You know that the birds in your neighborhood love sunflower seeds. Being scientifically minded you decided to test whether this known preference for sunflower seeds influences their choice of bird feeders. Before sunrise, you set up these feeders: Feeder A: 70% sunflower seeds by volume, 30% other; Feeder B: 50% sunflower seeds by volume, 50% other; Feeder C: 30% sunflower seeds by volume, 70% other. All the feeders are physically identical and hold the same total volume of seed. The birds arrive and begin pulling sunflower seeds out of each feeder, but as the day goes by you notice the birds prefer Feeder A and use Feeders B and C much less. Assuming the birds treat these feeders as separate patches of food, what would be reasonable to predict

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explanation:

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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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