Chapter 10 Flashcards
how does a mutant phenotype arise?
from a change in the protein’s amino acid sequence
transcription
information in a DNA sequence is copied into a complementary RNA sequence
translation
RNA sequence is used to create the amino acid of a polypeptide
template strand
transcribed to produce an RNA strand by complementary base pairing
mRNA
processed in nucleus and moves to the cytoplasm
ribosome
protein synthesis factory
rRNA
one of them catalyses a peptide bond formation between amino acids to form a polypeptide
tRNA
can bind specific amino acid and recognise a specific sequence of nucleotides in mRNA
how many kinds of RNA polymerases are there in bacteria and archaea?
just one
how many kinds of RNA polymerases are there in eukaryotes?
several kinds
do RNA polymerases require a primer?
no
promoter
a special DNA sequence to which RNA polymerase binds very tightly
transcription initiation site
part of the promoter where transcription begins
elongation
RNA polymerase unwinds the DNA and reads the template strand in the 3’ to 5’ direction
how does RNA polymerase add new nucleotides to the RNA molecule?
by complementary base pairing with nucleotides in the template strand of the DNA
how is the termination of transcription specified?
by particular base sequences
coding regions
sequences within a DNA molecule that are eventually translated as proteins
introns
noncoding sequences that interrupt the coding region
exons
transcribed regions that are interspersed with the introns
pre-mRNA
primary mRNA transcript
nucleic acid hybridisation
allows us to locate introns within a eukaryotic gene
probe
single-stranded nucleic acid from another source
RNA splicing
removes the introns and splices the exons together
consensus sequences
short stretches of DNA that appear with little variation in many different genes
snRNPs
bind the consensus sequences
spliceosome
a large RNA-protein complex that cuts pre-mRNA, releases introns, and joins the ends of the exons together
5’ cap
added to the 5’ end of the pre-mRNA as it is transcribed to facilitate the binding of mRNA to the ribosome for translation
poly A tail
added to the 3’ end of the pre-mRNA at the end of transcription
codons
genetic information in an mRNA molecule, specifies a particular amino acid
start codon
the initiation signal for translation (methionine)
stop codons
terminate translation (UAA, UAG, and UGA)
redundant code
more than one codon for the amino acid
ambiguous code
single codon specifies two or more different amino acids
silent mutatinos
can occur because of the redundancy of the genetic code
missense mutations
result in a change in the amino acid sequence
nonsense mutations
result in a premature stop codon
frame-shift mutations
result from the insertion or deletion of one or more base pairs within the coding sequence
what are the functions of tRNA?
bind to specific enzyme, bind to mRNA, interact with ribosomes
anticodon
triplet of bases at the midpoint on the tRNA chain which is complementary to the mRNA codon
wobble phenomenon
cell can get by with two-thirds of the total number of RNA species
what does the large subunit of eukaryotic ribosomes contain?
3 different ribosomal RNA molecules and 49 protein molecules
what does the small subunit of eukaryotic ribosomes contain?
1 rRNA molecule and 33 proteins
A site
where the charged tRNA anticodon binds to the mRNA codon
P site
where the tRNA adds its amino acid to the polypeptide chain
E site
where the tRNA resides before being released from the ribosome
what is the order of the three binding sites in ribosomes?
A, P, E
initiation complex
consists of a charged tRNA and a small ribosomal subunit
what does the large subunit catalyse?
breaks the bond between methionine and its tRNA in the P site, and catalyses the formation of a peptide bond between the methionine and the amino acid attached to the tRNA in the A site
peptidyl transferase activity
breaks and reforms peptide bond
ribozyme
RNA and enzyme
what happens when a stop codon enters the A site?
it binds a protein release factor, allowing for hydrolysis of the bond between the polypeptide chain and the tRNA in the P site
polyribosome
assemblage consisting of a strand of mRNA with its beadlike ribosomes and their growing polypeptide chains
where does protein synthesis begin?
on free ribosomes floating in the cytoplasm
signal sequence
short stretch of amino acids that indicates where in the cell the polypeptide belongs
proteolysis
the cutting of a polypeptide chain
glycosylation
addition of carbohydrates to proteins to form glycoproteins
phosphorlyation
addition of phosphate groups to proteins and is catalysed by protein kinases
