This set of Class 12 Biology Chapter 5 Multiple Choice Questions & Answers (MCQs) focuses on “Inheritance Principles – Linkage and Recombination-1”.
1. What type of crosses were carried out by Morgan on Drosophila?
Explanation: Morgan was trying to observe the phenomenon reported by Mendel. Hence, he did dihybrid crosses on Drosophila. These dihybrid crosses allowed him to understand the process of meiosis. He also identified the phenomenon of linkage. This was used later by his student to create the first genetic map.
2. Which of the collect cross that was performed by Morgan?
a) Yellow-bodied, white-eyed females with brown-bodied, red-eyed males
b) Yellow-bodied, white-eyed males with brown-bodied, red-eyed females
c) Yellow-eyed, white-bodied females with brown-eyed, red-bodied males
d) Yellow-eyed, white-bodied males with brown-eyed, red-bodied females
Explanation: Morgan used Drosophila as a genetic model to visualize the changes in the chromosomal patterns and explain the observations of Mendel. For this, he performed a dihybrid cross of yellow-bodied, white-eyed females with brown-bodied, red-eyed males.
3. What was the observation made by Morgan based on his dihybrid crosses?
a) Genes segregate independently
b) Genes do not segregate independently
c) Genes disappear
d) New genes appear
Explanation: If the segregation law was to hold, the expected phenotypic ratio of F2 was 9:3:3:1. However, Morgan saw a deviation from this ratio. This implied that the genes do not segregate independently.
4. What chromosome were the genes located on that were used by Morgan in his dihybrid cross?
a) X chromosome
b) Y chromosome
c) W chromosome
d) Z chromosome
Explanation: The genes were located on X-chromosome. These are called sex-linked genes because their expression depends on the sex of the fly. The X chromosome is present in copies of two in females, but the males have only one copy of X. Thus, a recessive mutant might remain suppressed in females, but the males will always exhibit the phenotype.
5. For genes located on the same chromosome, the proportion of parental gene combinations are higher than the non-parental combinations.
Explanation: For genes that are located on the same chromosome, segregation is weak as they are linked. This leads to more chances of parental combinations than of the non-parental ones.
6. What is the physical association of genes located on a chromosome called?
Explanation: Linkage is the phenomenon of the physical association of genes that are located on the same chromosome. This leads to fewer chances of genes undergoing independent segregation.
7. What is the process of the production of non-parental phenotypes called?
Explanation: Recombination leads to combinations of genes. Hence leads to newer phenotypes. The parental phenotypes occur without recombination hence are more frequently observed in the progeny. Recombination events are rare and hence the non-parental phenotypes are rare.
8. Linkage and recombination frequencies have been used to generate ______
a) solutions for global warming
b) genetic maps
c) genetic networks
d) mutation maps
Explanation: Linkage and recombination frequencies give the relative distance of genes on the chromosome. Thus, it can be used to construct genetic maps.
9. Genes located on different chromosomes have a high probability of getting recombination than those present on the same chromosome.
Explanation: Genes located on different chromosomes are weakly linked. This allows them to recombine more frequently. Linkage is inversely related to recombination. Genes are located close to each other have low chances of recombination, and thus have high linkage. Genes on different chromosomes are far from each other, hence they have almost no linkage, hence having higher chances of undergoing recombination.
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