PRODUCTION OF GAMETES MEIOSIS 1. eo/phases-of- meiosis?playlist=Biology KHAN ACADEMY LINK TO MEIOSIS

PRODUCTION OF GAMETES

MEIOSISMEIOSIS

1

http://www.khanacademy.org/video/phases-of-meiosis?

playlist=Biology

KHAN ACADEMY LINK TO MEIOSIS

http://www.khanacademy.org/video/phases-of-meiosis?playlist=Biology

Click on link to watch Mr. Anderson talk about meiosis

• http://www.safeshare.tv/w/OALswNWWbc

ASEXUAL REPRODUCTION Bacteria and Amoeba reproduce

using ___________________________

BINARY FISSION

BACTERIAAmoeba

ASEXUAL REPRODUCTION

HYDRA PLANARIA

BUDDING & REGENERATION are used by organisms to reproduce asexually by MITOSIS

BINARY FISSION & MITOSIS Produces cells that are __________copies of parent cellIDENTICAL

HumanSomatic (body) cell

Diploid (2n)

2n=46

2n=46

2n=46

MITOSIS Makes ___ cells genetically _________ to parent cell & to each other Makes ___ cells Makes _______________ Used by organisms to: increase size of organism, repair injuries, replace worn out cells

2IDENTICAL

2n SOMATIC (body)

ADVANTAGES OF ASEXUAL REPRODUCTION

• Can make offspring at a faster rate: some bacteria can reproduce every 20 minutes

• Don’t need a partner

DISVANTAGES OF ASEXUAL

REPRODUCTION• ALL ALIKE

• Species CAN’T change and adapt

• One disease can wipe out whole population

SEXUAL REPRODUCTION

Combines genetic material

from 2 parents (sperm & egg)

so offspring aregenetically __________ from parents

DIFFERENT

ADVANTAGES OF SEXUAL REPRODUCTION

Allows for variation in population

Individuals can be different

Provides foundation for EVOLUTION: genetic diversity

Allow species adapt to changes intheir environment

MEIOSIS is the way…

to make cells with ½ the number of chromosomesfor sexual reproduction

CHARACTERISTICS OF LIVING THINGS ALL LIVING THINGS ______________

REPRODUCE

15

MEIOSIS

• Occurs only in ______________ (testes or ovaries)

• Male: _____________________

• Female: ___________________

GONADS

SPERMATOGENESIS

OOGENESIS

MAKING SPERM & EGGS

___________________= MAKING MATURE SPERM

Mature & grow flagella

SPERMATOGENESIS

Replication(interphase)

Meiosis I

Meiosis II

SPERMSPERMATOGENESISSPERMATOGENESIS

POLAR BODIES

Produces: 1 “good” egg

3

CYTOPLASM DIVIDES UNEVENLY

__________________ = MAKING a MATURE EGG

OOGENESIS

Life History of OVUM(EGG)• as a fetus, oogonia divide to produce millions

by mitosis but most degenerate

• Some develop into primary oocytes & stop in prophase stage of meiosis I– 200,000 to 2 million present at birth– 40,000 remain at puberty but only 400

mature during a woman’s life

• Each month, hormones cause meiosis I to resume in several follicles so that metaphase II is reached by ovulation

• Penetration by the sperm causes the final stages of meiosis to occur

Sperm donates DNA

WHY MAKE ONLY ONE “GOOD” EGG?

Most of the cell parts and nutrients needed for baby come from EGG!

“Self digest”

Using ______________

POLAR BODIES DEGENERATE (DIE)

LYSOSOMES

= __________________ “cell suicide” for good of organism

APOPTOSIS

OVUM (EGG)

Replication(interphase

Meiosis I

Meiosis II

24

FERTILIZATION• The fusion of a spermsperm and eggegg to form a

ZYGOTEZYGOTE.• A ZYGOTE is a fertilized egg

n=23egg

sperm n=23

2n=46zygote

Sperm provides DNA

All the starting nutrients, organelles, molecule building blocks, etc. have to come from the egg.

