Genetic Foundations to Human Behavior: Part I — Behavioral Genetics & Molecular Genetics (Week 2)

Flashcards covering Behavioral Genetics concepts (heritability, shared/nonshared environments, twin/adoption/family studies) and foundational molecular genetics (DNA, genes, alleles, SNPs, transcription/translation).

What does Behavioral Genetics (BG) study?

How genetics and environment influence the development of behaviors and traits (phenotypes).

Define phenotype.

An observable characteristic that can be measured (e.g., hair color, height, IQ).

What does variance measure in BG?

Differences (heterogeneity) among people who share a phenotype.

What is the Shared Environment (c2)?

Settings shared by siblings that tend to make them more similar (parents, SES, neighborhood, shared school).

What is the Nonshared Environment (e2)?

Different settings across siblings that make them different; includes different peer groups, prenatal environments, experiences, and interpretations of events.

What is heritability (h2)?

The proportion of phenotypic variance due to genetic differences; h2 + c2 + e2 = 1.

What does h2 = 0 imply?

No genetic contribution to the phenotypic variance.

What does h2 = 0.50 imply?

50% of phenotypic variance is due to genetic factors.

What does c2 = 1 imply?

100% of phenotypic variance is due to the shared environment.

What is the typical range for heritability estimates of most behaviors?

Between 0.50 and 0.90.

Which source is usually the second most influential after genetics?

Nonshared environment (e2).

What did Polderman et al. (2015) find about genetic influence?

Approximately 49% of variability across about 70% of traits is explained by genetic differences; roughly 50% genes and 50% environment.

What BG study methods are commonly used?

Classic Twin Study, Monozygotic Twins Reared Apart (MZAs), Adoption Studies, Family Studies.

What does the Classic Twin Method compare and why?

Monozygotic twins (MZ, 100% DNA) vs dizygotic twins (DZ, 50% DNA) to infer genetic influence; greater similarity in MZ suggests genetic effects.

What are MZ Twins Separated at Birth (MZAs)?

Monozygotic twins reared apart; used to isolate genetic influence from environment; similarities can be striking even without shared environment.

What is the logic of Adoption Studies?

If adoptees resemble biological parents, genetics influence; if they resemble adoptive parents, environment influences.

What do Family Studies examine?

Full-siblings, half-siblings, step-siblings, etc., within households to assess genetic versus environmental influences.

What are the shared genetic material percentages for key relations?

MZ twins 100%; DZ twins 50%; Full siblings 50%; Half-siblings 25%; Cousins 12.5%; Unrelated 0%.

What is DNA?

Deoxyribonucleic acid; the genetic code containing instructions for building and operating an organism.

What are the four nucleotide bases and their pairings?

Adenine (A) pairs with Thymine (T); Guanine (G) pairs with Cytosine (C) — A-T and G-C.

What is a gene?

A set of base pairs in DNA that codes for a protein; about 25,000 genes in the genome; genes code for all body functions.

What is a protein?

A chain of amino acids produced by ribosomes translating RNA; proteins are the workhorses that carry out bodily functions.

What is a nucleotide and what is a codon?

Nucleotide: a base in DNA/RNA; Codon: a sequence of three nucleotides that codes for one amino acid.

How do we get from gene to protein?

Transcription (DNA to RNA) and Translation (RNA to protein) via ribosome; the ribosome assembles amino acids into a protein.

What is genotypic variance?

Differences in DNA sequences that lead to different phenotypes.

What is an allele?

Alternative versions of a gene (e.g., B and b).

What is genotype?

The combination of alleles that produces a phenotype.

What is polymorphism in genetics?

A gene with two or more alleles that can produce different phenotypes.

What are homozygous and heterozygous genotypes?

Homozygous: BB or bb; Heterozygous: Bb.

What is a SNP?

Single Nucleotide Polymorphism; a single base pair difference that can alter RNA/protein; ~90% of DNA differences are SNPs; ~85% of genetic disorders are due to SNPs.

What are microsatellites and minisatellites?

Repeats of base pairs in DNA; differ from SNPs and can affect genotypes and phenotypes; not required to know detailed differences for this course.

What is the base-pairing rule to remember?

A pairs with T and G pairs with C (A-T, G-C).