KEY CONCEPT Gametes have half the number of chromosomes that body cells have.

Mom Dad Human body cells have 23 pairs of chromosomes and 46 total Each pair of chromosomes is called Homologous pairs and have copies of the same genes In each pair, one chromosome comes from each parent. *Homo= same

You have two types of specialized cells: Somatic cells and Germ cells Will become…

Somatic cells- are body cells and make up most of your body tissues and organs. Liver cells Lung cells Heart cells etc… Red blood cells skin cells bone cells intestinal cells

Somatic (body) cells are Diploid (2n) cells have two copies of every chromosome (23 from mom, 23 from dad) for a total of 46 chromosomes *di= 2 n n 2n

Germ cells- are the cells in your reproductive organs located in the ovaries and testes Develop into gametes

Gametes are sex cells: egg and sperm Both have DNA that can be passed to offspring. Egg Sperm

Gametes are Haploid (n) cells have one copy of every chromosome. Have 22 autosomes + 1 sex chromosome = 23 chromosomes each 23 23

You have two types of specialized cells: Somatic cells Germ cells Undergo meiosis Cells in reproductive organs (ovaries/testies) Become gametes (sperm/eggs) Haploid 23 chromosomes Each are Unique Undergo mitosis body cells Diploid 46 chromosomes Identical to parent cell

You have two types of chromosomes: Autosomes and Sex Chromosomes

Chromosome pairs 1-22 are called autosomes Contain genes not directly related to your gender

XX XY XX= female XY= male Pair #23=Sex chromosomes: X and Y determine gender Control the development of sexual characteristics XX= female XY= male XX XY

Where are germ cells located in the human body (2 places) Points to Ponder Where are germ cells located in the human body (2 places) Do you think that Y chromosomes contain genes that are critical for an organism’s survival? Explain.

Where are germ cells located in the human body (2 places) Points to Ponder Where are germ cells located in the human body (2 places) In the reproductive organs: The ovaries in women and the testes in men. 2. Do you think that Y chromosomes contain genes that are critical for an organism’s survival? Explain. No, a Y chromosome is not necessary for survival. Females do not have a Y chromosome, and they are able to survive.

Mitosis= makes more diploid cells. Produces genetically identical cells Results in diploid cells (46 chromosomes each) Takes place throughout an organism’s lifetime Involved in asexual reproduction Somatic (body) Cells

DNA replicates 2 identical daughter cells

Meiosis= makes haploid cells (23) from diploid germ cells (46). produces gametes (sperm/eggs) Produces genetically unique cells Takes place only at certain times in an organism’s life cycle Involved in sexual reproduction Germ cells

(diploid- 46) Germ cell 4 haploid (23) unique daughter cells