Chapter 17: Gene Expression: From Gene to Protein

Question 1

Gene Expression

Answer 1

• Process by which information encoded in DNA directs the synthesis of proteins
• In some cases, RNAs that are not translated into proteins are translated and function as RNAs

Question 2

Transcription

Answer 2

Synthesis of RNA from a DNA template

Question 3

Messenger RNA (mRNA)

Answer 3

• Type of RNA synthesized from DNA
• Attached to ribosomes in the cytoplasm
• Specifies the primary structure of a protein

Question 4

Translation

Answer 4

Synthesis of a polypeptide using the genetic information encoded in an mRNA molecule

Question 5

Primary Transcript

Answer 5

• Initial RNA transcript from any gene

- Also called pre-mRNA when transcribed from a protein-coding gene

Question 6

Triplet Code

Answer 6

• Genetic information system

- Series of three-nucleotide-long words specifies a sequence of amino acids for a polypeptide chain

Question 7

Template Strand

Answer 7

DNA strand that provides the pattern/template for ordering by complementary base pairing the sequence of nucleotides in an RNA transcript

Question 8

Codon

Answer 8

• Three-nucleotide sequence of DNA or mRNA that specifies a particular amino acid or termination signal
• Basic unit of the genetic code

Question 9

Reading Frame

Answer 9

On an mRNA, the triplet grouping of ribonucleotides used by the translation machinery during polypeptide synthesis

Question 10

RNA Polymerase

Answer 10

Enzyme that links ribonucleotides into a growing RNA chain during transcription based on complementary binding to nucleotides on a DNA template strand

Question 11

Promoter

Answer 11

Specific nucleotide sequence in DNA that binds RNA polymerase and indicates where to start transcribing RNA

Question 12

Transcription Unit

Answer 12

Region of DNA that is transcribed into an RNA molecule

Question 13

Transcription Initiation Complex

Answer 13

Completed assembly of transcription factors and RNA polymerase bound to a promoter

Question 14

TATA Box

Answer 14

DNA sequence in eukaryotic promoters crucial in forming the transcription initiation complex

Question 15

RNA Processing

Answer 15

• Modification of RNA primary transcripts
• Includes:
  
  • Splicing out of introns
  • Joining together of exons
  • Alteration of the 5’ and 3’ ends

Question 16

5’ Cap

Answer 16

Modified form of guanine nucleotide added onto the 5’ end of a pre-mRNA molecule

Question 17

Poly-A Tail

Answer 17

Sequence of 50-250 adenine nucleotides added onto the 3’ end of a pre-mRNA molecule

Question 18

RNA Splicing

Answer 18

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

Question 19

Intron

Answer 19

• Non-connecting, intervening sequence within a primary transcript that is removed from the transcript during RNA processing
• Also refers to the region of DNA from which this sequence was transcribed

Question 20

Exon

Answer 20

• Sequence within a primary transcript
• Remains in the RNA after RNA processing
• Also refers to the region of DNA from which this sequence was transcribed

Question 21

Spliceosome

Answer 21

Large complex made up of proteins and RNA molecules that splices RNA by interacting with the ends of an RNA intron releasing the intron and joining the two adjacent exons

Question 22

Ribozyme

Answer 22

• RNA molecule
• Functions as an enzyme
• Example= intron that catalyzes its own removal during RNA splicing

Question 23

Alternative RNA Splicing

Answer 23

• Type of eukaryotic gene regulation at the RNA-processing level in
• Different mRNA molecules are produced from the same primary transcript
• Depends on which RNA segments are treated as exons and which are treated as introns

Question 24

Domain

Answer 24

Discrete structural and functional region of a protein

Question 25

Transfer RNA (tRNA)

Answer 25

• RNA molecule that functions as an interpreter between nucleic acid and protein language
• Picks up specific amino acids and recognizes the appropriate codons in the mRNA

Question 26

Anticodon

Answer 26

• Nucleotide triplet at one end of a tRNA molecule

- Base-pairs with a particular complementary codon on an mRNA molecule

Question 27

Aminoacyl-tRNA Synthetase

Answer 27

Enzyme that joins each amino acid to the appropriate tRNA

Question 28

Wobble

Answer 28

• Flexibility in the base-pairing rules
• The nucleotide at the 5’ end of a tRNA anticodon can form hydrogen bonds with more than one kind of base in the third position (3’ end) of a codon

Question 29

Ribosomal RNA (rRNA)

Answer 29

• RNA molecules
• Together with proteins make up ribosomes
• Most abundant type of RNA

Question 30

P Site

Answer 30

• One of a ribosome’s three binding sites for tRNA translation
• Holds the tRNA carrying the growing polypeptide chain

Question 31

A Site

Answer 31

• One of a ribosome’s three binding sites for tRNA during translation
• Holds the tRNA carrying the next amino acid to be added to the polypeptide chain

Question 32

E Site

Answer 32

• One of a ribosome’s three binding sites for tRNA during translation
• Place where discharged tRNAs leave the ribosome

Question 33

Silent Mutation

Answer 33

• Nucleotide-pair substitution
• Has no observable effect on the phenotype
• Example= mutation that results in a codon that codes for the same amino acid

Question 34

Missense Mutation

Answer 34

• Nucleotide-pair substitution

- Results in a codon that codes for a different amino acid

Question 35

Nonsense Mutation

Answer 35

• Mutation that changes an amino acid codon to one of the three stop codons (UAA, UAG, UGA)
• Results in a shorter and usually nonfunctional protein

Question 36

Insertion

Answer 36

Mutation involving the addition of one or more nucleotide pairs to a gene

Question 37

Deletion

Answer 37

Mutational loss of one or more nucleotide pairs from a gene

Question 38

Frameshift Mutation

Answer 38

• Mutation occuring when nucleotides are inserted or deleted from a gene and the number added or removed is not a multiple of three
• Results in the improper grouping of subsequent nucleotides into codons

Question 39

Mutagen

Answer 39

Chemical/physical agent that interacts with DNA and causes a mutation

Question 40

Signal Peptide

Answer 40

• Sequence of about 20 amino acids at or near the leading (amino) end of a polypeptide
• Targets the polypeptide to the endoplasmic reticulum (ER) by binding to a receptor protein on the ER

Question 41

Signal-Recognition Particle (SRP)

Answer 41

Protein-RNA complex

• Recognizes a signal peptide as it emerges from a ribosome
• Helps direct the ribosome to the endoplasmic reticulum (ER) by binding to a receptor protein on the ER

Question 42

Polyribosome (Polysome)

Answer 42

Group of several ribosomes attached to and translating the same mRNA molecule

Question 43

Mutation

Answer 43

Change in the nucleotide sequence of an organism’s DNA or in the DNA or RNA of a virus

Question 44

Point Mutation

Answer 44

Change in a single nucleotide pair of a gene

Question 45

Nucleotide-Pair Substitution

Answer 45

• Type of point mutation

- One nucleotide in a DNA strand and its partner in the complementary strand are replaced by another pair of nucleotides