im just struggling to understand variation vs mutation. So diseases and stuff caused by environmental factors will never be passed down to offspring because they were affected by environmental factors? the question from the online tutorial and 2021 paper has got me confused. thank you
The definition for mutation is a permanent change to the DNA base sequence.
Note that a “change to the DNA base sequence” can happen in two places.
Either in gametic cells (sperm/egg) or in somatic (body) cells.
So if the mutation happens in the gametic cells, this means that there is chance it can be passed on because if the sperm/egg carrying this mutation gets fertilised, it will form a zygote and thus an organism.
(This should help with your understanding for Q1 - d and Q2 - b)
The key point for Q1 is that the disease is caused by the environment and NOT due to genetics (having inherited from birth). If you are not born with a trait/characteristic, then that means you do not have the gene/allele for that trait, hence, would not be able to pass it down.
The key point for Q2 is that the question resource clearly states the mutation is in the human gene. This means that individuals who have that gene must be able to pass it on. Since the gene has a protective benefit for individuals who have it, it will give them a higher survival chance than those who do not have the gene/allele. This means those individuals who have the gene will be more likely to have offspring, and hence pass on that beneficial allele. Eventually, those offspring will inherit that beneficial allele and they will themselves have offspring and the gene/allele will increase in frequency within the population.
Genetic variation in a population is the combinations (differences) in genes/alleles found within a population. The more genetically varied a population is, the more likely there will be individuals who may have alleles that can help them, should the environment change.
For Q3, it is important to note that the Himalayan wolves have the combination of genes/alleles that allows them to live in high altitudes (4000m above sea level), and those wolves that did not (the ancestral or earlier population of wolves) would not have survived well in those high altitude conditions. Hence, gradually over many many many generations (many years as well) of wolves, those who inherited the combination of genes/alleles that allowed them to have a higher survival chance, would then pass on those alleles to the next generation.
Hope that helps.