exercise 43 physiology of reproduction: gametogenesis and the female cycle

Exercise 43Exercise 43

Physiology of Reproduction: Physiology of Reproduction: Gametogenesis and the Female Gametogenesis and the Female

CycleCycle

Objectives:Objectives:

Haploid, diploid, homologous Haploid, diploid, homologous chromosomes, sister chromatids, chromosomes, sister chromatids, synapsis, crossoversynapsis, crossover

Events & endproducts of Meiosis I and Events & endproducts of Meiosis I and Meiosis IIMeiosis II

Spermatozoa and ovarian structuresSpermatozoa and ovarian structuresReproductive hormones & functions Reproductive hormones & functions

CHROMOSOMESCHROMOSOMES

Chapter 3 Chapter 3 Cell DivisionCell Division

Mitosis, MeiosisMitosis, MeiosisDNA coils and DNA coils and

coils during cell coils during cell division to form division to form chromosomeschromosomes

Fig. 3-14Fig. 3-14

23 pairs of chromosomes

Fig. 29-15Fig. 29-15

CHROMOSOMESCHROMOSOMES

Homologous Homologous chromosomeschromosomes: : members of a members of a chromosomal PAIRchromosomal PAIR 1 comes from mom, 1 comes from mom,

1 comes from dad1 comes from dad Sister chromatidsSister chromatids: :

each “half” of the each “half” of the same chromosomal same chromosomal pairpair Each chromosome Each chromosome

consists of 2 consists of 2 duplicate chromatidsduplicate chromatids

http://www.phschool.com/science/biology_place/labbench/lab3/homologs.htmlhttp://www.phschool.com/science/biology_place/labbench/lab3/homologs.html

Mitosis orMitosis or

Meiosis IMeiosis I

Lighter colorLighter color Darker colorDarker color

PLOIDYPLOIDYDiploidDiploid cells cells (2n) (2n)

contain TWO (both) contain TWO (both) members of each members of each pair of pair of chromosomeschromosomes Majority of your cells Majority of your cells

(somatic cells)(somatic cells) 23 23 pairspairs of of

chromosomeschromosomes Endproduct of Endproduct of

MITOSISMITOSIS

2n 2n2n 2n

1 of the 2 copies of both chromosomes 1 of the 2 copies of both chromosomes (1 maternal (1 maternal && 1 paternal) in each cell 1 paternal) in each cell

Fig. 28-7Fig. 28-7

MITOSIS: somatic cellsMITOSIS: somatic cells

InterphaseInterphaseProphaseProphaseMetaphase Metaphase AnaphaseAnaphaseTelophaseTelophase

2 (2n) daughter cells with 2 (2n) daughter cells with 23 pairs of chromosomes 23 pairs of chromosomes 46 chromosomes, maternal 46 chromosomes, maternal & paternal copies& paternal copies

Fig. 28-6Fig. 28-6


Fig. 3-29Fig. 3-29

PROPHASEPROPHASEINTERPHASEINTERPHASE METAPHASEMETAPHASE


Fig. 3-29Fig. 3-29

2 (2n) daughter 2 (2n) daughter cells with 23 cells with 23 pairs of pairs of chromosomeschromosomes

46 46 chromosomes, chromosomes, maternal & maternal & paternal copiespaternal copies

ANAPHASEANAPHASE TELOPHASETELOPHASE CYTOKINESISCYTOKINESIS

PLOIDYPLOIDYHaploid cellsHaploid cells (1n) (1n)

contain only ONE contain only ONE member of each pair member of each pair of chromosomesof chromosomes 23 23 “chromosome “chromosome

halves”halves” Endproduct of Endproduct of

MEIOSISMEIOSIS Sex cells/Gametes: Sex cells/Gametes:

sperm cells, sperm cells, egg cellsegg cells

Fig. 28-6Fig. 28-6

1n 1n 1n 1n1n 1n 1n 1n

1 copy of either maternal 1 copy of either maternal oror paternal paternal chromosome in each cellchromosome in each cell

