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17. Which histone is required to compact the “beads on a string” chromatin into higher-order chromatin structures such as the 30 nm fiber?

18. Certain lysine amino acids (K’s) in the core histone tail can be acetylated. How would this chemical modification of the nucleosome affect the transcription of a gene?

19. Certain protein/protein complexes do not bind DNA, but regulate processes such as transcription and replication. These proteins can associate with the chromatin by recognizing chemical modifications in the core histone tails of the nucleosome. This process represents the “histone code”. Separately, a protein that folds into its three-dimensional functional structures can have different domains with different functions. Assume that a certain protein that increases transcription does not recognize a specific DNA sequence, but rather associates with acetylated lysine amino acids in the histone tails. What domain in this protein would allow it to associate with these acetylated lysine amino acids?

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Beverley SmithLv2
28 Sep 2019
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Related questions

QUESTION 3

What is the purpose of chromatin-remodeling enzymes in human cells?

The enzymes control the rate of translation of an mRNA transcript

The enzymes add phosphate or methyl groups to histone tails

The enzymes slide nucleosomes farther apart or closer to each other

The enzymes send damaged proteins to the proteasome for degradation

The enzymes cause DNA looping to occur

QUESTION 10

If you can drink milk as an adult, it means that you have inherited a mutation in the an enhancer for your lactase gene (the gene that encodes the enzyme you need to break down lactose). Predict the effect of this mutation:

The mutation changes the number of domains in the enzyme, which makes it work more efficiently

The mutation changes the amino acid sequence of the lactase protein

The mutation increases the number of copies of the lactase gene that will be found in your genome

The mutation changes whether the lactase sequence is found in an intron or exon

The mutation affects the expression of the lactase gene

QUESTION 12

What determines where in the genome a transcription regulator will bind?

Transcription regulators bind to the 5' UTR region of a gene

Regulators bind via complementary base-pairing to certain DNA molecules

Covalent bonds form between the transcription regulator and the atoms of the DNA backbone

Every eukaryotic gene has a different transcription regulator that will bind to the 5' end of the gene

Transcription regulators bind to specific DNA sequences via multiple weak non-covalent interactions

QUESTION 15

What is the histone code used for?

Phosphorylation and acetylation of DNA affect its ability to be compacted

Changes to the sequence of DNA change whether DNA will wrap around histone proteins

Covalent modifications of histones affect the ability of the transcription initiation complex to form

Histones provide the codon sequences needed for translation to occur

The histone code affects which amino acids will get added to a polypeptide

The bacterium E. coli, which is a major model system for the study of genes and DNA, has a singular circular chromosome of about 4x106 bp. In contrast, human diploid cells have __1__ chromosomes, of __2__ different types (don’t forget that the X ¹ Y!). The total amount of DNA found in a haploid cell such as a sperm or egg is called the organism’s “C-value”; the human C-value is __3__.

Also in contrast to the E. coli circular chromosome is the fact that eukaryotic chromosomes are not circular, but instead are __4__. Eukaryotic chromosomes are complexed heavily with protein to form a DNA-protein complex generically called __5__. The proteins found can be considered to fall into two general classes: __6__ and __7__. The first class is made up of 5 major proteins called __8__, __9__, __10__, __11__, and __12__. On a weight to weight basis, these proteins make up about __13__% of the total mass of a chromosome. Since these proteins must associate relatively non-specifically with DNA, they are rich in the basic amino acids __13__ and __14__, which gives the proteins a net __15__ charge.

One goal of packaging the DNA into chromatin is to compact the genome so it will fit into a nucleus. The basic unit of chromatin structure is the __16__, which has __17__ base pairs of DNA wrapped around a “core particle” composed of __18__ copies each of the core histones. Each nucleosome is separated by a stretch of “linker” DNA so that the repeating unit is approximately 200 bp. Lets do a little arithmetic: If we consider that the nucleosome is approximately __19__ nm in diameter, that there is about 200 bp in this structure, and that 200 bp of DNA would normally occupy __20__ nm if stretched out straight (recall that each base is spaced about 0.34 nm from the next), we can see that the nucleosome alone allows for a __21__-fold compaction ratio.

