Gene Expression Flashcards
(27 cards)
What does gene expression involve?
The transcription and translation of certain genes DNA sequences to make a specific protein
How many genes are expressed in a (specialised) cell
Only a fraction of genes are expressed
What are the three types of RNA transcription and translation involve?
mRNA
tRNA
rRNA
What is the structure of RNA
Single stranded
What is RNA composed of?
Nucleotides
What are the nucleotides made up of?
Ribose sugar, phosphate and a base
What are the base pairs in RNA?
Guanine-cytosine
Adenine-uracil(instead of thymine)
What does messenger RNA(mRNA) carry?
Where is it carried from and to?
(FUNCTION)
Carries a copy of the DNA code
From the nucleus to the ribosome
What is mRNA transcribed from?
What is mRNA translated into?
Transcribed(copied) from the DNA in the nucleus
Translated into proteins by ribosomes in the cytoplasm
What is each triplet of bases on the mRNA molecules called?
What do they code for?
They’re called a codon
Codons code for a specific amino acid
Why does transfer RNA(tRNA) fold?
What does it then carry and where does it carry it to?
It folds due to complementary base pairing
It carries its specific amino acid to the ribosome
What is the structure of tRNA?
(Two things)
A tRNA molecules has an anticodon(exposed triplet of bases) at one end and an attachment site for a specific amino acid at the other end
What does ribosomal RNA(rRNA) and proteins form
The ribosome
What are the two roles of RNA polymerase in transcription of DNA?
1) RNA polymerase moves along the DNA unwinding the double helix and breaking hydrogen bonds between bases
2) RNA polymerase synthesises(copies) the DNA code which is called a primary transcripts and is made of mRNA from RNA nucleotides using complementary base pairing
Results in primary mRNA transcripts
Where do the two roles of RNA polymerase in transcription take place?
The nucleus
What are the coding and non coding regions of the primary mRNA transcript?
Non coding-introns
Coding-exons
What does RNA splicing form?
Mature mRNA transcript
What happens to the introns and exons during RNA splicing
Introns are removes and the exons that are left join to form the mature mRNA transcript
Is the order of the exons changed during splicing?
No it remains unchanged
What is alternative RNA splicing?
When different proteins are expressed from one gene
What happens during alternative RNA splicing?
Different mature mRNA transcripts are produced form the same primary transcript, depending on which exons are retained
What type of RNA is involved in the translation of mRNA into a polypeptide(chain of amino acids)?
Where does this translation take place?
tRNA
At a ribosome
What are the 3 stages of translation of mRNA?
1) the translation begins at a start codon and ends at a stop codon
2) the anticodons on the the tRNA bond to codons on mRNA mature transcript by complementary base pairing, translating the genetic code into a sequence of amino acids
3)peptide bonds join the amino acids together, each tRNA then leaves the ribosome as the polypeptide is formed (amino acids are linked by peptide bonds to form polypeptides)
When polypeptide chains fold what to they form?
The three dimensional shape of a protein, held together by hydrogen bonds and other interactions between individual amino acids
