Anthropology Week 5

Mutation

A change in DNA sequence; the original source of all genetic variation

Allele

Different versions of the same gene

Beneficial mutation

A mutation that improves survival or reproduction

Deleterious mutation

A mutation that harms survival or reproduction

Somatic cells

Body cells; mutations here are not inherited

Gametes

Reproductive cells (sperm and egg); mutations here can be inherited

Spontaneous mutation

A new mutation that appears randomly in a lineage

DNA repair mechanisms

Enzymes that detect and fix DNA damage

Point mutation

A single nucleotide (letter) change in DNA

Codon

A three-nucleotide “word” that codes for an amino acid

Synonymous mutation

A DNA change that does not change the protein

Nonsynonymous mutation

A mutation that does change the protein

Insertion

Addition of nucleotides into DNA

Deletion

Removal of nucleotides from DNA

Indels

Insertions and deletions

Frameshift mutation

An indel that shifts the reading frame, altering all downstream codons

Transposable elements (transposons)

DNA sequences that can move within the genome

Retrotransposons

Transposons that move via an RNA intermediate

DNA transposons

Transposons that move directly as DNA

Crossover

Exchange of DNA between homologous chromosomes during meiosis

Nondisjunction

Failure of chromosomes to separate properly during cell division

Trisomy

Presence of three copies of a chromosome (e.g., Trisomy 21)

Monosomy

Presence of only one copy of a chromosome

Chromosomal translocation

DNA exchanged between nonhomologous chromosomes

Balanced translocation

No genetic material lost or gained

Unbalanced translocation

Genetic material is duplicated or deleted

Derivative chromosome

A chromosome formed from parts of two different chromosomes

Genetic drift

Random changes in allele frequencies over generations

Population bottleneck

A sharp reduction in population size due to a random event

Founder effect

When a new population is formed by a small number of individuals

Inbreeding

Mating within a small, closed population, increasing genetic similarity

Gene flow

Movement of alleles between populations (often via migration)

Admixture

Gene flow between human populations

Hybridization

Gene flow between nonhuman populations or subspecies

Unidirectional gene flow

Gene flow occurring in only one direction

Natural selection

Differential survival and reproduction based on phenotype

Phenotype

Observable traits of an organism

Selective pressure

Environmental factors that influence survival/reproduction

Directional selection

Favors one extreme phenotype

Stabilizing (balancing) selection

Favors intermediate phenotypes

Disruptive (diversifying) selection

Favors both extremes over intermediates

Sexual selection

Selection based on mating success rather than survival

Species

A group that can interbreed and produce viable, fertile offspring

Viable offspring

Offspring capable of surviving to adulthood

Fertile offspring

Offspring capable of reproducing

Subspecies

Geographically distinct populations that can still interbreed

Hybrid

Offspring from two different species (usually sterile)

Microevolution

Changes in allele frequencies within a species

Macroevolution

Evolutionary changes that lead to new species

Speciation

Formation of new species

Allopatric speciation

Speciation due to physical separation

Sympatric speciation

Speciation without physical separation

Adaptive radiation

Rapid diversification of one species into many

Ecological niche

A species’ role and resource use in an environment

Protein

Molecule that performs most cellular functions

Lipids

Fats and oils; form cell membranes and hormones

Carbohydrates

Sugars used for energy

Nucleic acids

DNA and RNA; store genetic information

Cell

Basic unit of life

Prokaryote

Single-celled organism without membrane-bound organelles

Eukaryote

Organism with membrane-bound nucleus and organelles

Organelle

Specialized structure inside a cell

Nucleus

Organelle that contains DNA

Mitochondria

Produce ATP (energy)

Phospholipid bilayer

Structure of the cell membrane

Cytoplasm

Jelly-like substance inside the cell

DNA (deoxyribonucleic acid)

Molecule that carries genetic information

Double helix

Twisted ladder shape of DNA

Nucleotide

Building block of DNA (A, T, C, G)

Complementary base pairing

A pairs with T; C pairs with G

Chromatin

DNA wrapped around histone proteins

Chromosome

Condensed form of DNA

Histones

Proteins that DNA wraps around

Centromere

Central region of a chromosome

Telomere

Protective ends of chromosomes

DNA replication

Copying DNA before cell division

Semi-conservative replication

Each new DNA molecule has one old strand

Helicase

Enzyme that unwinds DNA

DNA polymerase

Enzyme that builds new DNA strands

Mutation

Change in DNA sequence

Somatic cells

Body cells

Germ cells (gametes)

Sperm and egg cells

Diploid (2n)

Two sets of chromosomes

Haploid (n)

One set of chromosomes

Mitosis

Cell division for growth and repair

Meiosis

Cell division that produces gametes

Recombination

Exchange of DNA between chromosomes during meiosis

Genotype

Genetic makeup (alleles)

Phenotype

Observable traits

Allele

Different versions of a gene

Homozygous

Two identical alleles

Heterozygous

Two different alleles

Dominant

Allele that masks another

Recessive

Allele expressed only if two copies are present

Punnett square

Diagram predicting inheritance

Law of Segregation

Alleles separate during gamete formation

Antigen

Protein on red blood cells

Antibody

Protein that reacts to antigens

ABO blood system

Blood types A, B, AB, O