The nucleosome structure is further compacted by histone __22__, which is not a part of the core particle. Instead, this histone __23__ (does what?) to cause the nucleosomal 10 nm fiber to condense into a higher-order structure referred to as the __24__ nm fiber. In the nucleus, chromosomes do not just float around freely: they are tethered to a proteinaceous structure called the __25__ at specific DNA regions called “SARs”, which stands for __26__. SARs are rich in topoisomerases, to allow the winding and unwinding of the DNA that accompanies replication and transcription to occur, despite this constraint.

The 30 nm fiber discussed above is the form in which transcriptionally active DNA is believed to exist in the nucleus; however, further condensation leads to a highly condensed inactive form called __27__; in this terminology, the active form is referred to as __28__. The inactive condensed form can be divided into two types: one type is essentially invariant between cell types, and since it is “on all t time”, it is referred to as __29__. The other type comes and goes, depending on the expression of the genes present in that region of the chromosome; it is referred to as __30__.

Eukaryotic chromosomes carry the genes, of course, but also have other functional regions. One such region is the place where the spindle apparatus attaches during mitosis and meiosis; this region of the chromosome is called the __31__. Another important part of the linear eukaryotic chromosome is the ends; these are called __32__. In humans, the end of each chromosome is composed of many repeats of the short sequence __33__. One more type of functional region on each chromosome is the place where DNA replication starts; in humans, each chromosome has several of these __34__. Thus, eukaryotic chromosomes carry several different types of functional sequences, which together allow for their __35__ during S phase, __36__ during mitosis and meiosis, and the __37__ of their genes

Second messengers play an important role in cellcommunication.

Which of the following best describes their role?

None

integrate, amplify and distribute messages throughout thecell

Release messages to other cells?

Receive information at the cell surface

What is true of disulfide bonds?

a.

They often occur in the cytosol

b.

They are a noncovalent bond

c.

They are formed enzymatically in the ER

d.

They act as reducing agents

e.

they increase protein flexibility

Which of the following is NOT an example of a cell communicationmolecule?

nucleases

nitric oxide

hormones

kinases

What is true of binding pockets?

a.

They only occur in the membrane

b.

They occur in unfolded proteins

c.

They contain electrostatic interactions

d.

They contain variable amino acids

e.

What is true of cell signaling?

a.

Extracellular signals transduced by rectors always alter cellbehavior very quickly

b.

Some cells require cell signals just to survive

c.

Cell signals can be interpreted differently by differentcells

d.

B and C only

e.

All of the above (A, B and C)

Histone tails can be modified to change the shape and"tightness" of the nucleosomes. Acetylated histones result in whicheffect?

Open DNA

increased transcription

closed DNA

decreased transcription

1+2

1+4

3+4

2+3

Shifting the two bound tRNA from the A and P sites to the E andP sites of the ribosome involves:

a.

The movement of the small ribosome subunit down the mRNAchain

b.

The degradation of the A site on ribosome

c.

The synthesis of the E site on the ribosome

d.

The movement of the large subunit relative to the smallsubunit

e.

All of the above

Intracellular signaling pathways are awesome! What is the onething they can NOT do?

a.

relay the signal, to spread it through the cell

b.

nothing, they can communicate any cellular need

c.

distribute the signal to more than one effector protein

d.

integrate the signal from more than one cellular pathway

e.

Amplify the signal received, making the signal stronger

Specificity of protein/protein and protein/DNA binding isdetermined by what?

Non-covalent bonds

Hydrophobic interactions

Covalent bonds

shape of the binding site

all of the above

none of the above

1,2,3

1,2,4

1,3,4

The coiling structure of the DNA into chromosomes is achieved bywhat?

alpha helix

beta pleated sheets

chaperone proteins

DNA/Protein complexing

Which regions (s) of the DNA are found in the final protein?

a.

poly-A tail

b.

A and B

c.

Exons

d.

UTRs

e.

Introns

Metabolic processes can be turned "on" and "off" by chemicalmodifcation.

Which chemical modification do we associate with changing theactivity of an enzyme in a transient/non-permanent manner?

Phosphorylation

Ubiquitination

Methylation

Acetylation

DNA hybridization involves attaching a florescent dye towhat?

a.

Antibody

b.

Nuclear stain

c.

Probe DNA

d.

tRNA

e.

rRNA

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