Scotland Well, that taxi driver sounds pretty strange to me. What’s he waiting for? And you don’t mention if the girlfriend wants children as well, and is annoyed that he wants to wait till they have more money. It’s probably plagued more couples than people will admit. A woman can feel pressured into having children quickly, if she marries somebody later on in life. She might have wanted children at a younger age, but perhaps now she feels her choices are getting fewer which they are and she’d better do it fast while she still can.

Biological Clock Discoveries by 3 Americans Earn Nobel Prize The work, done in fruit flies and dating back to , identified genes and proteins that work together in people and other animals to.

Genetic diversity and Population genetics An individual organism’s phenotype results from both its genotype and the influence from the environment it has lived in. A substantial part of the phenotypic variation in a population is caused by genotypic variation. The frequency of one particular allele will become more or less prevalent relative to other forms of that gene. Variation disappears when a new allele reaches the point of fixation —when it either disappears from the population or replaces the ancestral allele entirely.

Before the discovery of Mendelian genetics, one common hypothesis was blending inheritance. But with blending inheritance, genetic variance would be rapidly lost, making evolution by natural selection implausible. The Hardy—Weinberg principle provides the solution to how variation is maintained in a population with Mendelian inheritance. The frequencies of alleles variations in a gene will remain constant in the absence of selection, mutation, migration and genetic drift.

Despite the constant introduction of new variation through mutation and gene flow, most of the genome of a species is identical in all individuals of that species.