OVUM

SPERM

COMPARISON OF

OOGENESIS & SPERMATOGENESIS

DIPLOID & HAPLOID Most cells have 2 copies of each chromosome = _____ or_________

(one from mom; one from dad)

All BODY (___________) cells are diploid

DIPLOID2n

HOMOLOGOUSCHROMOSOMES

SOMATIC

http://www.biostudio.com/d_%20Replication%20of%20a%20Chromosome.htm

WATCH AN ANIMATION OF HOW A CHROMOSOME IS REPLICATED

DIPLOID & HAPLOID

Sex cells or Gametes have only

one copy of each chromosome =

_____or __________ All sperm and egg cells are haploid

HAPLOID1n

MEIOSIS• Makes ____ cells

genetically different from parent cell & from each other

• Makes _____ cells• Makes ______________

• Used for ____________

4

1n

GAMETES (sperm & eggs)

sexual reproduction

MEIOSIS

32

INTERPHASE IINTERPHASE I

• Similar to mitosismitosis interphase• CHROMOSOMESCHROMOSOMES REPLICATE (S phase) (S phase) • Each duplicated chromosomechromosome consist of

TWO IDENTICAL SISTER CHROMATIDSCHROMATIDS attached at their centromerescentromeres

• CENTRIOLECENTRIOLE PAIRS also replicate.

33

Interphase I

• NUCLEUSNUCLEUS AND NUCLEOLUSNUCLEOLUS visible.

Nuclear membrane

Nucleolus

Cell membrane

Chromatin

34

MEIOSIS IMEIOSIS I

35

Stages of Meiosis IStages of Meiosis I

• Cell division Cell division that reduces the chromosomechromosome number by one-one-halfhalf

• FourFour phases phases:a.a. Prophase IProphase Ib.b. Metaphase IMetaphase Ic.c. Anaphase IAnaphase Id.d. Telophase ITelophase I

36

Prophase IProphase I• Longest and most complexLongest and most complex phase phase

(90%)(90%)• ChromosomesChromosomes condense• SynapsisSynapsis occurs: homologous homologous

chromosomes chromosomes come together to form a tetradtetrad

• TetradTetrad is two chromosomeschromosomes or four chromatidschromatids (sister and nonsister chromatids)

37

Prophase IProphase I - - SynapsisSynapsis

Homologous chromosomes

Sister chromatids Sister chromatidsTetrad

39

Homologous ChromosomesHomologous Chromosomes

• Pair of chromosomeschromosomes (maternalmaternal and paternalpaternal) that are similar in shape and size

• Homologous pairs (tetrads)(tetrads) carry genes controlling the same inherited traits

• Each locuslocus (position of a gene)(position of a gene) is in the same position on homologues

40

Homologous ChromosomesHomologous Chromosomes

Paternal Maternal

eye color locus

eye color locus

hair color locus

hair color locus

41

Crossing OverCrossing Over

• Crossing overCrossing over (variation) (variation) may occur between nonsister chromatidschromatids at the chiasmatachiasmata

• Crossing overCrossing over: segments of nonsister chromatidschromatids break and reattach to the other chromatidchromatid

• Chiasmata (chiasma) Chiasmata (chiasma) are the sites of crossing overcrossing over

42

Prophase IProphase I

CentriolesSpindle fiber

Asterfibers

43

Metaphase IMetaphase I

• ShortestShortest phase phase• TetradsTetrads align on the metaphase metaphase

plateplate• Independent assortment occursIndependent assortment occurs• Chromosomes separate randomlyChromosomes separate randomly

to the poles of the cellsto the poles of the cells

44

Metaphase IMetaphase I• Independent assortment causes

variation in the forming cells• Orientation of homologous pair to

poles is random• Formula for determining variation: Formula: 2n

ExampleExample: 2n = 4: 2n = 4 then n = 2then n = 2

thus 2thus 22 2 = 4 combinations= 4 combinations

45

Metaphase IMetaphase I

Metaphase plate

OR

Metaphase plate

46

Question:Question:

• In terms of Independent In terms of Independent Assortment, Assortment, how many different how many different combinations of sperm could a combinations of sperm could a human male produce? human male produce?

