Chapter 12

In the presence of the sugar galactose, the expression levels of GAL1, GAL2, GAL7, and GAL10 are ______________ as compared to the absence of galactose.

1000-fold higher

Why are histone tails not visible in the crystal structure of the nucleosome core particle?

Because the histone tails are flexible regions with different patterns of post-translational modification. In order to be visible in a crystal structure, the region needs have a determined secondary/tertiary structure.

Which of the following GAL genes are located on the same chromosome?

GAL1 and GAL10

Analyzing mutations in the GAL80 and GAL3 indicate that

GAL80 inhibits GAL gene expression, and GAL3 promotes GAL gene expression.

What are the two general mechanisms by which histone acetylation affects transcription?

H3 tail modifications or histone modifications are collectively known for ' epigenetic regulation of gene expression' where there gene expression can be regulated without change in the DNA sequence by itself. The most common modifications in the histone tail are methylation and acetylation.

What are the two general mechanisms by which histone acetylation affects transcription?

Histone acetylation increases the protein transcription. It is explained below. Histone is a positive charged protein. The acetylation of histones happen in the lysine residues amino-terminal tails of the histones, along these lines killing the positive charge of the histone tails and diminishing their affinity for DNA. Histones are proteins that arrange chromatin into nucleosomes and eventually higher structures.A nucleosome is made out of 147 base sets of DNA looped around an octamer of histone proteins, two molecules every one of histone H2A, H2B, H3 and H4. Histone H1 gets combine with chromatin outside the center octamer unit and manages higher request chromatin structure. Acetylation eliminates the positive charge on the histones proteins. This decrease the interaction of the N ends of histones with the contrarily charged phosphate group of DNA. As an outcome, the dense chromatin is changed into a more loosened up structure that is related with more noteworthy degrees of gene transcription. Loose, transcriptionally dynamic DNA is reffered to as 'EUCHROMATIN'.

A researcher has identified a mutant cell line that has reduced transcription of gene X relative to the parental cell line. The mutant cell line has a single point mutation in the entire genome. Describe five possible mechanisms by which the point mutation could reduce the transcription of gene X.

Reduced efficacy of enhancer sequence: enhancers are basically DNA binding elements which enhances the rate of transcription. Reduced efficacy of these can lead to reduced transcription. Reduced efficacy of coactivator binding: the coactivator binds to activator and helps in increasing the rate of transcription. Reduced efficacy of this can reduces the rate of transcription. Disruption of TATA box: Tata box act as a promoter in transcription. Disruption of TATA box will lead to severe reduction in rate of transcription. Increased efficacy of silencer sequences: silencers can bind to repressors and decrease the rate of transcription. So increase in the efficacy of this reduces the rate of transcription.

The Gal4 protein has which of the following functional domains?

a DNA-binding domain and an activation domain

What is an enhanceosome?

a large complex that acts synergistically to activate transcription

The "domain-swapping" experiment that grafts the Gal4 activation domain to the LexA DNA-binding domain generates a chimeric protein that will

bind to the LexA site.

Epigenetic inheritance is defined as the inheritance of

chromatin states from one cell generation to the next.

The sequences of ________ are among the most highly conserved in evolution.

core histones

Regions of a chromosome that are bundled in highly condensed chromatin are known as

heterochromatin.

The enzyme responsible for removing acetyl groups from histone proteins is called

histone deacetylase (HDAC).

In mice, the H19 allele is expressed only if it is

inherited from the mother.

Acetylation of lysines in histones by histone acetyltransferase

loosens interactions within and between nucleosomes.

Which of the following describes the histones associated with the nucleosomes of active genes?

rich in acetyl groups (i.e., hyperacetylated)

Compared to heterochromatin, euchromatin is

rich in genes and comprised of loosely packed nucleosomes

GAL80 inhibits GAL gene expression by

specifically binding to Gal4 and preventing activation.