Biology Unit 2

ends before genetic screening

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Gamete Production
gametes are produced from germline cells
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Male Gametes- Sperm
*Sperm - produced in the testes in the seminiferous tubules
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Male Gametes- Interstitial Cells
*Interstitial cells - in testes, produce hormone testosterone
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Male Gametes- Prostate Gland
*Prostate gland - secrete fluids which maintain the mobility and viability of the sperm (semen)
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Male Gametes- Seminal Vesicles
*Seminal Vesicles - secrete fluids which maintain the mobility and viability of the sperm (semen)
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Female Gametes- Ovaries
*Ovaries - contain immature ova in various stages of development
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Female Gametes- Ovum
*ovum - each is surrounded by a follicle which protects the developing ovum and secretes hormones
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Female Gametes- Mature ova
*Mature Ova - released into oviduct where they may be fertilised by sperm to form a zygote
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Hormonal Control of Reproduction
Hormones control the onset of puberty, sperm production and the menstrual cycle
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Hormonal onset of Puberty - Hypothalamus
Secretes releaser hormone that targets pituitary gland
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Hormonal onset of Puberty - Pituitary gland
Stimulates to release FSH & LH (females) and ICSH & FSH (males)
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Hormonal Control of Sperm Production 1
1 FSH promotes sperm production
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Hormonal Control of Sperm Production 2
2 ICSH stimulates testosterone production
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Hormonal Control of Sperm Production 3
3 Testosterone also stimulates sperm production and activates the prostate gland and seminal vesicles
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Hormonal Control of Sperm Production 4
4 FSH & ICSH exert negative feedback control on the pituitary gland and seminal vesicles
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Hormonal Control of The Menstrual Cycle
The menstrual cycle takes approx 28 days with the first day of menstruation regarded as the first day of the cycle
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Hormonal Control of The Menstrual Cycle (Follicular Phase) 1
1 FSH stimulates development of a follicle and the production of oestrogen by the follicle
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Hormonal Control of The Menstrual Cycle (Follicular Phase) 2
2 Oestrogen stimulates proliferation of the endometrium preparing it for implantation and effects the consistency of the cervical mucus making it more easily penetrated by sperm
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Hormonal Control of The Menstrual Cycle (Follicular Phase) 3
3 Peak levels of oestrogen stimulate a surge in the secretion of LH which triggers ovulation
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Hormonal Control of The Menstrual Cycle (Luteal Phase) 1
1 the follicle develops into a corpus luteum and secretes progesterone
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Hormonal Control of The Menstrual Cycle (Luteal Phase) 2
2 Progesterone promotes further development and vascularisation of the endometrium preparing it to receive a blastocyst if fertilisation occurs
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Hormonal Control of The Menstrual Cycle (Luteal Phase) 3
3 High levels of oestrogen and progesterone have an inhibitory effect on the pituitary gland decreasing lives of FSH and LH which prevents further follicles from developing
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Hormonal Control of The Menstrual Cycle (Luteal Phase) 4
4 The lack of LH leads to the degeneration of the corpus luteum with a subsequent drop in progesterone levels leading to menstruation
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Fertility Cycles - Continuous
males are continuously fertile due to relatively constant levels of pituitary hormones
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Fertility Cycles - Cyclical 1
1 females fertility is cyclical usually restricted to 1-2 days immediately after ovulation
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Fertility Cycles - Cyclical 2
2 females are most likely to conceive in a fertile period which is approx 6 days around the time of ovulation
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Fertility Cycles - Cyclical 3
3 the time of ovulation can be estimated by the number of days after menstruation, a slight rise in body temp on day of ovulation and thinning of cervical mucus
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Treatments for Infertility - failure to ovulate 1 (1&2 reversible)
can be treated with drugs which mimic FSH and LH, these drugs may cause super ovulation that can result in multiple births or be used to collect ova for in vitro fertilisation (IVF) programmes
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Treatments for Infertility - failure to ovulate 2 (1&2 reversible)
drugs can be given to prevent the negative feedback effect of oestrogen on FSH secretion
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Treatments for Infertility - Low sperm count
artificial insemination - multiple samples of semen are collected over a period of time
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Treatments for Infertility - Sterile
Doner egg/sperm etc may be used
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Treatments for Infertility - IVF 1
ova are surgically removed from ovaries after hormone stimulation
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Treatments for Infertility - IVF 2
ova then mixed with sperm in culture dish outside the female's body
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Treatments for Infertility - IVF 3
fertilised eggs incubated until they have formed at least 8 cells and are then transferred to the uterus for implantation
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Treatments for Infertility - IVF 4
Intracytoplasmic sperm injection (ICSI) can be used in IVF if mature sperm are defective or in very low number. The head of the sperm is injected directly into the egg to achieve fertilisation
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Treatments for Infertility - PGS
Pre-Implantation Genetic Screening - used to check embryos for single cell disorders and chromosomal abnormalities
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Treatments for Infertility - PGD
Pre-Implantation Genetic Diagnosis - used to check for a known chromosomal or gene defect
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Treatments for Infertility - risks and ethics - FOR PGS/PGD
offers reassurance to couples at high risk of having a child with a genetic disease, supporters claim a reduced frequency of genetic diseases and disorders is of great benefit to society as a whole
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Treatments for Infertility - risks and ethics - AGAINST PGS/PGD
morally wrong to interfere with conception, argued that these procedures are the start of eugenics- selective breeding in humans- and lead to 'designer babies'
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Contraception - Barrier Methods
*a device which physically blocks the ability of sperm to reach the ova* Condom, cervical cap, intra uterine device (IUD), sterilisation and avoiding fertile periods (NOT AS EFFECTIVE)
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Contraception - Chemical Methods
*contraceptives based on combinations of synthetic hormones that mimic negative feedback preventing the release of FSH/LH* e.g. mini pill, morning after pill, progesterone only pill
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Antenatal screening
identifies the risk of a disorder so that further tests and a prenatal diagnosis can be offered
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Ultrasound Imaging
Anomaly scans may detect serious physical problems, dating scans for pregnancy stage and due date are used with tests for marker chemicals which may vary normally during pregnancy
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Biochemical Testing
Detect the normal physiological changes during pregnancy, blood pressure, type and general health checks are included in this.
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Biochemical Testing - False Positives/Negatives
Measuring a substance at the wrong time could lead to a false positive result
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Other cards in this set

Card 2

Front

*Sperm - produced in the testes in the seminiferous tubules

Back

Male Gametes- Sperm

Card 3

Front

*Interstitial cells - in testes, produce hormone testosterone

Back

Preview of the back of card 3

Card 4

Front

*Prostate gland - secrete fluids which maintain the mobility and viability of the sperm (semen)

Back

Preview of the back of card 4

Card 5

Front

*Seminal Vesicles - secrete fluids which maintain the mobility and viability of the sperm (semen)

Back

Preview of the back of card 5
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