In humans, the male has an X and a Y sex chromosome. The human female has two X chromosomes. In birds, the female has a Z and a W sex chromosome while the male has two Z chromosomes. Which of the following statements is accurate about which parent determines the gender of the offspring based on inheritace of the necessary sex chromosome?

Question

A.  In humans and birds, the male determines the gender of all the offspring.
B.  In humans and birds, the female determines the gender of all the offspring.
C.  In humans, the male determines the gender of the offspring, and in birds the female determines the gender.
D.  In humans, the female determines the gender of the offspring, and in birds the male determines the gender.
E.  Determination of the gender of any human or bird offspring is related to the environmental conditions at the time of conception.

Clarify Question
· What is the key concept addressed by the question?
· What type of thinking is required?
· What key words does the question contain?
 
Gather Content
· What do you already know about sex determination?
 
Consider Possibilities
· Consider the different answer options. Which can you rule out?
 
Choose Answer · Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?

  Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?

Answer 1

C.  In humans, the male determines the gender of the offspring, and in birds the female determines the gender.

Clarify Question
· What is the key concept addressed by the question?
        o This question addresses sex determination.
· What type of thinking is required?
        o Although you may not have seen this example before, you know enough about the concept to Apply your knowledge and understanding to this unfamiliar situation.
· What key words does the question contain?
        o Sex chromosomes are the chromosomes that determine the sex of offspring. X and Y are the names of the sex chromosomes in some animals. When the female carries different sex chromosomes, they are called Z and W.
 
Gather Content
· What do you already know about sex determination?
        o In humans, the Y chromosome determines maleness, due to the SRY gene.
        o In some fish and reptiles, sex is determined by environmental factors like temperature.
        o In birds, the female is the heterogametic sex – she carries two different sex chromosomes. In those species the female is ZW and the male is ZZ.
 
Consider Possibilities
· Consider the different answer options. Which can you rule out?
        o In both humans and birds, sex is determined by the chromosomes, not the environment, so we can rule out that option.
 
Choose Answer · Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
        o Write out the gametes produced by a human male and female.
        o The male produces half X gametes and half Y gametes. The female only produces X gametes.
        o So the baby always receives an X from the mother. If she gets another X from her father she will become a girl; if he gets a Y from his father he will be a boy.
        o Thus we say the male’s contribution determines the gender.
        o The opposite is true for birds. The male always contributes a Z gamete. So the gender of the offspring is determined by whether the female contributed a Z or W.

  Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
        o This question required you to Apply your knowledge and understanding of sex determination to answer the question.
        o Did you understand that the sex is decided by the contribution of one particular parent?
        o Did you consider the types of gamete each parent produces?