Q. No.In Drosophila melanogaster cinnabar eye is a sex-linked recessive trait. A female fly having cinnabar eyes is crossed with a wild-type male. The percentage of the male progeny of this cross with cinnabar eyes is expected to be:
1.
0%
2.
25%
3.
50%
4.
100%
Nondisjunction of a pair of homologous chromosomes occurs during the anaphase of meiosis I. The four gametes produced as a result of this nondisjunction event will be:
| 1. | n + 1; n + 1; n - 1; n - 1 | 2. | n + 1; n - 1; n; n |
| 3. | n + 1; n - 1; n - 1; n - 1 | 4. | n + 1; n + 1; n; n |
Identify the chromosomal aberration:
| 1. | Inversion | 2. | Reciprocal translocation |
| 3. | Deletion | 4. | Duplication |
A couple comes to you for genetic counselling. Both have a sister affected with albinism but all other members are normal. Your advice regarding the risk of their child being affected with albinism would be:
| 1. | They must both be heterozygotes so their risk of having an affected child is ¼. |
| 2. | They might both be heterozygotes so they should get tested to see if they carry the disease allele or not. |
| 3. | Since neither one of them is affected, they are not at risk of having an affected child. |
| 4. | You can't give them any firm answers because you don't know their genotypes. |
Linkage maps:
| 1. | always have a total of 100 map units. |
| 2. | can be used to pinpoint the precise physical position of a gene on a chromosome. |
| 3. | are a genetic map based on recombination frequencies. |
| 4. | reflect the frequency of crossing over between X and Y chromosomes. |
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A true breeding red striped tree frog is crossed with a true breeding plain green frog. All progeny have red stripes. This is because:
| 1. | Stripes are dominant to plain green coloration. |
| 2. | Striped frogs are camouflaged better. |
| 3. | Plain green frogs are easily predated upon. |
| 4. | Striped frogs are more common. |
A plant breeder is raising many varieties of plants. As a part of the breeding program, he raises pure line varieties by continuous inbreeding over several generations – one with red flowers and another with white flowers. How can Mendel's laws be demonstrated by hybridization between these varieties?
| 1. | Set up a monohybrid cross and determine if your F2 results are predicted by a 3:1 ratio based on the law of segregation. |
| 2. | Set up a dihybrid cross and determine if your F2 results are predicted by a 9:3:3:1 ratio based on the law of independent assortment. |
| 3. | Set a test cross to demonstrate that your traits breed true. |
| 4. | Set up a two-point test cross to demonstrate that your genes are linked. |
All the following are mechanisms of sex determination in living organisms except:
1. The Z-W system
2. The X-O system
3. The haplo-diploid system
4. The parthenogenetic system
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Pedigree analysis rather than conventional methods are used to study genetic traits because:
| I. | Number of progeny is limited |
| II. | Choice matings are not possible |
| III. | Sexual dimorphism is seen in humans |
| 1. | I only | 2. | II only |
| 3. | III only | 4. | Both I and II |
Match the disorder in Column I with the location of the gene causing it in Column II and select the correct option from the codes given:
|
|
COLUMN I |
|
COLUMN II |
|
A. |
Sickle cell anaemia |
a. |
Chromosome 11 |
|
B. |
Phenylketonuria |
b. |
Chromosome 12 |
|
C. |
Cystic fibrosis |
c. |
Chromosome 7 |
|
D. |
Huntington’s disease |
d. |
Chromosome 4 |
Codes:
| A | B | C | D | |
| 1. | a | b | c | d |
| 2. | b | a | c | d |
| 3. | a | b | d | c |
| 4. | b | a | d | c |
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