Inbreeding 1. How does the inbreeding coefficient vary in a small population ver
ID: 259402 • Letter: I
Question
Inbreeding
1. How does the inbreeding coefficient vary in a small population versus a large population? Explain showing equations, and interpret it biologically.
2. What is the inbreeding coefficient of the offspring of a full-sibling mating? If this individual also mates with its sibling, what would be the inbreeding coefficient of their offspring? What can you state about the rate of change in inbreeding coefficient due to regular full-sibling mating?
3. Compute (a) coefficient of consanguinity, (b) coefficient of relatedness between a grandparent and a grandchild.
4. What is the difference between inbreeding and subpopulation structure? Explain.
Explanation / Answer
Inbreeding in simple words is the mating among the individuals who are genetically and biologically close to each other. We can say, closely related individuals, like brother-sister, or among first cousins or self - fertilized plants. In breeding tends to increase the number of individuals that are homozygous for a trait and therefore increases the appearance of recessive traits.
Answering to (1) ,
Inbreeding coefficient denotes the probability that two alleles at the locus in an individual are identical by descent from a common ancestor, i.e., the chance that an individual is homozygous for an ancestral allele by inheritance, not by mutation.
The inbreeding coefficient for first cousins would be 1/8, for second cousins would be 1/64, for third cousins would be 1/256.
In case, only one of the parent is common at the starting generation, then the inbreeding coefficient for half-sibs at uncle - neice or aunt - nephew marriage is 1/16, for first cousins would be 1/32, for second cousins would be 1/128, for this cousins would be 1/512.
However we observe higher breeding coefficient in population with known higher levels of consanguinity or genetic isolation, and in population with increased effect of genetic drift, and decreased genetic diversity.
Not surprisingly, smaller population tends to have more animals with higher inbreeding coefficient than larger population simply because there are fewer candidate animals to select from.
Answering to (2) ,
Inbreeding coefficient for a full - sibling mating would be 25%. However full sib mating doubles the total genetic variation if all the sub-lines are kept. Similarly, all the genetic variation will be then due to differences between sub-lines, will show no genetic variation among the sub-lines.
Answering to (3) ,
Consanguinity or coancestry is a similar concept but the coeffecient of coancestry indicates the chances that one allele in two individuals would be identical by descent.
Relatedness is the probability that two individuals share an allele due to recent common ancestory. This probability is referred in terms of coeffecient of relatedness. It is denoted by 'r' and ranges from 0 - 1.
Coeffecient of relatedness would be 25% between a grandparent and a grandchild.