which of the following is expected among the adult progeny? (a) 1/2 long-tailed progeny (b) 2/3 of males long-tailed (c) 1/4 of all progeny long-tailed females (d) 1/3 of all progeny long-tailed males (e) problem is ambiguous; insufficient information
- A pair of codominant sex-linked alleles in a mammal produce red pigment when homozygous or hemizygous for A1, colorless when homozygous or hemizygous for A2, and pink when heterozygous. If a pink female is crossed to a white male, we expect among the progeny (a) 50% of females are white (b) 50% of all progeny are pink (c) 50% of males are pink (d) 25% of all progeny are white (e) none of the above
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