Chapter 12

Question 1

What is gene expression?

Answer 1

Gene function either at the level of traits or at the molecular level.

Question 2

What are mutations?

Answer 2

A heritable change in the genetic material of an organism.

Question 3

Transcription:

Answer 3

The process that produces an RNA copy of a gene.

Question 4

What is messenger RNA? (mRNA)

Answer 4

RNA that contains the information to specify a polypeptide with a particular amino acid sequence.

Question 5

Translation:

Answer 5

The process of synthesizing a specific polypeptide on a ribosome.

Question 6

What is the central dogma.

Answer 6

Refers to the steps of gene expression at the molecular level: DNA is transcribed into mRNA, and mRNA is translated into a polypeptide.

Question 7

What is a gene?

Answer 7

A unit of heredity. At the molecular level, a gene is an organized unit of base sequences in a DNA strand that can transcribed into RNA and ultimately results in the formation of a functional product.

Question 8

What is transfer RNA? (tRNA)

Answer 8

An RNA that carries amino acids and is used to translate mRNA into polypeptides.

Question 9

What is ribosomal RNA? (rRNA)

Answer 9

An RNA that forms part of ribosomes, which provide the site where translation occurs.

Question 10

What are two type on non-coding RNAs?

Answer 10

tRNA and rRNA

Question 11

What is a codon?

Answer 11

A sequence of three nucleotide bases that specifies a particular amino acid or a stop codon; codons function during translation.

Question 12

What is an anticodon?

Answer 12

A three-base sequence in tRNA that is complementary to a codon in mRNA.

Question 13

What is a protein-encoding gene?

Answer 13

A gene that serves as a template to make an mRNA molecule that contains the information to specify a polypeptide with a particular amino acid sequence; most genes are protein-encoding genes.

Question 14

What is non-coding RNA (ncRNA)?

Answer 14

An RNA molecule that does not encode the amino acid sequence of a polypeptide.

Question 15

What does “inborn error of metabolism” mean?

Answer 15

A genetic defect that produces an inability to metabolize a certain compound.

Question 16

pre-mRNA:

Answer 16

In eukaryotes, the mRNA transcript before any biochemical modifications are made to it.

Question 17

What is the additional step in the central dogma of eukaryotic cells?

Answer 17

RNA undergoes modification so that it is functionally active mRNA.

Question 18

sigma factor:

Answer 18

A protein that recognizes the promoter in a bacterial gene and binds RNA polymerase to the promoter

Question 19

RNA polymerase:

Answer 19

The enzyme that synthesizes strands of RNA during gene transcription.

Question 20

open complex:

Answer 20

A separation between the two DNA strands that occurs near the promoter during transcription; also called a transcription bubble.

Question 21

template strand:

Answer 21

The DNA strand that is used as a template for RNA synthesis or DNA replication

Question 22

coding strand:

Answer 22

The DNA strand opposite to the template (or noncoding strand). Contains the information that codes for a polypeptide.

Question 23

transcription factor:

Answer 23

A protein that influences the ability of RNA polymerase to transcribe genes.

Question 24

What are the three common types of RNA modification?

Answer 24

Capping, Tailing, and Splicing

Question 25

What is splicing?

Answer 25

The process in which introns are removed from an RNA molecule, such as a pre-mRNA, and the remaining exons are connected to each other.

Question 26

What is capping?

Answer 26

The process in which 7-methylguanosine is covalently attached at the 5´ end of pre-mRNAs of eukaryotes. Results in a 5' cap.

Question 27

What is a poly A tail?

Answer 27

A string of adenine nucleotides at the 3′ end of most mature mRNAs in eukaryotes. Added enzymatically.

Question 28

What are introns?

Answer 28

Intervening DNA sequences that are found in between the coding sequences of genes. They are transcribed, but not translated or expressed.

Question 29

What is an exon?

Answer 29

A portion of RNA that is found in the mature mRNA molecule after splicing is finished. Contain coding information a polypeptide.

Question 30

spliceosome:

Answer 30

A complex of several subunits known as snRNPs that removes introns from eukaryotic pre-mRNA

Question 31

alternative splicing:

Answer 31

The splicing of pre-mRNA in more than one way to allow the production of two or more different polypeptides from the same gene.

Question 32

self-splicing:

Answer 32

The phenomenon in which an rRNA or a tRNA catalyzes the removal of its own intron(s).

Question 33

genetic code:

Answer 33

A code that specifies the relationship between the sequence of bases in the codons found in mRNA and the sequence of amino acids in a polypeptide.

Question 34

What does degenerate mean in relation to codons?

Answer 34

The characteristic of the genetic code that more than one codon can specify the same amino acid.

Question 35

start codon:

Answer 35

A three-base sequence—usually AUG—that specifies the first amino acid in a polypeptide.

Question 36

coding sequence:

Answer 36

The region of a gene or a DNA molecule that encodes the information for the amino acid sequence of a polypeptide.

Question 37

stop codon:

Answer 37

One of three three-base sequences—UAA, UAG, and UGA—that signals the end of translation; also called a termination codon or codon.

Question 38

reading frame:

Answer 38

Refers to the way in which codons are read during translation, in groups of three bases beginning with the start codon.

Question 39

What is a peptide bond?

Answer 39

The covalent bond between a carboxyl and amino group that links amino acids in a polypeptide.

Question 40

aminoacyl-tRNA synthetase:

Answer 40

An enzyme that catalyzes the attachment of amino acids to tRNA molecules. There are 20 distinct types.

Question 41

initiation factor:

Answer 41

A protein that facilitates the interactions between mRNA, the first tRNA, and the ribosomal subunits during the initiation stage of translation.

Question 42

elongation factor:

Answer 42

A protein that is needed for polypeptide synthesis during the elongation stage of translation.

Question 43

peptidyl transfer reaction:

Answer 43

During translation, the transfer of the polypeptide from the tRNA in the P site to the amino acid at the A site.

Question 44

polysome:

Answer 44

The complex of a single mRNA and multiple ribosomes.

Question 45

release factor:

Answer 45

A protein that recognizes a stop codon in the termination stage of translation and promotes the termination of translation.

Question 46

termination:

Answer 46

The final stage of transcription, in which the RNA dissociates from the DNA, or of translation, in which the polypeptide is released from the ribosome.

Question 47

What is an antibiotic?

Answer 47

A chemical, usually made by microorganisms, that inhibits the growth of certain other microorganisms.