The Human Genome
Chapter 14
Human Chromosomes
• Karyotype: chromosomes arranged with
their pairs in order.
• Sex Chromosomes: two of the 46
chromosomes
– XX = female
– XY = male
• Autosomes: the remaining chromosomes
Human Traits
• Pedigree: chart which shows the
relationship within a family
– box= a male
– circle = a female
– colored in = shows the trait
– blank shape = does not have the trait
– half color and half blank = carries the trait
Hemophilia Pedigree
• Hemophilia has played an important role in
Europe’s history, for it suddenly cropped
up in the children of Great Britain’s Queen
Victoria. It became known as the “Royal
disease” because it spread to the royal
families of Europe through Victoria’s
descendants.
• It first appeared in Victoria’s family in her eighth
child, Prince Leopold, Duke of Albany.
Throughout his short life, he suffered severe
hemorrhages, and always was described as
“very delicate.” Leading the life of a normal
youngster was impossible because any cut or
bump could lead to death. It was necessary to
keep him always under strict surveillance. In
spite of all the protection, he died at the age of
31 as the result of a minor fall.
Pedigree Problem
• A man who had purple ears came to the
attention of a human geneticist. In this family,
purple ears proved to be an inherited trait due to
a single genete. The man's mother and one
sister also had purple ears, but his father, his
brother, and two other sisters had normal ears.
The man and his normal-eared wife had seven
children, including four boys and three girls. Two
girls and two boys had purple ears.
Human Genes
• The human genome: the complete set of
genetic information that includes tens of
thousands of genes.
Sex-Linked Genes
• found on the X chromosome
• More than 100 genetic sex-linked
disorders
• In males: inherits an X chromosome from
the mother that has the recessive gene
• In Females: inherits X chromosomes that
have the recessive gene from the mother
and father
Hemophilia
• Two genes carried on the X chromosome
control blood clotting
• Caused by a recessive gene
• 1 in every 10,000 males
• Symptoms: bleed to death from minor cuts
and bruises
• Treatment: injections of clotting proteins
Color Blindness
• Three genes associated with color vision
located on the X chromosome
• recessive gene produces colorblindness
• Symptoms: Inability to distinguish certain
colors
• red green color blindness
Muscular Dystrophy
• the progressive weakening and loss of
skeletal muscle
• 1 out of every 3000 males
• Caused by a defective version of the gene
that codes for a muscle protein
• No cure as of now
Problem
• Cross a color blind male with a normal
female. What is the genotype of their
offspring?
• A females father is color blind and she is
not. Her husband is not color blind. What
is the probability that they will have color
blind children