How many harmful de novo (mutations not found in either parent) mutations would

Question

How many harmful de novo (mutations not found in either parent) mutations would you expect a child with a 29 year old father to have? In order to answer this question, there are a couple of things you have to know; how many de novo mutations would a child with a 29-year-old father have, and what fraction of the human genome is under selection.

If there were a mutation that inactivated the gene coding for fibroblast growth factor 3, what would you expect the phenotype of the individual to be? Would the mutation be recessive or dominant? Which would you expect to be more quickly scrubbed from the population, a mutation that increased FGF3 activity, or a mutation that decreased FGF3 activity? (Assume both mutations decrease fitness by the same amount.)

What types of mutations increase with paternal age? Why? What types of mutations increase with maternal age? Why?

What determines the frequency of a trait? Would a neutral mutation be lost more rapidly from a large population, or a small one? What happens to genetic heterozygosity when population sizes decrease? Why is that harmful?

Explanation / Answer

A gene mutation is a permanent alteration of the DNA, thus differing from what others carry. A mutation can be on a single base or can include multiple genes. De novo mutation can be defined as the first line of mutation which is present in the germ cells of either parent or can arise during the early embryogenesis. It is thus a new mutation.

During DNA replication, replisomes make a mistake for every 100 million bases incorporated. the error rate is 10-8. the DNA repair mechanism rectifies 99% of these mistakes but the remaining 1% escapes and is passed on to the offsprings.

3 × 109 bp is the size of a genome in a haploid human. 0.3 mutation is passed on to one of the daughter cells each time the genome replicates. in order to know how many mutations are passed to the offspring, we have to know the number of replication that happened when one parental zygote was formed and the time that the egg or sperm cell that unites to form the progeny zygote is produced.

Human .females have about 500 eggs. The female egg is a product of 30 cell divisions from the time the zygote is formed, hence in the case of females the number is 30.

In a 30-year-old man, the number of cell division leading to the formation of a mature sperm is around 400. (0.3x30=9) that means 9 mutations accumulate in the egg while (0.3x400=120)120 mutations accumulate in sperm In males. Thus, each newly formed human zygote has approximately 129 new spontaneous mutations.

FGFR3 is the gene coding for the fibroblast growth factor3. The gene function is regulation of cell proliferation, differentiation, and apoptosis. It plays an essential role in the regulation of chondrocyte differentiation, proliferation, and apoptosis, and is required for normal skeleton development.

A mutation in the gene can lead to a condition called Achondroplasia (ACH) a form of short-limb dwarfism. It is characterized by a long, narrow trunk, short extremities. ACH is an autosomal dominant disease. Another disease caused is Hypochondroplasia that resembles ACH. It is an Autosomal dominant disease and is characterized by disproportionate short stature

Related Questions

Navigate

• Browse (All)
• Browse H
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.