Question

(Genetic principles of Ancestry DNA) What is variations due to mutation, chromosomal, maternal inheritance?

Answer 1

Genetic variation can be defined as the differences between individuals in a population and between populations. These variations are differences in DNA sequences between individuals resulting in a genotypic and phenotypic differences among them. Variations can occur in both germ cells as well as somatic cells. But only those which occur in germ cells will be inherited from one individual to its offspring.

Variations dur to mutation:

Mutation is a permanent alteration of the nucleotide sequence in the genome of an organism. These may be caused due to errors during DNA replication, exposure to radiations or carcinogens, insertions or deletions due mobile transposable elements or other DNA damages. These mutations bring about rondom changes in the DNA sequences and they are inheritable. Thus mutations are one important causes of variations among individuals.

Variation due to chromosomal inheritance:

During meiosis of the cell division, there is a stage where recombination or crossing over can occur between the chromosome arms. This results in a new gene combination and the offsprings who inherit these will be varient from its parents. ie, crossing over during cell division can enhance genetic variations. Also variations can be caused if the number of chromosomes inherited by the offsprings vary which often leads to diseases.

Variations due to maternal inheritance:

Maternal inheritance is the condition wherein the traits of the offspring are maternal in origin due to expression of extranuclear DNA present in ovum during fertilization. This is made possible because of high amount of maternal mitochondria that is retained within the ovum. The mitochondria have its own genetic material and mitochondria exhibit a maternal mode of inheritance. Hence any variations seen in the mtDNA will be inherited and expressed in the offspring. This may also result in variations in an individual.