MCGB - Gene Expression Flashcards
What is the name given to the transformation of DNA to mRNA?
Transcription
What is the name given to the transformation of mRNA to proteins?
Translation
What is a gene?
A stretch of DNA with a chromosomal locus, sometimes also referred to as a unit of inheritance/transcription.
Where is the info for where to initiate/terminate transcription and translation stored?
In the genes.
Is a ribosome required for making RNA?
No, it is required for making a polypeptide.
What are the three stages of making a polypeptide from DNA called?
Initiation, elongation, termination.
Describe the three stages of DNA replication (initiation, elongation, termination).
I - recognition of the origin of replication.
E - DNA polymerase extends the strand in the 5’ to 3’ direction.
T - replication forks meet
Describe the three stages of transcription.
I - the promoter is recognised by the transcription factor
E - 5’ to 3’ chain growth
T - This is sequence dependent
What is a “promoter”?
A region of DNA that initiates transcription of a particular gene.
What is a TATA box?
A section of DNA in the promoter region that the transcription factor binds to, which causes transcription to start.
Does transcription travel towards or away from the promoter?
Away, and always the same direction on the same gene.
In what two ways is mRNA protected from degradation by exonucleases and other enzymes?
CAPPING (an altered base at the 5’ end) and TAILING (also called polyadenylation, lots of A bases are added to the end)
What does splicing remove from pre-mRNA?
It removes the introns as they do not code for proteins.
DNA is very stable. Why is RNA required to be less stable?
It must be able to be degraded when it is finished with.
What is a polyribosome (or polysome)?
A complex of an mRNA molecule and two or more ribosomes that is formed during active translation.
Which organelle is formed from rRNA and protein?
Ribosomes
What are the five kinds of RNA?
Ribosomal RNA (rRNA), messenger RNA (mRNA), transfer RNA (tRNA), microRNA (miRNA), noncoding RNA
Which type of RNA makes up roughly 80% of all RNA?
rRNA
Which type of RNA has 100,000s of versions but only a few copies of each?
Messenger RNA
What is meant by the statement that the genetic code is “comma-less”?
It has no gaps (and is non-overlapping)
Why are there short sections of identical code at the start and end of almost every protein (what do they do)?
They are start and stop codes
What is a “stem loop”?
This occurs when a section of RNA folds around and hydrogen bonds are formed between anti-parallel, complementary sequences.
What is inosine?
A nucleoside that is formed when hypoxanthine is attached to a ribose ring.
Explain the “wobble base pair”.
Due to the degeneracy of the genetic code (different codons code for same amino acid) the third base in the codon has slightly less strict base pairing rules and will form bonds with different bases (eg G can pair with U).
