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transcription and translation Flashcards

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Biology 101 flashcards
1
Q

gene expression

A

the process by which DNA directs protein synthesis, includes 2 stages:
- transcription
- translation

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2
Q

gene expression sequence

A

DNA -> transcription -> RNA (mRNA) -> translation -> protein

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3
Q

Beadle and Tatum

A

the one gene-one enzyme hypothesis
- bread mold Neurospora by changing genes, bread couldn’t grow a certain protein
- different classes of these mutants were blocked at a different step in the biochemical pathway for arginine biosynthesis
- revises to one gene- one protein/polypeptide hypothesis

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4
Q

RNA

A

single stranded, uracil, ribose sugar

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5
Q

transcription

A

synthesis of RNA using information in DNA
- produces messenger RNA (mRNA)

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6
Q

translation

A

the synthesis of a polypeptide, using information in the mRNA
- ribosomes are site of translation

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7
Q

transcription and translation: bacteria

A

both can happen at the same time

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8
Q

transcription and translation: eukaryotes

A

nucleur envelope separates the two; translation happens in cytoplasm

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9
Q

primary transcript

A

the initial RNA transcript from any gene prior to processing

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10
Q

central dogma

A

cells are governed by a cellular chain of command

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11
Q

triplet code

A

a series of non overlapping, 3 -nucleotide words
- 20 amino acids, 64 codons

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12
Q

template strand

A

provides a template for ordering the sequence of complementary nucleotides in a RNA transcript

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13
Q

codons

A

base triplets; read in 5’ to 3’ direction
- 64 codons, 61 for amino acids, 3 STOP codon’s
- redundant but not ambiguous

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14
Q

RNA polymerase

A

pries DNA strands apart and joins together RNA nucleotides
- assembles in 5’ to 3’ direction
- doesn’t need a primer
- attaches to the promoter (starting DNA sequence)
- terminator (is ending sequence)

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15
Q

transcription unit

A

stretch of DNA that is transcribed

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16
Q

transcription factors, TATA box and terminator in eukaryotic transcription

A

transcription factor: mediate the binding of RNA polymerase and the initiation of transcription

promoter has TATA box, transcription initiation complex forms (transcription factors + RNA polymerase II bound to promoter)

terminator in eukaryotes: RNA polymerase II transcribes polyadenylation signal sequence (AAUAAA) - RNA released 10-35 nucleotides after

17
Q

transcription: DNA -> RNA steps

A
  1. initiation
    - RNA polymerase attaches to promoter
  2. Elongation
    - RNA polymerase unwinds DNA and elongates RN transcript
  3. Termination
    - RNA polymerase detaches and RNA is made
18
Q

RNA processing

A

both ends of primary transcript are altered, enzymes in the eukaryotic nucleus modify pre-mRNA
- introns cut out, exons spiced together
- addition of 5’ cap (5’ end) and poly A-tail (3’ end)

19
Q

5’ cap and poly A-tail

A
  • facilitates export of mRNA to cytoplasm
  • protects mRNA from hydrolytic enzymes
  • helps ribosomes attach to 5’ end
19
Q

RNA splicing

A

removes introns (noncoding) and joins exons (coding)
- different segments of exons used alternative RNA splicing
- carried out by splicesomes (proteins and small RNA)

20
Q

Ribozymes

A

RNA molecules that function as enzymes
- introns can catalyze own splicing

21
Q

transfer RNA (tRNA)

A

helps translate mRNA message into protein
- can translate a particular mRNA code into a amino acid
- has amino acid on one end and nucleotide triplet that can base-pair with complementary codon on mRNA (anticodon)

22
Q

Translation two steps: tRNA

A
  1. aminoacetyl-tRNA synthesase enzyme matches tRNA with amino acid
  2. tRNA anticodon matched with mRNA codon
    - wobble: flexible pairing of third base of a codon
23
Q

Ribosomes

A

facilitate coupling of tRNA anticodons with mRNA codons
- large and small subunits made of proteins and ribosomal RNAs (rRNAs)
- 3 binding sites for tRNA

24
Q

3 binding sites for tRNA

A
  • P site: holds the tRNA that carries growing polypeptide chai
  • A site: holds tRNA that has next AA
  • E site: exit site, tRNA discharges
25
Q

Three Stages of translation

A

initiation, elongation, termination
- energy by hydrolysis of GPT
- require protein “factors” to aid
1. intiation
-mRNA and tRNA and ribosomal subunits bind (large binds last)
2. elongation
- AA’s added to previous AA at C-terminus
- elongation factors, occur in 3 steps: codon recognition, peptide bond formation and translocation
- 5’ to 3’ direction
3. termination
- when stop codon reaches A site (accept a release factor)

26
Q

elongation factors steps

A
  1. codon recognition
  2. peptide bond formation
  3. translocation
27
Q

release factor

A

addition of water molecule instead of AA so it ends

28
Q

Two types of ribosomes

A

free (make proteins for cytosol) and bound (make proteins for ER)

29
Q

signal peptide

A

mark polypeptides destined for ER or for secretion
- signal recognition partial (SRP): binds to signal peptide, brings it and ribosome to ER

30
Q

polyribosomes

A

string of ribosomes

31
Q

mutations

A

changed in the genetic material of a cell or virus

32
Q

point mutations

A

chemical changes in just one nucleotide pair of a gene (ex: sickle-cell disease)
- single nucleotide-pair substitutions: replaces one nucleotide and its partner with another pair of nucleotides
- nucleotide-pair insertions or deletions: additions or losses of nucleotide pairs in a gene (disastrous effect)

33
Q

Substitutions

A
  • silent: no effect on AA because of redundancy of codons
  • missense: still code for an AA, but the wrong way
  • nonsense: change a AA codon into a stop codon, not functioning protein
34
Q

Insertion/deletion

A

frameshift: altered reading from genetic message
- can be missense and nonsense

35
Q

mutagens

A

physical/chemical agents that can cause mutations

bio (10 decks)

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