U1.3 Gene expression Flashcards
What does gene expression involve?
Transcription and translation of DNA sequences.
Are a lot or a few of the genes in a cell expressed?
A fraction (a few).
What are the three types of RNA?
Messenger (mRNA), transfer (tRNA), and ribosomal (rRNA).
What do RNA nucleotides comprise of?
Ribose sugar, phosphate, and one of four bases: cytocine, guanine, or uracil.
What is the function of mRNA?
To carry a copy of the DNA code from the nucleus to a ribosome.
What happens to mRNA in the nucleus?
It is transcribed from DNA.
What happens to mRNA in the cytoplasm?
It is translated into proteins by ribosomes.
What is a codon, and what does it code for?
A triplet of bases on mRNA, codes for a specific amino acid.
Why is tRNA folded?
Due to the complementary base pairing.
State the function of tRNA.
To carry a specific amino acid to a ribosome.
What two things are attached to the ends of tRNA?
An anticodon at one end and an attachment site for a specific amino acid at the other.
What do ribosomes comprise of?
rRNA and proteins.
What is transcription?
The production of a copy of the genetic code on DNA as mRNA which can move out of the nucleus.
What does RNA polymerase do?
It moves along DNA, unwinding the double helix and breaking hydrogen bonds between bases.
How is the primary transcript of mRNA made?
From RNA nucleotides using complementary base pairings.
What base is complementary to adenine in RNA?
Uracil- it replaces thymine.
How is a mature transcript formed?
The primary mRNA transcript is spliced to remove the introns and join the remaining exons together.
What are introns?
Non-coding regions of the primary mRNA transcript.
What are exons?
Coding regions of the mRNA primary transcript.
What sequence are exons found in the mRNA mature transcript?
They remain in the same sequence.
Where does translation of mRNA into a polypeptide occur and what does it involve?
At a ribosome and it involves tRNA
What does sequential translation of mRNA codons ensure?
The correct sequence of amino acids in a polypeptide.
Where does translation start and end?
Starts at a “start” codon and ends at “stop” codon on the mRNA mature transcript.
How do tRNA anticodons bind to mRNA codons?
By complementary base pairings.
