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Lecture 02 - January 17th.docx

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Psychology 2040A/B

Lecture two – January 17 th Genetics and Hereditary Influences Genetics in general Genotype: inherited gene which is expressed through…. Phenotype: observable characteristics and behaviours *We need the environment (If we’re genetically supposed to be tall, but are malnourished… Then no) What do genes do? Direct production of amino acids necessary for forming new cells Guide cells to develop different parts of the body Regulate the pace and timing of development May “turn on” or “turn off” other genes (Fetuses start off the same – amino acid help with sex) Impacted by environmental factors Gene Expression Alleles influence many characteristics One pair of genes One member from mother, one from father Patterns of genetic expression 1 – Simple/dominant/recessive inheritance *Your genes match up in one spot *Dominant genes have to appear once *Recessive genes must appear on both sides If too alleles are homozygous They are both dominant or both recessive If two alleles are heterozygous One is dominant and one is recessive 2 – Codomination or incomplete dominance *If your mum has A type blood and your dad has B then you can end up with AB type *Single cell anemia 3 – Sex-Linked Inheritance *23 chromosomes that are similar and should match up, but the sex one is different 4 – Polygenic Inheritance *Multiple genes need to be active and activating in sequence or tandem or groups *Most of our characteristics are not dominant/recessive but cascading on/off from many genes Twins Monozygotic (identical): a zygote that divides to form two genetically identical individuals *1 in 250 births Dizygotic (fraternal): occurs when two ova are released simultaneously and both are fertilized by different sperm *1 in 124 births (higher with fertility drugs) *In Canada, we’re seeing a decrease in the birth rate, but an increase in multiple births Congenital problems Babies may have problems at birth due to hereditary or environmental causes *Often requires an environmental cue to get it started – but possibly a combination These problems are present at birth but always apparent Environmental Prenatal exposure to damaging effects, complications in the birth process Inherited Chromosomal – too many or too few, broken or damaged Genetic – recessive genes (both parents), dominant genes, genetic mutation s Chromosomal abnormalities How do they occur? During cell division in meiosis, distribution of chromosomes may be uneven (mix up) May also occur through mutation Most abnormalities are lethal (miscarriage, or the child will be sterile, etc.) Some are not, and some babies are born with an extra chromosome or missing one Autosomes: First 22 pairs of chromosomes Abnormalities – Down Syndrome (trisomy 21) most common st Extra 21 chromosome Mental retardation Distinctive physical features Risk increases with age
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