Ch. 15 Flashcards
set of 3 nucleotides that specifies a particular amino acid
codon
information flows in one direction: DNA to RNA to protein
central dogma
flow of info from DNA to RNA
transcription
flow of info from RNA to protein
translation
each enzyme of the arginine pathway was encoded by a separate gene
one gene - one polypeptide hypothesis
how many possible codons?
64
stop codons
UAA, UGA, UAG
start codon
AUG
Template strand
strand of DNA
antisense strand
3’ to 5’
coding strand
complementary to template strand
sense strand
5’ to 3’
transcription initiation
rna ploymerase idetneifies where to begin transcription - at the promoter region
transcription elongation
rna nucleotides are added to the 3’ end of RNA strand
Transcription termination
RNA polymerase stops translation when it encounters stop codon
mRNA
messenger
carries info from RNA that encodes protein
rRNA
ribosomal
structural component of ribosome
tRNA
transfer
carrier amino acids to the ribosome for translation
snRNA
small nuclear
involved in pre-RNA splicing
transcription buble
moves at rate of 50 nucleotides/sec
consists of:
RNA poly
DNA template
growing RNA transcript
RNA pol I
transcribes tRNA
RNA pol II
transcribes mRNA and some snRNA
RNA pol III
transcribes tRNA and some other small RNA
common promoter region
TATA box
for transcript to leave the nucleus into cytoplasm it needs
5’ cap
3’ poly-A tail
removal of non-coding sequences (introns)
organelle responsible for removing introns and splicing exons together
splicesome
non-coding sequences
introns
sequences that will be translated
exons
what is alternative splicing?
recombination of different exons
importance of alternative splicing
major source of genetic diversity in eukaryotes
final 3-D structure of tRNA
L-Shaped structure
tRNA carry
amino acids to ribosome to make polypeptide
P Site
binds the tRNA attached to growing peptide chain
A site
binds the tRNA carrying next amino acid
E site
binds the tRNA that carried the last amino acid
2 primary functions of the ribosome
decode mRNA
form peptide bonds
enzyme component of the ribosome that forms peptide bonds between amino acids
peptidyl transferase
translation initiation
joining of 5’ end of mRNA with large and small ribosomal subunit
first tRNA molecule in translation is at
P Site
translation elongation
requires elongation factors
addition of amino acids
charged tRNA binds to A site
peptidyl transferase forms peptide bond
ribosome moves down the mRNA in 5’ to 3’ direction
wobble phenomenon
allows less stringent pairing between 3’ base of the codon and the 5’ base of anticodon
translation termination
elongation continues until stop codon
stop codons recognized by release factors
point mutation
alter single base
classification of mutation
silent mutation
substitute one base for another doesn’t change amino acid
missense mutation
substitutes one base for another cause coding for another amino acid
nonsense mutation
subsites one base for another, coded for stop codon
frameshift mutation
caused by insertion or deletion of a single base
triple repeat expansion mutation
sequence of 3 DNA nucleotides are repeated many times
chromosomal mutation
change structure of chromosome
deletion
part of chromosome is lost
duplication
part of chromosome is copied
inversion
part of the chromosome in reverse order
