10.1 Meiosis

Click for Meiosis Animation

MeiosisSection 10.1

Body Cells & Gametes· somatic cells = body cells

do NOT pass on DNA to offspring46 chromosomes (23 pairs)

· gametes = sex cellseggs (females) and sperm (males)pass on DNA to offspring23 chromosomes, NO pairs

· a.k.a. homologues· matching chromosomes (same length and genes)· 1 from mom and 1 from dad· carry genes that control the same inherited traits· duplicated during "S" phase of interphase

Homologous Chromosomes

To see what the homologous pairs look like after the "S" stage.

Homologous Chromosomes and Chromatids

How many chromatids in a pair of duplicated homologous chromosomes?

(instant math question)

· autosomeschromosome pairs 1 - 22

· sex chromosomeschromosomes pair 23X + X = femaleX + Y = malecontrols the development

of sexual characteristics

Autosomes & Sex Chromosomes

10.1 Meiosis

1 MATA: Cells in your stomach, liver, or heart are considered

A sex cells

B body cells

C somatic cells

D gametes

2 Which of the following describes gametes?

A sperm and egg

B sex cells

Chave 23 chromosomes to pass on to offspring

D all of the above describe gametes

3 Homologous chromosomes contain genes for the same traits. You get one from mom and one from dad. After the "S" phase they contain only 2 sister chromatids.

True False

4 The first 22 pairs of chromosomes are called ______, pair 23 are called ______ chromosomes. (separate terms with a space)

5 What is the sex/gender of this person? · fusion of 2 gametes (egg and sperm)· results in offspring that are genetic combinations of mom and dad (genetically unique)· fertilization - fusion of egg and sperm

Sexual Reproduction

10.1 Meiosis

Diploid and Haploid

DIPLOID· diploid = 2n· 2 copies of each chromosome

1 from mom1 from dad

· body cells

HAPLOID· haploid = n· 1 copy of each chromosome· gametes (sex cells)

egg & sperm

6 MATA: Fertilization

A is the fusion of egg and sperm

B results in genetically unique offspring

C requires 2 gametes

D can happen sexually or asexually

7 Diploids cells (n) contain 2 copies of each chromosome and are found in gametes.

True False

My, oh my, Meiosis· form of nuclear division that creates 4 haploid (n) cells from one diploid cell (2n)· "reduction division"

reduces the number of chromosomes (2n to n) then divides into 4 cells (1 cell becomes 4)· essential for sexual reproduction

ensures the same # of chromosomes in each generation

creates genetic diversity· requires 2 rounds of cell division

meiosis I and meiosis II· GOAL: to produce 4 genetically unique daughter cells

gametes (egg & sperm)

body cells

n + n = 2N

Mitosis Vs. MeiosisMitosis

1 cell becomes 2 cells

genetically identical

two set of chromosomes

diploid (2n)

Meiosis1 cells becomes 4 cells

genetically unique

one set of chromosomes

haploid (n)

10.1 Meiosis

· PURPOSE: homologous chromosomes separate creating 2 cells each with duplicated chromosomes #1-23 (haploid)· Interphase - 46 chromosomes replicate

Meiosis I Prophase I· homologous chromosomes find each other (synapsis)· tetrads form

tetra = four4 chromatids

· crossing over occursportions of chromatids

break and change placeslike wearing two different socks

· tetrads line up in the center of the cell· spindle fibers attach to chromosomes· independent assortment occurs

homologous chromosomes line up randomly8,388,608 possibiliites

Metaphase I Anaphase I & telophase I· Anaphase I

homologous chromosomes separate

· Telophase Iresults in 2 cells each with

chromosomes #1-23 (haploid)

8 What is the purpose of MEIOSIS?

Ato produce 4 genetically unique daughter cells

B to separate homologous chromosomes

C to separate sister chromatids

Dto produce 4 genetically identical daughter cells

9 What is the purpose of MEIOSIS I?

Ato produce 4 genetically unique daughter cells

B to separate homologous chromosomes

C to separate sister chromatids

Dto produce 4 genetically identical daughter cells

10.1 Meiosis

10 MATA: What happens during Prophase 1?

A independent assortment

B synapsis

C triplets form

D crossing over

11 Homologous chromosomes separate during _______________

12 At the end of meiosis I, chromosomes are __________ (diploid or haploid).

Meiosis II· PURPOSE: sister chromatids separate creating 4 unique cells· no Interphase between meiosis I and meiosis II

PMAT II· Prophase II

chromosomes still replicated

· Metaphase IIsister chromatids line up in

the center of the cell

· Anaphase IIsister chromatids separate

· Telophase II4 haploid daughter cells

13 What is the purpose of MEIOSIS II?

A to create 4 genetically unique daughter cells

B to separate homologous chromosomes

C to separate sister chromatids

D to create 4 genetically identical cells

10.1 Meiosis

Complete the venn diagram.

Mitosis Meiosis

Labelnuclear divisiongenetically unique cells

1 cell becomes 4

2 sets of chromosomes1 cell becomes

2reduction division

genetically identical cells

growth & repairdiploidhaploidsexual reproduction

PMAT