Meiosis One pager

Meiosis main goal

Produce gametes for sexual reproduction

Fertlization

Each parent donates one copy of each chromsomes

Diploid simple definition

2 copies of each chromosomes

Haploid simple definition

1 copy of each chromsomes

Germline Stem Cells

GMCs produce gametes that are haploid cells

• Live in ovaries or testicles

What unique of meisosis

Includes two rounds of divsion that ultimatley produce 4 haploid cells

First step of meisosis

DNA replication within GSC’s

Germaine stem cells make an exact copy of their DNA

What happens to Germline stem cells after DNA replcication

Undergo two rounds of division

Meisosis I and Meiosis II

Meiosis I goal

to seperate the homologous chromsomes into two new cells

How is Meiosis I different from mitosis

Mitosis separates duplicated chromosomes while Meiosis I separates homologous chromosomes

Prophase I

Replicated homogenous chromosomes are aligned together and can swap regions of DNA with eachother (crossing over)

Metaphase I

Homologous chrosmomes are aligned in the center

Anaphase I

Homologous chromsomes are pulled to the opposite ends of the cell

Telophase I

2 new cells are created containing a mixture of homologous chrosomes from each panret

• Not genetically identical as parent cell

Crossing over signifinace

Increases genetic diversity

Increases the possible combination of genes inherited from each parent

Meisosis II goal

Resulting cells from Meiosis I divide again splitting up sister chromatids resulting in 4 haploid cells

No S phase

Metaphase II

New combination chromosomes are lined up again

Anaphase II

Sister chromatids (duplicated DNA) are seperated

Telophase II

Left with 4 total cells with 1 copy of 23 chromsomes

Overall image of Meiosis I and II

Both cells that were created in Meiosis I go through Meiosis II

Goal of meiosis

Produce gametes (egg or sperm cells)

Crossing over signifance in reproduction

ensures that resulting zygote has a unique combination of DNA

What happens during fertilization

Egg and sperm combine to produce zygote with 2 copies of each chromsomes

What happens to problems in cell division

Carrys on to next generation

Non-Disjunction

Sister chromatids fail to seperate proeprly in meiosis II which can lead to offspring having an extra copy of a chromosomes (Trisomy 21)

Trisomy 21

Extra #21 chromosomes and is strongest genetic link to down syndrome

Overall Mitosis

4 stages in total

Happens in somatic cells

Purpos is cell proliferation

produces 2 diploid daughter cells

Chromsomes number remains the same

genetic variation dosent change

Meiosis overall

8 stages in total

Happens in germline stem cell

Purpose is sexual reproduction

produces 4 haploids daughter cells

Simularties between Mitosis and Meiosis

Produce new cells

Similar basic steps

Start with a single parent cell