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BIOLOGY| NOTES

Human Reproduction

Anatomy of the Male Reproductive System.

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Testes: Note: !"en t"e #uestion is pointin$ to

% testis& ma'e sure you (rite it as sin$ular)

Structure: Mass of sperm producing tubes

Function:To produce sperm and testosterone.

Scrotal Sac:

Structure: Literally an abdominal cavity in a sac

Function:To keep the testes at temperature slightly lower

than that of the body, which is suitable temperature for

sperm production.

Epididymis:

Structure: ucts that originate from the sperm producing

tubes of the testes, form the coiled epididymis which is

about !m long.

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Function: "perm pass to the base of this tube for a short

period of storage.

*as +e,erens-Sperm +uct:

Structure: "traight, muscular tube about #$ cm long.

Function:Transports sperm from %pididymis to &rethra. 't is

also the site of sperm storage before e(aculation.

.ret"ra:

Structure: ) sperm ducts, one from each testis will lead to

the urethra. 't is a tube which passes through the center of

the penis to the e*terior.A circular band of muscles calledthe sphincter muscles exist at the base of the urinary

bladder to prevent urine from coming out of the bladder

during ejaculation or release of semen.

Function: +assage in which urine and semen are discharged

at dierent times.

/ccessory Glands Seminal *esicle& 0rostate

Gland& 1o(per2s Gland:

Structure:

"eminal vesicle is a gland that opens into the sperm

duct. e have ) of these vesicles.

At the base of the urinary bladder, where the ) sperm

ducts (oin into the urethra is the prostate gland. e

have of this gland.

/owper0s 1land e*ists below the prostate gland. e

have ) of these glands.

Function: All the glands secretes seminal 2uids that forms a

part of semen. The seminal 2uid contains fructose, mucus,

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and prostaglandins to facilitate fertilisation.

0enis:

Structure: /ontains erectile tissue with numerous blood

spaces that will 3ll with bood when se*ually e*cited.

Function: eposits sperm into the female vagina when

inserted.

Ureter:

Function:Transports urine from kidney to urinary 3ladder.

45ote that the accessory gland in the diagram is actually thecowper0s gland.6

Anatomy of the 4emale Reproductive System.

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Ovaries:

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Structure:Two ovoid bodies 7-8cm.

Function:To produce the female gametes, the eggs or the

ova, to produce the female se* hormones oestrogen and

progesterone.

Oviducts:

Structure: 5arrow muscular tubes that leads from ovary to

uterus. They have a funnel like opening and have feathery

processes called 3mbriae. /ilia lining the 3mbriae beat and

cause a current that draws in the egg9secondary oocyte after

it has been released from ovary. /ilia lining the oviduct beat

and smooth muscle contractions, causing peristalticmovements, moving secondary oocyte down the oviduct to

the uterus.

Function:To allow the egg9secondary oocyte to be released

from the ovary and provide a location for it to undergo

fertilisation.

.terus-!om3:

Structure: "hape of an inverted pear. 't has smooth muscles

lining its outer wall 4myometrium6, contracting strongly

during birth. The inner walls, 4endometrium6, contains glands

and blood vessels.

Function:To allow the embryo to implant on the

endometrium of the uterus and grow.

1ervi5:

Structure: 5arrow entrance from uterus leading to vagina,

made up of strong muscles.

Function:To direct sperms into the uterus during intercourse,

and to provide a passage for the birth of a baby from the

uterus out through the vagina during labour

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*a$ina:

Structure: Muscular tube, walls contain elastic tissue.

Function: "tretches during childbirth to allow passage of the

baby and during se*ual intercourse to allow the penetration

of the penis.

/omparison of Male and :emale 1ametes.

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Male:

"mall %longated and "treamlined.

Large numbers mature at the same time and all

the time.

+resence of a tail 42agellum6 for motility to swim

to the egg9secondary oocyte.

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;ery little cytoplasm to reduce its mass so it can

swim rapidly.

+ossesses a lot of mitochondria so that more

energy in the form of AT+ can be released formotility.

4emale:

Large, spherical and fat because its literally a

round egg

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1reen represents the &terine /ycle.

@lue represents the

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+ay 96%:

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increase.

+ay %

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progesterone and oestrogen 4until placenta

takes over6.

Overall: +rogesterone levels increase,

endometrium thickens. :"B and LB levelsdecrease.

'f fertiliDation fails to occur> /orpus Luteum

degenerates. +rogesterone levels decrease.

%ndometrial walls are sloughed o and

discharged. 5e*t cycle occurs.

'f fertiliDation occurs> Eygote develops intoembryo, implantation into uterine lining occurs.

h/1 is produced, corpus luteum remains active.

