Meiosis - Weebly

Meiosis

Dr. Bertolotti

11/18/2016

How is meiosis different from mitosis?

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3 Types of Cell Division

? 1. Binary fission- cell division in prokaryotes ? 2. Cell Cycle (with Mitosis)- cell division in eukaryotes to form new

somatic cells

? 3. Meiosis- cell division in eukaryotes to form gametes/sex cells (egg and

sperm)

Cell division Asexual reproduction

? Mitosis ? produce cells with same information ? identical daughter cells ? exact copies ? clones ? same number of chromosomes ? same genetic information

Aaaargh! I'm seeing double!

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Asexual reproduction

? Single-celled eukaryotes ? yeast ? Paramecium ? Amoeba

? Simple multicellular eukaryotes ? Hydra ? budding

11/18/2016

Meiosis makes sperm & eggs

egg

? 46 chromosomes to 23 chromosomes

? half the number of chromosomes

46

23

meiosis

sperm

46

diploid

23

haploid

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Paired chromosomes

? Homologous chromosomes

? both chromosomes of a pair carry "matching" genes

? control same inherited characters ? homologous = same information

diploid 2n 2n = 4

eye color (brown?)

eye color (blue?)

11/18/2016

homologous double stranded chromosomes homologous chromosomes

Lesson Overview

Meiosis

Haploid Cells

Some cells contain only a single set of chromosomes, and therefore a single set of genes.

Such cells are haploid, meaning "one set."

The gametes of sexually reproducing organisms are haploid.

For fruit fly gametes, the haploid number is 4, which can be written as N = 4.

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Meiosis 1 overview

? 1st division of meiosis

Copy DNA

Line Up 1

double stranded

Divide 1

4 chromosomes diploid 2n

prophase 1

gamete

2

metaphase 1

telophase 1 2 chromosomes haploid 1n

Meiosis 2 overview

telophase 1

? 2nd division of meiosis

? looks like mitosis

Line Up 2

metaphase 2

telophase 2

4

2 chromosomes haploid 1n or N

gametes

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