Past papers Flashcards
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SEX DIFFERENTIATION
Sex differentiation:
- 4 steps:
- Chromosomal (genetic)
- Gonadal (hormonal)
- Somatic (phenotypic)
- Psychic (brain)
- chromosomal:
- mammals xx & xy
- birds zw(female) & zz
- Some reptiles have no heteromorphic sex chromosomes
- temperature determines sex in many reptiles (pivotal temp)
- TDF
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SEMINAL PLASMA
sperm +seminal plasma = semen
ejaculated sperm delivered to female repro tract via seminal plasma
Seminal plasma derived from accessory glands
–Prostate gland
–Seminal vesicle
–ampulla
Produced by accessory sex glands
Varies widely between species
Provides a fluid vehicle for sperm (buffer and
metabolic support)
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RAM EFFECT
- synchronised oestrus cycle
- cycling approx 2- 3 months earlier (from mid Dec to late October)
- sheep are short day breeders
- works best close to anticipated breeding season
- melatonin works best with ram effect
- progesterone injection to prime females - avoids short cycle
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REGUMATE
- supresses oestrus in mares
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LEYDIG CELLS
- primary source of testosterone and androgen in males
- ## in the testes (between seminiferous tubules)
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INDUCTION OF PARTURITION
Stage 1: Initiation of myometrial contractions
- regular uterine contractions
- P4 converted to E2
- pressure on cervix = oxytocin from pituatry
- Placenta produces PGF2α
Stage 2: Expulsion of the fetus
- Strong uterine and abdominal contractions
- Relaxin loosens supportive tissue of the birth canal
- cervix and vagina produce mucus
- Fetal movement promotes further myometrial contraction
Stage 3: Expulsion of the fetal membranes
- uterine contractions decrease
- Vasoconstriction of vessels at fetal/maternal interface
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SPERM SEXING
- differentiates based on x and y DNA content
- stained and the separated with a lazer
- used in cattle
- currently researching to use in sheep
Benefits: - female selection: replacement of dairy heifers and stopping unwanted male calves
- male selection: desirable genes –> increased stud production
- manage endangered species breeding in captivity
- control sex-linked diseases in humans
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PUBERTY
Puberty – “the period or age at which a person is first capable of sexual reproduction of offspring”
• animal gains ability to produce offspring
• Requires physiological, physical and behavioural maturation
• Not a dramatic event; can take months - years.
- indicators of puberty in males and females
- puberty initiated by Influence of the pineal gland and melatonin
- different factors affect puberty
Immediately before puberty starts:
• Pituitary contains Gn’s but they are not secreted in large quantities
• Peaks of Gn’s gradually increase closer to puberty
• Follicles develop and secrete low levels of E2 but ovulation does not occur
• Low level spermatogenesis may occur
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GnRH PULSE GENERATOR
located in hypothalamus
Elicit release of FSH and LH from the anterior pituitary gland, which in turn stimulate release of steroid from the testes
melatonin stimulates GnRH secretion
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MORULA
- say 3-4 after oocyte fertilised
Morula Compaction:
– Occurs at around 16- to 32-cell stage
– Tight junctions form between outer cells
– Individual cells become less distinct
– Cells merge into an “amorphous mass”
– Sodium is pumped into the interior, creating an osmotic gradient
– This causes water to enter the embryo
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LORDOSIS
Lordosis = curving of the spine
- a visual cue of errection
- mice/ rats/ cats/ rabbits assume lordosis as a mating behaviour
- response of increased estrogen
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EPIDIDYMIS
• Mature and store sperm
– Sperm subsequently transported by muscles in epididymis
– Passage through epididymis takes 6-14 days
Maturation of sperm through epididymis:
- Caput (head): Sperm immotile, infertile, Proximal cytoplasmic droplet
- Cauda (tail): Sperm forward progressive motile, Fertile, Distal cytoplasmic droplet
Sperm require further maturation in the epididymis and inside the female tract before fertilisation
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BEHAVIOURAL OESTRUS
- mating behaviour --> changes depending on species Rats: Pre-copulatory • Genital sniffing • Display of “ear quiver response” Copulatory • Assumes lordosis position Post-copulatory • Genital licking
Horses: Pre-copulatory • Frequent urination • Tail deviation (exposure of genitals) • Winking • Genital sniffing Copulatory • Acceptance of male Post-copulatory • Minimal
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FOLLICULAR WAVES
Lecture notes, oestrus cycle
(slide 16)
First, second and 3rd waves
Continuous follicular waves give constant high E2
In Proestrus: P4 decreasing, E2, LH and FSH increasing with FSH suddnly dropping at end of prestrus
In estrus: E2 reaches a peak and LH spikes, FSH comes back up to its highest point. ALL 3 decrease rapidly at end of estrus phase
- length of follicular phase variable between species
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JUVENILE IN VITRO EMBRYO TRANSFER
WHY?
