Evolution and Gene Regulation

Pedigree

Pattern of trait inheritance within a family

Modes of Inheritance

Autosomal Dominant, Autosomal Recessive, X-linked Dominant, X-linked Recessive

Autosomal Dominant

Traits do not skip generations, equal gender distribution

Autosomal Recessive

Traits can skip generations, affected pairs always have affected children

X-linked Dominant

Very rare, affected father always has affected daughter

X-linked Recessive

Males more likely impacted, affected female always has affected daughters

DNA

Genetic molecule, double-stranded, antiparallel strands

Griffith Experiment

Questioned DNA composition, showed transformation in bacteria

Hershey Chase Experiment

Differentiated DNA and Protein, used radioactive S/P in viruses

Chargaff

Observed DNA base pairing rules, A=T, C=G

Wilkins/Franklin

Used X-ray crystallography to study DNA structure

Watson/Crick

Developed DNA double helix model, Nobel Prize winners

DNA Replication

Occurs during S phase, semi-conservative model

Lagging Strand

DNA polymerase works 5' to 3', Okazaki fragments formed

Gene Expression

Central dogma: DNA to RNA to Protein

Transcription

RNA synthesis from DNA template, initiation, elongation, termination

Promoter

DNA region where RNA polymerase binds to initiate transcription

Translation

Conversion of nucleotides to amino acids, occurs at ribosomes

mRNA

Messenger RNA, carries genetic information from DNA to ribosomes

tRNA

Transfer RNA, carries amino acids to ribosomes during translation

Ribosomes

Cellular machinery for protein synthesis, has A, P, E sites

Ribosome

Cellular machinery for protein synthesis

Start Codon

AUG; initiates translation

Stop Codon

Does not code for amino acid; ends translation

Release Factor

Binds to stop codon, disassembling translation complex

Genetic Code

Universal, unambiguous, and redundant code for amino acids

Codon

Three-nucleotide sequence encoding an amino acid

Frameshift Mutation

Insertion/deletion altering reading frame, often leading to non-functional protein

Point Mutation

Mutation in a single nucleotide

Silent Mutation

Mutation with no impact on amino acid sequence

Introns

Non-coding DNA segments in genes

Gain of Function Mutation

Enhances protein function

Loss of Function Mutation

Reduces or eliminates protein function

Chromosomal Mutation

Large-scale DNA alterations like duplication or deletion

Gene Regulation

Control of gene expression based on genetic or environmental cues

Feedback Cycle

Product inhibits its own production

Positive Feedback

End product encourages more cycle feedback loop

Negative Feedback

End product inhibits cycle

Negative Regulation

Gene turned off by regulatory protein

Positive Regulation

Gene turned on by regulatory protein

Operon

Series of regulated genes with a single regulatory element

Repressor Protein

Binds to operator under certain conditions

Lac Operon

Involved in lactose metabolism in E. coli

Trp Operon

Involved in tryptophan production

RNA Polymerase

Enzyme that synthesizes RNA from DNA template

Eukaryotic Gene Regulation

Centers around transcription factors influencing transcription

Fitness

Measure of reproductive success

Natural Selection

Organisms with advantageous traits survive and reproduce

Stabilizing Selection

Favors intermediate phenotypes

Directional Selection

Favors one extreme phenotype

Disruptive Selection

Favors both extreme phenotypes

Sexual Selection

Selection based on mating success

Genetic Drift

Random change in allele frequency

Population Bottleneck

Reduction in allele diversity due to a small population

Founder Effect

Starting allele frequencies determined by small colonizing population

Speciation

Divergence of populations into separate species

Reproductive Isolation

Prevents gene flow between populations

Allopatric Speciation

Population division by geography leading to speciation

Sympatric Speciation

Population division by other factors within the same area

Prezygotic Isolation

Prevents formation of zygotes

Postzygotic Isolation

Zygotes formed but have lower fitness

Phylogenetics

Classifying organisms based on evolutionary relationships

Cladistics

Grouping organisms into clades based on shared characteristics

Phylogenetic Tree

Diagram showing evolutionary relationships

Homology

Similarity due to common ancestry

Vestigial Structures

Organs reduced in size with no important function

Analogous Structure

Similar function but different ancestry