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
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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
MITOSIS: somatic cellsMITOSIS: somatic cells
Fig. 3-29Fig. 3-29
PROPHASEPROPHASEINTERPHASEINTERPHASE METAPHASEMETAPHASE
MITOSIS: somatic cellsMITOSIS: somatic cells
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
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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
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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
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