To increase the rate of genetic gain by decreasing generation interval
HOW?
♀Prime juvenile animals at a time to capture the follicular development,
cause ovulation and collect ova
♂Initiate spermatogenesis and collect sperm by testicular biopsy or castration
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GnRH PULSES
GnRH pulses elicit release of FSH and LH from the anterior pituitary gland, which in turn stimulate release of steroid from the testes
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OOCYTE MATURATION
– In primordial and pre-antral follicles
– Oocyte diameter increases from 25 µm to 130 μm
– Zona pellucida (protein coat) formed
• Gap junctions maintain link between oocyte and the surrounding cells
– Cytoplasmic changes
• Large amounts of rRNA and mRNA synthesized
• Essential proteins accumulated
• Organelles formed (mitochondria, ER, Golgi complex)
– In antral follicles
– Oocyte diameter doesn’t increase further
– Protein accumulation and mRNA synthesis continues
– Surrounding cells promote oocyte maturation
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BLASTOCYST
5-6 days after ovulation
approx 70-100 cells
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MATERNAL RECOGNITION OF PREGNANCY
Conceptus provides a biochemical signal that prevents luteolysis (maternal recog of pregnancy)
different in different breeds
PGF2a blocked in all species but pigs
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SEX DETERMINATION
Mammals
xx(female) xy(male
Birds
females (zw)
males (zz)
reptiles
some have no heteromorphic sex chromosomes
temp determines sex in many reptiles
TDF
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ABNORMAL SEXUAL DIFFERENTIATION
androgen recpertor deficency
adrenal hyperplasia in XX females
Congenital adrenal hyperplasia in XY males
progestational steroids during pregnancy
XX males
freemartism in cattle
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SPERMATIDS
an immature male sex cell formed from a spermatocyte, which may develop into a spermatozoon without further division.
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PMSG
Pregnant Mare Serum Gonadotrophin or eCG
- can be used for moderate stimulation of ovulation
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MELATONIN
from pineal gland releases melatonin which acts on hypothalamus supre-chiasmatic nucleus –> GnRH pulse generator
increases twinning rate (in lambs)
advances breeding season
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OVASTIM
fecundity (fertility) vaccine that increases the eggs available for fertilisation by the ram, increasing twinning rates
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FEMALE SENESENCE
Human female senescence is abrupt – depletion of eggs
Farm animals is reduced ability of ovaries and uterus to support
pregnancy (unusual, as animal disposed of prior to this occurring)
embryo survival decreases
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PREIMPLANATION EMBRYO DEVELOPMENT
ootid –> zygote –> 2 celled embryo –> morula –> early blastocyst –> hatching blastocysts –> hatched blastocyst
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EXTRAEMBRYORIC MEMBRANES
chorion and amnion
There are 4 - They are the YOLK SAC, the ALLANTOIS, the AMNION, and the CHORION
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CLONING
creating an animal that is genetically identical to a donor animal through somatic cell nuclear transfer
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CRYOPROTECTANTS
pellets and straws
– Cryopreserved sperm require more sperm per dose due to having half the lifespan of fresh sperm
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METHODS OF SEXUAL CONGRESS
Incorporation
Separation
Alternation
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BEHAVIOURAL OESTRUS
a phrase used to describe the timeframe in which female animals are most receptive to sexual behaviors
express behavioural signs of oestrus
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SENESCENCE
Senescence – “growing old; aging”
Issues with reproducing in this phase
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SPERMATOGONIA
an undifferentiated male germ cell
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SERTOLI CELLS
somatic cells of the testis that are essential for testis formation and spermatogenesis
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BLOCK TO POLYSPERMY
the zona pellucida, a structure that surrounds mammalian eggs, becomes impermeable upon fertilization, preventing the entry of further sperm
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EMBRYO MORTALITY
- Vast majority of losses occur at early embryo stages – ~30% of all fertilised oocytes perish before day 35 – Embryo developmental arrest – Implantation failure – Very few losses occur after day 35 when attachment is complete
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PREGNANCY DIAGNOSIS
Ram harnesses
ultrasound
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ADOLECENSE
increased reproductive activity
