Question

question 49
why can identical twins develop different diseases even though they have the same dna?
a one twin secretly mutates into a different genome
b they grow different numbers of chromosomes over time
c their dna is replaced as they age
d genes can be turned on or off in different ways

Explanation:

• Option a: Identical twins come from the same zygote, so they have the same genome initially; secret mutation into a different genome is not a common or primary reason for disease differences.
• Option b: The number of chromosomes in identical twins is the same (barring rare chromosomal abnormalities not related to typical disease development differences), so this is incorrect.
• Option c: DNA is not "replaced" as they age; DNA undergoes changes like methylation but not replacement, so this is incorrect.
• Option d: Gene expression (genes being turned 'on' or 'off') can differ between identical twins due to epigenetic factors (like environment, lifestyle, etc.), leading to different disease development even with the same DNA.

Answer:

d. Genes can be turned 'on' or 'off' in different ways