Which does not add new alleles to a population gene pool? a. genetic drift b. mutation c. recombination d. gene flow

The right answer is A. genetic drift

From the point of view of a gene, genetic drift leads to the increase or decrease of the frequency in the population, of one of its versions (= allele).

In any population, it is statistically inevitable that some alleles (each variant of the same gene) are not transmitted by any adult to their offspring. In addition, some individuals have no descendants at all. The number of alleles (genetic variability) is therefore reduced. Among the "surviving" alleles, some will see their original frequency decrease or increase, all without implying the appearance or the addition of new alleles.

Two concrete examples are a foundation effect and a decrease in genetic diversity.

ocean expansion, global warming is melting icebergs and causing water levels to rise.

the level of progesterone is low at the pre-ovulatory phase of the cycle but it gradually increases and the levels are high at the luteal phase. if pregnancy occurs, the level of progesterone will be high throughout the pregnancy.

if egg is fertilized and the mother gets pregnant, progesterone starts preparing the uterus for the implantation. it starts building up the lining of uterus and make it hostile of the period of pregnancy.