Question

please answer all the questions
Question 8

0 / 1 pts

Our understanding of RNA

   

was non-existent until 2000

  

started with the identification of a tRNA which suggested a method of converting DNA to protein

   

began to identify that DNA-->protein--> RNA

   

stopped growing after it's original discovery in the 70s

IncorrectQuestion 10

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Enzymes allow for chemical reactions to occur in the cell that may not naturally occur at the right place at the right time. They are exceptionally useful as

  

their activity can be regulated by post-tranlational modifications

  

they can be localized within a cell to increase localized activity

   

none of the answers

   

all of the answers (except none of the answers)

  

their active site can be highly specific to distinguish between molecules

Question 1

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The acetylation of lysines on the histone tails … (double check the book for this one as I think I mis-spoke during the lecture)

  

can be performed on methylated lysines only after they are first demethylated.

   

is a covalent modification and is thus irreversible.

  

recruits the heterochromatin protein HP1, resulting in the establishment of heterochromatin.

  

oosens the chromatin structure because it adds positive charges to the histone.

  

is sufficient for the formation of an open chromatin structure.

Question 3

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The position effect variegation (PEV) phenotype described in this chapter can be used to identify new genes that regulate heterochromatin formation. For instance, strains of Drosophila melanogaster with the White variegation phenotype have been subjected to mutagenesis to screen for dominant mutations (in other genes) that either enhance or suppress PEV, meaning the mutations result in either lower or higher red pigment production, respectively. Which of the following mutations is expected to be an enhancer of variegation?

  

A gain-of-function mutation in a gene encoding a histone methyl transferase that trimethylates lysine 9 on histone H3, resulting in a hyperactive form of the enzyme.

  

A gain-of-function mutation in a gene encoding a histone acetyl transferase that normally acetylates lysine 9 on histone H3, resulting in higher expression of the protein.

  

A loss-of-function mutation in a gene encoding a histone deacetylase that deacetylates lysine 9 on histone H3.

  

A mutation that results in the loss of function of the fly's HP1 (heterochromatin protein 1) gene.

Question 7

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Imagine a chromosome translocation event that brings a gene encoding a histone acetyl transferase enzyme from its original chromosomal location to a new one near heterochromatin. Which of the following scenarios is definitely NOT going to happen?

  

The gene gets silenced due to heterochromatin expansion, leading to the misregulation of gene expression for a number of critical genes.

  

The translocation event also brings along a chromatin barrier that can prevent heterochromatin expansion into the gene, and there is no phenotypic anomaly.

  

Since the gene encodes a histone acetyl transferase, it resists heterochromatin expansion by acetylating its own histones.

  

The level of the gene product decreases due to a position effect, leading to an imbalance in the chromatin state of the cell that results in the activation of programmed cell death.

Question 9

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This Question requires that you look at the Quiz Figure for this

5 1 4 3

Indicate which numbered feature (1 to 5) in the schematic drawing below of the DNA double helix corresponds to each of the following. Your answer would be a five-digit number composed of digits 1 to 5 only, e.g. 52431.

( )     Hydrogen-bonding

( )     Covalent linkage

( )     Phosphate group

( )     Nitrogen-containing base

( )     Deoxyribose sugar

   

12345

   

32415

   

43215

   

43512

Question 10

0 / 1 pts

Most fish genomes are at least 1 billion nucleotide pairs long. However, the genome of the puffer fish Fugu rubripes is quite small at only about 0.4 billion nucleotide pairs, even though the number of Fugu genes is estimated to be comparable to that of its relatives which have larger genomes. What do you think mainly accounts for the Fugu genome being this small?

  

Evolutionary advantage of extremely small exon sizes in the Fugu lineage

  

Unusual disappearance of all intronic sequences from the Fugu genome

  

Increased abundance of transposable elements in the Fugu genome

  

Increased occurrence of mitotic whole-chromosome loss in the Fugu lineage

  

Low relative rate of DNA addition compared to DNA loss in the Fugu lineage

Answer 1

8) started with the identification of a tRNA which suggested a method of converting DNA to protein

10)  their active site can be highly specific to distinguish between molecules

1) loosens the chromatin structure because it adds positive charges to the histone.