Chapter 2 - Genetic and Environmental Foundations

Genetic Code

consists of DNA, chromosomes, and genes

Phenotype

directly observable characteristics of an individual, affected by both genetics and environment

Genotype

the complex blend of genetic information that determines our species and influences all our unique characteristics

Chromosomes

rodlike structures within the cell nucleus that store and transmit genetic information; humans have 23 pairs (46 total)

DNA

long, double-stranded molecules that make up chromosomes and carry genetic instructions

Gene

a segment of DNA along the length of the chromosome that contains instructions for making proteins

Gametes

s*x cells (sperm in males, ova in females) containing 23 individual chromosomes

Meiosis

the cell division process through which gametes are formed, halving the number of chromosomes so that offspring receive 23 from each parent

Zygote

• the single cell formed when a sperm and ovum unite at conception

• 0-2 weeks

Autosomes

the matching pairs of chromosomes that are not s*x chromosomes

S*X chromosomes

the 23rd pair of chromosomes that determines the genetic sx of the individual

• xx in females, xy in males

Fraternal twins (Dizygotic)

twins resulting from the release and fertilization of two separate ova; genetically no more alike than ordinary siblings

Identical twins (Monozygotic)

twins created when a single zygote duplicates and separates into two clusters of cells, resulting in identical genetic makeup

Allele

each of two or more alternative forms of a gene located at the same place on parallel chromosomes

Homozygous

having two identical alleles at the same locus on a pair of chromosomes

Heterozygous

having two different alleles at the same locus on a pair of chromosomes

Dominant-Recessive inheritance

a pattern in which only one allele (dominant) affects the child’s traits, while the second allele (recessive) has no effect

Carrier

a heterozygous individual who can pass a recessive trait to offspring without expressing the trait themseleves

Incomplete dominance

a pattern of inheritance in which both alleles are expressed in the phenotype, resulting in a combined trait or intermediate phenotype (ex. sickle cell trait)

X-linked intheritance

a pattern of inheritance where a harmful allele is carried on the X chromosome; males are more likely to be affected because they have only one X chromosome

Genomic imprinting

a pattern of inheritance in which alleles are chemically marked so that one pair member, either father or mother, is activated, regardless of its makeup

Mutation

a sudden, permanent change in a segment of DNA

Polygenic inheritance

a pattern of inheritance in which many genes affect the characteristic in question (ex. intelligence, personality)

Socioeconomic status (SES)

a measure of a person’s or family’s social position and economic well-being, combining years of education, prestige/skill of job, and income

Collectivist societies

cultures in which people define themselves as part of a group and prioritize group goals over individual goals

Individualistic societies

cultures in which people think of themselves as separate entities and are largely concerned with personal needs and goals

Epigenesis

development resulting from ongoing, bidirectional exchanges between heredity and all levels of the environment

Epigenetics

the study of environmental influences that modify gene expression without altering the underlying DNA sequence

Niche picking

a type of active gene environment correlation in which individuals actively choose environments that complement their hereditary

Down syndrome (Trisomy 21)

caused by an extra 21st chromosome; results in intellectual disability, distinct physical features, and health risks

Gene-Environment interaction

the concept that individuals, because of their unique genetic makeups, respond differently to identical environmental conditions

Gene-Environment correlation

the idea that our genes influence the environments to which we are exposed (includes passive, evocative, and active/niche picking correlations)

Heritability estimates

measures obtained from kinship studies that estimate the proportion of individual differences in complex traits due to genetic factors

Kinship studies

studies comparing the characteristics of family members to determine genetic influences