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Canada (162,364)
Psychology (9,699)
PSYB32H3 (1,174)
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ch2.docx

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Department
Psychology
Course Code
PSYB32H3
Professor
Diane Mangalindan

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 genotype o genes that a person inherits from their parents o except twins, no two people have the same genotype  phenotype o created by genotype and environment interacting o can observe it in physical and behavioural characteristics  ovum o female egg o largest human cell  sperm o smallest human cell  zygote o cell formed from male and female cells  chromosomes o thread-like structures in centre of cell o helps to direct development  copies of the 23 pairs of chromosomes all get copied to every cell in the human body except sex cells (they only get 23 single chromosomes) o go through meiosis in which they cross over and make genetic variability  mitosis o cell division where chromosomes are duplicated to daughter cells o occurs in autosomes and sex chromosomes  autosomes o non-sex chromosomes o have matching pairs Genes, DNA and Proteins  DNA o stores genetic info o made up of nucleotides  nucleotide o compound that has a  nitrogen base  simple sugar  phosphate group o AT, CG  genes o part of DNA that codes for certain kinds of protiens The Transmission of Traits: A Basic Model  Mendel studied pea plants, came up with 2 principles  principle of segregation o each inherited trait comes as a separate unit (e.g. flower colour), you do not get a set of traits in a bundle  principle of independent assortment o inheritance of traits occurs independently of each other e.g. flower colour does not influence inheritance of stem height  the notion that if one parent is tall and the other is short then the child will be in between is not accurate (since traits are inherited separately AA Aa aa)  alleles o gene, we usually have 2, one from each parent  homozygous o alleles for a trait are the same e.g. AA aa  heterozygous o alleles for a trait that are different e.g. Aa What happens when a trait is heterozygous? (3 possibilities)  combination of 2 dissimilar alleles can sometimes produce intermediate traits  both alleles express the trait at the same time, with equal force o the two traits do not blend though o e.g. blood type AB (A from one parent and B from the other)  only one of the alleles are expressed Recessive Alleles  many harmful alleles are recessive o this is very most societies prohibit incest o 2 recessive alleles become expressed Sex Chromosomes  23rd pair  female = XX  male = XY  X chromosome is longer and carries more genes  any recessive X-linked chromosomes in males will automatically be expressed (since they only have one x)  hemophilia o blood does not clot Modifier Genes  genes that affect the expression of other genes  e.g occurrence of early cataract is determined by a dominant gene, but the fo0rmation is influenced by modifier genes Why Harmful Alleles Survive  because many of them are not expressed if the allele is heterozygous o e.g. PKU (cannot break down phenylalanine), 1 out of 20 people have the gene but do not know it  some potentially harmful alleles are beneficial when paired with a normal allele o e.g. those with sickle cell anemia gene have protection against malaria Chromosomal Abnormalities  defects in entire chromosome e.g. down syndrome  usually not present in parents, but defect occurs during meiosis  down syndrome o trisomy 21 o father's age matters if mother is old as well o slower to learn to speak, difficulty articulating words Sex-Chromosomal Anomalies  X o Turner syndrome o short, stubby fingers, strangely shaped mouth and ear o deficits in visual and spatial processing and math o do not develop secondary sex characteristics (sterile) o docile and pleasant, but lack assertiveness  XXY o Klinefelter syndrome o sterile, with many female characteristics o verbal and memory difficulties  XYY o taller o not more a
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