Key Concepts in Genetics and Inheritance

Genetics

The study of heredity and variation in organisms, focusing on genes and how traits are inherited.

Molecular Genetics

Studies gene function and structure.

Population Genetics

Examines genetic variation in populations.

Quantitative Genetics

Focuses on traits controlled by many genes.

Genomics

Involves sequencing and analyzing genomes.

Selection

Non-random survival of individuals based on traits.

Genetic Drift

Random changes in allele frequencies due to chance events.

Natural Selection

Survival of the fittest based on environmental factors.

Sexual Selection

Selection based on traits that affect mating success.

Artificial Selection

Human-driven breeding for desired traits.

Evolution

Occurs as genetic changes accumulate over time.

GWAS (Genome-Wide Association Study)

A study that scans the genome to find genetic variations associated with traits or diseases.

Central Dogma

The process where DNA is transcribed to RNA, which is then translated to protein.

Transcription Factors

Proteins that help regulate the transcription of genes.

Genome

Complete set of genes.

Transcriptome

Set of all RNA transcripts in a cell.

Proteome

Complete set of proteins in a cell.

Consequences of Eugenics

Ethical issues, potential harm to diversity, and discrimination.

Gene

A unit of inheritance, a segment of DNA that codes for a protein, or an allele at a particular locus.

Selfish Genes

Genes that spread in a population due to their ability to replicate, even if not beneficial to the organism.

Genetic Screen

A method to identify genetic mutations in an organism.

Model Organism

A species used for experimental research because it is easy to study and has well-understood genetics.

Prokaryotic Cells

Lack a nucleus.

Eukaryotic Cells

Have a nucleus and organelles.

Nucleus

The organelle that contains the cell's genetic material and coordinates activities.

Telocentric Chromosome

Centromere at the end.

Acrocentric Chromosome

Centromere close to one end.

Metacentric Chromosome

Centromere in the middle.

Submetacentric Chromosome

Centromere slightly off-center.

Chromosome Landmarks

Centromere (joins chromatids), telomere (ends of chromosomes), p/q arm (short/long arms).

Allele

A variant of a gene.

Ploidy

Refers to chromosome sets.

Diploid

Has two sets of chromosomes.

Chromatids

Duplicated chromosomes.

Cytogenetic Nomenclature

Identifying gene locations based on banding patterns.

Cell Cycle Phases

G0 (resting), G1, S (DNA replication), G2, M (mitosis).

Mitosis

Produces identical cells.

Meiosis

Produces genetically diverse gametes.

Meiosis Variation

Independent assortment, crossing over, random fertilization.

Sexual Reproduction

Genetic diversity, but energy-intensive.

Asexual Reproduction

Reproduction without the fusion of gametes.

Asexual Reproduction

Faster reproduction, but less genetic variation.

Red Queen Hypothesis

Organisms must constantly evolve to survive due to co-evolving parasites.

Evolutionary Arms Race

Continuous adaptation by competing species or organisms.

Ploidy Terms

Haploid (1 set), Diploid (2 sets), Polyploid (multiple sets).

Homozygous

Same alleles.

Heterozygous

Different alleles.

Homologous

Chromosomes that pair in meiosis.

Homologous Chromosomes in Reproduction

Each parent contributes one homologous chromosome per pair.

Loci on Chromosomes

Position of a gene on a chromosome.

Cell Cycle Phases

G1, S, G2, M; G0 is a resting phase.

Mitosis/Meiosis Phases

Mitosis (prophase, metaphase, anaphase, telophase); Meiosis I and II (similar to mitosis, with crossing over and two divisions).

Gamete Formation

Involves meiosis, producing haploid gametes.

Genotype vs. Phenotype

Genotype is genetic makeup; phenotype is the observable trait.

Dominant vs. Recessive

Dominant alleles mask recessive traits.

Gain/Loss of Function Mutation

Gain enhances gene activity; loss reduces or eliminates function.

Wildtype

The normal, most common phenotype in a population.

True-breeding Crosses

Parents are homozygous for traits, producing offspring with consistent traits.

Mendel's Laws

Law of Segregation (alleles separate) and Independent Assortment (genes segregate independently).

Test Cross vs. Backcross

Test cross determines genotype using a homozygous recessive; backcross crosses with a parent.

Punnett Squares

Diagram to predict offspring ratios for gene combinations.

P, F1, F2 Generations

P (parental), F1 (first offspring), F2 (second generation from F1).

Probability Rules

Multiplication for independent events, addition for mutually exclusive events.

Dihybrid Cross

Examines inheritance of two traits, predicting a 9:3:3:1 ratio.

Chi-Squared Test

Statistical test for expected vs. observed ratios.

Sexual Dimorphism

Differences in traits between males and females of a species.

Binary Fate Decisions

When a cell or organism can follow one of two developmental paths.

Human Sex Determination

Based on the presence of X and Y chromosomes, with SRY gene determining male development.

X vs. Y Chromosomes

X carries many genes; Y carries genes for male characteristics.

Sry, Sox9, Dmrt1 Genes

Key in male development.

Aromatase and Hormones

Control sexual differentiation.

Morgan and Sex Linkage

Genes on X and Y chromosomes have different inheritance patterns.

Sex-linked Traits

Traits linked to X or Y chromosomes, like hemophilia.

Hemizygous

Having one copy of a gene, typically in males for X-linked traits.

Sex Development in Humans

Involves X/Y chromosome interaction and gene expression.

Androgen Insensitivity Syndrome

Genetic condition where the body doesn't respond to androgens, leading to female-like traits.

Barr Bodies

Inactivated X chromosomes in females.

Aneuploidy

Abnormal number of sex chromosomes, such as Turner syndrome or Klinefelter syndrome.

X Inactivation

Random inactivation of one X chromosome in females.

Sex Determination in Birds

ZW system, with males ZZ and females ZW.

Genic Sex Determination

Sex determined by specific genes, not chromosomes.

Haplodiploidy

In some species (e.g., bees), males are haploid and females are diploid.

Environmental Sex Determination

Temperature, social factors, or other environmental cues can determine sex.

Sex in Flies and X:A Ratio

X chromosome number relative to autosomes determines sex in Drosophila.

Multiple Alleles

More than two alleles for a gene, such as in blood type inheritance.

Heterozygote Advantage

When heterozygotes have higher fitness than homozygotes, e.g., sickle cell trait and malaria resistance.

Epistasis

Interaction between genes where one gene masks the expression of another.

Complementation Test

Used to determine if two mutations are in the same gene or different genes.

Pedigree Analysis

Traces inheritance patterns to determine whether traits are dominant, recessive, etc.

Consanguinity

Mating between relatives, increasing risk for genetic disorders.

Genetic Counseling

Helps individuals understand genetic risks and inheritance patterns.

Chi-Squared Test

Used to test hypothesis about genetic ratios, based on expected vs. observed outcomes.

Sexual Dimorphism

Physical differences between males and females of a species.

Binary Fate Decisions

Cell differentiation decisions between two paths.

Sex Determination in Humans

Determined by SRY gene on the Y chromosome.

Sex Chromosomes in Humans

X and Y chromosomes differ in size and function, with X carrying many genes and Y determining male sex.

Aromatase and Sex Hormones

Critical in sexual differentiation.

Morgan and Sex Linkage

Research showed that traits linked to sex chromosomes follow different inheritance patterns.

Sex-Linked Traits

Traits associated with X or Y chromosomes, e.g., color blindness.

Dosage Compensation

Mechanism to equalize gene expression from X chromosomes in males and females.