Heterochromatic regions at the ends of chromosomes that function to control how
ID: 300459 • Letter: H
Question
Heterochromatic regions at the ends of chromosomes that function to control how many times the cell will divide are called:
An individual has two homologs of chromosome 21 and both homologs came from the same parent. Which phenomenon caused this condition?
Although natural selection works to decrease the frequency of deleterious alleles in a population's gene pool, deleterious recessive alleles often remain in the gene pool. What maintains deleterious recessive alleles in a population?
centromeres.Explanation / Answer
1) Telomeres. Telos in Greek means the "end". And since the question asks which region is at the end of the chromosome the answer is telomere. Telomeres are very important regions. They form caps at the end of the chromosome that protects the chromosome from nucleases and other damage-causing agents. Telomeres also prevent the chromosomes from fusing into one another.
2) Uniparental Disomy - As the name suggests, a single parent is involved. And Disomy refers to two(di) chromosomal homologous.
There are two types of Disomy - Heterodisomy - In this case, the offspring inherits two non-identical chromosomes from one of the parents.
Isodisomy- In this case, the offspring inherits two identical copies of a chromosome from the parent.
The case mentioned in the questions is isodisomy.
3)Non-random mating. For natural selection to work, there must be random mating that occurs in a population. The re-emergence of a deleterious recessive allele is mostly seen in animals that are closely bred. If an animal line is bred with another line of animals that are close in ancestry, homozygosity is promoted, and thus recessive alleles begin emerging and are expressed in these populations. This phenomenon is known as inbreeding depression. Usually, it can be overcome by out-crossing, i.e. breeding with an unrelated member of the population.