GENETICS EVOLUTIONARY BEHAVIOR AP PSYCHOLOGY GENETICS BEHAVIOR Behavioral

GENETICS & EVOLUTIONARY BEHAVIOR AP PSYCHOLOGY

GENETICS & BEHAVIOR • Behavioral Geneticists: study the role genes and • • • the environment on behavior Monozygotic Twins: one egg, one sperm Dizygotic Twins: two eggs, two sperm Heritability: the proportion of variation among individuals in a population due to genetic causes. Applied to the population, not the individual. Twin Studies: nurture vs. nature in the study of identical twins & fraternal twins Adoption studies: are similarities of behavior, thinking, emotion similar to biological or adoptive parents?

GENETICS & BEHAVIOR • Phenotype: the physical expression of a trait • Genotype: the genetic makeup of a trait • For traits determined by one set of genes: Ø Dominant gene: the expressed gene Ø Recessive gene: hidden gene ØHomozygous: both genes are the same – either dominant or recessive ØHeterozygous or Hybrid: one dominant and one recessive gene – the dominant gene is expressed

DOMINANT & RECESSIVE GENES

HEREDITARY TRAITS • Chromosomes are composed of genes. • Genes are made up of DNA segments that contain the blueprint for a specific trait (protein) • During replication of cells, the DNA code is semiconserved from cell to cell. • Normal human body cells have 46 chromosomes; gametes (sperm and egg) have 23 chromosomes. • Both males & females have 22 pairs of autosomal chromosomes and 1 pair of sex chromosomes (males XY; females XX). • During fertilization, gamete nuclei & the normal 46 chromosome number is restored. The fertilized egg is called a ZYGOTE.

SYNDROMES RESULTING FROM CHROMOSOMAL ABNORMALITIES Turner Syndrome females (XO): (XO typically of normal intelligence, may have cognitive deficiencies in math, spatial organization, & visual form perception.

SYNDROMES RESULTING FROM CHROMOSOMAL ABNORMALITIES Klinefelter’s Syndrome males (XXY): becomes evident at puberty when secondary sex characteristics fail to develop. May have learning disabilities such as dyslexia and often are passive individuals.

SYNDROMES RESULTING FROM CHROMOSOMAL ABNORMALITIES Down’s Syndrome (Trisomy 21): results from the nondisjunction of the 21 st chromosome, so each cell has 47 chromosomes. Are usually cognitive challenged, have a protruding tongue, small round ears, fold in each eyelid, more muscle tone & coordination.

RECESSIVE GENES & DISEASE Tay-Sachs Disease: fatal autosomal recessive disease caused by a buildup of undigested lipids (ganglioside GM 2) in nerve cells in the brain. In the first few months of their life infants seen to be normal, but as nerve cells become swollen with the undigested lipid, symptoms appear. Mental and physical abilities deteriorate.

RECESSIVE GENES & DISEASE Albinism: recessive disorder that arises from the failure to synthesize or store pigment. • Symptoms include light color to white hair, irises that are more translucent so they can reflect the inner pigment of the eye and appear read. • Vision problems including inability to perceive depth or 3 -D with both eyes. • Abnormal pathways to the brain result in quivering eyes.

RECESSIVE GENES & DISEASE Phenylketonuria(PKU): Recessive disorder, can lead to irreversible brain damage, infant lacks an enzyme to break down phenylalanine, which builds up and poisons cells in the nervous system.

HUNTINGTON’S DISEASE Huntington's disease is an autosomal dominant disorder that involves the deterioration of the nervous system. • Most people with this disease start to see symptoms between the ages of 30 and 50. • Symptoms include poor memory, depression and/or mood swings, lack of coordination, twitching or other uncontrolled movements, and difficulty walking, speaking, and/or swallowing. • In the late stages of the disease, a person will need help doing even simple tasks, such as getting dressed.

SEX LINKED TRAITS • Color Blindness, Hemophilia, & Male Pattern Baldness are all recessive traits linked to the X chromosome. • As a result, there are more males with such afflictions than there are females.