3 Gene Organisation And Transcription I Flashcards
Q: What does the human genome consist of?
A: 22 pairs of autosomal chromosomes and one pair of sex chromosomes
Q: What are housekeeping genes? need?
A: genes are expressed in all cells. needed for normal cell function.
Q: Explain the basic differences between DNA and RNA.
A: DNA is a long polymer with deoxyriboses and phosphate backbone. Having four different nitrogenous bases: adenine, guanine, cytosine and thymine. RNA is a polymer with a ribose and phosphate backbone. Four different nitrogenous bases: adenine, guanine, cytosine, and uracil
dna is double stranded and rna is single
Q: Explain what is meant by “Transcription”. Which molecules does it involve?
A: particular segment of DNA is copied into RNA by the enzyme RNA polymerase
Transcription involves special gene regulatory factors called Transcription Factors.
Q: What is the antisense strand?
A: DNA strand which gets transcribed. It is ‘antisense’ because it is the opposite of the RNA that is produced.
Q: In which way are ribonucleotides joined in transcription?
A: Ribonucleotide bases are joined by phosphodiester bonds and the RNA chain grows in a 5’ to 3’ direction.
Q: What are the 3 types of RNA polymerases in eukaryotic cells? What do they transcribe?
A: RNA Polymerase I - Transcribes rRNA genes
RNA Polymerase II - Transcribes genes encoding proteins into mRNA
RNA Polymerase III - Transcribes tRNA and 5S RNA genes
Q: List the major functional classes of RNA. (3)
A: messenger, transfer, ribosomal
Q: What is the gene promoter?
A: DNA sequence at which the transcription complex assembles (ribosome)
Q: What is the gene operator?
A: location on DNA where transcription factor binds
Q: What are transcription factors? 2 types.
A: DNA binding proteins that regulate the amount of transcription of a gene
Transcriptional Activators activate gene expression.
Transcriptional Repressors suppress gene expression.
Q: What does the basal transcription complex produce? What does it allow?
A: low level of transcription in the absence of other transcription factors
allows RNA Polymerase II to be phosphorylated and then engage in transcription.
Q: Draw a diagram representing the anatomy of a gene promoter.
A: specify the initiation point for transcription by ^ RNA pol II
TRANSCRIPTION FACTOR BINDING SITE TATA
^ controls the rate of transcription by transcription factor binding
Q: What are the 4 steps when transcribing a eukaryotic gene? With diagrams.
A: 1. TF IID binds to TATA: TF IID consists of TATA Binding Protein (TBP) and TBP Accessory Factors (TAFs)
When they bind to TATA:
Partially unwinds the DNA and widens minor groove thus allowing extensive contact with bases. (Unwinding is asymmetrical with respect to TBP-TATA complex thus assuring transcription is unidirectional)
- TF IIA and TF IIB bind: TF IIB is particularly important because it can bind to TF IID and RNA Polymerase II
- RNA Polymerase II binds to TF IIB with TF IIF bound onto it
- TF IIE, TF IIH and TF IIJ bind to RNA Polymerase II: TF IIH promotes further unwinding of the DNA helix to facilitate RNA synthesis by RNA Polymerase II
Q: How do transcription factors facilitate transcription? method?
A: by helping to remodel chromatin. This is done by recruiting proteins with enzymatic activity that modify histones.
