RNA Transcription and Processing Flashcards

1
Q

What are the components of a nucleotide?

A

phosphate, deoxyribose sugar, and a nitrogen base (C, G, A, T)

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2
Q

What is transcription?

A

The process by which RNA chains are made from DNA template strands

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3
Q

What is RNA made of/what does it stand for?

A

ribonucleic acid

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4
Q

What type of bonds are the bases in RNA connected by?

A

phosphodiester bonds like DNA

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5
Q

What’s different about RNA structure vs. DNA?

A

Antiparallel strands! One strand is in the 5’ to 3’ direction the other in the 3’ to 5’ direction

The two strands are of opposite polarity

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6
Q

What are the purine bases for RNA?

A

A or G

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7
Q

What are the pyrimidine bases for RNA?

A

U or C

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8
Q

What’s the major difference between DNA and RNA formation of base pairs?

A

DNA forms base pairs with adjacent strands of DNA

RNA forms base pairs with itself within the RNA molecule

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9
Q

What hybrid structure is critical to the process of transcription?

A

RNA forms a hybrid with DNA strand by way of base-pairing

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10
Q

What is rRNA?

A

Ribosomal RNA

The majority of RNA in the cells is this type

95% of all RNA

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11
Q

What are the 3 major species of rRNA?

A

28S, 18S and 5.8S

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12
Q

What is tRNA?

A

Transfer RNA that brings amino acids to the ribosome for protein synthesis

Structural RNA molecules which serve as adaptors for translating the information in the sequence of mRNAs into specific amion acids

There is at least 1 tRNA per amino acid

Has cloverleaf structure

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13
Q

Which RNA species is the most stable?

A

rRNA

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14
Q

Which is more stable tRNA or mRNA?

A

tRNA

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15
Q

What happens at the acceptor stem of the tRNA?

A

That’s where the amino acid attachment site is

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16
Q

What happens at the anticodon loop at the bottom of all tRNAs?

A

That’s where binding to codons along the mRNA will occur

17
Q

Which other RNA types are found in the nucleus?

A

ncRNA (noncoding RNA)

miRNA (micro RNA)

18
Q

What do micro RNA do?

A

They help regulate gene expression by binding to other RNA molecules to form hybrids

19
Q

Are mRNA stable?

A

no

20
Q

How are mRNAs degraded?

A

RNAses

21
Q

What is the structure of a mRNA?

A

guanine methylated cap, nontranslated sequence, coding sequence, nontranslated trailing, poly A tail

22
Q

Why do you want mRNA to be unstable?

A

Because the cell needs to be able to make and degrade mRNAs as it needs them - quickly and efficiently

23
Q

Which items are necessary for RNA Transcription?

A

DNA, Transcription Factors, RNA polymerase and ATP

24
Q

What does RNA polymerase 1 do?

A

makes rRNA

25
Q

What does RNA pol 2 do?

A

Makes mRNA

26
Q

What does RNA polymerase 3 do?

A

makes tRNA and other small RNA

27
Q

How many RNA polymerases do plants have?

A

5

28
Q

What are the steps of RNATranscription?

A

The promotor box including TATA box (usually) markes the binding site for TFIID transcription factors at the initiation site

Other transcription factors IIA and IIB attach too

This complex prepares for successful binding of RNA polymerase which binds now

Then more transcription factors come in to complete the complex.

Energy is released into the system

RNA polymerase 2 synthesizes RNA template from strand of DNA

Factors Release

RNA polymerase dissociates and releases the new RNA strand

Modifications can facilitate this whole process especially local unwinding of the DNA to faciliate transfer

29
Q

What signals RNA synthesis promoters?

A

DNA sequences

30
Q

According to Dr. Mickelson there are 4 distinct steps to RNA transcription - what are they?

A

1) Biinding of RNA polymease and local unwinding of DNA
2) Initiation of RNA synthesis
3) Elongation of RNA
4) Termination

Each step requires energy!

31
Q

How are pre-mRNA’s processed?

A

1) Cap placed on 5’ end
2) Poly A tail put on 3’ end
3) Introns spliced out - producing mature transcript with exons next to each other
4) mRNA ready to leave the nucleus to go to the cytoplasm to be translated to protein

32
Q

What is the dystrophin gene?

A

it codes for a protein important in maintaining the sarcolema of muscle cells

33
Q

Which gene is mutated in the case of muscular dystrophy?

A

Dystrophin gene!

mutation near splice junction so the spliceosome can’t catalyze the event to remove the introns!

34
Q

Why is the dystrophin gene so important or significant?

A

It is the largest gene in any animal or human genome - it’s introns are huge so it’s mostly introns

Without a functioning gene the muscles become more fragile, they break and atrophy :(

35
Q

How are introns removed from the pre-mRNA transcript?

A

Spiceosome activity - splice junction recognition

36
Q

What is a spliceosome?

A

A large ribonucleoprotein complex that catalyzes the removal of introns from a pre-mRNA transcript

37
Q

How does a spliceosome remove the introns from a pre-mRNA?

A

U1 and U2 are catalytic and can break mRNA molecule at exon/intron junction and splice two pieces together

5’ end of intron has a GU to signal U1’s landing

3’ end has AG to signal U2’s landing

38
Q

Does the spliceosome only occur in one tissue type?

A

no. the splicing reaction can occur in a tissue specific form - any tissue