IBHL - Genetics transcription HL content

To be used with Bioninja

What does the vast majority of the human genome comprise of?

Non-coding DNA sequences (98%)

What are the functions of non-coding DNA sequences?

S: Satelite DNA sequences are used in DNA profiling

T: Telomeres (the ends of chromosomes) prevent chromosomal deterioration during replication

I: Introns are non-coding sequences in eukaryotic genes that are removed during pre-RNA processing

N: Non-coding genes produce tRNA and rRNA

G: Gene regulatory sequences mediate transcriptional activity (enhancer and silencer sequences)

A gene is composed of what three main sections?

promoter, coding sequence, and terminator

What are the functions of the promoter region? (TATA box)

1: Responsible for the initiation of transcription

2: Functions as a binding site for RNA Polymerase (the enzyme responsible for transcription)

What are the functions of transcription factors?

1: Bind directly to the promoter or associate with distal regulatory sequences (enhancers or silencers)
2: Promote the binding of RNA polymerase (increase transcription) or inhibit binding (decrease transcription)

What happens at the coding sequence when RNA polymerase II and general transcription factors bind to the promoter

1: DNA strands unwind and separate

2: Coding strand gets transcribed by RNA polymerase

What happens at the terminator

1: RNA polymerase stops transcribing DNA

What kind of genes does RNA Polymerase I, II, and III transcribe in eukaryotes?

1: transcribes the genes for rRNA

2: transcribes all protein-coding genes for mRNA

3: transcribes for tRNA

What is transcription?

The process by which a gene is copied into a complementary RNA sequence by RNA polymerase

What three post-transcriptional modifications occur in order to form mRNA in eukaryotic cells?

Capping, Polyadenylation, and Splicing

What is capping in mRNA processing?

A methyl group is added to the 5' end of the pre-mRNA which provides protection against degredation and allows the transcript to be recognised by ribosome and nuclear export proteins

What is polyadenylation in mRNA processing?

The addition of adenine nucleotides (poly-A tail) to the 3' end of the transcript which improves stability and facilitates its export from the nucleus

What is splicing in mRNA processing?

The removal of introns and joining of exons to form mature mRNA

What is the removal of exons called and its purpose in mRNA processing?

Alternative splicing, results in the formation of different polypeptides from a single gene depending on outside factors