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MCAT Biochemistry > RNA and Genetic Code (CH7) > Flashcards

RNA and Genetic Code (CH7) Flashcards

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MCAT flashcards
1
Q

Carries the information specifying the amino acid sequence of the protein to the ribosome. It is also transcribed from template DNA strands by RNA polymerase enzymes in the nucleus of cells.

A

Messenger RNA (mRNA)

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2
Q

In eukaryotes, each mRNA molecule translates into only one protein product.

A

Monocystronic

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3
Q

In prokaryotes, the starting process of translation is at different locations in the mRNA and can result in different proteins.

A

Polycystronic

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4
Q

Responsible for converting the language of the nucleic acids to the language of amino acids and peptides.

A

Transfer RNA (tRNA)

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5
Q

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

A

Ribosomal RNA (rRNA)

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6
Q

Basic unit of a gene sequence or “three letter word”.

A

Codon

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7
Q

When there are more codons per single amino acid in a genetic code, this is called?

A

Degeneracy

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8
Q

Mutations in the “wobble position” tend to be called what (hint: there is no effect on the expression of the amino acid and therefore no adverse effects on the polypeptide sequence)?

A

Silent or Degenerate

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9
Q

If a mutation occurs and it affects one of the nucleotides in a codon, it is known as?

A

Point Mutation

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10
Q

Because point mutations can affect the primary amino acid sequence of a protein, they are called?

A

Expressed Mutations

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11
Q

A mutation where one amino acid substitutes for another.

A

Missense Mutation

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12
Q

A mutation where the codon now encodes for a premature stop codon.

A

Nonsense Mutation (AKA Truncation Mutation)

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13
Q

RNA polymerase locates genes by searching for specialized DNA regions known as?

Also named for its high concentration of thymine and adenine bases.

A

Promoter Regions ( AKA TATA Box (Eukaryotes))

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14
Q

Is located in the nucleus and synthesizes hnRNA (pre-processed mRNA) and some small nuclear RNA (snRNA). Hint: main player in transcribing mRNA.

A

RNA polymerase II

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15
Q

Help the RNA polymerase locate and bind to the promoter region of DNA, which helps establish where transcription will start.

A

Transcription Factors

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16
Q

Is located in the nucleolus and synthesizes rRNA.

A

RNA polymerase I

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17
Q

Located in the nucleus and synthesizes tRNA and some rRNA.

A

RNA polymerase III

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18
Q

What is added to the 5’ end of the hnRNA molecule? This cap is actually added during the process of transcription and is recognized by the ribosome as the binding site. It also protects the mRNA from degrading in the cytoplasm.

A

7- methyguanylate triphosphate cap

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19
Q

What is added to the 3’ end of the mRNA transcript and protects the message from rapid degradation (hint: mostly composed of adenine bases)?

A

polyadenosyl (poly-A) tail

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20
Q

During initiation of translation in prokaryotes, the small subunit will bind to what?

A

The 5’ untranslated region of the mRNA called the Shine-Dalgarno sequence.

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21
Q

During initiation of translation in eukaryotes, the small subunit will bind to what?

A

The 5’ cap structure.

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22
Q

The “start” amino acid in prokaryotes?

A

N-formylmethionine (fMet)

23
Q

This site on a ribosome holds the incoming aminoacyl-tRNA complex. This is where the next amino acid that is being added to the growing peptide chain, and is determined by the mRNA codon within this area.

A

A Site

24
Q

This site on a ribosome holds the tRNA that carries the growing polypeptide chain. It is also where the first amino acid binds and starts the peptide chain.

A

P Site

25
Q

This site is where the inactivated (uncharged) tRNA pauses transiently before exiting the ribosome.

A

E Site

26
Q

These factors assist by locating and recruiting aminoacyl-tRNA along with GTP, while helping to remove GDP once the energy has been used to make peptide bonds.

A

Elongation Factors

27
Q

A specialized class of proteins that function to assist in the postranslational protein-folding process.

A

Chaperones

28
Q

Addition of a phosphate group by protein kinases to activate or deactive proteins (most common in eukaryotes: serine, threonine, and tyrosine).

A

Phosphorylation

29
Q

Addition of carboxylic acid groups that usually serve as calcium-binding sites.

A

Carboxylation

30
Q

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

A

Glycosylation

31
Q

Addition of lipid groups to certain membrane-bound enzymes.

A

Prenylation

32
Q

A particular cluster of genes in E.coli that transcribe as a single mRNA.

A

Trp Operon

33
Q

This is used to describe the structure and function of operons. In this model, operons contain structural genes, an operator site, a promoter site, and a regulator gene.

A

Jacob-Monod Model

34
Q

A gene that codes for the protein of interest.

A

Structural Gene

35
Q

A nontranscribable region of DNA that is capable of binding to a repressor protein.

A

Operator Site

36
Q

Provides a place for RNA polymerase to bind.

A

Promoter Site

37
Q

A gene that codes for a protein known as the repressor.

A

Regulator Gene

38
Q

What are the two types of prokaryotic operons?

A
  1. Inducible Systems

2. Repressible Systems

39
Q

In this system, the repressor is bonded tightly to the operator system and thereby acts as a roadblock. Therefore, RNA polymerase is unable to get from the promoter to the structural gene because the respressor is in the way.

A

Inducible Systems

40
Q

A transcriptional activator used by E.coli when glucose levels are low to signal that alternative carbon sources should be used (hint: is activated by increases in it’s binding to cAMP).

A

Catabolite Activator Protein (CAP)

41
Q

In this system, there is a constant production of a protein product. The repressor made by the regulator gene is inactive until it binds to a corepressor.

A

Repressible Systems

42
Q

From 5’ to 3’, what are the compenents of the operon?

A

Regulator Gene > Promoter Site > Operator Site > Structural Gene

43
Q

Transcription-activating proteins that search the DNA looking for specific DNA-binding motifs.

A

Transcription Factors

44
Q

Transcription factors tend to have what two recognizable domains?

A
  1. DNA-Binding Domain

2. Activation Domain

45
Q

Binds to a specific nucleotide sequence in the promoter region or to a DNA response element to help in the recruitment of transcriptional machinery.

A

DNA-Binding Domain

46
Q

A sequence of DNA that binds only to specific transcription factors.

A

Response Element

47
Q

Allows for the binding of several transcription factors and other important regulatory proteins, such as RNA polymerase and histone acetylases.

A

Activation Domain

48
Q

Several response elements are grouped together to form a type control mechanism (specifically of one’s gene’s expression by multiple signals).

A

Enhancer

49
Q

Tightly coiled DNA that appears dark under the microscope; its tight coiling makes it inaccesible to the transcription machinery, so these genes are INACTIVE.

A

Heterochromatin

50
Q

Looser coiled DNA and appears light under the microscrope; the transcription machinery can access the genes of interest, so these genes are ACTIVE.

A

Euchromatin

51
Q

This decreases the positive charge on lysine residues and weakens the interaction of the histone with DNA, resulting in an open chromatin conformation that allows for easier access of the transcriptional machinery to the DNA.

A

Histone Acetylation

52
Q

Proteins that function to remove acetyl groups from histones, which results in a closed chromatin conformation and overall decrease in gene expression levels in the clel.

A

Histone Deacetylases

53
Q

Add methyl groups to cytosine and adenine nucleotides. Often linked with silencing of gene expression.

A

DNA Methylation

MCAT Biochemistry (7 decks)

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