Protein synthesis Flashcards
what is transcription
when DNA is used to make RNA
what is translation
when RNA is converted to proteins
what is codon
specific 3 letter RNA sequence that codes for a specific amino acid
what do 4^2
4^3
mean
that since only four bases, if only 2 as exponent, then they are only 16 possible
if all 3 as exponent then 64 amino acids possible because AAA can also be same as GAG
What is the dictionary of genetic code
the rosetta stone of bio which shows which Codons translate for which proteins.
U A G C
U UGCA
G UGCA
A UGCA
C UGCA
what proteins code for start and stop
AUG = start
UAA
UAG
UGA stop
what is ambiguity
edundancy
no codon represents more than 1 amino acid
two codons can serve 1 amino acid
RNA restriction enzyme + details
first DNA must seperate
only one strand needed for template
In RNA only U not T
what links RNA nucleotides
RNA polymerase
what is inititiation
the “start working” signal called promoter
RNA polymerase attaches here
what does the promoter indicate also
also indicates which strand shall be synthesized
what happens in elongation
Second phase RNA gets longer and it peels off from DNA template and let the oignal 2 strands cometogetther
what is the termination
3rd phase
RNA reaches halt to specias sequences in DNA called terminator
Polymerase goes away
what is messenger
in bacteria, RNA can quickly be messenger and used
In us, RNA scrubbed feat
how is it different in eukayrotes
the messenger RNA is modified before it is sent to cytoplasm
what is cap and tail
tips of strand of MRNA that resist attack from cellular enzymes and help ribosomes recognize mRNA. They are just extra nucleotides
what also are introns and exons
introns code for nothing just come in the way of exons that do code for amino acids.
wht happens in RNA splicing
DNA contains introns and exons
RNAtranscribesalso introns and exons
Introns removed
EXONS SPLICED together to form mRNA with cap and tail
now can leave nucleus
what does translation require
mRNA
enzymes
ATP
RIBOSOME
tRNA
translation requires what
it requires interpreter who can recognize the words of a language and convert them to another.
translation requires the codons to one letter amino acid and a molecular interpreter called tRNA
what does cell need to make proteins
a supply of amino acids obtained from food other chemicals
what do tRNA do
they match amino acids to appropriate codons to form polypeptide
two tasks
pick up appropriate amino acids
recognize appropiate codons in mRNA
what does tRNA look like
single stranded RNA of 80 nucleotides
twists and folds upon itself forming several double stranded regions in which short stretches base pair with other sstretches. at one end is a special triplet called anitcodon . it is complementrary to a codon triplet in mRNA. at other end is amino acid attachment side carrying amino acid corresponding to codon. slightly different version for each amino acid or codon
what is ribosome
they are organelles that coordinate the functioning of mRNA and tRNA and make protein
2 subunits
ribosomes are made of protein and rRNA (ribosomal RNA)
a fully assembled ribosome has binding site for mRNA on its small subunit and binding sites for tRNA on its large subunit.
P site holds tRNA carring the growing poypeptide
while another site called A holds tRNA carring the next amino acid to be added to the chain. the ribosome acts like a vise, holding P A and mRNA together. ribosome can connect the amino acid from A to P site to the growwing polypeptide
what happens in initiation
brings mRNA, the first amino acid with its attached tRNA and two subunits of a ribosome . nucleotides end and start, but along with cap and tail in eukayorotes only, they help mRNA bind to ribosome.
the process determines exactly where translation will begin so mRNA codons will be translated exactly into the correct sequence of amino acids. later occurs in two steps
what happens in elongation
amino acids are added one by one to first amino acid
each addition occurs in 3 step process
codon recognition: the anticodon of an incoming tRNA molecule pairs with the mRNA codon in A site of ribosome
what happens in peptide bond formation
the polypeptide leaves the tRNA in the P site and attaches to the amino acid in A site . ribosome makes peptide bond. Now one more amino acid.
what is translocation
the P site in tRNA now leaves the ribosome and ribosome translocate (moves) the remaining tRNA , carrying the polypeptide to the P site. the mRNA and tRNA move together, the movement brings a next mRNA codon to be translated and the process can start again
how termination happens.
elongation continues until a stop codon reaches the ribosome A site. they are UAA, UAG, UGA dont code for anything but tell ribosome to stop. the polypeptide is freed and ribosome splits in 2.
what are mutations
Normal hemoglobin: CTT
mRNA: GAA
protein GLU
Mutant hemoglobin: CAT
mRNA GUA
protein Val
what is a mutation
any change in the nucleotide sequence of DNA is mutation.
can involve large regions of a chromosome or just a single nucleotide pair as in sickle cell allele.
silent mutation
when a base a substituiton goes from GAA to GAG, no change because coding for same protein
what are missense mutation
if GGC to AGC
then SEr to GLY
may have little or no effect
but may causes major change in protein
still substitution
what are effects of substitution
can lead to improved protein with other capabilities enhance the success of the mutant organism and its descendants. Mutations are BADoften!!
what are nonsense mutations
if an AGA codon is turned into a stop codon, it will be terminated, turned not functioning protein
what happens in insertion and deletion
mutations involving insertion or deletion of one or more nucleotides in a gene often have disastrous effects
mRNA is read a series of triplets and adding or deleting may alter reading frame(triplet grouping) of genetic message. all nucleotides “downstream” will be regrouped in different codons.
will be nonfucntional and same as inserting or deleting
what is mutagenesis
creation of mutations occur variously. errors during DNA replication or recombination are sponatneous
other sources of mutation are physical and chemical agents called mutagens.
common are high energy radiation X ray. UV
incorrect base-pair with DNA
carcinogens
mutations that cause cancer.
sunscreen etc
what is evolution
mutations creat diversity
which codons code for start and end
AUG= start
UAA= end
UAG=end
UGA=end
