D1.2 Protein Synthesis Flashcards
transcription definition
synthesis of messenger RNA using a DNA template
what is rna polymerase
enzyme that catalyses the synthesis of RNA molecules from a DNA template
where does transcription occur
cytoplasm for prokaryotes
nucleus in eukaryotes
process of transcription simple
part of dna unwinds because hydrogen bonds between complementary base pairs break
complementary copy of code from gene is made by building mRNA
RNA nucleotides pair up with complementary bases on unzipped DNA molecule
double stranded dna re-formed when hydrogen bonds between mRNA and DNA strands break
coding strand `
strand of dna that carries the genetic code
not used as template during replication
template strand
opposite dna strand which doesnt carry genetic code
used during transcription to produce mRNA
complementary to coding strand of DNA
role of hydrogen bonds in transcription
broken in dna to unzip it
formed between mRNA strand and DNA strand for complementary base pairing
which strand is transcribed to form MRNA molecule
template strand
to get an rna transcript of coding strand
why is dna is a very stable molecule
due to hydrogen bonding between the DNA bases of the 2 strands and the strong phosphodiester bonds between adjacent nucleotides in each strand
what does sugar phosphate backbone ensure
ensures stability of base sequence
why is stability important
so that genetic code is not prone to spontaneously breaking or changing
allows dna to act as reliable templates for transcription
gene expression
the process by which the information encoded in a gene is used to direct the synthesis of a protein molecule
what to specialised cells do to match requirements of cell
switch them on or off
which genes get switched on
genes that are expressed and undergo transcription and translation
which genes get switched off or silenced
genes that are not expressed and do not go through transcription or translation
translation definition
the information. of mRNA is decoded into proteins
involves taking the genetic code from the mRNA and synthesising a polypeptide
where does translation occur
in the cytoplasm
when does translation occur
after transcription as the mRNA template comes from transcription
what are the parts of a ribosome
2 - big and small
what are ribosomes made of
protein and rRNA
ribosomal rna
where in a ribosome does mRNA bind to
small subunit
where in a ribosome does tRNA bind to
2 of them bind simultaneously to the large subunit
what does complementary base pairing in translation happen between
codons and anticodons
triplet
a sequence of 3 DNA bases that codes for a specific amino acid
codon
a sequence of 3 mRNA bases that codes for a specific amino acid
what is codon complementary to
triplet
Anticodon
a sequence of 3 tRNA bases that are complementary to a codon
what does tRNA carry
the appropriate amino acid to the ribosome
what commands to codons carry
start and stop
to start and stop translation when the polypeptide chain is complete
what are the stop codons
UAA
UAG
UGA
sites of an amino acid
A - aminoacyl
P - pepticyle
E - exit site
how many amines are there to be coded for
20
how many bases for one amino
3
what translations 3 base sequence to an amino acid sequence
tRNA
to what are the amino acids bonded
bonded covalently to the site at the bottom of tRNA
only 1 particular amino can be bonded for one particular tRNA
why are enzymes important in attaching amino to tRNA
enzymes are specific to amino acids which is a way of making sure that the correct amino acids are used in the right sequence
how are amino acid completes held in position
temporarily held in position by hydrogen bonds
the genetic code ideas
- common original of life on earth
- process of reading the code and process of protein synthesis through use of ribosomes and RNA are very similar in prokaryotes and eukaryotes
universality of genetic code
means that almost every organisms uses the same code
genetic info is transferable between species
reason why genetic engineering is possible
result of start and stop codons
reads dna correctly and produces the correct sequences of amino acids that it requires to function properly
how many codons possible
64 because 4 bases (ATCG)
4^3=64
degenerate
multiple codons can be coded for the same amino acid
why can codes be degenerate
because 20 amino acids but 64 codons possible
can limit effect of mutation s
how can the amino be read - table
first convert DNA to mRNA or any RNA
check table from that and name it
how is the polypeptide chain elongated
- during translation the ribosome moves in steps along mRNA
- in each step the ribosomes moves 3 bases along the mRNA
- repetition leads to a polypeptide being formed and elongated
what are gene mutations
copying errors that take place when DNA is replicated during synthesis and interphase
what mutations are not inherited
mutations preset in normal body cells are not inherited and eliminated when affected cells die
what mutations are inherited
mutations within gametes are inherited by offspring
point mutations
when one base in the DNA sequence is altered
can result in changed amino acid at location
examples of point mutation
sickle cell disease
why is sickle cell disease caused
caused by a single point mutation within the gene that codes for alpha global peptide in haemoglobin
most humans have the allele HbA
mutation results in HbB
effects of sickle cell disease
have limited oxygen carrying capacity
blocks the capillaries and limit flow for normal RBCs
