Do NowDo Now Take out 10.2 vocabulary homeworkTake out 10.2 vocabulary homework Complete handoutComplete handout

– Remember Remember hhaploid = aploid = hhalfalf DDiploid = iploid = ddoubleouble

– So if 20 is the diploid number, thenSo if 20 is the diploid number, then

10 is the haploid number.10 is the haploid number.- If 5 is the haploid number, thenIf 5 is the haploid number, then

10 is the diploid number10 is the diploid number

HOMEWORK: STUDY FOR YOUR MIDTERM!HOMEWORK: STUDY FOR YOUR MIDTERM!

Meiosis:Meiosis:Making haploid reproductive Making haploid reproductive

cellscells

Goal of MeiosisGoal of MeiosisThe purpose is to make The purpose is to make haploid cells haploid cells so that when 2 so that when 2

haploid cells combine you have a haploid cells combine you have a new diploid new diploid offspring offspring that has an original combination of that has an original combination of genes.genes.

++ = =

Haploid cellHaploid cell + + Haploid cellHaploid cell = = Diploid cell Diploid cell (2n) (2n) (1n)(1n) (1n)(1n) that turns into a that turns into a

muticellular offspring muticellular offspring

Meiosis OverviewMeiosis Overviewo Makes Makes 4 haploid cells4 haploid cellso Takes place in Takes place in sex cells sex cells (gametes) such as (gametes) such as

egg & sperm cellsegg & sperm cellso Location: Location: TestesTestes (male) and (male) and ovaries ovaries (female)(female)

o The Goal:The Goal:o To make 4 haploid daughter cells for To make 4 haploid daughter cells for

reproduction that are genetically different from reproduction that are genetically different from the parent cells. the parent cells.

o Each haploid daughter cell will contain a mixture Each haploid daughter cell will contain a mixture of the parents chromosomes, so that the 4 of the parents chromosomes, so that the 4 daughter cells should be different.daughter cells should be different.

MeiosisMeiosis InvolvesInvolves 2 2 cell divisionscell divisions

The cell will go through interphase The cell will go through interphase (G1, S, G2)…but (G1, S, G2)…but then will divide then will divide twice twice resulting in 4 haploid cells resulting in 4 haploid cells

There are 2 parts in Meiosis:There are 2 parts in Meiosis:– Meiosis 1 Meiosis 1 – Meiosis 2Meiosis 2

Meiosis I and Meiosis IIMeiosis I and Meiosis II Both go through each of Both go through each of

the phases of mitosis the phases of mitosis (PMAT)(PMAT)

After each one After each one cytokinesis occurscytokinesis occurs

The goal is to The goal is to reduce reduce chromosome number to chromosome number to haploid haploid so that 2 cells so that 2 cells can combine to make a can combine to make a diploid organismdiploid organism

Meiosis 1: Prophase Meiosis 1: Prophase 11

DNA coils into DNA coils into chromatidschromatids

Spindle fibers Spindle fibers appearappear

Nucleus/nucleolus Nucleus/nucleolus disappeardisappear

**Homologous Homologous chromosomes pair chromosomes pair up up into tetrads of 4 into tetrads of 4 chromatids, called chromatids, called synapsissynapsis

**Crossing over Crossing over may may occur causing occur causing genetic genetic recombinationrecombination

What is crossing over?What is crossing over? When a homologous pair bumps into each When a homologous pair bumps into each

other during prophase I and they other during prophase I and they exchange portions one chromatid exchange portions one chromatid leads to leads to genetic recombinationgenetic recombination

Metaphase I & Anaphase IMetaphase I & Anaphase I Metaphase I:Metaphase I:

TetradsTetrads line up line up randomly in the randomly in the centercenter. Spindle . Spindle fibers attach to each fibers attach to each end of the end of the homologous pairhomologous pair

Anaphase I:Anaphase I:

Homologous pairs Homologous pairs split randomlysplit randomly

Independent AssortmentIndependent AssortmentThe random lining up of homologous pairs during The random lining up of homologous pairs during

metaphase Imetaphase I. This allows for different gametes to be . This allows for different gametes to be possible and also leads toward genetic recombinationpossible and also leads toward genetic recombination

More independent assortmentMore independent assortment

What is genetic What is genetic recombination?recombination?

