Twin studies document similarities and differences between twins. when two twins raised under very circumstances display similar personality traits, that suggests a strong influence on personality. critics of twin studies suggest that some documented similarities between twins are based on the fact that the twins are still the same age and may have some because of it.

The correct answers are: "identical", "different", "genetic", and "coincidental"

Explanation:

Twin studies are helpful to investigate the degree of influence that inheritance and environmental factors have in traits such as personality. Two identical twins raised under very different circumstances are very interesting cases of study, because if they show similar personality traits it would suggest that genetic plays an important role in the development of personality. However, critics of twin studies argue that identical twins obviously are the same age, therefore it could be coincidental that they could share some personality traits.

an individual’s sex (i.e., whether they are a male or female) is determined by the sex chromosomes. most people have two sex chromosomes, one that is inherited from their mother and one that is inherited from their father. typically, females have two x chromosomes (xx) and males have one x chromosome and one y chromosome (xy). conditions caused by changes (“mutations”) in genes located on the x chromosome are considered x-linked.

x-linked recessive inheritance

most x-linked conditions are recessive. this means that in a person with two x chromosomes (most females), both copies of a gene (i.e., one on each x chromosome) must have a change or mutation whereas in a person with one x chromosome (most males), only one copy of a gene must have a mutation. a female with a mutation in one copy of a gene on the x chromosome is said to be a “carrier” for an x-linked condition. a male with a mutation in a gene on the x chromosome is typically affected with the condition. because females have two copies of the x chromosome and males have only one x chromosome, x-linked recessive diseases are more common among males than females. however, x-linked recessive diseases can occur in both males and females.

for x-linked recessive disorders, an unaffected carrier mother who has a mutation in a gene on the x chromosome can transmit either the x chromosome with this mutation or a “normal” x chromosome to her children. if the father is unaffected, none of her daughters will be affected and all of her daughters will be unaffected—since they will inherit at least one normal x chromosome from their father. however, each daughter will have a 50% chance of being an unaffected carrier like her mother and a 50% chance of both x chromosomes being normal.

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