NEW 3 Flashcards
Amino acid sequence of protein is written…
in DNA
RNA has a series of…
NONoverlapping three base “words” called codons
Transcription rewrites the DNA —> RNA, substituting..
U for T
Uracil for Thymine
A + U in RNA**
Each amino acid is…
specified by codon
__ codons are possible
64
Some amino acids have more than…
one possible codon
Genetic code decides how codons are…
translated into amino acids
Three nucleotides specify ONE…
amino acid in the genetic code
61 codons correspond…
to amino acids
AUG
- START of TRANSLATION
- codes for methionine
3 “stop” codons signal…
end of translation
Genetic Code
is universal, shared by organisms from simple to complex
RNA molecule is _______ from gene
transcribed
RNA polymerase
RNA nucleotides linked by transcription enzyme
Promoter
nucleotide sequence signal = “start transcribing”
Cap and tail of extra nucleotides are added to ends of the mRNA to…
- help RNA leave nucleus
- protect RNA from damaging enzymes
- help RIBOSOMES bind to mRNA
INITIATION
RNA polymerase CONNECTS to promoter
ELONGATION
- amino acids added ONE by ONE
- RNA grows longer
Removes introns and joins exons producing continuos coding sequence
RNA splicing
TERMINATION
- RNA polymerase reaches base in DNA template called TERMINATOR, signals the END of gene
- polymerase detaches from RNA molecule and gene
tRNA molecules
picks up _____ _____ and brings them to _______
amino acids
cytoplasm
Translation - can be divided into same…
three phases as transcription:
1 ) initiation
2) elongation
3) termination
Ribosomes are composed of…
ribosomal rRNAs and protein
Ribosomes have binding sites for…
mRNA and tRNAs
Messenger RNA (mRNA)*
-encodes amino acid sequence
tRNA molecules use special…
TRIPLET of bases called anticodon
P site
first tRNA occupies the p site, which holds growing polypeptide chain
A site
available for next tRNA (transfer RNA)
Translation termination
- ribosome reaches STOP codon
- completed polypeptide is released from the last tRNA
- ribosome goes back into separate subunits
3 types of Mutations
1) base substitution
2) insertions
3) deletions
anticodon
- triplet bases
- complements codons in mRNA
Any change in nucleotide sequence of DNA
mutation
Base substitution
1) have NO effect, silent mutation
2) leads to IMPROVED protein that helps enhance survival
3) nonsense mutation
Mutations can involve large chromosomal regions or…
just single nucleotide pair
Mutations caused by…
random errors during DNA replication
Mutagens: cause _______
mutations
ex. high energy radiation, chemicals
Nonsense mutation
CHANGES amino acid into stop codon
Insertions & Deletion mutations
- alter reading frame
- produce NONFUNCTIONAL polypeptide
- change in amino acid sequence downstream of mutation
Codons are ____ to each other, NO gaps in between
next
mRNA contains INtrons…
interrupts sequences that separates exons
