44 terms

Molecular Mechanisms - Molecular Genetics

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substitution
small change in DNA basepair where one nucleotide is replaced with another
reading frame
triplet grouping of genetic message
frameshift mutation
when number of nucleotides added/lost is not multiple of 3; this alters reading frame
insertion
addition of >=1 nucleotide pairs in gene
deletion
loss of >=1 nucleotide pairs in gene
missense mutation
altered codon codes for different amino acid (may have effect on protein fxn)
nonsense mutation
changes amino acid codon into stop codon --> truncated protein that is digested by cell; lethal at embryonic stage
silent mutation
altered codon codes for same amino acid; no effect on protein fxn
transposon
DNA segment that naturally moves around genome (transposable elements, mobile genetic elements); no known function
Chargaff
ratio - A = T and C = G
Watson and Crick
inspired by proteins' alpha-helical structure; determined rules for base pairing (AT GC judging by width of purine-pyrimidine)
mRNA
carries info specifying amino acid sequences from DNA to ribosomes; made by RNAP II
tRNA
carries amino acid to make pp chain; made by RNAP III
codon
mRNA nucleotide triplets that code for amino acids
anticodon
complementary sequence on tRNA
Shine-Dalgarno sequence
helps find and bind to 5' end (mRNA has one, rRNA on ribosome small subunit has anti-one)
methionine
starting amino acid in eukaryotes
methionine
starting amino acid
release factor
protein that binds to A site; adds H2O to ppt, hydrolyzed from tRNA and released
helicase
enzyme that disrupts H bonds between two strands of DNA to separate the template DNA strands at the replication fork
SSBP
protein that binds to unwound single-stranded regions of DNA to keep the template strands apart during replication
topoisomerase
enzyme that can break bonds in DNA and then reform the bonds (e.g. DNA gyrase)
primer
a short segment of RNA needed to initiate DNA replication
primase
an RNA polymerase (RNAP) which synthesizes the primer by adding ribonucleotides that are complementary to the DNA template
polymerase
enzyme that makes polymers
DNA Polymerase III
elongates and proofreads daughter DNA strands
pyrophosphate
last two phosphate groups hydrolyzed to form this when DNAP III adds nucleotides
DNA Polymerase I
replaces RNA primer with DNA nucleotides
leading strand
synthesized continuously
lagging strand
synthesized in short, discontinuous segments of 1000-2000 nucleotides (Okazaki fragments)
Okazaki fragment
short DNA segments formed on lagging strand
DNA ligase
joins broken pieces of DNA by catalyzing phosphodiester bonds
DNA termination
happens when replication reaches end of chromosome, OR bubble/fork meets another
origin of replication
special site on DNA where replication begins
exonuclease
Mechanism in place to proofread errors as DNA is being replicated; binds to ends of nucleotide chain (5' or 3'); hydrolyzes phosphodiester bond, which releases last nucleotide added
Central Dogma of Biology
snRNP
binds to splice site, excises introns and rejoins exons
spliceosome
snRNP + other proteins
wobble hypothesis
third base of mRNA codon can change and still code for same amino acid
mutation
change in genetic info of organism
transcription
(genetics) the organic process whereby the DNA sequence in a gene is copied into mRNA
translation
decoding of a mRNA message into a polypeptide chain
5' to 3'
Direction all new genetic material is made
replication fork
a Y-shaped region where the parental strands of DNA are being unwound