7.2 Transcription and Gene Expression

Question 1

sections of a gene

Answer 1

promoter, coding sequence, terminator

Question 2

promoter

Answer 2

-non coding sequence responsible for initiation of transcription
- located immediately upstream of genes coding sequence
- functions as binding site for RNA pol
- binding of RNA pol to promoter is mediated and controlled by an array of transcription factors in eukaryotes

Question 3

coding sequence

Answer 3

• after RNA pol has bound to promoter, it causes DNA strands to unwind and separate
• region of DNA that is transcribed by RNA pol is called coding sequence

Question 4

terminator

Answer 4

• RNA pol will continue to transcribe the DNA until it reaches a terminator sequence
• mechanism for transcriptional termination differs between prokaryotes and eukaryotes

Question 5

antisense strand

Answer 5

strand that is transcribed into RNA (aka template strand)

Question 6

sense strand

Answer 6

not transcribed into RNA (coding strand)

Question 7

transcription

Answer 7

process which a DNA sequence is copied into complementary RNA sequence by RNA pol
- initiation
- elongation
- termination

Question 8

initiation

Answer 8

RNA pol binds to promoter and causes unwinding and separating of DNA strands

Question 9

elongation

Answer 9

RNA pol moves along coding sequence, synthesizing RNA in 5’ to 3’ direction

Question 10

terminator

Answer 10

both enzyme and nascent RNA strand detach and DNA unwinds

Question 11

capping

Answer 11

• addition of methyl group to 5’ end of transcribed RNA
• methylated cap provides protection against degradation
• allows transcript to be recognized by cell’s translational machinery

Question 12

polyadenylation

Answer 12

• describes the addition of long chain of adenine to 3’ end of transcrip
• poly-A tail improves stability of RNA transcript and facilitates its export from the nucleus

Question 13

splicing

Answer 13

• in eukaryotic genes are non-coding sequences called introns, which must be removed prior to forming mature mRNA
• coding regions are called exons and are fused together when introns are removed to form continuous sequence
• introns are intruding sequences whereas externs are expression sequences
• process by which introns are removed is called splicing

Question 14

enhancer sites

Answer 14

activator proteins bind to these sites and increase the rate of transcription

Question 15

silencer sequences

Answer 15

repressor proteins bind to these sequences and decrease the rate of transcription

Question 16

epigenetics

Answer 16

study of changes in phenotype as a result of variations in gene expression levels
- DNA methylation patterns change over the course of a lifetime
- influenced by heritability
- environmental factors may influence level of DNA methylation