Chapter 18 Mastering Biology

Part A – Operon vocabulary

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

-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?

-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

-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.

Part C – Alternative RNA splicing

ACGI ACEI ACEGI

_____ bind(s) to DNA enhancer regions.

activators

What is the event that IMMEDIATELY follows the last event of this animation?

binding of RNA polymerase to the promoter

Which of these indicates an enhancer region?

A

Which of these directly bind(s) to the promoter?

C and D

The operon model of the regulation of gene expression in bacteria was proposed by _____.

Jacob and Monod

Which of these is NOT a component of the lac operon?

regulatory gene only

Regulatory proteins bind to _____.

the operator

In the presence of a regulatory protein the lac operon is _____.

nor transcribed

Click on the diagram to start the animation. In this animation the blue sphere represents _____.

lactose

Click on the diagram to start the animation. In this animation the orange object represents _____.

RNA polymerase

Which of these is a regulatory gene?

D

A high concentration of bicoid protein at the opposite ends of a developing Drosophila embryo would result in the development of a _____.

two-headed fly

The bicoid gene product is directly responsible for _____ in a developing Drosophila embryo.

the establishment of the anterior-posterior axis

The region of a Drosophila embryo with the highest concentration of bicoid protein will develop into the _____.

head

What triggers the translation of bicoid mRNA?

fertilization of the egg

The bicoid gene is a type of _____ gene.

egg-polarity

The region of a Drosophila embryo with a low concentration of bicoid protein will develop into the _____.

male flowers

What process produces the gradient of bicoid protein in a fertilized egg?

diffusion

Bicoid mRNA is translated in _____.

the fertilized egg

Which of these regions is most likely to develop into the Drosophilia’s head?

A

The bicoid gene is transcribed by _____.

nurse cells