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GnRH AGONISTS
Two weeks pre-treatment with GnRH agonist suppresses follicle development
GnRH agonists (long acting) decrease gonadotrophin secretion in most species (down regulation of receptors)
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R STRATERGISTS
- Small body size
- Short lifespan
- Short gestation
- Large litter
- Rapid rate of development
- Short birth interval
- Variable popn size
e.g. rodents
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PROSTOGLANDIN
• Prostaglandin F2α secretion increases during parturition
Causes deterioration of cervical mucus
used to synchronise oestrus
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FSH
Follicular stimulating hormone
acts on sertoli cells
FSH and LH required to initiate spermatogenesis
granulosa cells –> Responds to FSH to produce oestrogen, inhibin and follicular fluid
• Repeat injections of GnRH to stimulate FSH/LH activity (to manipulate breeding season)
FSH action early in diestrus may produce a mid-cycle follicle that will
sometimes ovulate, but more usually regresses
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CHORIONIC GONADOTROPHINS
hCG
a hormone produced by the placenta during pregnancy. It helps thicken a person’s uterine lining to support a growing embryo and tells the body to stop menstruation
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REPRODUTIVE SENILITY IN MALE MAMMALS
• Males generally fertile until death – continue to produce spermatozoa
but fertility does decline
BUT
• May become physically incapacitated and unable to mount
• There is a gradual decline in sexual interest from peri-pubertal stage
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OXYTOCIN
increase during parturition
Stimulates muscular contractions –> sperm transport
in ejaculation Oxytocin, sympathetic controlled contraction of smooth muscle
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PHEROMONES
attract over a considerable distance
social factors –> caused by pheromones in saliva, urine and sweat
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PROSTATE GLAND
– Seminal plasma
derived from
accessory glands
– Prostate gland
role: produce the fluid that nourishes and transports sperm (seminal fluid)
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INTRAUTERINE INSEMINATION
sperm is placed directly into the uterus using a small catheter
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CONGRUENCE OF BRAIN (BEHAVIOURAL) SEX AND PHENOTYPIC SEX
Hormonal and Phenotypic Sex
Males
Presence of TDF, AMH and testosterone
Wolffian ducts form epididymis, vas deferens
and accessory sex glands
Penis and scrotum develop
Females
Absence of TDF, AMH and testosterone
Müllerian ducts form oviducts, uterus, cervix and
cranial vagina
Clitoris, labia and vagina develop
Brain Sex
Exposure of fetus to sex hormones alters
brain structure and function
Affects adult sexual behaviour
Examples
In rats, brain of newborn female masculinized by
17β-oestradiol
In sheep, female fetus exposed to androgens
fails to respond to LH in later life
Genotypic vs. Phenotypic Sex
Genotypic (chromosomal) sex
X + X = female
X + Y = male
Phenotypic (hormonal) sex
What happens when hormone levels
aren’t right during fetal development?
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PENILE ERECTION MECHANISMS
psychogenic stimuli (visual cues, sniffing, pheromones) Nervous Stimulation (tactile stimulation, olfactory cues)
Erection
– Parasympathetic neurons fire, release NO
from terminals, activates enzyme
• Causes arterial dilation and increased blood
flow into corpus cavernosa
• Intracorporal pressure increases,
compressing emissary venules; blood
‘trapped’
– Relaxation of the retractor penis muscle
–Straightening of the sigmoid flexure
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ENDOCRINE CONTROL OF TESTES
The hypothalamus and pituitary gland control how much testosterone the testes produce and secrete.
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SEMINAL VESICLES
glands that produce the fluids that will turn into semen
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BEHAVIOURAL SEX
Female sex behaviour • Maternal behaviour • Mammary glands • Vaginal mucus • Uterus • Odour
Male sexual behaviour • Aggressive behaviour • Horns or Antlers • Neck musculature • Mane • Odour
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SPERMIOGENESIS
the process by which haploid round spermatids complete an extraordinary series of events to become streamlined spermatozoa capable of motility
- mitotic proliferation
- meitoic division
- cytodifferentiation (spermatogenesis)
different sperm initiate division at diff times.
- sperm going through school to graduation (gonia –> cyte –> cyte –> tid)
RATE OF SPERMATOGENESIS IS CONSTANT
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EMBRYO SPLITTING
Zona then splits at the weakest point
– Part of the embryo herniates through the hole in the zona
– Embryo completely sheds zona as split widens
monozygotic conjoined twins embryo doesn’t split completely
What causes embryo splitting?
