2 - Biological foundations, genetics, prenatal development & birth

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Learning objective: Genetic inheritance and the transmission of genetic differences

Genotype: specific info we inherit

Phenotype: traits actually exhibited by an individual

Mitosis: process that ensures the duplicate cell is identical in genetic make-up to the original cell

Meiosis: process of reduction and division which halves the number of chromosomes

23 chromosomes from mother and 23 from father

Dominant gene: influences the phenotype

Recessive gene: needs to be paired with another recessive gene to be seen in phenotype

Polygentic traits: transmitted through combined action of several genes

Learning objective: How genetic abnormalities occur & what responses can be made

Downs Syndrome: extra 21st chromosome, risk increases as woman gets older (36+)

Sickle-cell disease: recessive gene disorder; circulatory/oxygen issues due to shape of red blood cells

Haemophilia: blood clotting, x-linked, genetic and sex-linked

Huntingtons's disease: gradual deterioration of CNS, causing uncontrollable movement, mental deterioration, death

Cystic fibrosis: difficulties in breathing & digestion, delayed growth & sexual maturation, vulnerability to infection, short life expectancy

Congenital heart disease: abnormalities of the heart

Neural tube defect: spine tube fails to close completely, brain absent or underdeveloped. Death of sever intellectual impairment.

Cleft lip/palate: causes diff. in breathing, speech, hearing, eating.

Responses

Genetic counselling and prenatal diagnosis

Cultural factors may influence decisions: collective vs personal autonomy, directive vs non-directive

Learning objective: The joint influences of genetics and environment

Range of reaction: a range of possible phenotypes an individual with a particular genotype might exhibit in response to the specific sequence of env. influences experienced.

Identical twin and adopted children studies show that both heredity and env. jointly influence developmental change

Learning objective: Prenatal development & risks

Prenatal Development

Conception - zygote formed by sperm and egg combining and consists of discrete periods (stages)

Germinal - 1st 2 wks - zygote forms a blastocyst and embeds

Embryonic - 3 - 8 wks - placenta, umbilical cord form and basic organs and and bio. systems begin to develop

Foetal stage - 9 - end - all physical complete

Risks

Infertility - unable to conceive after a year of trying

Critical periods - usually during 1st trimester where embryo can be affected by teratogens

Drugs, (medical and non-medical), diseases (gonorrhoea, AIDS, syphillis), other hazards

Learning objective: The birth process

Labour - Stage 1 - contractions up to 10cm wide cervix

Labour - Stage 2 - dilation complete and birth takes place

Labour - Stage 3 - delivery of placenta

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