Chapter 18 Mastering Biology Exam
Questions and Answers
Part A - Operon vocabulary - Answer -1. A(n) (operonis) a stretch of DNA consisting of
an operator, a promoter, and genes for a related set of proteins, usually making up an
entire metabolic pathway.
2. The (genes of an operon) is/are arranged sequentially after the promoter.
3. A(n) (promoteris) a specific nucleotide sequence inDNA that binds RNA polymerase,
positioningit to start transcribing RNA at the appropriateplace.
4. A(n) (regulatory genecodes) for a protein,such as a repressor, that controls
thetranscription of another gene or group ofgenes.
5. Regulatory proteins bind to the (operator) to control expression of the operon.
6. A(n) (repressoris) a protein that inhibits gene transcription.In prokaryotes, this protein
binds tothe DNA in or near the promoter.
7. A(n) (inducer)is a specific small molecule that binds toa bacterial regulatory protein
and changes its shape so that it cannot bind to anoperator, thus switching an operon
on.
Part B - Regulation of model operons - Answer --Operon is not transcribed: trp operon
tryptophan present. lac operon lactose abset
-operon is transcribed, but not sped up through positive control: lac operon lactose
present, glucose present trp operon tryptophan abset
-operon is transcribed quickly through positive control: lac operon lactose persent,
glucose absent
Part A - Modification of chromatin structure
Which statements about the modification of chromatin structure in eukaryotes are true?
- Answer --Methylation of histone tails in chromatin can promote condensation of the
chromatin.
-Acetylation of histone tails in chromatin allows access to DNA for transcription.
-Some forms of chromatin modification can be passed on to future generations of cells.
-Acetylation of histone tails is a reversible process.
-DNA is not transcribed when chromatin is packaged tightly in a condensed form.
Part B - Regulation of transcription initiation - Answer --Control elements C, D, and E
are distal control elements for the imaginin gene.
-The fantasin gene will be transcribed at a high level when activators specific for control
elements A, B, and C are present in the cell.
-Both the fantasin gene and the imaginin gene will be transcribed at high levels when
activators specific for control elements A, B, C, D, and E are present in the cell.
Questions and Answers
Part A - Operon vocabulary - Answer -1. A(n) (operonis) a stretch of DNA consisting of
an operator, a promoter, and genes for a related set of proteins, usually making up an
entire metabolic pathway.
2. The (genes of an operon) is/are arranged sequentially after the promoter.
3. A(n) (promoteris) a specific nucleotide sequence inDNA that binds RNA polymerase,
positioningit to start transcribing RNA at the appropriateplace.
4. A(n) (regulatory genecodes) for a protein,such as a repressor, that controls
thetranscription of another gene or group ofgenes.
5. Regulatory proteins bind to the (operator) to control expression of the operon.
6. A(n) (repressoris) a protein that inhibits gene transcription.In prokaryotes, this protein
binds tothe DNA in or near the promoter.
7. A(n) (inducer)is a specific small molecule that binds toa bacterial regulatory protein
and changes its shape so that it cannot bind to anoperator, thus switching an operon
on.
Part B - Regulation of model operons - Answer --Operon is not transcribed: trp operon
tryptophan present. lac operon lactose abset
-operon is transcribed, but not sped up through positive control: lac operon lactose
present, glucose present trp operon tryptophan abset
-operon is transcribed quickly through positive control: lac operon lactose persent,
glucose absent
Part A - Modification of chromatin structure
Which statements about the modification of chromatin structure in eukaryotes are true?
- Answer --Methylation of histone tails in chromatin can promote condensation of the
chromatin.
-Acetylation of histone tails in chromatin allows access to DNA for transcription.
-Some forms of chromatin modification can be passed on to future generations of cells.
-Acetylation of histone tails is a reversible process.
-DNA is not transcribed when chromatin is packaged tightly in a condensed form.
Part B - Regulation of transcription initiation - Answer --Control elements C, D, and E
are distal control elements for the imaginin gene.
-The fantasin gene will be transcribed at a high level when activators specific for control
elements A, B, and C are present in the cell.
-Both the fantasin gene and the imaginin gene will be transcribed at high levels when
activators specific for control elements A, B, C, D, and E are present in the cell.
