exam 3

polymorphism

common rare mutation within a population

variant

relatively rare mutation within a population

reversion

restoration of the original phenotype to a mutant

haploinsufficiency

single functional copy of a gene is not sufficient

pleotropic

single mutation that affects two or more seemingly unrelated traits

somatic mutations

mutations in non-reproductive cells - only affect a portion of an organism

germline mutations

mutations in reproductive cells - affect some of the offspring

silent mutation

no effect on protein

synonymous mutation

minimal effect on protein

evident mutation

clearly see a phenotypic change

amorph

null allele, a complete loss of function, usually recessive

hypomorph

partial or reduced function, usually recessive

hypermorph

increased function or expression

neomorph

protein has a new and different function

antimorph

activity that is dominant and opposite to the wild-type function; also known as dominant negative mutations

multimorphs

show multiple effects

non-conditional mutation

mutant phenotype present under all conditions

conditional mutation

mutant phenotype expressed only under certain conditions

spontaneous DNA damage

damage due to natural processes

induced DNA damage

damage from external sources

point mutation

change a base pair to a different base pair

transition mutation

purine → purine or pyrimidine → pyrmidine

transversion mutation

purine → pyrimidine or pyrimidine → purine

missense mutation

DNA change leads to change in amino acid

nonsense mutation

DNA change leads to formation of a transcriptional stop site

TAG

amber

TAA

ochre

TGA

opal

frameshift

insertion or deletion of 1 or more bases that is not a multiple of 3

deletion mutation

removal of a large section of a gene, entire gene, or multiple genes

insertion mutation

large amount of DNA added into gene - prevents normal function

inversion mutation

chromosomal rearrangement, affects multiple genes, not leaky, can revert

duplication mutation

have additional copies of a gene or region, due to unequal recombination events between daughter chromosomes

depurination

purine is removed by hydrolysis resulting in an apurinic site

depyrimidation

pyrimidine is removed by hydrolysis resulting in an apyrimidinic site

deamination

amine group on cytosine, or 5-methylcytosine can be removed

oxidation

reactive forms of oxygen produced during metabolism react with and alter DNA bases

base analogues

compounds similar in structure to a DNA base that can be incorporated into DNA during replication

nitrous acid

deaminates bases

autonomous transposable elements

encode all enzymes needed to move

non-autonomous transposable elements

can only move if supplied with enzyme from another transposable element

pericentric

inversion includes the centromere

paracentric

inversion does not include the centromere

translocation

joining of non-homologous chromosomes

true reversion

mutation exactly restores original DNA sequence

pseudo-reversion

second mutation restores the original phenotype

interaction suppressors

• suppress mutations by restoring protein-protein interactions

• allele specific

bypass suppressors

turn on a new pathway (or upregulate another pathway) that eliminates the need for a particular gene

physiological suppressors

general changes in cell physiology suppress the effects of the original mutation

informational suppressors

• changes how the cell reads the information encoded in the mRNA

• misreading the mutant mRNA allows the production of a functional protein from the mutant gene

micronucleus

particle in a cell that contains nuclear DNA; it might contain whole chromosomes, or broken pieces of chromosomes

photolyase

cleaves TT dimers in the presence of visible light

MutS

binds to G-T mismatch

MutL

helps recruit Vsr to T:G mismatch

Vsr

• forms complex with MutS & MutL

• endonuclease

• cuts DNA backbone 5’ to the incorrect T

MutM

removes 8oxoG

MutY

removes A

MutT

degrades 8oxoGTP

synapse

point at which 2 DNA molecules held together by complementary base pairing between strands

heteroduplex

region of complementary base pairing in the synapse

translational coupling

mRNA secondary structure prevents binding of ribosomes unless previous region is being translated

catabolic operons

involved in the breakdown of sugars to provide energy for growth

anabolic (biosynthetic) operons

involved in the synthesis of various essential compounds, such as amino acids

effector molecules

bind a regulatory molecule and change its activity

inducers

bind to repressor or activator and allows initiation of transcription

corepressors

bind to a repressor molecule allowing it to block transcription

aporepressor

inactive repressor without bound corepressor

negative regulation

• repressor must release the DNA to allow for transcription

• may require the presence of a co-repressor to prevent transcription from occurring

positive regulation

• activator must bind the DNA to allow for transcription

• may or may not require the presence of an inducer molecule to activate activator protein

MacConkey lactose plates

pH sensitive dyes that turn colour if sugar is metabolized

X-gal

colorless compound that turns an intense blue colour when cleaved by β-galactosidase (product of lacZ)

lac operon

required for lactose metabolism

lacZ (β-galactosidase)

cleaves allolactose into useable sugar monomers

lacY (lactose permease)

allows lactose to enter the cell

lacA (transacetylase)

transfers acetyl group to galactose to prevent buildup in cell

lacI (repressor)

repressor protein binds lacO operator

CAP binding site

location where cAMP-CAP activator proteins at low glucose levels

promoter

location of RNA polymerase binding

lacO (operator region)

repressor binding location

glucose

cell’s preferred carbon source

Trp operon

encodes enzymes for synthesizing L-tryptophan

regulation by attenuation

transcription starts normally, but is terminated prior to transcription of the first structural gene of the operon