47

AnswerAnswer

• Formula: 2Formula: 2nn

• Human chromosomes:Human chromosomes: 2n = 462n = 46 n = 23n = 23 222323 = ~8 million combinations = ~8 million combinations

48

Anaphase IAnaphase I

• Homologous chromosomes Homologous chromosomes separate and move towards the poles

• Sister chromatids Sister chromatids remain attached at their centromerescentromeres

49

Anaphase IAnaphase I

50

Telophase ITelophase I

• Each pole now has haploidhaploid set of chromosomeschromosomes

• 1n = 23 (human)1n = 23 (human)• CytokinesisCytokinesis occurs and two

haploid daughter cells are formed

51

Telophase ITelophase I

52

53

MEIOSIS IIMEIOSIS II

54

Meiosis IIMeiosis II

• Short or NoShort or No interphase II interphase II • DNA NOT replicatedDNA NOT replicated again again• Remember: Meiosis II Remember: Meiosis II is similar

to mitosismitosis• Prophase I, Metaphase II, Prophase I, Metaphase II,

Anaphase II, and Telophase IIAnaphase II, and Telophase II

55

Prophase IIProphase II• Same as prophaseprophase in mitosismitosis• Nuclear envelope breaks down and the Nuclear envelope breaks down and the

spindle apparatus formsspindle apparatus forms

56

Metaphase IIMetaphase II• Same as metaphasemetaphase in mitosismitosis• Chromatids lined up at equatorChromatids lined up at equator

Metaphase plateMetaphase plate

57

Anaphase IIAnaphase II

• Same as anaphaseanaphase in mitosismitosis• Sister chromatids separateSister chromatids separate

58

Telophase IITelophase II

• Same as telophasetelophase in mitosismitosis• Nuclei reform• CytokinesisCytokinesis occurs• Remember: Remember: Four haploid Four haploid

daughter cellsdaughter cells produced produced• GametesGametes = sperm or egg = sperm or egg

59

Telophase IITelophase II

60

61

Genetic VariationGenetic Variation

62

Variation

• Important to the survival of Important to the survival of populationspopulations

• Aids in natural selectionAids in natural selection• Strongest individuals are able Strongest individuals are able

to survive and reproduceto survive and reproduce

63

QuestionQuestion• What are the three sources of What are the three sources of

genetic variation in sexual genetic variation in sexual reproduction?reproduction?

64

Answer:Answer:

1.1. Crossing OverCrossing Over (Prophase I)(Prophase I)

2. 2. Independent AssortmentIndependent Assortment (Metaphase I)(Metaphase I)

3. 3. Random FertilizationRandom Fertilization(sperm joins with egg)(sperm joins with egg)

65

Remember: Variation is helpful to the

survival of a species!

66

Question:Question:

• A diploid cell containing 20 20 chromosomeschromosomes (2n = 20)(2n = 20) at the beginning of meiosis would, at its completion, produce cells containing how many chromosomeschromosomes?

67

Answer:Answer:

• 10 chromosomes (haploid)10 chromosomes (haploid)• 1n = 101n = 10

68

Question:Question:

• A cell containing 40 CHROMOSOMES 40 CHROMOSOMES at the beginning of meiosis would, at its completion, produce how many cells and how many chromosomes in each cellchromosomes in each cell?

69

ANSWER:ANSWER:

• FOUR CELLS with 20 FOUR CELLS with 20 chromosomes eachchromosomes each

Chromosome Numbers of Some Common OrganismsORGANISM BODY CELL

(2n) DIPLOIDGAMETES

(n) HAPLOID

HUMAN 46 23

GARDEN PEA 14 7

FRUIT FLY 8 4

TOMATO 24 12

DOG 78 39

CHIMPANZEE 48 24

LEOPARD FROG 26 13

CORN 20 10

MICROSCOPIC ROUNDWORM 12 6

CHICKEN 78 39

ANT 2 1

HOUSE MOUSE 40 20

CRAYFISH 200 100

RABBIT 44 22

DEER 68 34

ADDERS-TONGUE FERN (PLANT) 1200 600HORSE 64 32

EARTHWORM 36 18

DOVE 78 39

DOLPHIN 44 22

MEIOSIS I

Section 11-4

Figure 11-15 Meiosis

Section 11-4


MEIOSIS I

Meiosis I

Section 11-4


MEIOSIS I

Section 11-4


MEIOSIS I

Section 11-4


MEIOSIS I

Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original.