+rogesterone and

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Note: %stradiol refers to ects o, Hormones involved in Menstruation8

GnRH: 41onadotrophin Celeasing Bormone6

/auses secretion of :"B hormones.

4SH: "timulates development of small number

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of follicles in ovaries. "timulates secretion of

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fertiliDation occurs6 ?

4ERTILIA/TION& /N+ +E*ELO0MENT O4EMBRYO

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1. :ertiliDation occurs when the haploid sperm

nucleus fuses with the haploid egg nucleus to

produce a diploid Dygote.

2. As the Dygote passes down the oviduct, itdivides successively into a small ball of cells

called the embryo 4blastocyst6.

3. 't embeds itself onto the endometrium

4implantation6.

/mniotic 4luid and t"e 0lacenta

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/mniotic 4luid:

"tructure> 'ncompressible, absorbs shocks.

:unction> Absorbs shocks to protect the

embryo9foetus against mechanical in(ury.

0lacenta:

4unction

Allows glucose, amino acids, mineral salts to

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pass from the mother0s blood to the foetus0s

blood via diusion and active transport.

Allows metabolic waste products such as /

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4unction:The blood pressure in the maternal

blood spaces are low so as to create a steep

diusion gradient, allowing increased rate of

diusion of dissolved nutrients and wasteproducts in and out of the foetus.

Structure: @lood capillaries of foetus

separated from mother0s blood system by a

thin layer of tissue.

4unction:Thin barrier decreases the diusion

distance, hence diusion of nutrients or waste

materials occurs at a faster, eFcient rate. 9 Toensure that the ) blood systems do not mi* as

agglutination might occur due to the

dierence of the foetus0s and the mother0s

blood group.

Note: T"e ,oetus "as = um3ilical arteries

and % um3ilical vein8

Note: Intervillous space re,ers to maternal3lood spaces8

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BeneCts o, Breast Mil'

------------------------------------------------------------------------ /ontains fat, lactose and proteins that are easily

digested by the baby.

/ontains vitamins A and / and antibodies to any

diseases from which the mother has recovered.

This helps defend the baby against infection

when the immune system has not been fully

developed.

@reast Milk is free of bacteria.

Ho( are t(ins ,ormed

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'dentical twins arise when a Dygote forms )

separate embryos.

:raternal twins occur when two ova released

during ovulation are fertilised by ) separate

sperm to form ) Dygotes that develop into )

separate embyros.

Met"ods o, 1ontraception

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Chythm method 4Baving se*ual intercourse

based on mGoGoGnGGcGyGcGlGeGsG menstrual cycles.6

ithdrawal

Male /ondom 4prevents sperm from entering

vagina6

iaphragm9/ap 4inserted top of vagina over

cervi*6

:emale /ondom

'ntra &terine evice 4inserted into uterus topevent implantation6

"permicide

/ontraceptive +ills 4contains oestrogen and

progesterone to limit :"B and LB and therefore

prevent follicle development and ovulation6.

Morning After +ill

;asectomy 4"perm uct is cut or tied6

Tubal Ligation 4Tying oviducts6

0lant Reproduction

4ertiliDationof +lants

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After pollination, the pollen grain germinates in

response to fructose secreted by stigma. causing

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a pollen tube to grow out of the grain.

The cytoplasm of the pollen grain, the pollen

tube 4vegetative6 nucleus and the generative

nucleus pass into the pollen tube. 4The growth ofthe pollen tube is controlled by the pollen tube

nucleus6.

The pollen tube secretes enDymes to digest the

tissue of the stigma and the style as the tube

grows.

The generative nucleus divides via mitosis toform two non-motile male gametes. The

vegetative nucleus disintegrates. The pollen

tube enters the ovule at the micropyle 4a small

hole at the bottom of the ovule6.

'n the ovule, the tip of the pollen tube absorbs

sap and bursts, releasing the ) male gametes.

haploid male gamete nucleus fuses with the

haploid egg cell nucleus to form the diploid

Dygote.

The other haploid male gamete will fuse with the

diploid de3nitive nucleus to form the triploid

endosperm nucleus. 4ouble fertilisation occurs,

which ensures that the endosperm will onlydevelop in ovules where the egg has been

fertilised, preventing wastage of nutrients6.

%ach egg cell in the ovule in an ovary is fertilised

by separate male gametes from separate pollen

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grains.

5ote> The central cell refers to the de3nitive nucleus.

0ost ,ertilisation-4ruits

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Ay$ote 6 Em3ryo8The Dygote divides

repeatedly to form the embryo of the seed.

