BIOL 214 Exam #3

Gene Regulation,

No Regulation/Control

constitutive gene expression for proteins that are needed all the time

Transcriptional Control

no mRNA synthesis

Translational Control

no protein synthesis

Enzyme Activity Control

no product

Negative Inducible

repressor is synthesized in active form & becomes inactive when inducer/activator binds; binds to operator; active → inactive

Negative Repressible

repressor is synthesized in inactive form & becomes active when corepressor binds; binds to operator; inactive → active

Positive Inducible

activator is synthesized in inactive form & becomes active when inducer/activator binds; binds to activator binding site; inactive → active

Positive Repressible

activator is synthesized in active form & becomes inactive when product accumulates; binds to activator binding site; active → inactive

Negative Control

transcriptional control involving repressor protein

Positive Control

transcriptional control involving activator protein

Inducible Operon

inactive → active

Repressible Operon

active → inactive

Anabolic

synthesis reaction that typically involve repressible genes

Catabolic

breakdown reaction that typically involves inducible genes

lac Operon

laci + promoter + operator + lacZ + lacY + lacA; lactose → allolactose + repressor → transcription; negative inducible

laci Regulatory Gene

regulatory gene that encodes lac repressor

lac Repressor

repressor that binds to operator & prevents transcription in absence of lactose

Catabolite Repression

high glucose levels → inactivated adenylyl cyclase → low cAMP levels → no CAP activation → low transcription; low glucose levels → high adnylyl cylclase levels → high cAMP levels → CAP activated → CAP binds to CAP region of promoter → RNAP binds at promoter → high transcription

trp Operon

tryptophan present → trpR encodes trp repressor → trp repressor + tryptophan → no RNAP binding to promoter → inactive operon → no transcription; tryptophan absent → inactive trp repressor → RNAP binds to promoter → high transcription; negative repressible

Transcription Unit

5’ UTR + exons + introns + 3’ UTR

Promoter Proximal Region

region adjacent to promoter containing promoter proximal elements (regulatory sequences)

Enhancers

sets of regulatory sequences that bind to particular activators

Mediator

large coactivator that forms bridge between activators at enhancer & proteins at promoter & promoter proximal region to form DNA loop

Activator

increases rate of transcription; attracts, positions, & releases RNAP; accelerates binding & assembly of general transcription factors; attracts coactivators

Repressor

masks activation site, interferes w/ general transcription factors, & remodels chromatin to decreases rate of transcription

MicroRNAs (miRNAs)

small regulatory RNAs transcribed from miRNA genes that are involved in RNA interference by regulating mRNA translation & stability

Short Interfering RNAs (siRNAs)

small regulatory RNAs produced from double stranded RNA that’s from viruses/transposons & are involved in RNA interference; used as cell defense mechanism

Blending Theory of Inheritance

prevailing thought prior to Mendel; offspring look a little like their moms & a little like their dads

Particulate Theory of Inheritance

Mendel’s theory establishing that characteristics passed to offspring in form of discrete hereditary factors referred to as genes

Reciprocal Cross

respective traits of male & female in 1 cross become respective traits of male & female in other cross; sexes of parents reversed to determine if trait inherited via autosomal, sex, or maternal effects

Test Cross

crossing dominant expressing individual w/ unknown genotype & homozygous recessive individual to determine unknown genotype

Self Cross

self fertilization

Back Cross

crossing F1 & P to isolate desirable traits

Mendel’s Principle of Segregation

pairs of alleles segregate as gametes are formed; half of gametes carry 1 allele & other half carry other

Mendel’s Principle of Independent Assortment

orientation of 1 pair of homologous chromosomes at metaphase has no influence on orientation of any other pair of homologous chromosomes; alleles on separate chromosomes sort independently of each other

Incomplete Dominance

expression of 2 extreme alleles in heterozygote as intermediate phenotype

Codominance

complete & simultaneous expression of both alleles for same characteristic in heterozygote

Epistasis

antagonistic interaction between genes so that 1 gene masks/interferes w/ expression of another

Recessive Epistasis

homozygous recessive alleles at 1 locus mask/suppress phenotypic expression of alleles at other locus; phenotypic ratio of F2 = 9:3:4

Dominant Epistasis

dominant allele at 1 gene locus masks/suppresses expression of alleles at other locus; phenotypic ratio of 12:3:1

Polygenic Inheritance

phenotypic characteric caused by 2+ genes

Pleiotropy

single gene influences multiple seemingly unrelated phenotypic traits/bodily systems

Thomas Hunt Morgan

established that genes were physically located on chromosomes; discovered sex linkage; studied fruit fly eye color

Alfred Sturtevant

undergraduate in Morgan’s lab; constructed first map of chromosome based on recombination frequencies from many crosses that resulted from crosses w/ incomplete linkage

Recombination Frequency

average # of crossovers between 2 alleles; higher recombination frequency indicates larger distance between genes on same chromosome; 50% RF indicates genes are on separate chromosomes or on same chromosome but so far apart that they segregate as if independent

Sex Linked Genes

genes found on chromosomes (X or Y) that determine sex

Chi-Square Test

statistical procedure that determines significance of difference between expected & observed results

Autosomal Recessive Inheritance

trait expressed when 2 identical copies of gene on nonsex chromosome inherits; often skips generations