MEIOSIS: sex cells ONLYMEIOSIS: sex cells ONLY

Interphase I Interphase I Meiosis I: Meiosis I: Prophase I, Metaphase I, Anaphase I, Prophase I, Metaphase I, Anaphase I,

Telophase I (cytokinesis I)Telophase I (cytokinesis I) Interphase II Interphase II Meiosis II: Meiosis II:

Prophase II, Metaphase II, Anaphase II, Prophase II, Metaphase II, Anaphase II, Telophase II (cytokinesis II)Telophase II (cytokinesis II)

Two cycles of cell division Two cycles of cell division 4 (1n) cells with only 1 member of each 4 (1n) cells with only 1 member of each pair of chromosomespair of chromosomes


InterphaseInterphase

Meiosis IMeiosis I

Prophase IProphase ISynapsis & crossing over occurSynapsis & crossing over occur

TetradTetrad

Metaphase IMetaphase ITetrads line up @ metaphase plateTetrads line up @ metaphase plate

Anaphase IAnaphase IHomologous pairs separateHomologous pairs separate

Telophase ITelophase I

Cytokinesis ICytokinesis I

Meiosis IIMeiosis II

Prophase IIProphase II

Metaphase IIMetaphase IIChromosomes line up @ Chromosomes line up @

metaphase platemetaphase plate

Anaphase IIAnaphase IISister chromatids Sister chromatids

separateseparate

Telophase IITelophase II

Cytokinesis IICytokinesis II

4 (1n) cells formed, each w/only 1 4 (1n) cells formed, each w/only 1 chromosome of each homologous pairchromosome of each homologous pair

Fig. 28-6Fig. 28-6

In In meiosismeiosis, maternal , maternal & paternal & paternal chromosomes chromosomes (homologous (homologous chromosomes) come chromosomes) come together & pair uptogether & pair up

(matched set of 4 (matched set of 4 chromatids = chromatids = tetradtetrad))

SYNAPSISSYNAPSIS

CrossoverCrossover

Fig. 28-6Fig. 28-6

Some exchange of Some exchange of genetic material genetic material occurs at this stage occurs at this stage of of meiosismeiosis (synapsis) (synapsis)

Increases genetic Increases genetic variation among variation among offspringoffspring


Fig. 28-6Fig. 28-6

1n 1n 1n 1n1n 1n 1n 1n

End Meiosis I:End Meiosis I: Both Both copies (sister copies (sister

chromatids) of either chromatids) of either the maternal the maternal

chromosome or the chromosome or the paternal chromosome paternal chromosome

in each cellin each cell

End Meiosis II:End Meiosis II: the the sister chromatids sister chromatids

separateseparate

MEIOSIS—different from MitosisMEIOSIS—different from Mitosis

Anaphase I—tetrads break up—maternal & Anaphase I—tetrads break up—maternal & paternal (homologous) chromosomes paternal (homologous) chromosomes separateseparate

After meiosis I, have both copies of either After meiosis I, have both copies of either maternal OR paternal chromosomes from maternal OR paternal chromosomes from each tetradeach tetrad

Then maternal/paternal chromosomes are Then maternal/paternal chromosomes are randomly distributedrandomly distributed into two daughter cells into two daughter cells at end of meiosis Iat end of meiosis I

Anaphase II: Sister chromatids separateAnaphase II: Sister chromatids separate Telophase II: 4 (1n) cells with only 1 member Telophase II: 4 (1n) cells with only 1 member

of each pair of chromosomes (23)of each pair of chromosomes (23)

Mitosis vs. MeiosisMitosis vs. Meiosis

Fig. 28-6Fig. 28-6

MEIOSISMEIOSIS MITOSISMITOSIS

InterphaseInterphase Begins with a diploid cellBegins with a diploid cell

4 chromosomes combine to 4 chromosomes combine to form 2 tetradsform 2 tetrads

Begins with a diploid cellBegins with a diploid cell

ProphaseProphase The chromosomes in the The chromosomes in the tetrad cross over each other, tetrad cross over each other, allowing them to exchange allowing them to exchange genetic materialgenetic material

