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Bio 243 > Theme 2B > Flashcards

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 the desire tissue type by turning on and off the corresponding genes through molecular techniques

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3
Q

What is a promoter

A

The DNA sequence on a gene that specifies where transcription begins on the chromosome

Promoter is recognized by RNA polymerase and transcription factors to start transcription

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4
Q

Where is the promoter located on the DNA strands?

A

On the five prime end of the start point of the coding strand

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5
Q

What is the transcriptional unit?

A

The part of the DNA that is coded (transcribed) into RNA

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6
Q

What does RNA polymerase do

A

Synthesizes RNA transcript in 5-3 direction
Read DNA template in 3 to 5

Doesn’t need primer to initiate rna synthesis (unlike dna pol)

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7
Q

Why don’t we need helicase in RNA transcription process?

A

Because RNA pol can unwind and rewind DNA strands on its own

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8
Q

What are the three types of RNA polymerase

A

RNA POL 1: rRNA, ribosomal rna
RNA POL 11: mRNA, only makes coding rna
RNA POL 111: tRNA

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9
Q

What is step one of transcription

A

Transcriptional initiation

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10
Q

How is transcriptional initiation mediated

A

The interaction of DNA-binding proteins to regulatory sequences of the gene (this determine whether gene is highly expressed or not)

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11
Q

Describe the first type of transcriptional initiation process

A

Initial General transcription factor bind to a TATA box in the promoter that is on DNA strand and recruit /call over RNA polymerase ll and other transcription factors

Has a low basal level of transcription (only one or two mRNA per hour)

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12
Q

Describe second type of transcriptional initiation process

A

Transcriptional, activator proteins, bind to regions far from the promoter that are enhancer regions. This causes DNA looping, which brings the enhancer and promoter closer together, resulting in high levels of transcription 

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13
Q

What is step two of the transcriptional process?

A

Transcriptional elongation

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14
Q

What happens in transcriptional elongation?

A

RNA POL ll moves along template DNA strand in 3 to 5 direction

RNA pol ll unwinds DNA at the front, and reanneals DNA at the back in the transcription bubble

The growing RNA transcript is separated from the template strand, and the two strands of DNA are reannealed into double stranded

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15
Q

What is step three of the transcription process?

A

Transcriptional termination

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16
Q

How does transcriptional termination start?

A

The sequence in the five prime end of the DNA template causes RNA POL to stop transcribing into RNA

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17
Q

What happens in RHO independent termination, what organisms does it occur in

A

Occurs in prokaryotes

Inverted coding repeats in dna are coding into rna causing the rna to pair with itself. This forms the GC hairpin and transcription stops. Rna strand separates from the template dna strand because of the hair pin

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18
Q

What happens in rho dependent termination, in what organisms does it occurs

A

In prokaryotes

The terminators sequence in mRNA is recognized by rho helicase. The rho helicase binds to the sequence and unwinds the RNA from the template dna and rna polymerase. This causes separation of rna from dna

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19
Q

What is cleavage and polyadenylation specific factor

What organisms does it occur in

A

Eukaryotes

The polyA sequence in mRNA signals the CPSF to cleave the finished mRNA transcript. This separates is from the rna polymerase

20
Q

What is post transcriptional regulation of gene expression

A

The processing of rna molecule for stability and proper translation

21
Q

What regions of mRNA is not translated

A

The ends (5 and 3 untranslated regions)

22
Q

What do 5’ and 3’ UTR’s do.

A

Regulate mRNA stability and translational efficiency

If mRNA stable, it stays a long time, if unstable it degrades

23
Q

What do 5 prime UTRS have and what do they do in translation

A

They have a ribosome binding site or a shine dalgarno sequence and kozack box sequences that help translational initiation (starting translation)

24
Q

What is the open reading frame?

A

The part of the mRNA that is translated and includes the start and stop codons at the ends

25
Q

What is the 5’ cap? What does it do?

A

It is a modified guanasine triphosphate on the five end of the pre-mRNA.

Acts as the ribosome binding site so that the ribosome can start translation. protects mRNA from degradation by 5 to 3 exoribonuclease

26
Q

What is the poly a tail? What does it do?

A

It is a 50 to 250 string of adenine nucleotides on the 3’ end of the pre-mRNA. Added onto the end by poly-a polymerase

It protects the pre-mRNA from being degraded by 3 to 5 exoribonuclease and increases translational efficiency

27
Q

How can poly a tail influence initiation in the 5’ cap.

A

mRNA that is being translated is circular, so the cap and tail are actually close together. This makes it so that the proteins that are binding to the tail facilitate ribosomes getting onto the 5’ end.

28
Q

What are exons?

A

Coding segments and UTRS

contain codons

29
Q

What are introns

A

Non coding segment of the pre mRNA

Don’t contain codons

30
Q

What is left when introns are spliced out of ore mRNA

A

You get the open reading frame which is just the continuous stretch of codons and UTRs

31
Q

Where does the pre mRNA go after introns are spliced out

A

Exported out of nucleus to go into cytoplasm for translation by ribosomes

32
Q

Splicing only occurs in ______

A

Eukaryotes

33
Q

How do introns get removed from the pre mrna to make mature mrna

A

The spliceosome (made up of several snRNPS with 5 snRNA inside each) binds to intron-exon junctions.

It then loops the introns and brings exons close together

Once loop is made it clips the 5’ end of looped intron and 3’ end of exons 1. then joins the two exons together

34
Q

What is alternative splicing

A

Making different proteins from one gene

35
Q

What are isoforms?

A

Related protein products that are made from the same gene, but the mRNA is spliced differently.

This makes tissue specific phenotypes

36
Q

How does alternative splicing help?

A

Helps increase the number and variety of proteins encoded by the genome

37
Q

What is miRNA and siRNA?

A

They are micro RNA, and small interfering RNA, that are transcribed by RNA pol and make a hairpin shape .

This shape is then transported from nucleus to the cytoplasm

38
Q

What does dicer RNase do?

A

It cuts the pre miRNA hairpin that’s in the cytoplasm to 21-23 base pairs long (cuts of the loop)

39
Q

What does the protien complex do in “RNA interference”

A

Bind to the double stranded miRNA and creates RISC which degrades one of the strands

40
Q

What does the remaining miRNA strand in the miRISC do?

A

Bind to other mRNA strand that is almost complimentary to is, but not exactly.

This causes imperfect painting which then block translation initiation. If perfectly paired it induced mRNA degradation

41
Q

Why it RNA interference important

A

It evolved as a antiviral mechanism to block viral rna from being translated

42
Q

What does transcriptional regulation mean? What does the transcriptional rate depend on

A

What is the control of synthesis. Depends on the speed of transcriptional initiation. 

43
Q

What is post-transcriptional regulation

A

The processing of mRNA, which affects its stability and translational efficiency

44
Q

What does the stability of mRNA depend on?

A

Presence of the five prime cap and length of the poly a tail

45
Q

What does the abundance of RNA depend on?

A

The rate of synthesis (transcription) and degradation of mRNA (post-transcriptional)

Bio 243 (8 decks)

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