Answer:
Explanation:
Four conditions are needed for natural selection to occur: reproduction, heredity, variation in fitness or organisms, variation in individual characters among members of the population.
ORR
Struggle for existence, variation and inheritance. These are said to be the necessary and sufficient conditions for natural selection to occur.
Answer:
44
Explanation:
A somatic cell is diploid - it has 46 chromosomes. Half of these are from the mother, so there are 23 maternal chromosomes
A sex cell (gamete) is haploid - it has 23 chromosomes. There are (usually) two sex chromosomes in a diploid genome, either XX or XY, so there is one 1 in a haploid cell, giving a total of 22 autosomes
Barr bodies are inactive X chromosomes in a female somatic cell. This occurs to control dosage compensation (otherwise all the genes on the X in females would be expressed twice as much as they are in males). In a healthy female, there is normally one Barr body
A person with Kleinfelter's syndrome has two X chromosomes and one Y (XXY). They are biologically male, but have two X chromosomes. Therefore, one of these becomes a Barr body, as in females.
23 + 22 - 1 = 44
