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Psychology (9,545)
PSYB32H3 (1,174)
Chapter 2

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University of Toronto Scarborough
Mark Schmuckler

Chapter 2 CHROMOSOME AND GENES  23 pairs of chromosome; 46 chromosomes; 1 sex pair and 22 autosomes  Chromosomes carry genetic info on the strands  Sperm and egg unite to form a zygote consisting of 23 pairs of chromosomes  Genetic variability comes from mixing of the chromosomes and crossing over GENES, DNA AND PROTEINS  DNA: Deoxyribonucleic acid; made up of nucleotides THE TRANSMISSION OF TRAITS: A BASIC MODEL  Gregor Mendel: studies pea plants and found out the basic principles of inheritance of traits from one generation to the next o Principle of segregation: each inherited trait comes from one’s parent as a separate unit o Principle of independent assortment: inheritance of various traits occurs independently of one another meaning expression of one trait should not effect the expression of another  Two crucial principles: o There can more than one form of a gene called ALLELES o Homozygous and Heterozygous  If the organism is homozygous (TT): it will be tall  If the organism is Heterozygous (Tt or tT) o An intermediate between the traits o Co dominance: the two will combine but not blend (black cow with white spots) o Dominant allele outperforms the recessive allele and the dominant allele’s trait is expressed GENES ON THE SEX CHROMOSOMES  Determines the individual’s gender  Female: XX Male: XY  X chromosome is longer and carries more genes thus any recessive X-Linked gene will automatically be expressed in males if they don’t have any counteracting dominant genes very likely INTERACTIONS AMONG GENES  Many traits are determined by interactions of many pairs of alleles  Is not likely to be passed on from parent to child  Modifier genes: effect the expression of other genes indirectly DOWN SYNDROME  Physical and mental retardation  High susceptibility to leukemia, heart disorders and respiratory infections  Improvement with treatments have increased the lifespan; 70% live into their 60’s st  Most often comes with the mothers egg;in older women when the 21 pair fails to separate in meiosis  Combination of male over 40 and female over 35= high risk  The children with down syndrome develop fairly normal in the first 6 months; unless they receive special therapy, their rate of intellectual grown begins to drop after about a year SEX-CHROMOSOME ANOMALIES  TURNER SYNDROME o In females; XO pattern o Remain short; weird mouth and eyes o Normal intelligence but deficits in visual and spatial processing; o Do not develop breasts and pubic hair o Have difficulty differencing and interpreting emotional cues and facial expressions  TRIPLE X SYNDROME o In girls; XXX pattern o Normal physical and secondary sex developments but cognitive impairment in short term memory and verbal skills  KLINEFELTER’S SYNDROME o In males; XXY o Is sterile and have man boobs and many female characteristics o Verbal and reading problems, sometimes retarded  XYY PATTERN o In males; XYY pattern o Taller than average o Cognitive impairment  FRAGILE X SYNDROME o X- chromosome that appears to be narrowed or pinched at one point o Physical abnormalities, psychological and social problems GENETIC COUNSELLING AND GENETIC ENGINEERING  Genetic counselling: a healthcare service that provides information about genetic disorders and risks to couples  2 dozen in North America; 3 in Canada  Preventive genetic counselling: get tested for defective alleles and if they have it then adopt or assisted reproductive techniques o In-Vitro Fertilization:  For a woman whose fallopian tubes are bloc
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