……when the combination of genes in an when the combination of genes in an offspring are different from the gene offspring are different from the gene combination found in the parentscombination found in the parents

Occurs in 2 ways in meiosisOccurs in 2 ways in meiosis1. 1. Crossing overCrossing over where homologous pairs where homologous pairs

exchange portions of one chromatidexchange portions of one chromatid

2. 2. Independent assortmentIndependent assortment where the where the homologous pairs line up randomly or without homologous pairs line up randomly or without influences like which parent they came from or influences like which parent they came from or whether they are dominant or recessive. whether they are dominant or recessive.

Telophase I and Cytokinesis Telophase I and Cytokinesis II

Chromosomes reach Chromosomes reach polespoles

Cytokinesis occurs Cytokinesis occurs forming forming 2 new cells.2 new cells.

Nuclear membrane Nuclear membrane may or may not reform may or may not reform before meiosis IIbefore meiosis II

Meiosis II Meiosis II (2(2ndnd cell division, similar to mitosis steps, PMAT) cell division, similar to mitosis steps, PMAT)

Prophase IIProphase II: Spindle fibers form: Spindle fibers form Metaphase IIMetaphase II: Chromosomes move to center (along equator): Chromosomes move to center (along equator) Anaphase II:Anaphase II: Chromatids separate toward the poles Chromatids separate toward the poles Telophase II:Telophase II: Nuclear membrane reforms. Spindle fibers disassemble. Nuclear membrane reforms. Spindle fibers disassemble. CytokinesisCytokinesis occurs forming occurs forming 4 haploid cells with 1 copy of each 4 haploid cells with 1 copy of each

chromosomechromosome..

Do Now – complete on a blank piece of paper with the date and place in your do now

section 1. Where does Meiosis take place in the

body?– Sex cells

2. What kind of cells does Meiosis produce?– Haploid

3. What are the two ways that Meiosis causes genetic recombination?– Crossing over and independent assortment

Homework: Meiosis handout

How does Meiosis differ in males vs. How does Meiosis differ in males vs. females?females?

Since meiosis is producing sex cells (Since meiosis is producing sex cells (sperm & eggssperm & eggs) it ) it takes place in the testes (males) & the ovaries (female)takes place in the testes (males) & the ovaries (female)

In malesIn males::– SpermatogenesisSpermatogenesis - - the formation of 4 the formation of 4

spermatids spermatids (haploid cells) which will turn into (haploid cells) which will turn into spermatozoa (sperm cells).spermatozoa (sperm cells).

In femalesIn females: : – OogenesisOogenesis - - the formation of 1 egg cell the formation of 1 egg cell (ova) (ova)

with with more cytoplasm than the other 3 cellsmore cytoplasm than the other 3 cells. . The remaining 3 cells are The remaining 3 cells are called polar bodies called polar bodies and will disintegrate and will disintegrate

The The phasephases of s of

MeiosiMeiosiss

DiagramsDiagrams

Let us compareLet us compareMitosis VS. MeiosisMitosis VS. Meiosis

Mitosis makes Mitosis makes IDENTICAL cells to IDENTICAL cells to the parentthe parent

Mitosis make Mitosis make DIPLOID cellsDIPLOID cells

Mitosis occurs in Mitosis occurs in BODY cellsBODY cells

Mitosis makes 2 Mitosis makes 2 DAUGHTER CELLSDAUGHTER CELLS

Meiosis make Meiosis make DIFFERENT cells DIFFERENT cells from the parentfrom the parent

Meiosis makes Meiosis makes HAPLOID cellsHAPLOID cells

Meiosis occurs in Meiosis occurs in REPRODUCTIVE cellsREPRODUCTIVE cells

Meiosis makes 4 Meiosis makes 4 DAUGHTER CELLSDAUGHTER CELLS

Meiosis square dance

Take a set of lyrics AND Get ready to sing

Meiosis square danceMeiosis square dance

AnimationsAnimationsJohnkyrk.comJohnkyrk.com

http://www.lewport.wnyric.org/http://www.lewport.wnyric.org/jwanamaker/animations/meiosis.htmljwanamaker/animations/meiosis.html

http://www.stolaf.edu/people/giannini/http://www.stolaf.edu/people/giannini/

Meiosis square danceMeiosis square dance