Understanding DNA and CPG Islands

What are the four bases that make up DNA?

• Cytosine, Guanine, Thymine, Adenine

• Cytosine, Guanine, Uracil, Adenine

• Cytosine, Guanine, Thymine, Uracil

• Cytosine, Thymine, Uracil, Adenine

What is the expected frequency of CPGs in human DNA?

• 1%

• 6.25%

• 10%

• 3.5%

What happens to unmethylated cytosines during spontaneous deamination?

• They turn into thymine

• They turn into uracil

• They turn into adenine

• They remain unchanged

Why is mismatch repair inefficient in correcting certain DNA mutations?

• It cannot recognize uracil

• It is too slow to keep up with mutations

• It only works on methylated DNA

• It requires specific enzymes that are often absent

What defines a CPG Island?

• Regions with a high percentage of uracil

• Regions with a high percentage of adenine

• Regions with a GC percentage greater than 50%

• Regions with a low percentage of guanine

Why are CPG Islands typically unmethylated?

• They are not involved in gene expression

• They are protected by transcription factors

• They are not recognized by DNA repair mechanisms

• They are located in inactive genes

What role do CPG Islands play in gene expression?

• They act as promoters

• They silence genes

• They degrade mRNA

• They inhibit transcription

How does methylation affect CPG Island promoters?

• It increases DNA replication

• It stabilizes the DNA structure

• It enhances gene expression

• It prevents transcription factor binding

What is a potential consequence of hypermethylation in cancer?

• Decreased mutation rates

• Loss of gene expression

• Increased gene expression

• Enhanced DNA repair

Where do most methylation differences occur in cancerous tissues?

• At CPG Island shores

• In the non-coding regions

• Within the CPG Islands

• In the coding regions