Prophase II Metaphase II Anaphase II Telophase IIThe chromosomes line up in a similar way to the metaphase stage of mitosis.

The sister chromatids separate and move toward opposite ends of the cell.

Meiosis II results in four haploid (N) daughter cells.

Figure 11-17 Meiosis IISection 11-4

Meiosis II

Meiosis II





Section 11-4

Figure 11-17 Meiosis II





Section 11-4


Meiosis II





Section 11-4


Meiosis II





Section 11-4


Meiosis II

81

REVIEWREVIEW

WHAT MAKES MEIOSIS DIFFERENT FROM MITOSIS?

1. SYNAPSIS & CROSSING OVER (PROPHASE I)

2. SEGREGATION & INDEPENDENT ASSORTMENT

(ANAPHASE I)

3. Skip INTERPHASE II (NO S) CELL DIVIDES TWICE, BUT…

ONLY COPIES DNA ONCE

WHAT MAKES MEIOSIS DIFFERENT ?

1. Homologous chromosomes pair up during ________________

= ______________SYNAPSIS

This group of FOUR (4)chromatids is called a_________________TETRAD

PROPHASE I

WHAT MAKES MEIOSIS DIFFERENT?

1. Exchange of DNA betweenhomologous pairs = _____________during PROPHASE I

CROSSING OVER

Allows shuffling of genetic material=

________________

GENETIC VARIAION

http://www.biostudio.com/d_%20Meiotic%20Recombination%20Between%20Linked%20Genes.htm

CLICK ON LINK BELOW TO WATCH A CROSSING OVER ANIMATION

HOMOLOGOUS CHROMOSOMES

• SAME SIZE• SAME SHAPE• CARRY GENES for the

SAME TRAITS• BUT ______________!NOT IDENTICAL

CROSSING

OVER

• Allows for_________________in different combinations

• After crossing over, chromatid arms are________________ anymore

Image modified by Riedell

http://sps.k12.ar.us/massengale/genetics%20tutorial.htm

rearranging of DNA

NOT IDENTICAL


2.Separation during ANAPHASE I

INDEPENDENT ASSORTMENT

Separates gene choices and allows shuffling of genetic material or genetic diversity

SEGREGATION &

SEGREGATION(Anaphase I)

SEGREGATION & CROSSING OVER together make even more combinations

INDEPENDENT ASSORTMENT

INDEPENDENT ASSORTMENTat ANAPHASE I

Lots of different combinations are possible!

This is why you don’t look exactly like your brothers and sisters even though you share the same parents!


Crossing over Segregation Independent assortment

are ALL ways MEIOSIS results in =______________________________

So daughter cells are ______________ from parents and from each

other

DIFFERENT

GENETIC RECOMBINATION


3. Skip INTERPHASE II (No S) CELL DIVIDES TWICE, BUT … ONLY COPIES ITS DNA ONCE

G1 G2S P M A T C

G1

MITOSIS:

MEIOSIS:

S G2 P M A T CP M A T C

( I )

( II )

98

REVIEW: COMPARING MITOSIS AND

MEIOSIS

MITOSIS vs MEIOSIS INTERPHASE INTERPHASE I

• DNA is spread out as chromatin• Nuclear membrane/

nucleolus visible• DNA is copied during S phase• Makes everything new cell

needs in G2

SAME AS MITOSIS

MITOSIS vs MEIOSIS PROPHASE PROPHASE I

DNA shortens and thickens into chromosomes

Nuclear membrane/ nucleolus disassembleCentrioles/

spindle fibers appear

SAME AS MITOSIS EXCEPT:

Homologous pairs match up

MITOSIS vs MEIOSIS METAPHASE METAPHASE I

• Chromosomes line up in middle(no homologs) with homologous partner

SAME AS MITOSIS EXCEPT:

