The rest of module 2 Flashcards
What is a gene
A defined region (sequence) of DNA that produces a type of RNA molecule that has some function
Gene expression definition
The process by which information from a gene is used in the synthesis of a functional gene product
How does RNA polymerase synthesise mRNA
Catalyses formation of phosphodiester bonds between ribonucleotides
What are the three stages of transcription
Initiation, elongation, termination
What occurs in the initiation stage of transcription
Transcription factors bind to promoter region (TATA box), RNA polymerase II binds forming a transcriptional initiation complex together with transcription factors. 2 DNA strands separate and RNA pol II starts synthesis without the need of a primer
What occurs in the elongation stage of transcription
RNA polymerase II uses the template strand which runs in the 3’->5’ direction as a template and inserts complementary RNA nucleotides in the 5’ -> 3’ direction
What parts of the gene are transcribed
5’ UTR, coding sequence, 3’ UTR
What parts of the gene are translated
Exons
What is splicing
Removal of introns from mRNA strand to make continuous coding sequence
What is pre mRNA
mRNA stored while still containing introns, so that proteins can be made quickly when required
Purpose of promoter region
DNA segment recognised by RNA polymerase to initiate transcription
5’UTR purpose
Contain regulatory elements, facilitates addition of 5’ G cap
3’UTR purpose
Contain regulatory elements, facilitates addition of poly-A tail
5’G cap
Prevents mRNA degradation, promotes intron excision and provides a binding site for the small ribosomal subunit
Poly-A tail
Prevents mRNA degradation, promotes intron excision and facilitates export of mRNA from the nucleus to the cytoplasm
Where does transcription occur in eukaryotes
In the nucleus
Where does translation occur
In the endoplasmic reticulum or cytoplasm
Where does transcription occur in prokaryotes
In the cytoplasm
What is a functional gene product
Protein or non-coding RNA (doesn’t give rise to a protein but has some other function, e.g tRNA, rRNA)
What is a monohybrid cross
Crossing two heterozygotes for one gene
What is the expected phenotype ratio of a monohybrid cross
3:1
What is a test cross
Crossing an unknown genotype but dominant phenotype with a known genotype, recessive phenotype
What are Mendel’s two laws
Law of segregation, law of independent assortment
What is a dihybrid cross
Crossing two heterozygotes for two genes