4 chromatids combine to 4 chromatids combine to form two chromosomes form two chromosomes linked by a centromerelinked by a centromere

MetaphaseMetaphase The two tetrads line up in the The two tetrads line up in the centercenter

The two chromosomes line The two chromosomes line up in the centerup in the center

AnaphaseAnaphase The two tetrads split up into The two tetrads split up into four chromosomes which go four chromosomes which go to both polesto both poles

The two chromosomes The two chromosomes split up into four split up into four chromatids which move to chromatids which move to both of the poles (2 each)both of the poles (2 each)

TelophaseTelophase The two sets of The two sets of chromosomes are enclosed chromosomes are enclosed by the nuclear envelopeby the nuclear envelope

The two sets of chromatids The two sets of chromatids are enclosed by the nuclear are enclosed by the nuclear envelopeenvelope

CytokinesisCytokinesis Two cells are formed with Two cells are formed with two sets of chromosomes in two sets of chromosomes in each oneeach one

Two cells are formed with Two cells are formed with two chromatids in each one two chromatids in each one Mitosis is now complete.Mitosis is now complete.

MEIOSISMEIOSIS MITOSISMITOSIS

Prophase IIProphase II DNA replication is skipped and the two cells’ DNA replication is skipped and the two cells’ nuclear envelopes are dissolved and the spindle nuclear envelopes are dissolved and the spindle reformed reformed The four chromatids in each cell are connected The four chromatids in each cell are connected together to form two chromosomestogether to form two chromosomes

Metaphase IIMetaphase II The two chromosomes line up in the centerThe two chromosomes line up in the center

Anaphase IIAnaphase II The two chromosomes are split up into their The two chromosomes are split up into their daughter chromatids and move towards daughter chromatids and move towards opposites polesopposites poles

Telophase IITelophase II The nuclear envelope is reformed around the The nuclear envelope is reformed around the two poles on each cell.two poles on each cell.

CytokinesisCytokinesis The cells are split up again and four haploid The cells are split up again and four haploid cells result cells result Meiosis is now completeMeiosis is now complete

SpermatogoniaSpermatogonia undergo undergo mitoticmitotic divisions divisions throughout normal adult throughout normal adult lifelife

Daughter cells move to Daughter cells move to the lumen of the lumen of seminiferous tubuleseminiferous tubule and and differentiate into differentiate into primary primary spermatocytesspermatocytes

MeiosisMeiosis produces produces gametes (gametes (spermatidsspermatids))

Spermiogenesis: Spermiogenesis: spermatids develop into spermatids develop into haploid haploid spermatozoaspermatozoa

Fig. 28-7Fig. 28-7Spermatogenesis: sperm productionSpermatogenesis: sperm production

Head: flattened ellipse, Head: flattened ellipse, contains DNAcontains DNA Acrosome: tip of head, Acrosome: tip of head,

membrane “cap”—has membrane “cap”—has enzymes to aid fertilizationenzymes to aid fertilization

Nucleus: in head, contains Nucleus: in head, contains DNADNA

Midpiece: mitochondria Midpiece: mitochondria arranged in a spiral, arranged in a spiral, provide ATP for tail provide ATP for tail movementmovement

Tail: flagellum—Tail: flagellum—corkscrew movement corkscrew movement

Fig. 28-8Fig. 28-8

Spermatozoa AnatomySpermatozoa Anatomy

Mature Mature spermatozoonspermatozoon

No ERNo ERNo golgi apparatusNo golgi apparatusNo lysosomesNo lysosomesNo peroxisomes or many other partsNo peroxisomes or many other partsReduces cell’s mass and sizeReduces cell’s mass and size““Carrier for the chromosomes”Carrier for the chromosomes”

http://www.astrographics.com Image copyright http://www.astrographics.com Image copyright © Dennis Kunkel. © Dennis Kunkel.

