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DO NOW
1.What is the correct number of
autosomes and sex chromosomes in
the somatic cell of a human male?
2. How many autosomes and sex
chromosomes would be in the ovum
of the human female?
ANSWERS
1. 44 autosomes and 2 sex
chromosomes(X and Y)
2. 22 autosomes and an X
WHAT
DO YOU
SEE?
WHAT DO
YOU SEE?
A person with normal color vision sees the number 5.
Color blindness (color vision deficiency)
• is a condition in which certain colors cannot be
distinguished, and is most commonly due to an
inherited condition.
•Problems in distinguishing reds and greens are the
most common.
A pedigree for color-blindness
Normal male
Carrier female
P1
F1
Carrier
female
Normal
female
Colorblind
male
Normal
male
Thomas Hunt Morgan was
awarded the Nobel Prize in
Physiology or Medicine in 1933.
The work for which the prize was
awarded was completed over a 17year period at Columbia
University, commencing in 1910
with his discovery of the whiteeyed mutation in the fruit fly,
Drosophila.
•Morgan’s work with Drosophila demonstrated that genes for
certain traits are located on the X chromosomes.
•These genes are said to be sex-linked.
•These genes do not appear to have corresponding alleles on
the Y chromosome.
•Since many sex-linked genes are recessive, they are expressed
more frequently in males than in females.
XX x X’Y where X’=allele for white eye
X
X’
Y
X
X’ X
X’ X
X Y
X Y
Summary of Results
PARENTS
(Female: +) x (Male: W)
OFFSPRING
Phenotype Female: +
Male: +
Number
5087
5016
Proportion 0.49649
Ratio
1.000
0.50351
:
1.014
TOTAL 10103
X’X x XY where X’=allele for white eye
X’
X
Y
X
X’ X
X X
X’ Y
X Y
Summary of Results
PARENTS
(Female: +) x (Male: +)
OFFSPRING
Phenotype Female : +
Male: +
Number
2521
5056
Proportion 0.50339
Ratio
2.049
Male: W
2467
0.25100
0.24562
1.022
1.000
TOTAL10044
HEMOPHILIA
•Hemophilia is often called the disease of kings
because it was carried by many members of
Europe’s royal family.
Queen Victoria
•Queen Victoria of England was a carrier of
hemophilia and passed The disease to many
of her descendants (including the Russian
emperor’s family and the Spanish royal
family).
Family of Queen Victoria
The history of Queen Victoria's
descendants illustrates the hereditary
characteristics of hemophilia. We can take
a look at her family tree(pedigree).
Explanation of the inheritance of hemophilia