I.MEIOSIS INTRO Look Who’s Talking Video Sperm and egg are used to create life. Sperm and egg are used to create life. How are sperm and egg created How.

I.I. MEIOSIS INTROMEIOSIS INTRO

Look Who’s Talking VideoLook Who’s Talking Video Sperm and egg are used Sperm and egg are used

to create life.to create life. How are sperm and egg How are sperm and egg

createdcreated

MEIOSISMEIOSIS

CHAPTER 10.1CHAPTER 10.1

I.I. MEIOSIS INTROMEIOSIS INTRO

A. Organisms have tens of A. Organisms have tens of thousands of genesthousands of genes

B. Genes are not free B. Genes are not free floating, they are lined floating, they are lined up on chromosomesup on chromosomes

1. Chromosomes can be 1. Chromosomes can be about 1000 genes long!about 1000 genes long!

II. MEIOSIS VOCABII. MEIOSIS VOCAB

B. B. HaploidHaploid- When a cell has - When a cell has oneone kind of chromosome kind of chromosome (n)(n)

1. AKA “gamete,” “sex 1. AKA “gamete,” “sex cell,” “sperm” or “egg.” cell,” “sperm” or “egg.”

F

L Q G

F

MEIOSIS VOCABMEIOSIS VOCABA. A. DiploidDiploid- When a cell has - When a cell has twotwo

of each kind of chromosome of each kind of chromosome (2n).(2n).

1.1. Each chromosome has one Each chromosome has one allele (1 from mom, 1 from allele (1 from mom, 1 from daddad

2.2. AKA AKA ““Body Cell”Body Cell”

F f

L LQ q

G G

F f

MEIOSIS VOCAB (CONT.)MEIOSIS VOCAB (CONT.)

C. C. Homologous Homologous ChromosomesChromosomes- The - The two two chromosomes that make up chromosomes that make up each pair in a diploid cell.each pair in a diploid cell.

F f

L LQ q

G G

F f

They aren’t always identical, but they are similar and have the same genes

D. D. ReductionReduction- “Reducing” the - “Reducing” the number of chromosomes by number of chromosomes by ½ (haploid)½ (haploid)

1. Why? So after fertilization 1. Why? So after fertilization the new organism will have the new organism will have the normal number of the normal number of chromosomes (diploid)chromosomes (diploid)

MEIOSIS VOCAB (CONT.)MEIOSIS VOCAB (CONT.)

REDUCTIOREDUCTIONN

(Making (Making eggs or eggs or sperm) sperm)

Chromosomes Duplicate

III. PHASES OF MEIOSISIII. PHASES OF MEIOSIS

A. Similar to mitosis (Interphase - A. Similar to mitosis (Interphase - PMAT- Cytokenesis)PMAT- Cytokenesis)

B. Goes through PMAT twiceB. Goes through PMAT twice1. Prophase I1. Prophase I 5. Prophase II5. Prophase II2. Metaphase I2. Metaphase I 6. Metaphase II6. Metaphase II3. Anaphase I3. Anaphase I 7. Anaphase 7. Anaphase IIII4. Telophase I4. Telophase I 8. Telophase II8. Telophase II

C. InterphaseC. Interphase

1. Cell growth & 1. Cell growth & metabolismmetabolism

2. Chromosomes 2. Chromosomes duplicate (forms the X)duplicate (forms the X)

3. Centrioles duplicate3. Centrioles duplicate

III. PHASES OF MEIOSISIII. PHASES OF MEIOSIS

D. Prophase ID. Prophase I

1. Chromosomes coil 1. Chromosomes coil (visible)(visible)

2. Nuclear membrane 2. Nuclear membrane disappearsdisappears

3. Spindle fibers form3. Spindle fibers form

PHASES OF MEIOSIS PHASES OF MEIOSIS (cont.)(cont.)

D. Prophase I (cont)D. Prophase I (cont)

3. The duplicated 3. The duplicated homologous homologous chromosomes pair up to chromosomes pair up to form a form a tetradtetrad

PHASES OF MEIOSIS PHASES OF MEIOSIS (cont.)(cont.)

D. Prophase I (cont.)D. Prophase I (cont.)

4. 4. Crossing OverCrossing Over-When -When homologous chromosomes homologous chromosomes pair so tightly that they pair so tightly that they actually exchange pieces of actually exchange pieces of chromatidschromatids

a. See pg. 267 & 269 a. See pg. 267 & 269

PHASES OF MEIOSIS PHASES OF MEIOSIS (cont.)(cont.)

4. 4. Crossing OverCrossing Over (cont.) (cont.)

b. Causes genetic b. Causes genetic variationvariation

c. In humans about 2 c. In humans about 2 crossovers occur in every crossovers occur in every pair of homologous pair of homologous chromosomeschromosomes

PHASES OF MEIOSIS PHASES OF MEIOSIS (cont.)(cont.)

