Darlene just found out that she made the dean's list, and she's in ecstasy -- singing and dancing down the hallway near her dorm room. which area of the brain is directing her emotional reaction?

The limbic system

Explanation:

The limbic system is responsible for emotional reaction and responses. It is a network of different parts of the brain:

Hypothalamus

Thalamus

Amygdala

Hippocampus

The limbic system also controls our behavioral reaction. It works to sort out pleasant and unpleasant states of mind. Depending on how it categorizes as situation, the limbic system will produce the hormones that trigger brain activity . The fluctuations in activity result in physical changes and reactions (like expressions, gestures, stance) in response to the situation.  

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.