genetics test 3 part 2

germinal mutation

egg or sperm, passed to offspring

somatic mutation

body cell, cannot be passed down

point mutation

change in single nucleotide

transition

one purine replaces another, same with pyrimidine

transversion

purine replaces pyrimidine

missense mutation

change a codon to code for another amino acid

nonsense mutation

changes a codon to a stop codon

silent mutation

DNA changes but the amino acid stays the same

neutral mutation

mutation has no significant effect on function

frameshift mutation

insertion or deletion of codon

purines

AG, 2 rings

pyrimidines

CT, 1 ring

amorphic

absent

hypomorphic

low function

hypermorphic

high function

antimorphic

interferes with function

neomorphic

new function

forward mutation

wild type to mutant

reverse mutation

mutant returns to wild type, restore function

mutagen

increases mutant frequency

mutational hotspot

DNA site where mutations are more frequent

polar mutation

affects expression of downstream genes

thymine dimers

UV induced covalent links between adjacent thymines that distort DNA

photolyase

use light energy to reverse UV induced pyrimidine dimers

AP endonuclease

cuts DNA backbone at AP site

Glycosylase

removes damaged base

excision repair

removes damaged DNA and replaces it using intact strand as a template

mismatch repair

corrects incorrectly paired bases left behind after DNA replication

specific locus test

estimates mutation frequency by examining mutations at known genetic loci

replica plating

transfers pattern of colonies to new plates to identify mutations

1 gene - 1 enzyme

each gene specifies an enzyme

intragenic recombination

recombination between different sites within the same gene, restoring functional arrangement

cis-trans test

tests whether 2 recessive mutations are in the same or different genes

cistron

segment of DNA that encodes a single polypeptide chain or functional RNA molecule

complementation

2 mutations restore the wild type

operon

genes controlled together by shared regulatory DNA

inducer

molecule that turns on gene expression

inducible

gene system normally low or off

polycistronic

1 mRNA contains coding regions for multiple proteins

repressor

protein that decreases transcription by binding regulatory DNA or blocking transcription

operator

regulatory DNA site where repressor can bind

promoter

DNA sequence where RNA polymerase binds to initiate transcription

constitutive expression

gene is expressed continuously or independently of a specific regulatory sequence

cis-acting

DNA sequence that affects genes on the same DNA molecule

trans-acting

diffusible product that can act on other DNA molecules

negative control

a repressor inhibits transcription

positive control

an activator increased transcription

allosteric protein

protein whose function changes when a molecule binds at a regulatory site, changing its activity

cis-dominant

a regulatory effect limited to the linked DNA molecule

lactose present

lac genes can turn on

tryptophan present

trp genes turn off

CAP

activator protein that helps RNA polymerase transcribe certain operons efficiently