Modifications and Epigenetics - Biochemistry
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Which statement concerning DNA methylation in mammals is false?
Which statement concerning DNA methylation in mammals is false?
Unmethylated cytosine spontaneously deaminates to uracil. Over time, methylated cytosine is spontaneously deaminated to thymine. Random deamination of methylcytosines causes mutation, creating hot spots. The vast majority of DNA methylations in mammals occurs at CpG (cytosine-phospate-guanine) sites.
Unmethylated cytosine spontaneously deaminates to uracil. Over time, methylated cytosine is spontaneously deaminated to thymine. Random deamination of methylcytosines causes mutation, creating hot spots. The vast majority of DNA methylations in mammals occurs at CpG (cytosine-phospate-guanine) sites.
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Which of the following describes a mutation in which a segment of DNA detaches from a chromosome and reattaches to another chromosome?
Which of the following describes a mutation in which a segment of DNA detaches from a chromosome and reattaches to another chromosome?
A null mutation is one that deactivates a gene entirely. Point mutations are those that occur within a single, small site in a gene. Inversion involves the reversal of orientation of a DNA segment. Deletion occurs when a whole part of a chromosome is removed, joining two ends that were far apart. Translocation involves the exchange of genetic material from two chromosomes that are not homologous.
A null mutation is one that deactivates a gene entirely. Point mutations are those that occur within a single, small site in a gene. Inversion involves the reversal of orientation of a DNA segment. Deletion occurs when a whole part of a chromosome is removed, joining two ends that were far apart. Translocation involves the exchange of genetic material from two chromosomes that are not homologous.
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Generally, silencing of a gene is accomplished by __________?
Generally, silencing of a gene is accomplished by __________?
The silencing of a gene is most often accomplished via methylation of the DNA. The methyl groups are added to the gene's promoter region and thus, the DNA is not read by transcriptional enzymes.
The silencing of a gene is most often accomplished via methylation of the DNA. The methyl groups are added to the gene's promoter region and thus, the DNA is not read by transcriptional enzymes.
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How does methylation cause the silencing of a gene?
How does methylation cause the silencing of a gene?
In order to silence a gene by methylation, methyl groups are added to the promoter region of DNA. This area is upstream of the coding sequence and is responsible for initiation of transcription. Thus, methylating the promoter region inhibits further transcription of the gene.
In order to silence a gene by methylation, methyl groups are added to the promoter region of DNA. This area is upstream of the coding sequence and is responsible for initiation of transcription. Thus, methylating the promoter region inhibits further transcription of the gene.
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Which of the following DNA bases can be methylated in the promoter region to silence a gene?
Which of the following DNA bases can be methylated in the promoter region to silence a gene?
The only two bases that can be methylated are cytosine and adenine.
The only two bases that can be methylated are cytosine and adenine.
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Formation of thymine dimers in DNA can lead to conditions such as melanoma when unrepaired. This DNA mutation is primarily caused by __________.
Formation of thymine dimers in DNA can lead to conditions such as melanoma when unrepaired. This DNA mutation is primarily caused by __________.
Alkylating agents and 
can also cause cancer, but they lead to methylation and mismatch mutations rather than the formation of pyrimidine dimers.
Alkylating agents and
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