MITOSIS vs MEIOSIS ANAPHASE ANAPHASE I

Chromatids splitAPART

Chromatids stay togetherHomologous pairs split

MITOSIS vs MEIOSIS TELOPHASE TELOPHASE I

See TWO nucleiNuclear membrane/ nucleolus reassembleDNA spreads out as chromatinSpindle/centrioles

disassemble

SAME AS MITOSIS

MITOSIS vs MEIOSIS CYTOKINESIS CYTOKINESIS I

Cytoplasm splits into 2 cells

SAME AS MITOSIS

MITOSIS vs MEIOSIS INTERPHASE II

• DNA is spread out as chromatin

• Nuclear membrane/ nucleolus visible

• DNA is copied during S phase

SKIP INTERPHASE IIDNA NOT COPIED

MITOSIS vs MEIOSIS PROPHASE PROPHASE II

• DNA scrunches into chromosomes

• Nuclear membrane/nucleolus disassemble

• Centrioles/ spindle fibers appear

SAME AS MITOSIS

MITOSIS vs MEIOSIS METAPHASE METAPHASE II

• Chromosomes line up in middle

SAME AS MITOSIS

MITOSIS vs MEIOSIS ANAPHASE ANAPHASE II

Chromatids split and move apart

SAME AS MITOSIS

MITOSIS vs MEIOSIS TELOPHASE TELOPHASE II

Two nucleiNuclear membrane/

nucleolus reassembleCentrioles/spindle fibers

disassembleDNA spreads out as chromatin

SAME AS MITOSIS

MITOSIS vs MEIOSISCYTOKINESIS CYTOKINESIS II

Cytoplasm splits SAME AS MITOSIS

Ways Meiosis is different?• Homologous pairs match up & trade DNA

(SYNAPSIS & CROSSING OVER) in PROPHASE I

•SEGREGATION

& INDEPENDENT ASSORTMENT in Anaphase I

create genetic recombination

• Skipping INTERPHASE II- (Dividing TWICE but copying DNA once)

produces 1n HAPLOID cells

CLICK TO WATCH ANIMATIONS OF MEIOSIS

http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120074/bio19.swf::Stages%20of%20Meiosis

http://www.sumanasinc.com/webcontent/animations/content/meiosis.html

Centrosomes(with centriole pairs)

Sisterchromatids

Chiasmata

spindle

Tetrad

Nuclearenvelope

Chromatin

Centromere(with kinetochore)

Microtubuleattached tokinetochore

Tetads line up

Metaphaseplate

Homologouschromosomesseparate

Sister chromatidsremain attached

Pairs of homologouschromosomes split upChromosomes duplicate

Homologous chromosomes(red and blue) pair and exchangesegments; 2n = 6 in this example

INTERPHASE MEIOSIS I: Separates homologous chromosomes

PROPHASE I METAPHASE I ANAPHASE I

• Interphase and meiosis I

1

23

45

6

7

89

10

11

12

TELOPHASE I ANDCYTOKINESIS

PROPHASE II METAPHASE II ANAPHASE II TELOPHASE II ANDCYTOKINESIS

MEIOSIS II: Separates sister chromatids

Cleavagefurrow Sister chromatids

separate

Haploid daughter cellsforming

During another round of cell division, the sister chromatids finally separate;four haploid daughter cells result, containing single chromosomes

Two haploid cellsform; chromosomesare still double

Telophase I, cytokinesis, and meiosis II

1 2 3

CLICK ON THE LINK TO WATCH AN ANIMATION OF THE

COMPARISON OF MEIOSIS AND MITOSIS

http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120074/bio17.swf::Comparison%20of%20Meiosis%20and%20Mitosis

When does it occur? When does it occur?

One or Two? One or Two?

Occurs or not?If yes when? Occurs or not?

If yes when?

One or two?Diploid or Haploid?

One or two?Diploid or Haploid?

What is purpose of Mitosis?

What is purpose of Mitosis?

diploid

diploid

haploid

Documents

PRODUCTION OF GAMETES MEIOSIS 1. eo/phases-of- meiosis?playlist=Biology KHAN ACADEMY LINK TO MEIOSIS