Meiosis

Read Pg. 98 and 99 and complete a Venn Diagram comparing sexual and asexual reproduction. Make a list of all vocabulary words that are important.

Asexual reproduction (mitosis)

Sexual reproduction(meiosis)

Read Pg. 98 and 99 and complete a Venn Diagram comparing sexual and asexual reproduction. Make a list of all vocabulary words that are important.

Asexual reproduction (mitosis)

Sexual reproduction(meiosis)

• 1 parent

• Exact copies of

the parent cell

• Somatic cells

• Types of

reproduction

in living things

• Pass DNA

• 2 parent

• Daughter cells

are diverse

• Traits from each

parent

• Sperm and egg

CHROMOSOMES

In the nucleus of each cell, the DNA molecule is packaged into structures called chromosomes.

CHROMOSOMES

Each chromosome is made up of DNA tightly coiled.

CHROMOSOMES

Do all living things have the same types of chromosomes?

Cat 38  Cotton 26 

Chicken 78 

Chimpanzee 48 

CHROMOSOMES

Humans Chromosomes

SOMATIC VS SEX CELLS

SOMATIC CELLS

Each one contains 46 chromosomes (23 pairs).

Chromosomes that carry the same set of genes are called

homologous (like a pair of shoes).

Diploid (2n) cells

Skin cells Eye cells Liver cells

SEX CELLS (gametes)

Each one contains 23 chromosomes, half of the usual.

Each sex cell (sperm and egg) has only one of the

chromosomes from each homologous pair.

Haploid (n) cells:

Egg Sperm

SOMATIC VS SEX CELLS

MITOISIS

Somatic cells clone themselves with the process of mitosis. Mitosis replicates a cell with a complete set of 23 chromosomes identical to each other.

MEIOSIS

Specialized diploid cells split in half twice to create four separated cells each one genetically different.

♂Male - Germ-line cell

Diploid (2n)

♀ Female - Germ-line cell

Diploid (2n)

↓Meiosis↓

Sperm Haploid (n)

Egg Haploid (n)

↓Fertilization↓

OffspringDiploid (2n)

MEIOSIS

The stages of meiosisReplication 1 Each chromosome make an exact copy of itself (Idem mitosis)

Meiosis IResult in two diploid cells

2 Arrenging: each chromosome (now made of two identical chromatids) pair with its homologous chromosomes at the equator of the cell.

3 Chromosomes separate and move to opposite ends of the cell.4 Nuclear membrane is formed.

Meiosis IIResult in four haploid cells

5 Each cell contains one member of each homologus chromosome pair.6 Arrenging II: line up at the equator.

7He chromatids pull appart and move to opposite ends of the cell. Nuclear membrane forms

MEIOSIS

During synapsis, sometimes there is an exchange of homologous parts between non-sister chromatids. This exchange is called crossing over.

MEIOSIS

Complete the following chard with the differences between mitosis and meiosis:

Mitosis Meiosis

DNA Replication

Number of divisions

Crossing over

Number of daughter cells

Chromosome number of products

Functions

MEIOSIS

Complete the following chard with the differences between mitosis and meiosis:

Mitosis Meiosis

DNA Replication

Number of divisions 1 2

Crossing over X

Number of daughter cells 2 4

Chromosome number of products 2n n

Functions Somatic Reproduction