please answer all the questions Question 3 0 / 1 pts The position effect variega
ID: 132492 • Letter: P
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please answer all the questions
Question 3
0 / 1 pts
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
0 / 1 pts
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
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?
5 1 4 3Explanation / Answer
Question 3.
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.
Question 7.
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.
43215.
(4) Hydrogen-bonding
(3) Covalent linkage
(2) Phosphate group
(1) Nitrogen-containing base
(5) Deoxyribose sugar
Question 10.
Low relative rate of DNA addition compared to DNA loss in the Fugu lineage.
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