Theme 2b Flashcards

1
Q

What does an organisms phenotype depend on

A

Cell number, type and function

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2
Q

What is regenerative medicine

A

Growing a desired tissue type by turning on/off the appropriate genes using molecular techniques

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3
Q

What are the two main structures of a gene

A

Include promoter and transcriptional unit

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4
Q

What is the promoter

A

-DNA sequence (including TATA box) that specified where transcription begins on the chromosome
-located immediately upstream of the transcriptional start point of the nontemplate or coding strand
-recognized and bound by the transcriptional machinery (RNA polymerase and transcription factors) that initiate transcription

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5
Q

What is the transcriptional unit

A

Part of the genome that is copied into RNA

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6
Q

What does the RNA polymerase do

A

Synthesizes RNA transcript in a 5’ to 3’ direction
Unwinds and rewinds DNA helix during RNA synthesis

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7
Q

Does RNA need a primer

A

No just DNA

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8
Q

What are the 3 types of RNA polymerase s

A

1) RNA pol l: transcribes rRNA (noncoding)
2) RNA pol ll: transcribes mRNA (coding)
3) RNA pol lll: transcribes tRNA (noncoding)

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9
Q

What are the 3 steps of transcription

A

1) initiation
2) elongation
3) termination

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10
Q

What are the 2 types of transcriptional initiation

A

1) general transcription factors bind to RNA polymerase and recruit RNA polymerase ll resulting in low transcription levels
2) transcriptional activator proteins bind to enhancer regions resulting I high levels of transcription

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11
Q

What is the rate determining step on transcription

A

Initiation

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12
Q

What happens in transcriptional elongation

A

RNA transcript gets longer by RNA polymerase synthesis (3’ to 5’)

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13
Q

What happens in transcriptional termination

A

5’ sequence in DNA template causes termination after transcribed into RNA

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14
Q

What are the 3 termination factors and which type of cells do they occur

A

1) Rho-independent (prokaryotes)
2) Rho-dependent (prokaryotes)
3) cleavage and polyadenylation specific factor (eukaryotes)

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15
Q

How does Rho-independent termination work

A

-helicase enzyme
-terminator sequence in mRNA base pairs with itself to form G-C hairpin
-causes RNA polymerase to stall and dissociate

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16
Q

How does Rho-dependent termination work

A

-relies on Rho helicase
-terminator sequence in mRNA is recognized and bound by the Rho helicase which unwinds RNA from template DNA and RNA polymerase

17
Q

How does the cleavage and polyadenlation specific factor work

A

-poly(A) sequence in mRNA signals the CPSF to cleave (pentose phosphate backbone) the completed mRNA transcript

18
Q

Are all the termination factors sequence driven

19
Q

What is the advantage of the 5’ and 3’ UTR’s

A

Regulate mRNA stability and translational efficiency

20
Q

What is the open reading frame

A

Region of mRNA that is translated and included the start and stop codons at the borders

21
Q

What is the 5’ cap

A

Modified guanosine triphosphate that is added to the 5’ end of the mRNA and acts as a ribosome binding site and protects mRNA from degradation

22
Q

What is the poly(A) tail

A

Long string of adenine nucleotides added to the 3’ end of the mRNA to protect the mRNA from being degraded and increases translational efficiency

23
Q

What are introns and exons

A

Introns: noncoding segments of DNA
Exons: coding segments of DNA

24
Q

What is the difference between pre-mRNA and mature mRNA

A

Pre-mRNA has introns and exons mature mRNA only has exons that code for amino acids

25
What is the splicosome (snRNA)
Recognizes sequence on the introns and forms loops to remove them
26
What is alternative splicing
Generating different proteins from one gene
27
What percent of human genes are alternatively spliced
75%
28
How does the cell regulate genes
Post transcriptional regulation by RNA interference
29
What are microRNAs (miRNAs) and small interfering RNAs (siRNAs)
-precursors that are cleaved to 21-23 by double-stranded RNAs by the diver Rnase -substrates of RISC (RNA induced-silencing complex)
30
What does RISC do
-unwinds one of the RNA strands which attract binding of the complementary mRNA -this interferes with translation initiation or induces mRNA degradation
31
What is transcriptional regulation and what does it depend on
-control of mRNA synthesis -depends on the speed of transcriptional initiation (promoter strength)
32
What is post transcriptional regulation
Processing of mRNA which affects wits stability and translational efficiency