E. Metaphase IE. Metaphase I

1. The spindle fibers pull 1. The spindle fibers pull the chromosomes to the the chromosomes to the centercenter

2. The homologous 2. The homologous chromosomes stay in chromosomes stay in tetradstetrads

PHASES OF MEIOSIS PHASES OF MEIOSIS (cont.)(cont.)

F. Anaphase IF. Anaphase I

1. The homologous 1. The homologous chromosomes are pulled chromosomes are pulled apart to opposite sides apart to opposite sides

2. This ensures that each 2. This ensures that each new cell will get only 1 new cell will get only 1 chromosomechromosome

PHASES OF MEIOSIS PHASES OF MEIOSIS (cont.)(cont.)

G. Telophase IG. Telophase I1. Nuclear membrane 1. Nuclear membrane reappearsreappears2. Cytokenis occurs (cell 2. Cytokenis occurs (cell splits)splits)3. You now have 2 cells 3. You now have 2 cells (each with 23 chromosome(each with 23 chromosome—in humans)—in humans)

PHASES OF MEIOSIS PHASES OF MEIOSIS (cont.)(cont.)

G. Meiosis II beginsG. Meiosis II begins

1. Prophase II, Metaphase 1. Prophase II, Metaphase II, Anaphase II, Telophase IIII, Anaphase II, Telophase II

2. It looks like mitosis 2. It looks like mitosis (same # of chromosomes), (same # of chromosomes), but there are more cells but there are more cells doing it!doing it!

PHASES OF MEIOSIS PHASES OF MEIOSIS (cont.)(cont.)

H. In the beginning…H. In the beginning…1. 1 diploid (2 of each 1. 1 diploid (2 of each homologous chromosomes) homologous chromosomes) parent cellparent cell

I. End ResultI. End Result1. 4 haploid (1/2 the original 1. 4 haploid (1/2 the original chromosome number) sex chromosome number) sex cells (gametes)cells (gametes)

PHASES OF MEIOSIS PHASES OF MEIOSIS (cont.)(cont.)

IV. MITOSIS VS. MEIOSISIV. MITOSIS VS. MEIOSISMITOSISMITOSIS MEIOSISMEIOSIS

Diploid (2n)Diploid (2n) Haploid (n)Haploid (n)Beginning: 1 Beginning: 1 cellcell

Beginning: 1 Beginning: 1 cellcell

End: 2 cellsEnd: 2 cellsIdentical to Identical to parentparent

End: 4 cellsEnd: 4 cells½ parent ½ parent chromes. chromes.

Dup. Chromos Dup. Chromos line up aloneline up alone

Dup. Chromos Dup. Chromos line up in pairs line up in pairs (tetrads)(tetrads)

V. NONDISJUNCTIONV. NONDISJUNCTION

A. A. NondisjunctionNondisjunction- When - When homologous chromosomes homologous chromosomes fail to separate.fail to separate.

1. One gamete will have an 1. One gamete will have an extra chromosome (extra chromosome (trisomytrisomy))

2. One gamete will be 2. One gamete will be missing a chromosome missing a chromosome ((monosomymonosomy))

V. NONDISJUNCTION V. NONDISJUNCTION (cont)(cont)

3. Trisomy example3. Trisomy examplea. Down syndrome a. Down syndrome

(extra 21(extra 21stst chromosome)chromosome)4. Monosomy example4. Monosomy example

a. Turner’s syndromea. Turner’s syndrome(missing X chromosome)(missing X chromosome)

V. NONDISJUNCTION V. NONDISJUNCTION (cont)(cont)

B. B. PolyploidyPolyploidy- Organisms with - Organisms with more than the usual number more than the usual number of chromosomes (3n, 4n, 6n)of chromosomes (3n, 4n, 6n)

1. Plant breeders purposely 1. Plant breeders purposely cause polyploidy to improve cause polyploidy to improve their producetheir produce

a. Bananas (3n), Wheat (6n)a. Bananas (3n), Wheat (6n)

VI. VARIATIONVI. VARIATIONA. A. AssortmentAssortment-The many -The many different ways chromosomes different ways chromosomes line up during metaphaseline up during metaphase1. See picture on 2701. See picture on 270

B. B. Genetic RecombinationGenetic Recombination--Major source of gene Major source of gene variation due to variation due to reassortment or crossing reassortment or crossing over.over.

VII. GENE MAPPINGVII. GENE MAPPINGA. Crossing over is used to A. Crossing over is used to help scientists map the help scientists map the genes on each genes on each chromosomechromosome

1. The farther apart the two 1. The farther apart the two genes are, the more genes are, the more crossing over there will be.crossing over there will be.

VII. GENE MAPPING (cont.)VII. GENE MAPPING (cont.)2. Scientists…2. Scientists…

1) Start with one known 1) Start with one known gene gene and one unknown geneand one unknown gene

2) Find the % of times 2) Find the % of times they cross overthey cross over

3) Compare that % to 3) Compare that % to other genes on the other genes on the

same chromosomesame chromosome3. See pg. 272 (Old Books)3. See pg. 272 (Old Books)