Meiosis

Sexual Reproduction

● The parent’s reproductive cells unite to form offspring● Gametes- reproductive cells

● Eggs and sperm

Sexual Reproduction Vocab:

● Gametes- reproductive cells (eggs and sperm)● Gametes are haploid, meaning they have

half the number of chromosomes

● Fertilization- two gametes unite

● Zygote- the fertilized cell● The zygote is diploid, meaning it has the

full number of chromosomes

What is Meiosis?● Only in eukaryotic cells

● A reduction division● The chromosome number is cut in half

● Forms gametes ● Sex cells- sperm and eggs

● 2 stages

Stages of MeiosisMeiosis I

Meiosis II

Stages of Meiosis

Karyotype

● A karyotype is a picture of an organism’s chromosomes● Can be used to diagnose genetic disorders

Karyotype● Notice anything about

the karyotype?

● There are TWO chromosomes for each number…● These are called

homologous chromosomes

Homologous Chromosomes● Homologous chromosomes are matched pairs of

chromosomes that contain information that codes for the same traits (or the same genes)● One chromosome from mom, one from dad

Meiosis I● Nuclear material is separated

● Phases:● Interphase I

● Prophase I- Crossing-Over Occurs● Metaphase I

● Anaphase I- Independent Assortment● Telophase I and Cytokinesis

Meiosis I

Meiosis I: Prophase ICrossing-Over:

● = Genetic recombination

● Parts of chromatids break off and re-join to adjacent chromatids on homologous chromosomes.

Meiosis I: Anaphase I● Homologous chromosomes separate

● Two chromatids (dyads) move to opposite poles● Independent assortment- the separation of the pairs is

random. This allows for genetic variation between parents and offspring

Meiosis II● Similar to mitosis (but in two cells!)

● Phases:● Prophase II

● Metaphase II

● Anaphase II

● Telophase IIand Cytokinesis

Meiosis II● The sister chromatids of each chromosome separate

● Ultimately, Meiosis II will result in 4 haploid daughter cells

Meiosis II

Diploid vs. HaploidDiploid

● The cell has the total number of chromosomes● 46 in humans

● Body cells are diploid● Ex: skin cells, heart

cells, lung cells, etc.● Zygotes (fertilized

eggs) are also diploid

Haploid

● The cell has HALF of the number of chromosomes● 23 in humans

● Gametes are haploid● Eggs and sperm

Mitosis vs. MeiosisProducts:

1. Mitosis produces 2 daughter cells that are identical to parent cell

2. Meiosis produces 4 daughter cells that are different from parent cell

Mitosis vs. MeiosisNumber of Divisions:

1. Mitosis has 1 division 2. Meiosis has 2 divisions

Mitosis vs. MeiosisChromosome Number:

1. Mitosis maintains chromosome number

2. Meiosis reduces chromosome number

46 46

46 4646 46

23 23 23 23

Mitosis vs. MeiosisType of Reproduction:

1. Mitosis is involved in asexual reproduction

2. Meiosis is involved in sexual reproduction

Meiosis Review

Meiosis: The Great Divide

Chromosome Numbers During Division: Demystified!

Meiosis: Recap● 2 stages- Meiosis I and Meiosis II

● Reduction division- chromosome number is cut in half (from 46 to 23 in humans)

● Forms gametes- sperm cells and egg cells

Meiosis: The Continuation of Life (11:48)

Mitosis & Meiosis Simulation (11:52 Bozeman Science)

Meiosis: The Great Divide (7:40 Amoeba Sisters)