Video notes:
1. Hemophilia is an X linked recessive trait that affects blood clotting. If a carrier woman
and a hemophiliac man have a daughter, what is the percentage chance that she will have
hemophilia? Answer: Out of the daughters produced, only one has hemophilia so the
probability is 50%
● DNA is wrapped around proteins called histones
○ In a cell with both x chromosome from mom and x chromosome from dad a a
chemical battle occurs where either the mom’s or dad’s x chromosomes become
inactivated and are no longer read
■ Inactive x chromosome shrivels up into a Barr body and goes silent
○ This happens through the DNA packing closely together and making
modifications to histone tails
● Stripey pattern in females occur to see where the mom’s or dad’s x chromosome has been
inactivated
Secrets of the X Chromosome
● Y chromosome determines maleness
● X chromosome cn control nervous system, skeletal system development
● If there are 2 x chromosomes that produce protein,development of embryos is impaired
● Inactivation causes some cells to express maternal x chromosome while other cells have
paternal x chromosome expressed
● In X-inactivation, one X chromosome from each embryo cell is shriveled and made into a
Barr body. Some clusters of cells show the maternal X-chromosome and some show the
paternal X-chromosome.
1. Hemophilia is an X linked recessive trait that affects blood clotting. If a carrier woman
and a hemophiliac man have a daughter, what is the percentage chance that she will have
hemophilia? Answer: Out of the daughters produced, only one has hemophilia so the
probability is 50%
● DNA is wrapped around proteins called histones
○ In a cell with both x chromosome from mom and x chromosome from dad a a
chemical battle occurs where either the mom’s or dad’s x chromosomes become
inactivated and are no longer read
■ Inactive x chromosome shrivels up into a Barr body and goes silent
○ This happens through the DNA packing closely together and making
modifications to histone tails
● Stripey pattern in females occur to see where the mom’s or dad’s x chromosome has been
inactivated
Secrets of the X Chromosome
● Y chromosome determines maleness
● X chromosome cn control nervous system, skeletal system development
● If there are 2 x chromosomes that produce protein,development of embryos is impaired
● Inactivation causes some cells to express maternal x chromosome while other cells have
paternal x chromosome expressed
● In X-inactivation, one X chromosome from each embryo cell is shriveled and made into a
Barr body. Some clusters of cells show the maternal X-chromosome and some show the
paternal X-chromosome.