Several factors for causes of embryo splitting were suggested, including maternal age, prolonged embryo culture, ovarian stimulation, and zona pellucida (ZP) manipulation
the formation of twins or multiples through artificial microsurgical splitting of an embryo at the cleavage or blastocyst stage
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PERINATAL MORTALITY
deaths commencing from at least 20 weeks gestation
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ACROSOME
head of sperm
contains enzymes required to get into egg (penetrate zona pellucida)
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TERMINAL BREEDERS
Individuals breed then die eg salmon
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COLD SHOCK SPERM
When sperm cells are cooled too fast to 5°C, they undergo irreversible damage called cold shock. The damage to the sperm cells is caused by changes in the plasma membrane as it is cooled.
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SPERM MOTILITY ASSESSMENT
sperm movement - how active they are
damage to sperm
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OESTROGENS
Oestrogens (E2; behaviour)
Dominated by oestrogen which
• Triggers LH surge
• Stimulates oestrous behaviour
• Prepares female tract for sperm and ovum transport and fertilisation
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CHORION
the outermost membrane around the embryo
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SERTOLI CELLS
somatic cells of the testis that are essential for testis formation and spermatogenesis.
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THERMOREGULATION OF TESTES
The tunica dartos, a thin sheet of smooth muscle under the scrotal skin, is controlled by sympathetic nerves and contracts and relaxes in cold and warm environments, respectively. The cremaster muscle also contracts to draw the testes closer to the body under cold ambient conditions
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FOLLICULAR DOMINANCE
Superovulation is more effective if the female is in the luteal
or early follicular phase
Presence of a dominant follicle can override the effect of FSH
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QUASI COPULATION
No female penetration but attempt at close deposition of gametes. eg
• Frogs
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TWINS
– Monozygotic twinning
– “Identical” twins
• Genetically identical, same sex
– Derived from the same embryo (one oocyte and one sperm)
– Dizygotic twinning
– “Fraternal” twins
• Can be same sex or opposite sexes
– Two oocytes fertilised separately by two sperm
Cows
– Dairy breeds 3.5%, beef breeds <1%
– Calf survival not reduced
– Chorioallantois of conceptuses fuses causing freemartinism
Ewes
– Some breeds are highly prolific eg. Finnsheep, Booroola
Mares
– Thoroughbreds 1-2%, draft-type 3%
– Fetuses prone to abortion, mummification or neonatal death
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GRANULOSA CELLS
supporting the developing oocyte, proliferating and producing sex steroids and disparate growth factors.
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ZONA PELLUCIDA
a relatively thick extracellular coat that surrounds all mammalian oocytes, ovulated eggs, and preimplantation embryos
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CAPACITATION OF SPERM
sperm undergo a change in the motility pattern called hyperactivation
the physiological changes spermatozoa must undergo in order to have the ability to penetrate and fertilize an egg
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ERRECTION OF STALLION PENIS
2) Musculovascular Penis – Stallion, Human – Large corpus cavernosum fills with blood during erection – No sigmoid flexure – Retractor penis muscle
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GLYCOPROTEIN HORMONES
LH
FSH
hCG
thyroid stimulating hormone
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ELECTROEJACULATION
Animals untrained or physically unable to mount
– Reliable method of semen collection
– Must be performed or under the supervision
of a veterinarian
– Sedation and restraint of male required
– Localised electrical stimulation of the nerves
controlling ejaculation
– Probe is inserted into rectum and series of
electrical pulses released
– increasing in voltage from 5-16 volts
– Duration of 1-2 sec each
– Rest period of 0.5-2 secs between pulses
– Continues until ejaculation
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K STRATEGISTS
- Large body size
- Long lifespan
- Long gestation
- Single offspring
- Slow rate of development
- Long birth interval
- Stable popn size
Elephants, humans, and bison
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HERMAPHRODITES
a person or animal having both male and female sex organs or other sexual characteristics, either abnormally or (in the case of some organisms) as the natural condition.
- Presence of both male and female gonads
- Common in fish and invertebrates (true hermaphrodites)
- Atypical in most vertebrates (intersex)
- May still be fertile (but only towards one sex)
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INHIBIN
Inhibin is a protein secreted by the Sertoli cells in men and by the granulosa cells in women. It inhibits the synthesis and release of the follicle-stimulating hormone in the pituitary gland and reduces the hypothalamic LH - releasing hormone content
