gene structure and expression Flashcards
gene expression
the flow of genetic information from the genotype ot the phenotype
order of replication
DNA -> RNA -> Protein
Transcription
(genetics) the organic process whereby the DNA sequence in a gene is copied into mRNA
Translation
Process by which mRNA is decoded and a protein is produced
Most of the genes are ______ into mRNA, and then the mRNA is _____ into polypeptide
transcribed, translated
Where do both transcription and translation occur in prokaryotes?
cytoplasm
Where does translation occur in eukaryotes
cytoplasm
Where does transcription occur in eukaryotes
nucleus
Transcription promoter
A DNA sequence that RNA polymerase binds
regulatory sequences
sections of DNA that are involved in controlling if the gene is turned on or off
transcribed region
contains the information that specifies an amino acid sequence
Terminator
A special sequence that causes the RNA strand to be released from the transcription complex.
transciption factors
Regulate transcription by binding to those promoters of to RNA polymerases
TATA box
A promoter DNA sequence crucial in forming the transcription initiation complex. Eukaryotes.
Pribnow box
Also known as the -10 sequence, consists of a sequence TATAAT that is used as a promoter for DNA transcription. Prokaryotes.
How many strands used as a template in transcription
- Runs in 3’-5’
3 phases of transcription
initiation, elongation, termination
Where does prokaryotic transcription occur?
cytoplasm
Where does eukaryotic transcription occur?
nucleus
how does transcription initiate in prokaryotes
A single sigma factor
how does transcription initiate in eukaryotes
5 general transcriptional factors
Process of Transcription
RNA polymerase uses ATP to read the DNA strand and form an mRNA strand in the nucleus
Exons
Coding segments of eukaryotic DNA.
Introns
Noncoding segments of nucleic acid that lie between coding sequences.
RNA splicing
Process by which the introns are removed from RNA transcripts and the remaining exons are joined together.
Alternate splicing of mRNA
primary mRNA transcript can be processed to include or exclude different exon such that the various mature mRNAs can be translated into proteins with different functions
Capping
The process of linking a 7-methylguanosine residue to the 5’ end of eukaryotic RNAs. The 5’ cap protects the mRNA from degradation and is required for translation in the cytoplasm.
Tailing
a poly A tail is added to the most mature eukaryotic mRNAs at the 3’ end
What does a a fully processed mRNA include?
5’cap, 5’ UTR, coding region between start and stop codon, 3’UTR, and a poly (A) tail.
start codon
AUG
stop codon
UAA, UAG, UGA
codon usage bias
A bias in which certain codons occur more frequently than others that specify the same amino acid
coding strand
the strand of DNA that is not used for transcription and is identical in sequence to mRNA, except it contains uracil instead of thymine
gene mutation
A change in the sequence of the nucleotides in a gene
base-pair substitution
A type of point mutation; the replacement of one nucleotide and its partner in the complementary DNA strand by another pair of nucleotides.
missense mutation
A base-pair substitution that results in a codon that codes for a different amino acid.
silent mutation
A mutation that changes a single nucleotide, but does not change the amino acid created.
nonsense mutation
A mutation that changes an amino acid codon to one of the three stop codons, resulting in a shorter and usually nonfunctional protein.
frameshift mutation
mutation that shifts the “reading” frame of the genetic message by inserting or deleting a nucleotide
What does translation require
AA, ATP/GTP, Enzymes and proteins, RNAs, Ribosomes.
Anticodon
group of three bases on a tRNA molecule that are complementary to an mRNA codon
Aminoacylation
the process by which a tRNA molecule is bound to its corresponding amino acid
prokaryote ribosome size
30S + 50S = 70S
Eukaryote ribosome size
40S + 60S = 80S
How many binding sites do each ribosome have
- A= Aminoacyl tRNA binding site. P=Peptidyl-tRNA binding site. E=Exit site.
