Genetics 210 (Exam 4)

Allosteric

A type of enzyme that changes its conformation and its function in response to a modifier

Catabolite activator protein (CAP)

A protein that unites with cAMP at low glucose concentrations and binds to the lac promoter to facilitate RNA polymerase action.

Constitutive

Always on, unless turned off

Corepressor

A small molecule that cooperates with a repressor protein to switch an operon off

Cyclic AMP (cAMP)

A compound formed from ATP that acts as a second messenger.

Inducer

A specific small molecule that inactivates the repressor in an operon.

Inducible

Gene regulation that turns genes on when a particular substance is present

lac operon

The operon that controls the metabolism of lactose

Operator

Region of DNA that controls RNA polymerase's access to a set of genes with related functions.

Posttranslational regulation

Determines availability of finished proteins

Repressible

genes in a series are turned off

Represser

A protein which "blocks off" genes

trp operon

tryptophan binds to the repressor protein and enables it to repress gene transcription.

Core element

Consensus sequences in the active regions of promoters recognized by RNA polymerase I

Glucocorticoid hormone

To raise the level of glucose in the bloodstream.

RNA pol II

Transcribes mRNA

Silencer

Site where negative regulators (repressors) bind.

Activator

A protein that binds to DNA and stimulates transcription of a specific gene.

Enhancer

A DNA sequence that recognizes certain transcription factors that can stimulate transcription of nearby genes.

Deamination

The removal of an amino group from an amino acid

Depurination

The loss of a purine base from a nucleotide

Induced mutation

Mutation that results from exposure to chemicals or environmental agents

Spontaneus mutation

A random change in the DNA arising from errors in replication

Tautomeric shift

Temporary change in base structure

Thymine dimer

Adjacent thymine bases covalently bond to one another causing a mutation

Mismatch repair system

Remove/replace incorrectly paired nucleotides resulting from replication errors

Photolyase

An enzyme that splits thymine dimers in the presence of visible light

Missense mutation

A base-pair substitution that results in a codon that codes for a different amino acid.

Nonsense mutation

Changes a normal codon into a stop codon that does not code for amino acid

Point mutation

Gene mutation in which a single base pair in DNA has been changed

Silent mutation

Alters a base but does not change the amino acid

oogonia

Cells that produce primary oocytes by mitotic division

Somatic mutation

A mutation that occurs in a body cell

Spermatogonia

The diploid cells in a testis that can give rise to primary spermatocytes.

Substitution

One nucleotide replaces another

Transition

purine to purine or pyrimidine to pyrimidine

Translocation

Moves a segment from one chromosome to another

Transversion

purine to pyrimidine or pyrimidine to purine

Allelic frequency

The percentage of any specific allele in the gene pool

Fitness

Ability of an organism to survive and reproduce in its environment

Genotypic frequency

The proportion of a given genotype within a population

Hardy-Weinberg equlibrium

A condition in which a population's allele frequencies for a given trait do not change from generation to generation

Directional selection

Occurs when natural selection favors one of the extreme variations of a trait

Disruptive selection

Favors individuals at both extremes of the phenotypic range

Fixation

Rise in frequency of a certain allele in a population

Heterozygote advantage

Occurs when heterozygotes have a higher fitness than do both homozygotes

Stabilising selection

when individuals near the center of the curve have higher fitness than at the end of the curve

Negative frequency-dependent selection

The fitness of a phenotype decreases as it becomes more common

Assertive mating

Mating based on preferred phenotypes rather than on random choices

Emigration

Movement of individuals out of an area

Founder effect

Genetic drift that occurs after a small number of individuals colonize a new area

Gene flow

Movement of alleles from one population to another

Genetic bottleneck

A sudden reduction in the number of alleles in a population

Heterozygosity

The average proportion of genes for which a randomly chosen individual is heterozygous

Immigration

Movement of individuals into a population

Natural selection

A natural process resulting in the evolution of organisms best adapted to the environment.

Non-random mating

Mating between individuals of the same phenotype or by those who live nearby