 Genetics  Heredity  DNA  Chromosomes  Genes  Genome  Genotype  Phenotype  Traits  Allele  Dominant  Recessive  Homozygous  Heterozygous  Sex-Linked Traits

 Genetics: Branch of biology that focuses on heredity.  Heredity: The transmission of genetic traits from parent to offspring.  DNA: Deoxyribonucleic Acid, composed of nucleotides. Molecule within the nucleus that contains genetic information.  Chromosome: DNA packaged into thread-like structures tightly coiled around proteins (histones).  Gene: Small segments of DNA that code for specific traits.  Genome: The complete set of genetic material within an organism.

 Genotype: The genetic make up of an individual, or the “types” of genes a person has. All possible combinations of genes. Example…TT, Tt, tt  Phenotype: The observable expression of genes, or the physical characteristics of a person. Example…tall or short.  Traits: Distinctive characteristics or behavior patterns determined by genetics.  Allele: Different forms of the same gene

 Dominant: The stronger allele  Dominant traits will appear as the phenotype if at least one dominant gene is present.  Recessive: The weaker allele  Recessive traits show up in the phenotype only when two recessive genes are present (no dominant allele)  Homozygous: Two of the same alleles (TT, tt)  Heterozygous: Two different alleles (Tt)  Sex-Linked Traits: Genes for these traits are located on the sex chromosomes(pair #23). These traits are usually recessive and appear more commonly in males.

FF or Ff = Free ear lobes (dominant) ff = Attached ear lobes (recessive) To represent alleles, we use symbols: FF = homozygous dominant Ff = heterozygous dominant ff = homozygous recessive

A diagram that predicts the expected outcome of a genetic cross by considering all combinations of gametes in the cross. MONOHYBRID CROSS: Involves ONE PAIR of contrasting traits

X Parent #1 Parent #2 f FFFF Ff ffFF

How many of their offspring will have free earlobes? 4 out of 4 – 100% (the dominant trait is stronger than the recessive trait) How many of their offspring have attached earlobes?0 Are the offspring homozygous or heterozygous?heterozygous

X Parent #1 Parent #2 FfFf FfFf FF Ff ff Ff

 What percent of the offspring are homozygous dominant? 1 out of 4 – 25%  What percent of the offspring are heterozygous? 2 out of 4 – 50%  What percentage of the offspring are homozygous recessive? 1 out of 4 – 25%  How many of offspring will have Free Earlobes? 75%  How many of the offspring will have Attached? 25%

The concept of heritability plays a central role in the psychology of individual differences. Heritability has two definitions. 1. Statistical definition: The degree of variance among individuals that can be attributed to genetic variations. 2. “Common Sense” definition: The extent to which genetic individual differences contribute to individual differences in observed behavior (phenotypic individual differences).

 The subfield of psychology that studies the molecular structure and function of genes.

 Tay-Sachs Syndrome: Recessive condition  Produces progressive loss of nervous function and death in a baby  Albinism: Recessive condition  Failure to synthesize or store pigment and involves abnormal nerve pathways to brain. Quivering eyes and inability to perceive depth or 3D with both eyes.  Phenylketonuria (PKU): Recessive condition  Infant lacks an enzyme to process the amino acid phenylalanine which can build up and poison the nervous system. Severe, irreversible brain damage unless baby is fed a special diet low in phenylalanine the first month. (Nature & Nurture)  Huntington’s Disease: Caused by a Dominant gene  Invovles degeneration of the nervous system. Forgetfulness, tremors, jerky motions, loss of ability to talk, personality changes, temper tantrums, blindness and death.  Color Blindness: Recessive sex-linked trait located on the X chromosome.  Found more frequently in males because males only have one X chromosome (XY).

 Down’s Syndrome: Caused by a break in the 21 st chromosomal pair, appears as 3 chromosome 21.  Mentally retarded, round head, flat nasal bridge, protruding tounge, small round ears, poor muscle tone and coordination.  Turner Syndrome: Females have only one X chromosome (X_ or XO)  Short with webbed neck, lack ovaries, and do not develop secondary sex characteristics). Normal intelligence with some specific cognitive deficits.  Kleinfelter’s Syndrome: Males that have XXY sex chromosomes.  Evident at puberty when secondary sex characteristic do not develop, but breast tissue does. Typically, very passive males.  Huntington’s Chorea: Caused by degeneration of the basal ganglia.  Usually does not occur until after age 40, so frequently passed on to next generation before symptoms appear. Results in muscle impairment

 It is a proportion with a numerical value  Ranges from 0.0 to 1.0  Genes do not contribute at - genes are the only reason for differences  For human behavior, almost all estimates of heritability are in the moderate range of.30 to.60.  The quantity gives the environmentability of the trait.  Environmentability has an analogous interpretation to heritability.  It is the proportion of phenotypic variance attributable to environmental variance or the extent to which individual differences in the environment contribute to individual differences in behavior.  If the heritability of most human behaviors is in the range of , then the environmentability of most human behaviors will be in the range of

There are five important attributes about estimates of heritability. 1. Heritability and environmentability are abstract concepts. 2. Heritability and environmentability are population concepts. They tell us nothing about an individual. 3. Heritability depends on the range of typical environments in the population that is studied. If the environment of the population is fairly uniform, then heritability may be high, but if the range of environmental differences is very large, then heritability may be low. 4. Environmentability depends on the range of genotypes in the population studied. This is the opposite of the point made above 5. Heritability is no cause for therapeutic nihilism. Because heritability depends on the range of typical environments in the population studied, it tells us little about the extreme environmental interventions utilized in some therapies. Therapeutic nihilism is a belief that curing people, or societies, of their ills by treatment is impossible.