18. The individual who committed the crime has SNPs from 2 individuals. These 2 individuals do not have SNPs in common. This means that there are 2 separate families/lineages with unique SNP DNA.
What is one possible way someone can have SNPs from 2 separate families? Through the families breeding together. Remember gene flow? It's the exchange of DNA between populations. In this case, our populations are the 2 families.
Now, we're looking for someone whose DNA/SNPs are inherited from both families. The only person who has this is Person D.
19. The somatic cell has 6 chromosomes. So, 2n = 6 and n = 3.
Metaphase 1: Chromosomes are in pairs and there can only be 6 chromosomes present. So, we eliminate C as it has 12 chromosomes.
Metaphase 2: Chromosomes are present in a singular line. There can only be 3 chromosomes present. So, we eliminate D as it has 6 chromosomes present in metaphase 2.
Remember what homologous chromosomes are? They're chromosomes with a similar structure. We eliminate B as those chromosomes are not homologous.
Hence, we are left with A.
20. Identical twins have DNA that's very similar to exact. Siblings have similar DNA, and adoptive siblings have less genetic similarity. So, with that in mind:
With Trait B, we see that there is a very high correlation between the identical twins, and dramatically less correlation as genetic similarity decreases. This trait is strongly influenced by genetics. For example, let's assume your favourite colour is determined by your genetics. The identical twins would have very similar favourite colours, whereas the adoptive siblings would have different colour choices. Because the adoptive siblings have such a low correlation in comparison to the identical twins, the environment doesn't really play a role here.
With Trait A, the gap is quite small between the identical and adoptive siblings, so genes don't have a significant impact. But all groups have a high correlation, so the environment plays a key role here. For example, let's assume the house you were raised in strongly determines your food preferences. Regardless of your genes, if you grow up in a house that loves having chicken every week, you will grow to like chicken. This is why there is a strong correlation between all the groups, as it is the environment causing this correlation.
With Trait C, there is little to no correlation. No strong correlation gap exists between identical and adoptive siblings, indicating genes don't play a significant role. There's also no strong correlation among all the groups, so the environment doesn't play a significant role either. For instance, hypothetically imagine all those siblings were raised in the same household. Now, I ask them what their favourite music is, and they all give vastly different answers. I can then conclude that music preference doesn't correlate with genes or the family environment they grew up in.