Chapter 6: 6.2 Genes and mRNA Flashcards
What is the basic structure of a gene?
A gene generally consists of 3 basic elements:
1. Promoter
2. Coding region
3. Terminator
Describe:
Promoter (on a gene)
A region of DNA just before a gene that initiates transcription
What counts as upstream?
A region of DNA just before a gene
Where does RNA polymerase binds to DNA?
Promoter
Describe:
Coding region (on a gene)
The part of the gene that codes for a particular RNA molecule (mRNA, rRNA, tRNA)
Define:
Terminator (on a gene)
A region of DNA just after a gene that signals transcription to stop
What counts as downstream?
A region of DNA just after a gene
True or False:
All genes are orientated in the same direction on a chromosome
False
Define:
Template strand
DNA strand that is to be transcribed
Define:
Coding strand
The complementary strand to the template strand
What is difference between the transcribed mRNA and the coding strand?
Thymines are Uracils in mRNA
Which direction is DNA read?
3’ to 5’
Which direction is the complementary RNA synthesized?
5’ to 3’
What is the general structure of bacterial mRNA?
- 5’ untranslated region (UTR)
- Start codon
- Stop codon
- 3’ untranslated region (UTR)
What does the 5’ UTR contain?
Ribosome binding site
What is the start codon?
Codon at which the ribosome begins translation
What is the stop codon?
Codon at which the ribosome stops translation
What is the 3’ UTR?
Region downstream of stop condon that is not translated
Bacterial mRNA is often polycistronic, what does this mean?
More than one protein can be encoded in a single strand of mRNA
What represents a codon?
Three consecutive nucleotides on a strand of mRNA
The genetic code is said to be redundant or degenerate, why?
More than one codon codes for each amino acid
What does AUG code for?
The amino acid methionine
* Start codon
What does the start codon set on the RNA strand?
The reading frame
How many stop codons are there?
3 (UAG, UGA, UAA)
Each mRNA codon is recognized by the complimentary ——— of a —- that carries the corresponding —– —-
- Anticodon
- tRNA
- Amino acid
What is aminoacyl tRNA synthetase?
The enzyme that “loads” the amino acids onto the appropriate matching tRNAs
How do mRNA and tRNA interact?
Interact in an antiparallel orientation via hydrogen bonds
Describe:
The Wobble Effect
There is a looser pairing between the 5’ nucleotide of the enticodon and the 3’ nucleotide of the codon
Define:
The Reading Frame
The sequence between the start codon and the stop codon
True or False:
A sequence has multiple reading frames
False, a sequence usually only has one reading frame
What happens when the reading frame is changed?
A different polypeptide chain will be made
If the reading frame changes and a different polypeptide chain is made, what might happen?
- Mutated protein that is nonfunctional
- Different functional protein is made
What usually causes a mutated protein that is nonfunctional?
A deletion or another mutation in the mRNA or in the DNA itself
