AP BIOLOGY

LABORATORY REVIEW

MITOSIS AND MEIOSIS

Question [CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
How many chromosomes does a human egg cell and sperm cell have?
A
23
B
25
C
46
D
only a sex chromosome
Explanation: 

Detailed explanation-1: -Each egg cell or sperm contains 23 chromosome whereas a normal cell has 46 chromosomes.

Detailed explanation-2: -Egg and sperm cells have just 23 chromosomes each. That’s half as many chromosomes as regular cells. 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.

Detailed explanation-3: -Healthy humans have 46 chromosomes, 23 from the sperm and 23 from the egg. An embryo with the wrong number of chromosomes is usually miscarried, or develops disorders such as Down’s syndrome, which is caused by an extra copy of chromosome 21.

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: -In humans, gametes are haploid cells that contain 23 chromosomes, each of which a one of a chromosome pair that exists in diplod cells. The number of chromosomes in a single set is represented as n, which is also called the haploid number. In humans, n = 23.

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