DNA to RNA to Protein Flashcards

1
Q

what is the purpose of RNA as an intermediary

A

allows for genes to be expressed with different efficiencies

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2
Q

what are the differences between RNA and DNA

A
  • ribose vs deoxyribose sugars
  • uracil vs thymine
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3
Q

what is the purpose of the template strand

A

to be used for transcription

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4
Q

what is the purpose of the coding strand

A

to provide sequence of the final product

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5
Q

what does RNA polymerase do

A

transcribes DNA to RNA

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6
Q

what are the characteristics of RNA polymerase

A
  • catalysis of ribonucleotide linkage
  • doesn’t need primer
  • makes more mistakes than DNA polymerase b/c it lacks exonuclease activity
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7
Q

what are the types of RNA made by cells

A

mRNA, rRNA, tRNA

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8
Q

what are the steps in transcription

A

binding, initiation, elongation, termination

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9
Q

what are the next steps for mRNA

A
  • must leave nucleus for translation
  • exits thru nuclear pores
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10
Q

what are the mechanisms of mRNA processing

A

RNA capping and polyadenylation

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11
Q

describe RNA capping

A
  • methylated guanosine (guanine attached to ribose ring) added to 5’ end
  • allows ribosome to bind mRNA
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12
Q

describe polyadenylation

A

series of adenine nucleotides added to 3’ end

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13
Q

what is the purpose of eukaryotic mRNA processing

A

to increase the stability of mRNA and indicates transcript is ready for translation

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14
Q

describe exons vs introns

A

exons are coding sequences, whereas introns are noncoding sequences

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15
Q

define spliceosomes

A

complex of proteins and RNA molecules that splice RNA

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16
Q

how are introns removed

A
  • excised by snRNPS (small ribonucleoprotein complexes)
  • the snRNPS recognize specific nucleotide sequences and determine where cuts should be made for intron removal
17
Q

describe translation

A

the process of reading the genome after protein synthesis

18
Q

what is the start codon; what is the name for it

A

AUG; methionine

19
Q

what are the stop codons

A

UAA, UAG, UGA

20
Q

what are codons

A

mRNA decoded in sets of 3 nucleotides, representing an amino acid

21
Q

how is a strand read

A

from 5’ to 3’ ends

22
Q

what is an anticodon

A

sequence of 3 nucleotides that base-pairs with a codon in mRNA

23
Q

what is a tRNA

A

molecular adaptor; reads the code and makes the proteins for it

24
Q

what two adaptors act together to translate the genetic code

A

aminoacyl-tRNA synthetase and tRNA

25
Q

briefly describe the process of translating the genetic code

A
  • aminoacyl-tRNA synthetase couples amino acids to the corresponding tRNA
  • anticodon forms base pairs with codon on mRNA
26
Q

describe the structure of a ribosome

A
  • one large and one small subunit
  • vary between prokaryotic and eukaryotic structures
27
Q

what are the types of ribosomes; where are they

A

bound and free; attached to ER and in cytoplasm respectively

28
Q

what is the function of bound ribosomes

A

make proteins for membranes and secretion

29
Q

when do ribosomal subunits dissociate

A

when translation of protein is complete

30
Q

what are the 3 binding sites for tRNAs

A

aminoacyl (A), peptidyl (P) and exit (E) sites

31
Q

what sites does the tRNA fit to and in what condition(s)

A

A & P; only when tRNA anti-codon binds to mRNA codon

32
Q

describe how a polypeptide is assembled at the ribosome

A
  • tRNA enters A site, where an anticodon binds to mRNA codon
  • 2 amino acids link to e/o and the large ribosomal subunit shifts
  • the first amino acid is rejected and mRNA moves 3 nucleotides further through the small ribosomal subunit
33
Q

describe how translation stops

A
  • needs presence of stop codon
  • when stop codon reaches A site, chain release factors bind instead of another tRNA amino acid
  • peptidyl transferase catalysis water addition to COOH to free the chain
  • the subunits dissociate, thereby the tRNA, mRNA and release factors releasing
34
Q

what are chemical examples of practical applications for translation inhibition

A

tetracycline, streptomycin, chloramphenicol, erythromycin, rifamycin

35
Q

describe tetracycline’s role in translation inhibition

A

blocks binding of aminoacyl tRNA to A site of ribosome (prevents the 1st step of translation)

36
Q

describe chloramphenicol’s role in translation inhibition

A

blocks peptidyl transferase reaction on ribosomes (prevents 2nd step of translation)

37
Q

describe erythromycin’s role in translation inhibition

A

blocks translation reaction on ribosomes (prevents 3rd step of translation)