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BCHM 4360 EXAM 1 LATEST 2026-2027 ACTUAL EXAM WITH
COMPLETE QUESTIONS AND CORRECT DETAILED ANSWERS (100%
VERIFIED ANSWERS) |ALREADY GRADED A+| ||PROFESSOR
VERIFIED|| ||BRANDNEW!!!||
Explain how DNA methylation allows bacteria to distinguish
genomic DNA from invading bacteriophage DNA. - ANSWER-
Restriction enzymes cut DNA at specific recognition sites so
bacteria defend their own DNA from being cut by methylating the
recognition sites. The bacteriophage DNA is not methylated and
will therefore be cut by the restriction enzymes and destroyed.
True or False: Methylation in eukaryotes is only used to silence
transcription, not activate it. - ANSWER-False
Eukaryotic methylation is usually at which two sites? - ANSWER-
CpG or CpXpG
Up to __% of human CpGs are methylated, and methylation state
can be _________. - ANSWER-inherited
,2|Page
What is an example of epigenetic silencing in mammals and how
does it work? - ANSWER-X-chromosome inactivation, one X
chromosome in each cell is inactivated in females so they have
the same amount of gene product as in males
Some gene activity is affected by __________, which is thought
to control expression of genes from mother and father in the
embryo. - ANSWER-imprinting
True or false: If one copy of a gene is silenced and the other is
absent, there is still some gene expression due to recombination.
- ANSWER-False, there will be no gene expression and no
recombination
Explain how fruit flies occasionally have white eyes. - ANSWER-
Fruit fly eyes are normally red, from expression of white+.
Occasionally, white eyes are seen as a result of white+ moving
near to heterochromatic regions and being silenced
,3|Page
How do boundary elements work to silence some genes? -
ANSWER-They slide down the chromosome, shutting down
genes due to the heterochromatin being able to spread
True or false: Boundary elements can both allow and prevent
heterochromatin spreading. - ANSWER-True
Give an example of how boundary elements prevent
heterochromatin spreading. - ANSWER-In S. pombe, two
boundary elements flank a region of silent heterochromatin
around the centromere. H3 histones between the boundary
elements are highly methylated at lysine 9 and are silenced. H3
histones outside the boundary elements are highly methylated at
lysine 4 and are active. Removal of the boundary elements will
allow spreading of lysine 9 methylation and will cause silencing
Boundary elements are like _____ that prevent the rapid
spreading of silencing and activation sites. - ANSWER-walls
, 4|Page
Boundary elements are _______ _________ that physically block
histones from sharing their messages. - ANSWER-protein
complexes
What could be an effect of a transposable element inserting
where boundary elements are? - ANSWER-Preventing proper
function, allowing for heterochromatin spreading
Besides heterochromatin silencing/activation, what is a major
function of boundary elements? - ANSWER-Anchor loops in the
nuclear periphery
What is a possible explanation for how some genes that do
similar functions can end up on different chromosomes? (hint:
boundary elements) - ANSWER-Boundary elements pull DNA
bundles to the edge of the nuclear envelope in loops, so genes
that would be nowhere near each other linearly could possibly
end up right next to each other when organized in a loop
True or false: Origins of replication are only used in bacteria.
Eukaryotes have a different means of initiating transcription. -
BCHM 4360 EXAM 1 LATEST 2026-2027 ACTUAL EXAM WITH
COMPLETE QUESTIONS AND CORRECT DETAILED ANSWERS (100%
VERIFIED ANSWERS) |ALREADY GRADED A+| ||PROFESSOR
VERIFIED|| ||BRANDNEW!!!||
Explain how DNA methylation allows bacteria to distinguish
genomic DNA from invading bacteriophage DNA. - ANSWER-
Restriction enzymes cut DNA at specific recognition sites so
bacteria defend their own DNA from being cut by methylating the
recognition sites. The bacteriophage DNA is not methylated and
will therefore be cut by the restriction enzymes and destroyed.
True or False: Methylation in eukaryotes is only used to silence
transcription, not activate it. - ANSWER-False
Eukaryotic methylation is usually at which two sites? - ANSWER-
CpG or CpXpG
Up to __% of human CpGs are methylated, and methylation state
can be _________. - ANSWER-inherited
,2|Page
What is an example of epigenetic silencing in mammals and how
does it work? - ANSWER-X-chromosome inactivation, one X
chromosome in each cell is inactivated in females so they have
the same amount of gene product as in males
Some gene activity is affected by __________, which is thought
to control expression of genes from mother and father in the
embryo. - ANSWER-imprinting
True or false: If one copy of a gene is silenced and the other is
absent, there is still some gene expression due to recombination.
- ANSWER-False, there will be no gene expression and no
recombination
Explain how fruit flies occasionally have white eyes. - ANSWER-
Fruit fly eyes are normally red, from expression of white+.
Occasionally, white eyes are seen as a result of white+ moving
near to heterochromatic regions and being silenced
,3|Page
How do boundary elements work to silence some genes? -
ANSWER-They slide down the chromosome, shutting down
genes due to the heterochromatin being able to spread
True or false: Boundary elements can both allow and prevent
heterochromatin spreading. - ANSWER-True
Give an example of how boundary elements prevent
heterochromatin spreading. - ANSWER-In S. pombe, two
boundary elements flank a region of silent heterochromatin
around the centromere. H3 histones between the boundary
elements are highly methylated at lysine 9 and are silenced. H3
histones outside the boundary elements are highly methylated at
lysine 4 and are active. Removal of the boundary elements will
allow spreading of lysine 9 methylation and will cause silencing
Boundary elements are like _____ that prevent the rapid
spreading of silencing and activation sites. - ANSWER-walls
, 4|Page
Boundary elements are _______ _________ that physically block
histones from sharing their messages. - ANSWER-protein
complexes
What could be an effect of a transposable element inserting
where boundary elements are? - ANSWER-Preventing proper
function, allowing for heterochromatin spreading
Besides heterochromatin silencing/activation, what is a major
function of boundary elements? - ANSWER-Anchor loops in the
nuclear periphery
What is a possible explanation for how some genes that do
similar functions can end up on different chromosomes? (hint:
boundary elements) - ANSWER-Boundary elements pull DNA
bundles to the edge of the nuclear envelope in loops, so genes
that would be nowhere near each other linearly could possibly
end up right next to each other when organized in a loop
True or false: Origins of replication are only used in bacteria.
Eukaryotes have a different means of initiating transcription. -
