6.1 Chromosomes and Meiosis

Section 6-1: “Chromosomes and Meiosis”

Write everything that is Write everything that is underlinedunderlined

6.1 Chromosomes and Meiosis

KEY CONCEPT Gametes (formed by Meiosis) have half the number of chromosomes that body cells have (which are formed by Mitosis).

6.1 Chromosomes and Meiosis

In your body there are “body cells” and “gametes”.

A. There are two categories of cells in your body.

1. Body cells (are also called somatic cells) - All Cells that are not Sex Cells are body cells

Ex: muscle, nerve, liver cells

body cells sex cells (sperm) sex cells (egg)

6.1 Chromosomes and Meiosis

In your body there are “body cells” and “gametes”.

2. Gametes are sex cells: egg and sperm- Germ cells in the ovaries & testes develop into

gametes- Only gametes have DNA that can be passed to

offspring

body cells sex cells (sperm) sex cells (egg)

6.1 Chromosomes and Meiosis

B. All cells have two types of

Chromosomes: Autosomes &

Sex chromosomes

1. (Somatic Cells) Body cells

have 23 pairs of chromosomes

- Pairs 1-22 are called “autosomes”

- Pair 23 (circled) are the Sex

chromosomes, X and Y; they

determine gender in Mammals.

Your cells have autosomes and sex chromosomes.

6.1 Chromosomes and Meiosis

Your cells have autosomes and sex chromosomes.

2. Each pair of chromosomes

is “homologous” – they have

the same genes

• For each homologous

pair, one comes from

each parent.

6.1 Chromosomes and Meiosis

Body cells are diploid; gametes are haploid.

C. Body cells have 2x as many chromosomes as Sex cells

1. Body cells are “DIPLOID” (2n) and have 2

copies of every chromosome – 44 autosomes

and 2 sex chromosomes

6.1 Chromosomes and Meiosis

Body cells are diploid; gametes are haploid.

2. Gametes are “HAPLOID” (n) and have one

copy of every chromosome

- Gametes have 22 autosomes and 1 sex

chromosome

6.1 Chromosomes and Meiosis

Body cells are diploid; gametes are haploid.

- Chromosome number must be maintained in

animals (from parent to daughter cells)

- Many plants, however, have more than two

copies of each chromosome.

6.1 Chromosomes and Meiosis

Think Fast!!!

• Are the following diploid or haploid?

• Retinal nerve cells in the eye• Cardiac muscle cells (heart cells)

6.1 Chromosomes and Meiosis

Answer….

• They are all Diploid, and have 2 copies of each chromosome

6.1 Chromosomes and Meiosis

1. Mitosis makes diploid body cells.

- Takes place all throughout life

- Is involved in asexual reproduction

D. Mitosis and Meiosis are types of cell division … that make different types of cells for animals.

6.1 Chromosomes and Meiosis

2. Meiosis makes HAPLOID SEX CELLS from

diploid cells in the ovaries and testes

- Meiosis occurs in ovaries and testes only & makes gametes- Meiosis takes place only at certain times in life- Meiosis is involved in sexual reproduction

6.1 Chromosomes and Meiosis

And…

• Which of the following is/are Haploid?

6.1 Chromosomes and Meiosis

Answer …

haploiddiploid

6.1 Chromosomes and Meiosis

Mitosis & Meiosis Graphic Organizer

• You have 4 minutes and 25 seconds to draw a You have 4 minutes and 25 seconds to draw a graphic organizer to show (with words, chart, or a graphic organizer to show (with words, chart, or a concept map) how these terms/ideas are related: concept map) how these terms/ideas are related:

Chromosomes, Body Cells, Gametes, Blood Cells,

Egg/Sperm, Mitosis, Meiosis, Diploid, Haploid,

46, 23, Homologous, Unique, Identical

6.1 Chromosomes and Meiosis

Graphic Organizer

Body Cells - Ex: Blood Cell

Gametes - Ex: Egg/ Sperm

Mitosis Meiosis

Chromosomes46 23

diploid haploidIdentical Unique

Homologous