6.1. Chromosomes and Meiosis

Meiosis

is a form of nuclear division that divides a diploid cell into haploid cells. This process is essential for sexual reproduction, and there are four cells produced during meiosis instead of the two produced in mitosis. It produces genetically unique cells, the cells are haploid, it only happens only at certain times in someone's life cycle, and it's involved in sexual reproduction.

Somatic Cell

they're body cells, and these cells make up most of your body(eyes, hair, kidneys, lungs, heart, skin). Somatic cells are diploid and have 23 pairs of chromosomes(46 individual ones.) The DNA in our body cells isn't passed onto our children.

Sexual Reproduction

this involves the fusion of two gametes, sperm and egg. The child becomes a genetic mixture of both parents. Once the egg and sperm fuse, it puts up a protective shell so no other sperm can penetrate it.

Diploid

this means that a cell has two copies of each chromosome: one copy from the mother and one copy from the father. Diploid also refers to the amount of chromosomes in a cell.(46). Most normal body cells are diploid. Diploid cells are produced by mitosis.

Haploid

means that a cell has only one copy of chromosomes. Each human egg or sperm has exactly 23 chromosomes, and haploid cells are produced through meiosis. These cells are typically sex cells.

Autosome

these are 22 of your 23 pairs of chromosomes, and they basically contain genes for your characteristics(eye color, skin color, height, hair color, finger length, nose shape, etc.) and they don't decide whether you're a male or a female.

Gamete

these are sex cells- they are either eggs in the female reproductive system or sperm in the male reproductive system. Gametes have only 23 chromosomes, which means they're haploid. The DNA in the cells does gets passed down to your children, and each chromosome in your sex cells is unique.

Homologous Chromosome

they are two pairs of chromosomes: one inherited from the father and one inherited from the mother- that have the same general appearance and length. They have copies of the same genes, but the copies may differ in little ways. There are 23 pairs of homologous chromosomes in each cell.

Sex Chromosome

this is the 23rd chromosome that controls the development of sexual characteristics(if you're male or female). Humans have two sex chromosomes: X and Y. If the person codes for an XX, she is a female. If a person codes for an XY, he is a male. TheX chromosome contains more genes, and the Y chromosome contains the least number of genes.

Fertilization

This is the actual fusion of the egg to the sperm. When fertilization occurs, the nuclei of the egg and sperm fuse to become one 'super-nucleus'. This nucleus must have the correct number of chromosomes, or else it won't develop into a healthy baby. That's why sex cells only have half the chromosomes as normal cells since the sperm and egg fuse and the 23 pairs of chromosomes combine.