AP BIOLOGY

Detailed explanation-1: -In humans, each cell normally contains 23 pairs of chromosomes, for a total of 46. Twenty-two of these pairs, called autosomes, look the same in both males and females. The 23rd pair, the sex chromosomes, differ between males and females.

Detailed explanation-2: -Through the process of fertilization, egg and sperm join to make a cell with 46 chromosomes (23 pairs), called a zygote. For each chromosome pair, one homologous chromosome came from each parent. They have the same genes arranged in the same order, but there are small variations in the DNA letters of those genes.

Detailed explanation-3: -A zygote, also known as a fertilized ovum or fertilized egg, is the union of a sperm cell and an egg cell. The zygote begins as a single cell but divides rapidly in the days following fertilization. The zygote’s single cell contains all of the 46 necessary chromosomes, getting 23 from the sperm and 23 from the egg.

Detailed explanation-4: -This is because our chromosomes exist in matching pairs – with one chromosome of each pair being inherited from each biological parent. Every cell in the human body contains 23 pairs of such chromosomes; our diploid number is therefore 46, our ‘haploid’ number 23. Of the 23 pairs, 22 are known as autosomes.

Detailed explanation-5: -Gametes are reproductive cells, such as sperm and egg. As gametes are produced, the number of chromosomes must be reduced by half. Why? The zygote must contain genetic information from the mother and from the father, so the gametes must contain half of the chromosomes found in normal body cells.