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