Question

what happened when pregnant mice were exposed to environmental toxins?
a. more yellow, obese offspring were born
b. the offspring all turned brown
c. no changes occurred in the next generation
d. the twins removed all methyl groups permanently
question 25
why does coat color in these mice serve as a useful indicator in these epigenetic experiments?
a. it reflects whether the agouti gene is turned on or off
b. it shows whether mutations have occurred
c. it measures how much the mice exercise
d. it tells researchers which mice are related
question 26
why do researchers study identical twins for epigenetic research?
a. twins mutate more frequently than non - twins
b. twins always have completely different epigenomes from birth
c. twins experience identical environments automatically
d. they share the same dna, so differences are due to environment and epigenetics

Explanation:

Question (First one: What happened when pregnant mice were exposed to environmental toxins?)

To answer this, we recall epigenetic experiments with mice and environmental toxins. When pregnant mice are exposed to environmental toxins, it can affect the offspring's epigenetics, often leading to changes like more yellow, obese offspring (related to Agouti gene effects). Option a matches this knowledge. Option b is incorrect (offspring don't all turn brown). Option c is wrong as changes do occur. Option d is incorrect (not about removing methyl groups permanently in that way).

Coat color in these mice (Agouti mice) is linked to the Agouti gene's expression. If the Agouti gene is turned on/off, it affects coat color (yellow when on, brown when off, related to methylation). Option a is correct as it reflects Agouti gene's on/off status. Option b is wrong (not about mutations). Option c is irrelevant (not about exercise). Option d is wrong (not about relatedness).

Identical twins share the same DNA (monozygotic). So any differences in traits (including epigenetic) are due to environment/epigenetics, as genetics are the same. Option d is correct. Option a is wrong (twins don't mutate more). Option b is wrong (they have similar epigenomes at birth). Option c is wrong (environments aren't always identical).

Answer:

a. More yellow, obese offspring were born

Question 25 (Why does coat color in these mice serve as a useful indicator in these epigenetic experiments?)