Begins before birth, peaks at Begins before birth, peaks at puberty, ends at menopausepuberty, ends at menopause

Ovarian cycle—monthly Ovarian cycle—monthly (puberty(pubertymenopause)menopause)

OogoniaOogonia complete complete mitosismitosis before before birth, then birth, then primary oocytesprimary oocytes go go through Prophase I and through Prophase I and stopstop until until pubertypuberty

Fig. 28-15Fig. 28-15

Oogenesis: ovum productionOogenesis: ovum production

Monthly after puberty, some Monthly after puberty, some primary oocytesprimary oocytes continue continue developmentdevelopment

Polar bodiesPolar bodies: nonfunctional : nonfunctional cells, later disintegrate; cells, later disintegrate; result of meiotic divisionresult of meiotic division

Primary Primary Secondary Secondary oocyteoocyte halts at halts at Metaphase II Metaphase II until until fertilizationfertilization

Fig. 28-15Fig. 28-15Oogenesis: Oogenesis:

ovum productionovum production

FollicleFollicle: ovarian : ovarian structure, where structure, where oocyte grows & oocyte grows & Meiosis I occurs Meiosis I occurs

Primary folliclePrimary follicle: : follicular cells follicular cells grow/divide, grow/divide, several layers several layers around around primary primary oocyteoocyte

Fig. 28-16Fig. 28-16

Ovarian Cycle

Secondary follicleSecondary follicle: :

(few of primaries (few of primaries further develop) further develop) inner and outer inner and outer layers expand and layers expand and separateseparate

generally only 1 @ generally only 1 @ day 8-10 of cycleday 8-10 of cycle

Fig. 28-16Fig. 28-16

Ovarian Cycle

Graffian (vesicular, Graffian (vesicular, tertiary) follicletertiary) follicle: : day 10-14 of cycle, day 10-14 of cycle, creates a bulge in creates a bulge in ovarian surface. ovarian surface.

Now formed, it will Now formed, it will complete Meiosis I complete Meiosis I (had been (had been suspended at suspended at Prophase I)Prophase I)

Fig. 28-16Fig. 28-16

Ovarian Cycle

Secondary oocyteSecondary oocyte + + small polar body small polar body formedformed

Secondary oocyte Secondary oocyte enters Meiosis II, enters Meiosis II, stops at stops at Metaphase II until Metaphase II until fertilizationfertilization

Fig. 28-15Fig. 28-15

Ovarian Cycle

Secondary oocyteSecondary oocyte & & small polar body small polar body formedformed

Secondary oocyte Secondary oocyte enters Meiosis II, enters Meiosis II, stops at Metaphase II stops at Metaphase II until fertilizationuntil fertilization

Fig. 28-16Fig. 28-16

Ovarian Cycle

Day 14-28: Day 14-28: secondary oocytesecondary oocyte releases from releases from follicular wall follicular wall throughthrough

OvulationOvulation: : tertiary tertiary folliclefollicle releases releases secondary oocytesecondary oocyte, , into into uterine tubeuterine tube

Fig. 28-16Fig. 28-16

Ovarian Cycle

Corpus luteumCorpus luteum: : endocrine structure endocrine structure created by follicle created by follicle rupture of oocyte rupture of oocyte (lutea = yellow)(lutea = yellow)

Fig. 28-16Fig. 28-16

Ovarian Cycle

Fig. 28-12Fig. 28-12

Reproductive Hormones: Males

Fig. 28-25Fig. 28-25

Reproductive Hormones: Females

Stimulates Stimulates ovulationovulation

Stimulates follicle devmt Stimulates follicle devmt & oocyte maturation& oocyte maturation

Reproductive Hormones: Summary

exercise 43 physiology of reproduction: gametogenesis and the female cycle

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