Chapter 17 Flashcards

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1
Q

Gene expression

A

the process b which DNA directs the synthesis of proteins (sometimes RNA)

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2
Q

One Gene- One Polypeptide Hypothesis

A

Each gene codes for a polypeptide, which can constitute part of a protein

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3
Q

Transcription

A

Synthesis of RNA under the direction of DNA. Produces mRNA

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4
Q

mRNA

A

Messenger RNA that is produced during transcription

Carries the genetic message of the DNA to the ribosome (protein making machinery)

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5
Q

mRNA differences in Prokaryotes and Eukaryotes

A

Eukaryotes- Nuclear envelope separates transcription from translation
mRNA is modified through RNA processing to yield finished mRNA
Prokaryotes- mRNA produced by transcription is immediately translated without further processing

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6
Q

Translation

A

Production of a polypeptide chain using the mRNA transcript

Occurs in the ribosomes in the cytosol

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7
Q

Template Strand

A

The strand of DNA that is transcribed in transcription

mRNA is complementary to this strand of DNA

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8
Q

Codons

A

mRNA nucleotide triplets

Smallest units are uniform length that can code for all the amino acids

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9
Q

Genetic Code

A

Redundant because more than one codon codes for an amino acid , but they are never vague

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10
Q

Reading Frame

A

The correct groupings in order for the specific polypeptides to be produced

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11
Q

RNA polymerase

A

Catalyzes the RNA synthesis, which follows the same base pairing rule, except uracil substitutes for thymine

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12
Q

Promoter

A

DNA sequences where RNA polymerase attaches

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13
Q

Terminator

A

Sequence signaling the end of transcription in bacteria

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14
Q

Transcription Unit

A

Entire stretch of DNA that is transcibed

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15
Q

Transcription Initiation Complex

A

The completed assembly of transcription factors and RNA polymerase II bound to a promoter

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16
Q

Steps of Transcription

A
  1. Initiation- Transcription factors bind to the promoter which helps the RNA polymerase II be able to bind to the promoter, creating a transcription initiation complex
  2. Elongation- RNA polymerase II untwists the DNA and adds complementary RNA bases
  3. Termination- After RNA polymerase transcribes the terminator sequence in the DNA, the RNA transcript is released and the RNA polymerase detaches
17
Q

Differences in Transcription between Prokayotes and Eukaryotes

A

RNA polymerase can bind to the promoter by itself in prokaryotes,
Prokaryotic polymerase stops transcription at the end of the terminator
Eukaryotes continues transcription after the pre-RNA is cleaved from the growing RNA chain, polymerase eventually falls of the DNA

18
Q

TATA box

A

Promoter that is crucial in forming the initiation complex in eukaryote

19
Q

Alteration of mRNA ends

A

Adds a 5’ cap to the 5’ end
The 3’ end receives a poly-A tail
Help to facilitate the export of mRNA, protects the mRNA from hydrolytic enzymes, and help ribosomes to attach to the 5’ end

20
Q

RNA Splicing

A

Removes introns and joins exons together creating a mRNA molecule with a continuous coding sequence

21
Q

Spliceosome

A

Consists of a variety of proteins and several small nuclear ribonucleicproteins that recognize splice sites

22
Q

Ribozyme

A

Catalytic RNA molecules that function as enzymes and cal splice RNA
Rendered obsolete the belief that all biological catalysts are proteins

23
Q

tRNA

A

Each tRNA carries specific amino acids on one end

Each has an anti codon on the opposite end that pairs with a codon on the mRNA

24
Q

Acute Translation

A
  1. A correct match between the tRNA and an amino acid (joined by the enzyme aminoacyl-tRNA synthetase)
  2. Correct match between tRNA anti codon and mRNA codon
25
Q

wobble

A

Flexible pairing at third base of a codon

Allows some tRNA to bind more than one codon

26
Q

Ribosomes

A

Made out of rRNA
Facilitate the specific coupling of tRNA anti codons with mRNA codons in protein synthesis
Two ribosomal subunits (large and small) that are made of proteins and rRNA

27
Q

3 Binding Sites

A

P- holds the tRNA that carries the polypeptide chain
A- holds he rRNA that carries the next amino acid to be added
E- Exit site, where discharged tRNA leave the ribosome

28
Q

Steps of Translation

A

initiation- a small ribosomal subunit binds to mRNA , anticodon matches up with the start codon on the mRNA, and the large subunit attaches, allowing tRNA to attach to the P site
Elongation- Amino acids are added to the preceding amino acid
Termination- Stop codon is reached and translation stops

29
Q

Signal Peptide

A

The sequence of the leading 20 or so amino acids that direct proteins to their final destination

30
Q

Point Mutations

A

alterations of just one base pair in a gene

31
Q

Missense mutation

A

substitutions that still allow for the codon to code for an amino acid

32
Q

Nonense mutation

A

subsitutions that change a regular amino acid codon into a a stop codon, ceasing translation

33
Q

Insertion/ Deletions

A

Additions and losses of nucleotide pairs in genes

34
Q

Frameshift Mutation

A

causes mRNA to be read incorrectly