The embryo consists of the contyledons 4seedleaves6, plumule 4developing shoot6, and radicle

4developing root6.

Endosperm Nucleus 6 Endosperm8 'n

monocot plants, endosperm remains as a food

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store. 'n dicot plants, the cotyledons already act

as a food store, hece the endosperm disappears.

Ovary 6 4ruit& Ovary !all 6 4ruit

!all-0ericarp

Ovule 6 Seed8

Inte$uments layer o, cells around t"e

ovule) 6 Seed 1oat-Testa8

Stamen& 0etals& Style and Sti$ma s"rivel

and ,all o>8

Molecular Genetics

5A

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A 5A molecule consists of ) polynucleotide chains

twisted in the shape of a double heli*.

%ach 5A molecule has a sugar phosphate

backbone. The ad(acent nucleotides within a strand

are held together by strong covalent phosphodiester

bonds.

1enetic information is read from the 80 end to the 70

end.

The two strands of polynucleotide chains are held

together by hydrogen bonds in between the

nitrogenous bases of opposite strands.

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/omplimentary base pairing occurs between Adenine

to Thymine 4)B bonds6, 1uanine to /ytosine 47B

bonds6.

+i>erences 3et(een +N/ and RN/8

5A>

Basic .nit: eo*yribunucleotide.

0entose Su$ar: eo*yribose

Nitro$enous Bases: Adenine, Thymine,

1uanine, /ytosine.

Ratio o, Bases: A>T H >, />1 H >

Strands: ouble "tranded

No o, Types:

SiDe: Celatively larger

Location: Mostly in nucleus, small amount in

Mitochondria and chloroplasts.

/mount: /onstant in all cells 4e*cept for in

dividing cells and gametes6.

C5A>

Basic .nit: Cibunucleotide.

0entose Su$ar: Cibose

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Nitro$enous Bases: Adenine, &racil, 1uanine,

/ytosine.

Ratio o, Bases: A>& H9 >, />1 H9 >

Strands: "ingle "tranded

No o, Types: 7 4mC5A, rC5A, tC5A6

SiDe: Celatively smaller

Location: Mostly in cytoplasm, synthesiDed in

nucleus

/mount: ;aries from cell to cell according to

level of protein synthesis.

1enetic %ngineering

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4. Isolate t"e $ene (it" t"e "elp o, restrictionenDymes8

-Cestriction enDymes cut the 5A at speci3c

palindromic seIuences of areas 2anking the

gene, or restriction sites.

- They remove the gene coding for a speci3c

product away from the rest of the genome.

5. .se t"e same restriction enDyme on

plasmids8

-+lasmids are circular double stranded C5A that

occurs naturally in bacteria. 't replicates

independently of the rest of the bacteria genome

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and carries useful genes.

-The same restriction enDyme should be used, as

it generates the same sticky ends as those

2anking the target gene. This allows forcomplementary base pairing and facilitates

insertion of the gene into the plasmid.

6. Mi5 t"e +N/ strand containin$ t"e $ene

and t"e cut up plasmids to$et"er (it" +N/

li$ase8

-The 5A ligase catalyses the formation of

phosphodiester bonds in the 5A backbone. Thisallows the formation of recombinant plasmids.

7. / "ost cell is induced to ta'e up t"e

recom3inant +N/ molecule8

Transcription and Translation.

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Transcription: T"e trans,er o, $enetic

in,ormation ,rom +N/ to RN/8

5A uncoils and its double heli* structure

unwinds.

strand of 5A acts as the template

This allows free ribonucleotides to bind via

complementary base pairings between

deo*yribose and ribose sugars.

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This also allows for transcription to occur

between the template 5A strand and the pre-

mC5A. %nDymes in the nucleus modify the pre-

mC5A in various ways before it leaves thenucleus through pores in the nuclear envelope.

Translation: T"e use o, $enetic in,ormation to

ma'e proteins8

mC5A binds to the small ribosomal subunit in a

ribosome on the rough endoplasmic reticulum.

tC5A carries speci3c amino acids.

The Anticodon of the initiator tC5A binds to the

codon of the mC5A.

The large ribosomal subunit serves as a scaold

for translation.

The Anticodon of the )nd tC5A binds to the )ndcodon of the mC5A.

This allows the amino acids attached to the tC5A

to form peptide bonds.

The bond between the 3rst amino acid and the

initiator tC5A breaks, allowing the peptide bond

to be now carried by the second tC5A.

The Cibosome shifts towards the 70 end of the

mC5A. This allows the ne*t tC5A to bind to the

subseIuent codon.

The peptide bond formation continues until the

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stop codon is read. The translation comple*

dissociates and the polypeptide chain folds to

form proteins.