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Biology 101 > Chapter 17 > Flashcards

Chapter 17 Flashcards

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1
Q

What are the 3 major classes of RNA?

A

mRNA, rRNA, and tRNA

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2
Q

What is the purpose of mRNA?

A

carries genetic information from the DNA to the ribosomes (m for messenger)

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3
Q

What is the purpose of rRNA?

A

composes ribosomes, site of protein synthesis (r for ribosome)

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4
Q

What is the purpose of tRNA?

A

brings amino acids to the ribosomes (t for transfer)

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5
Q

In eukaryotic cells, transcription cannot begin until…

A

several transcription factors have bound to the promoter.

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6
Q

The anticodon of a particular tRNA molecule is

A

complementary to the corresponding mRNA codon.

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7
Q

true of a codon

A
  • consists of three nucleotides
  • is the basic unit of the genetic code.
  • may code for the same amino acid as another codon
  • never codes for more than one amino acid.
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8
Q

initiation

A

binding of transcription factors and RNA polymerase II to a promoter- transcription initiation complex

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9
Q

elongation

A

RNA polymerase untwists the double helix and transcription progresses at a rate of 40 nucleotides per second in eukaryotes. Assembles mRNA in 5’-3’ direction. No primer needed, start the chain from scratch.

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10
Q

termination

A

transcribes polyadenylation signal (AAUAAA), then enzymes cut the pre-mRNA free from polymerase and release it.

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11
Q

base-pair substitution

A

replaces one nucleotide and its partner with another pair of nucleotides
Silent mutations have no effect on the amino acid produced by a codon because of redundancy in the genetic code

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12
Q

Missense mutations

A

still code for an amino acid, but not necessarily the right amino acid

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13
Q

Nonsense mutations

A

change an amino acid codon into a stop codon, nearly always leading to a nonfunctional protein

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14
Q

Insertions and deletions

A

are additions or losses of nucleotide pairs in a gene
These mutations have a disastrous effect on the resulting protein more often than substitutions do
Insertion or deletion of nucleotides may alter the reading frame, producing a frameshift mutation

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15
Q

Mutagens

A

are physical or chemical agents that can cause mutations

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16
Q

a gene can be defined as

A

a region of DNA that can be expressed to produce a final functional product, either a polypeptide or an RNA molecule

17
Q

polyribosome (or polysome)

A

A number of ribosomes can translate a single mRNA simultaneously,enable a cell to make many copies of a polypeptide very quickly

18
Q

The termination of translation

A

occurs when a stop codon in the mRNA reaches the A site of the ribosome
The A site accepts a protein called a release factor
The release factor causes the addition of a water molecule instead of an amino acid
This reaction releases the polypeptide, and the translation assembly then comes apart

19
Q

The elongation cycle of translation

A

Amino acids are added one at a time
Each new tRNA-amino acid complex at the second binding site receives a peptide from a tRNA at the first binding site, a peptide
bond forms, the first tRNA breaks away, and the ribosome moves forward one codon.

20
Q

The initiation of translation

A

Small ribosomal subunit attaches to mRNA at start codon
Codons read in the 5’ to 3’ direction along m RNA. Anticodon of the initiator tRNA-methionine complex binds to start codon
Large ribosomal subunit joins to the small subunit

21
Q

The initiation of translation

A

Chain initiation
Small ribosomal subunit attaches to mRNA at start codon
Codons read in the 5’ to 3’ direction along m RNA. Anticodon of the initiator tRNA-methionine complex binds to start codon
Large ribosomal subunit joins to the small subunit

22
Q

introns

A

The noncoding segments of nucleic acid that lie between coding regions are called intervening sequences

23
Q

exon

A

a sequence within the primary transcript that remains in the RNA, after RNA processing; also refers to the region of DNA from which this sequence was transcribed

24
Q

RNA splicing

A

After synthesis of a eukaryotic primary RNA transcript, the removal of portions of transcript (introns) that will not be included in the mRNA and the joining together of the remaining portions (exons)

25
Q

codon

A

A sequence of three nucleotides on an mRNA molecule

26
Q

During translation, nucleotide base triplets (codons) in mRNA are read in sequence in which direction?

A

5’ → 3’ direction along the mRNA.

27
Q

RNA polymerase

A

untwists a portion of the DNA double helix

28
Q

What is a key difference between eukaryotic and prokaryotic gene expression?

A

In prokaryotic cells, the RNA transcript is immediately available as mRNA without processing.

29
Q

Two different proteins with mostly different structures are translated from two different mRNAs. These mRNAs, however, were transcribed from the same gene. Which mechanism could best account for this?

A

Exons from the same gene could be spliced in different ways to make different mRNAs.

30
Q

Which statement correctly describes mRNA processing?

A

Introns are cut out of the primary transcript, and the resulting exons are spliced together.

31
Q

Which accurately describes the usual process of eukaryotic transcription?

A

Both introns and exons are transcribed, but the RNA transcribed from introns does not leave the nucleus.

32
Q

summary of protein synthesis

A

Messenger RNA is made on a DNA template, and then amino-acid-bearing transfer RNAs bind to the mRNA through codon-anticodon pairing.

33
Q

During translation in a eukaryotic cell, __________.

A

polypeptides are synthesized at ribosomes, according to instructions carried by mRNA

34
Q

During translation, amino acid chain elongation occurs until __________

A

the ribosome encounters a “stop” codon

35
Q

What is their proper sequence for these steps?

  1. translation
  2. RNA processing
  3. transcription
  4. modification of protein
A

3, 2, 1, 4

Biology 101 (10 decks)

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