the smiths have four chilkdren,all girls. thier fifth is a boy. why did this change occur?
a)the conception classes taken by the parents.
b)the mother copntribution of a y chromosome
c)the fathers contribution of a y chromosome
I assume the Smiths are mammals (if they are birds, it is different).
See g2 on this link.
http://www.biol.andrews.edu/gen/l7.htm
THE SMITH HAVE FOUR CHILDREN,ALL GIRLS.THEIR FIFTH CHILD IS A BOY.WHY DID THIS CHANGE OCCUR?
A)THE CONCEPTION CLASSES TAKEN BY THE PARENTS
B)THE FATHERS CONTRIBUTION OF A Y CHROMOSOME.
C)THE MOTHERS CONTRIBUTION OF A Y CHROMOSOME.
the father contribution of a y chromosome
The change in the Smiths' children from all girls to having a boy can be explained by the father's contribution of a Y chromosome.
In humans, the sex of a child is determined by the combination of sex chromosomes received from both parents. A typical male has one X chromosome from the mother and one Y chromosome from the father, while a typical female has two X chromosomes, one from each parent.
During the process of fertilization, the father's sperm carries either an X chromosome or a Y chromosome, while the mother's egg always carries an X chromosome. If the father's sperm carrying a Y chromosome fertilizes the mother's egg, the result is a boy. On the other hand, if the father's sperm carrying an X chromosome fertilizes the mother's egg, the result is a girl.
So, in the case of the Smiths, the fact that they had four girls first and then had a boy can be attributed to the father's contribution of a Y chromosome during fertilization.