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| 1 | |
In fruit flies, eye color is X-linked: Xw = red eye, Xw = white eye. If a white-eyed female is mated to a red-eyed male, the male offspring will |
| | A) | have red eyes. |
| | B) | have white eyes. |
| | C) | be one-half red-eyed and one-half white-eyed. |
| | D) | be three-fourths red-eyed and one-fourth white-eyed. |
| | E) | be one-forth red-eyed and three-forth white-eyed. |
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| 2 | |
If a woman is a carrier for the color-blind allele and her husband is perfectly normal, what are their chances of having a color-blind son? |
| | A) | None, because the father is perfectly normal. |
| | B) | 50%, because the mother is a carrier. |
| | C) | 100%, because the mother has the gene. |
| | D) | 25%, because the mother is a hybrid. |
| | E) | More information is needed to determine the chances. |
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| 3 | |
What determines the sex of a human? |
| | A) | Presence or absence of an X chromosome |
| | B) | Presence or absence of a Y chromosome |
| | C) | Presence of two X chromosomes |
| | D) | Absence of a Y chromosome |
| | E) | Environmental conditions |
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| 4 | |
What phenotypes would you expect to see in a cross between a white-eyed female and red-eyed male Drosophila melanogaster? This trait is X-linked. |
| | A) | All males and females red-eyed |
| | B) | All males and females white-eyed |
| | C) | Females all red; males all white |
| | D) | Females 3:1 red: white; males 1:1 red: white |
| | E) | Females 1:1 red: white; males 3:1 red: white |
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| 5 | |
In most mammals dosage compensation is achieved by random inactivation of one of the X chromosomes in the somatic cells of females. However, in the marsupials (kangaroos, etc.) activation is non-random, and it is the X chromosome that is inherited from the father (the paternal X) that is preferentially inactivated in all somatic cells of females. What are the consequences of this for X-linked traits in marsupials? |
| | A) | Both male and female heterozygotes will be somatic mosaics. |
| | B) | Heterozygous females will not be somatic mosaics but will show one phenotype or the other. |
| | C) | Heterozygous females will not occur. |
| | D) | Their individual cells may express different alleles, depending on which chromosome is inactivated. |
| | E) | None of the above. |
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| 6 | |
The maximum recombination frequency that can ever occur is: |
| | A) | 25% |
| | B) | 50% |
| | C) | 75% |
| | D) | 100% |
| | E) | None of the above |
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| 7 | |
Which of the following statement(s) is true about the sickle-cell allele? |
| | A) | It occurs in some parts of the world at much higher frequencies than can be due to mutation alone. |
| | B) | It is caused by mutations in multiple genes. |
| | C) | It confers some resistance to malaria in the heterozygous state. |
| | D) | Both 1 and 2 |
| | E) | Both 1 and 3 |
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| 8 | |
Which statement(s) is/are true about X-linked inheritance in Drosophila? |
| | A) | X-linked traits are only shown in males. |
| | B) | A male inherits his X chromosome from his mother. |
| | C) | A male inherits his X chromosome from his father. |
| | D) | There are many genes carried on the Y chromosome. |
| | E) | Both 1 and 2 |
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| 9 | |
Mitochondrial genes are inherited only from the female parent because: |
| | A) | after fertilization the mitochondria from the male parent are eliminated. |
| | B) | of dosage compensation. |
| | C) | males don't have mitochondria. |
| | D) | mitochondria come from the egg, not from the sperm. |
| | E) | mitochondrial genes are inherited equally from both parents. |
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| 10 | |
Nondisjunction can occur in meiosis I (Primary Nondisjunction) if the homologs do not separate, or in meiosis II (Secondary Nondisjunction) if the sister chromatids do not separate. What chromosome compositions could occur in the offspring from a couple where there was normal gamete formation in the female but nondisjunction of the Y chromosome in the male? |
| | A) | XX, XO, XY, YY |
| | B) | XX, XY, XXX, XYY |
| | C) | XX, XYY, XO |
| | D) | XX, XYY, XY, XO |
| | E) | XO, XYY |
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| 11 | |
What conclusion(s) is/are suggested if a normal and a mutant fly are crossed and the only mutant progeny observed are male? |
| | A) | Mutation is located on the X chromosome. |
| | B) | Mutation is located on the Y chromosome. |
| | C) | Mutation is lethal to females. |
| | D) | Mutation is lethal to males. |
| | E) | Both 1 and 3 are possible explanations. |
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| 12 | |
On which of the sex chromosomes is a sex-linked gene usually carried? |
| | A) | 13 |
| | B) | 15 |
| | C) | 18 |
| | D) | Y |
| | E) | X |
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| 13 | |
Morgan discovered that the white eye mutation in fruit flies is: |
| | A) | autosomal. |
| | B) | lethal in females. |
| | C) | sex-linked. |
| | D) | on the Y chromosome. |
| | E) | dominant. |
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| 14 | |
What molecular structure is responsible for the mosaic coloring of calico cats? |
| | A) | Y chromosome |
| | B) | Barr body |
| | C) | Nuclear envelope |
| | D) | Cell membrane |
| | E) | Mitochondria |
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| 15 | |
In humans, non-sex chromosomes are called |
| | A) | somatic. |
| | B) | polymorphic. |
| | C) | non-sex. |
| | D) | retrograde. |
| | E) | autosomal. |
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