protein synthesis Flashcards
what is a gene
the base sequene of DNA that codes for the amino acid sequence of a polyppetide, a functional RNA.
how does RNA differ from DNA
RNA has a U base instead of T base
what are the 3 types of RNA
-messenger RNA. transfer RNA. ribosomal RNA.
what is a codon
3 adjacent bases on the MRNA
what is mRNA
a single polynucleotide strand. mRNA carries the genetic code from the DNA in the nucleus to the cytoplasm/ribosomes, where its used to make a protein during translation.
what is tRNA structure
a single polynucleotide strand thats folded into a clover shape. has an anticodon at one end, and amino acid binding site at the other end
how is tRNA held in a clover shape
hydrogen bonds between specific base pairs hold the molecule in this shape
where do u find codons
in mRNA
where do u find anti codon
in tRNA
where is mRNA made
the nucleus, during transcription
where is tRNA found
the cytoplasm
what is tRNA for
carries the amino acids that are used to make proteins to the ribosomes
what is special between anticodons on tRNA and codons on mRNA
they are complimentary to one another
what is rRNA
it forms the 2 subunits in a ribosome, along w proteins
what does rRNA do
the ribosome moves along the rRNA strand during protein synthesis. the rRNA in the ribosomes helps to catalyse the formation of peptide bonds between the amino acids
what is the genetic code
the triplet code - ecah amino acid is coded for by a sequence of 3 bases
where are proteins made
ribosomes
what are the 2 stages of protein synthesis
transcription + translation
what does DNA code for
proteins
Why does DNA convert to MRNA
DNA (codes for proteins) is too big to leave the nucleus so cannot travel to ribosomes
What is the process of DNA turning to MRNA called
Transcription
Where does transcription occur
Nucleus
What are the 5 steps of transcription
1 - DNA helicase attaches to DNA at the beginning of a gene
2 - This causes unwinding of DNA helix and breaking of H bonds between the two DNA strands
3 - The template strand is used to make an MRNA copy of the DNA. U REPLACES T
4 - Free MRNA nucleotides line up by complementary base pairing next to exposed DNA bases on the template strand
5 - RNA polymerase joins the sugar phosphate backbone of the new MRNA molecule being made.
(after becoming functional the functional mrna leaves the nucleus + travels to a ribosome)
What are the two separated strands called
coding strand and template strand
What are introns
Non coding DNA
What is pre MRNA and why is is not functional huh
introns are located in the MRNA duh isis. introns make it unfuctional
Whar are exons penchodah
Coding DNA
HOW do u make functional MRNA
INTRONS ARE CUT OUT OF THE MRNA BEFORE IT LEAVES THE NUCLEUS. THE MRNA IS ALSO CAPPED BEFORE IT LEAVES TO PREVENT IT FROM BEING DAMAGED IN THE CYTOPLASM
when does translation happen
once the mrna leaves the nucleus and attaches to a ribosome (or on the RER)
what are the 9 steps for translation
1 - the genetic code on the MRNA will be used to assemble a corresponding chain of amino acids
2 - the MRNA attaches to a ribosome (free or on RER), every group of 3 bases on the mrna is called a codon
3 - trna molecule contain triplets of bases at one end called anticodons. these line up next to the codons on the MRNA by complementary base pairing
4 - the other end of the TRNA molecule has a specific amino acid attached
5 - the ribosome can hold 2 TRNA molecules in position at the same tie allowing their amino acids to join by a peptide bond
6 - the first TRNA molecule now leaves the ribosome, leaving its amino acid behind, and another TRNA arrives with its amino acid
7 - the ribosome moves along so that the next 2 TRNA molecules are in position allowing their amino acids to join then the 2nd TRNA molecule moves away and so the process continues
8 - this happens untila stop codon on the MRNA is reached, signaling the polypeptide is now complete
9 - the polypeptide is then released into the cytoplasm, this is the primary protein structure, and is then built up further into a complete functioning protein.
how can lots of the same polypeptide be made
if several ribosomes move along the same piece of MRNA at once
what does a degenerate code mean
code is non overlapping what does this mean
it means base triplets do not share their bases, each triplet is different from the next (GUC/UCA).
with the bases G U C, what orders would make them overlappin
GUC/UCU/CUC
code is universal, what does that mean
what are the 3 natures of the genetic code
degenerate, non overlapping, universal
what is splicing
removing introns
spliced pre MRNA =?
mrna
