Concept explainers
- a. What is a major source of
genetic variation for prokaryotes and viruses? - b. What is the major source of genetic variation for plants and animals?
- c. Explain why your answers to a and b are different.
a.
To explain: The major source of genetic variation for viruses and prokaryotes.
Introduction: Genetic variation is defined as the variance in DNA sequences between individuals within a given population. The genetic variation present in the population is measured using nucleotide variability and gene variability.
Explanation of Solution
The main source of genetic variation in viruses and prokaryotes is mutation. Mutation is defined as an alteration in the nucleotide sequence of DNA. Mutation may cause the origin of new alleles. The viruses and prokaryotes have very short generation spans. Due to their shorter generation period, mutation causes more rapid genetic variation in viruses and prokaryotes.
b.
To explain: The major source of genetic variation for animals and plants.
Explanation of Solution
The main source of genetic variation in plants and animals is sexual reproduction. In case of sexually reproducing population, the genetic variation occurs when the alleles reshuffle and produce new combinations in every individual progeny. In offspring, unique genetic combinations occur during the process of independent assortment and crossing over during meiosis as well as when the gametes combine randomly during fertilization.
c.
To explain: The reasons why the answers for a and b are different.
Explanation of Solution
The main source for genetic variation in viruses and prokaryotes is mutation, whereas in animals and plants, the main source is sexual reproduction. This is because mutation causes genetic variation very rapidly in viruses and prokaryotes, as both have very shorter generation spans. However, the average rate of mutation in plants and animals is one in 100,000 genes per generation. Although the mutation causes the origin of new alleles, mutations are infrequent and their contribution to the genetic variation is minimal in case of large, diploid population. However, in each generation, the zygotes with new allele combinations are produced during the fertilization when there is a random union of gametes.
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