Chapter 4 Flashcards
White eye color is an X-linked trait in one line of fruit flies. White eyes are recessive to red eyes. If a red-eyed female and a white-eyed male are crossed…
- All of their progeny will have white eyes
- None of their male progeny could have white eyes
- Some of their male progeny may have white eyes
- All of their female progeny will have white eyes
Some of their male progeny may have white eyes.
If the female is heterozygous, approximately half of the male progeny will have white eyes.
For x-linked traits in Drosophila, the male phenotype is determined by the maternally inherited allele.
- True
- False
True
Males inherit only one X chromosome. That chromosome is contributed by the female parent.
Eye color in Drosophila is an X-linked trait. White eyes are recessive to red eyes. If a drosophila male has white eyes, which of the following must also be true?
- His mother had at least one white allele
- His father must also have had white eyes
- Some of his female siblings from the same mating must also have white eyes
- All his male siblings from the same parents must also have white eyes
His mother had at least one white allele.
Because this male had white eyes, he must have inherited a white allele from his mother.
A gain-of-function mutation _____.
- Is usually recessive
- Results in absence of the gene product
- Results in an increased quantity of the normal gene product
- Is the wild-type allele
Results in an increased quantity of the normal gene product.
Gain-of-function mutations may affect regulation of transcription of the gene in question.
A mutation in a gene often results in a reduction of the product of that gene. The term for this type of mutation is ______.
- Incomplete dominance
- Loss of function or null (in the case of complete loss)
- Multiple allelism
- Codominance
- Gain of function
Loss of function or null (in the case of complete loss)
Assume that a mutation occurs in the gene responsible for the production of hexosaminidase A, such that only 50% of the enzyme activity is found in the heterozygote compared with a homozygous normal individual. If heterozygotes are phenotypically normal, we would say that the mutant allele is recessive to its normal allele.
- True
- False
True
Which of the following symbols indicates a wild-type allele? R¹ \+ D e
+
+ indicates a wild type allele, whether or not it is dominant or recessive to a mutant allele
Assume that a dihybrid cross is made in which the two genes are autosomal and independently assorting. Each gene has two alleles which show incomplete dominance. How many different phenotypes would be expected in the offspring?
9
In a mating between individuals with genotypes I^AI^B x ii, what percentage of the offspring would be expected to have the O blood type?
0%
Typical ratios resulting from epistatic interactions in dihybrid crosses would be _____.
- 9:3:4 , 9:7
- 3:1 , 1:1
- 1:1:1:1 , 1:4:6:4:1
- 1:2:2:4:1:2:1:2:1
- 9:3:3:1 , 1:2:1
9:3:4 , 9:7
The F2 phenotypic ratio from a dihybrid cross with epistasis was 9:3:4. If instead of a dihybrid cross, a double heterozygote was test crossed (crossed to a homozygous recessive individual), what phenotypic ratio would be expected among the offspring?
1:1:2
Alleles that are masked by an epistatic locus are said to be hypostatic to the genes at that locus.
- True
- False
True
The F2 phenotypic ratio of a dihybrid cross with epistasis was 15:1. If instead of a dihybrid cross, a double heterozygote was test crossed (crossed to a homozygous recessive individual), what phenotypic ratio would be expected among the offspring?
3:1
Complementation analysis is used to determine ____.
- Whether a gene is X-linked or autosomal
- Whether two alleles are codominant
- Whether a gene is pleiotropic
- Whether two mutations that produce the same phenotype reside in the same or different genes
Whether two mutations that produce the same phenotype reside in the same or different genes.
(If the mutations reside in different genes, when the two mutats are crossed, the offspring should be wild type for that trait. If the two mutations reside in the same gene, only mutant offspring will be obtained in a cross.)
With multiple alleles, there can be more than two genetic alternatives for a given locus.
- True
- False
True
