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Biochemistry MCAT > RNA and Genetic Code > Flashcards

RNA and Genetic Code Flashcards

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MCAT flashcards
1
Q

Central Dogma

A
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2
Q

Gene

A

A unit of DNA that encodes for a specific protein or RNA molecular, which can be expressed via transcription and translation

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3
Q

Types of RNA

A

1) Messenger RNA
2) tRNA
3) rRNA

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4
Q

Messenger RNA (mRNA)

A

Carries the message from DNA in the nucleus via transcription of the gene; it travels into the cytoplasm to be translated.

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5
Q

Transfer RNA (rRNA)

A

Bring the amino acids and recognizes the codon on the mRNA using its anticodon.

When bound to AA, it is charged.

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6
Q

Ribosomal RNA (rRNA)

A

Synthesized in the nucleolus and functions as an integral part of the ribosomal machinery used during protein assembly in the cytoplasm.

Makes up the ribosome and its enzymatically active.

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7
Q

Codon

A

A three-nucleotide sequence of DNA or mRNA that specifies a particular amino acid or termination signal; the basic unit of the genetic code.

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8
Q

Start codon

A

AUG

think starts school in AUGest

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9
Q

Stop codons

A

1) UGA - U Go Away
2) UAG - U Are Gone
3) UAA - U Are Annoying

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10
Q

Point Mutations

A

Specific mutations one piece of a codon:

1) Silent
2) Nonsense
3) Missense

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11
Q

Silent mutations

A

Causes no effect in the protein sequence due to redundancy in the wobble position.

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12
Q

Nonsense (truncation)

A

Mutation that produces a premature stop codon.

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13
Q

Missense mutation

A

Mutation that produces a codon that codes for a different amino acid.

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14
Q

Frameshift mutation

A

Mutation that results from nucleotide addition or deletion, and change the reading frame of subsequent codons.

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15
Q

RNA vs DNA

A

RNA has:
1) A ribose sugar instead of deoxyribose
2) Substitution of uracil for thymine
3) Single-stranded instead of double-stranded

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16
Q

Monocistronic

A

The coding pattern of eukaryotes in which one mRNA molecule codes for only one protein.

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17
Q

Polycistronic

A

The coding pattern of prokaryotes, in which one mRNA may code for multiple proteins.

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18
Q

Transcription

A

The creation of mRNA from a DNA template.

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19
Q

DNA strands to be transcribed

A

1) Coding strand
2) Template strand

20
Q

RNA polymerase

A

Enzyme that links together the growing chain of RNA nucleotides during transcription using a DNA strand as a template

1) Reads 3’ to 5’ but adds 5’ to 3’
2) Does no proof reading
3) Continues until it reaches a termination signal.

21
Q

hnRNA

A

Heterogeneous RNA.

RNA that has been freshly transcribed and has not underwent any post transcriptional modifications.

22
Q

Splicesome

A

a complex of specialized RNA and protein subunits that removes introns from a transcribed pre-mRNA segment.

Contain:
1) snRNA
2) snRNPs or “snurps”

23
Q

5’ Cap

A

A 7-methylguanylate triphosphate cap that protects mRNA from degradation in cytoplasm and is a recognized binding site for ribosomes.

24
Q

3’ Poly-A tail

A

A poly-A tail is composed of adenine and is added to the 3’ end of the mRNA transcript and protects the message against rapid degradation.

Longer the poly-A tail = longer time before degradation.

25
Q

Introns

A

Noncoding segments of nucleic acid that lie between coding sequences.

26
Q

Mechanism of transcription

A

1) Helicase and topoisomerase unwind the dsDNA.

2) RNA polymerase II binds to TATA box within the promoter region of the gene (25 base pairs upstream)

3) hnRNA is synthesized from the DNA template (antisense) strand and stopped once termination signal

27
Q

Describe the post transcriptional modifications.

A

4) A 7-methylguanylate triphosphate cap added to 5’ end.

5) Poly-A tail added to 3’ end

6) Splicing done by snRNA and snRNPs in the spliceosome. Process removes introns.

7) Alternatie splicing (combining of exons) allows more variability of gene products

8) Leave nucleus and into cytosol.

28
Q

Alternative splicing

A

Splicing of introns in a pre-mRNA that occurs in different ways, leading to different mRNAs that code for different proteins or protein isoforms. Increases the diversity of proteins.

29
Q

Exons

A

A coding region of a eukaryotic gene. Exons, which are expressed, are separated from each other by introns.

30
Q

Phosphorylation

A

The addition of phosphate group by protein kinases to activate deactivated proteins.

31
Q

Carboxylation

A

Addition of a carboxylic acid group, usually serves as calcium binding sites.

32
Q

Glycosylation

A

Addition of oligosaccharides as proteins pass through the ER and Golgi apparatus to determine cellular destination.

33
Q

Prenylation

A

Addition of lipid groups to certain membrane-bound enzymes.

34
Q

Operon Structure

A

Essentially an “on-off” switch that regulates gene expression. Composed of:
1) Regulator
2) Promoter
3) Operator
4) Structural

35
Q

Regulator gene

A

Codes for the protein known as a repressor that prevents gene transcription.

36
Q

Promoter site

A

Site where RNA polymerase will bind to begin transcription. About ~25 base pairs upstream

37
Q

Operator

A

A non transcribable region of the DNA that is capable of binding a repressor protein and preventing transcription.

38
Q

Structural gene

A

Codes for the protein of interest

39
Q

Inducible system

A

Systems that are bonded to a repressor under normal conditions.

1) They can be turned on by an inducer pulling the repressor from the operator site.

Ex) lac operon.

40
Q

Repressible system

A

System that is transcribed under normal conditions.

1) Can be turned off by a corepressor coupling with the repressor and binding to the operator.

Ex) Trp operon

41
Q

Transcription factors

A

Collection of proteins that mediate the binding of RNA polymerase and the initiation of transcription.

42
Q

Enhancers

A

Are more than 25 base pairs away from the transcription start site.

43
Q

Histone Acetylation

A

Acetylation of histones decreases positive charge on lysine residues and weakens histone-DNA interactions.

1) Results in open euchromatin formation that allows for easier asses for transcription factors.

44
Q

DNA methylation

A

Add methyl groups to cytosine and adenine nucleotides. Methylation of genes is often linked with silencing gene expression.

The heavily methylated DNA hinders transcriptional machinery.

45
Q

How to make DNA open/ closed for transcription?

A

Open = acetylation of histones causes them to form euchromatin that is open for business.

Closed = methylated DNA that will pack tightly into heterochromatin.

Biochemistry MCAT (12 decks)

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