CP 12 Gene Structure Flashcards
Which direction is RNA made
5’ –> 3’, uses 3’–>5’ dna strand as template
the DNA bases are:
the RNA bases are:
ATCG
AUCG
what are the differences between DNA replication and Transcription
- Only 1/2 DNA nucleotide strands acts as template for synthesis
- Relatively small part of DNA molecule serves as template
- RNA polymerases catalyze assembly of RNA nucleotides into RNA strand
what are the 2 main parts of a gene
- regulatory region
- Coding region
what is the regulatory region of a gene
a promoter (control sequence for transcription)
what is the coding region of a gene
a transcription unit (section of the gene that is
copied into an RNA molecule)
what is the basic structure of a prokaryotic coding gene from left to right
- promoter
- 5’ UTR
- start codon
- DNA being coded
- stop codon
- 3’ UTR
- terminator signal
what is the basic structure of a eukaryotic coding gene from left to right
- promoter
- 5’ UTR
- start codon
- DNA being coded (Exon 1, Intron, Exon 2) separated by splice signals
- Stop codon
- 3’ UTR
- Poly(A) Signal
TF Eukaryotes have a termination sequence
F
what are the 3 steps to transcription
- Initiation
- Elongation
- Termination
what are the steps to initiation
- promoter binds (TATA Box)
- Transcription factors (TF) bind
- RNA polymerase 2 binds
- additional TFs bind to form “transcription initiation complex”
what are the steps to elongation
- RNA polymerase moves along the DNA, it untwists double helix
- gene can be transcribed simultaneously by several RNA polymerases
- Nucleotides are added to the 3’ end of growing RNA molecule
what are the steps to termination
- Complete RNA is released
- RNA polymerase leaves
- dbl helix reforms
In eukaryotes the RNA polymerase 2 is responsible for ____ while RNA polymerase 1 is responsible for ___
- tRNA, 1/4 rRNAs, protein coding genes
- the three other rRNAs
Whats the difference between transcription in prok and euk cells
- prokaryotes, mRNA produced by transcription is immediately translated without more processing
- In eukaryotes, nuclear envelope separates
transcription from translation
what is pre-mRNA
- beginning RNA template in euk cells that are modified through RNA processing to yield
finished mRNA - Must be processed in nucleus to produce translatable mRNA
what is the 5’ cap on mRNA
- Site where ribosome attaches to mRNA
- Connected by 3 phosphate groups
what is the Poly(A) Tail in pre-mRNA
- substitute for terminator sequence
- Signals RNA polymerase to stop transcription
- Protects mRNA from RNA-digesting enzymes
what are the Introns and exons of pre-mRNA
- Introns = Non–protein-coding intervening sequences in the pre-mRNA
- Exons = Amino acid-coding sequences retained in finished mRNAs
TF Exons have to be removed before translation
F, Exons are expressed
how many variations of genetic code can be made with a 3 letter codon
64
TF Each codon specified same amino acid in all living organisms
T
How many sense codons and how many stop/start codons are there
- 61 sense codons
- 3 stop/start
what is the “Wobble Hypothesis”
First two nucleotides of anticodon and codon must match exactly, Third nucleotide has more flexibility