Autosomal Dominant Inheritance

trait expressed when 1+ copies of gene on nonsex chromosome inherits; present in every generation; genetically present when gene is present

X-Linked Recessive Inheritance

trait expressed when all X chromosomes carry gene; more commin in men; no male → male transmission

X-Linked Dominant Inheritance

trait expressed when 1 X chromosome carries; more commin in females

Hardy Weinberg Law

reproduction alone doesn’t change allele frequencies; allele frequencies can be used to determine genotypic frequencies; single generation of random mating produces equilibrium genotypic frequencies

Hardy Weinberg Conditions

no mutation, no migration, large population, no selection (all organisms equally fit), random mating

Positive Assortative Mating

nonrandom mating pattern where individuals w/ similar phenotypes/genotypes mate more frequently than by chance

Negative Assortative Mating

nonrandom mating pattern where individuals w/ dissimilar phenotypes/genotypes mate more frequently than by chance

Inbreeding

mating of closely related individuals; increases frequency of homozygotes & decreases frequency of heterozygotes

Agents of Microevolution

mutation, migration, genetic drift, natural selection, nonrandom mating

Mutation

ultimate source of variability in population; increases variability

Migration

immigration & emigration

Immigration

movement of individuals into population that increases variability within population

Emigration

movement of individuals out of population that decreases variability within population

Genetic Drift

effect of chance on population’s gene pool; decreases variability

Founder Effect

genetic drift event that initiates allele frequency change in part of population

Bottleneck Effect

magnified genetic drift caused by natural event/catastrophe

Gene Flow

flow of alleles in/out of population due to individual/gamete migration

Morphological Species Concept

idea that all individuals of species share measurable anatomical traits that distinguish them from individuals of other species; only method that applies to all fossil species; subjective since it’s dependent on opinion about within vs. between species anatomical differences

Biological Species Concept*

group of interbreeding natural populations that are reproductively isolated from other groups; reproductive isolation is synonymous w/ lack of gene flow & speciation; not relevant to species that don’t reproduce sexually

Ecological Species Concept

views species in terms of its occupied ecological niche; applies to sexually & asexually reproducing organisms; subjective since it depends on opinion about niche limits; undermined by convergent evolution & niche overlap

Phylogenetic Species Concept

defines species as population clusters that emerge from same small branch & share recent evolutionary history; objective since it uses DNA sequencing data; may lead to oversplitting

Reproductive Isolating Mechanisms

biological characteristics that prevent gene pools of 2 species from mixing

Prezygotic Isolating Mechanisms

reproductive isolation mechanism that occurs before production of fertilized egg; ecological, temporal, behavioral, mechanical, gamete

Postzygotic Isolating Mechanisms

reproductive isolating mechanism that occurs after zygote formation by reducing fitness of hybrid individuals; inviability, sterility, breakdown

Ecological Isolation

species live in different habitats in same region

Temporal Isolation

species breed at different times of day/year

Behavioral Isolation

signals of 1 species aren’t recognized by other

Mechanical Isolation

differences in structure of reproductive organs or body parts physically prevent mating

Gamete Isolation

species have nonmatching receptors on gametes

Hybrid Inviability

hybrid offspring are incompletely developed

Hybrid Sterility

hybrid offspring can’t produce functional gametes

Hybrid Breakdown

hybrid offspring have reduced survival/fertility

Subspecies

local variants of species that usually interbread where geographical dsitributions meet (e.g. human races)

Clinal Variation

species distributed over large, environmentally diverse area may exhibit pattern of smooth variation in traits along cline; often from gene flow between adjacent populations adapting to slightly different conditions (e.g. northern hemisphere mammals)

Cline

geographical gradient

Ring Species

species w/ ring shaped geographical dstribution surrounding uninhabitable terrain; often from adjacent populations directlt exchanging genetic material; gene flow between distant populations occur only through intermediary populations (e.g. lungless salamander)

Allopatric Speciation

speciation that involves physical splitting of population, typically by geographic barrier

Adaptive Radiation

speciation when 1 species radiates to form several other species

Species Cluster

group of closely related, distinct species that recently diverged from common ancestor while being geographically isolated; often results from adaptive radiation

Sympatric Speciation

speciation resulting from reproductive isolation developing from distinct subgroups that arise within 1 population; common among plants

Habitat Differentiation

subpopulation begins exploiting new habitat/niche within same geographic area as original population

Polyploidy

individual w/ incorrect # of chromosome sets

Autopolyploidy

polyploidy resulting from error in mitosis/meiosis; gametes receive same # of chromosomes as somatic cell; self fertilization

Allopolyploidy

polyploidy from 2 closely related species hybridizing & forming polyploidy offspring; resulting in extremely rapid speciation

Beta Galactosidase

enzyme that metabolizes disaccharide lactose into 2 monosaccharides

Permease

enzyme that brings lactose/substrate into cell

Transacetylase

enzyme w/ no clearly defined function; associated w/ lac operon

Tryptophan

amino acid used in protein synthesis

Protein Processing & Degradation

regulation via proteasomes

Loss of Function Alleles

alleles that lead to nonfunctional or absent protein/RNA product

Null Model

predicts data expected if process isn’t working or when causative agent isn’t impacting situation

Gene Pool

used to predict results of random mating by assuming all gametes produce offspring at random