Download Chapter 12 Inheritance Patterns and Human Genetics

Chapter 12
Inheritance Patterns and
Human Genetics
12.1 Objectives
Distinguish between sex chromosomes
and autosomes.
 Explain the role of sex chromosomes.
 Know the difference between chromosome
mutations and gene mutations.

I. Chromosomes
A.
What is a Chromosome?
A. A vehicle of genetic information
B.
Sex Chromosomes
A.
B.
C.
D.
Determine the sex of organisms
XX = female
XY = male
Information on these chromosomes gives
the organism the sex specific characteristics.
C. Autosomes
1. the remaining chromosomes
2. 22 pairs
II. Chromosome Mutations
A.
Chromosome Deletion
A. Loss of a piece of chromosome
B.
Chromosome inversion
A. Chromosome breaks off; flips and reattaches
C.
Chromosome translocation
A. One chromosome breaks and reattaches to another
D.
Nondisjunction
A. Chromosomes fail to separate correctly resulting in
an extra copy.
III. Diseases from Chromosome
Mutations
A.
Down Syndrome (Trisomy 21)
A.
B.
C.
D.
E.
F.
Extra copy of chromosome #21
Distinct facial features
Heart defects
Shorter lifespan
Early Alzheimers
Some degree of mental retardation

B. Turner’s Syndrome
A.
B.
C.
D.
E.
Only have 1 X chromosome; no other X or Y
Genetically female
Do not mature sexually; are sterile
Short stature
Normal intelligence
C. Klinefelter Syndrome
 A. males have an extra X chromosome (XXY)
 B. male sex organs
 C. may have feminine characteristics
 D. normal intelligence
D. Patau Syndrome (Trisomy 13)
A. serious eye, brain, and circulatory defects
B. Clef palate
C. Children only live a few months
Cleft Palate
Cleft Palate
E. Edward’s Syndrome
A. Trisomy 18
B. Most children only live a few months
C. All major organs affected
Sex Linked Inheritance
Gene for disease is found on X chromosome.
 Usually recessive.
 Affects less females.

– Females may have the recessive gene but it can be
covered up by the normal dominant gene on the 2nd X
chromosome

Affects more males
– Since males only have 1 X chromosome, the recessive
gene will be expressed if present.
Red/Green Colorblindness

The gene which allows us to
distinguish between red and green is
on the X chromosome.
XC XC
XC Xc
Xc Xc
= Female with normal vision
= Female carrier
= Female who is colorblind
Red/Green Colorblindness

The gene which allows us to
distinguish between red and green is
on the X chromosome.
XC Y
Xc Y
= Male with normal vision
= Male who is colorblind
Pedigree
XY
Marriage
XX
Mother
Father
Children
XX
XY
XY
Daughter
Son
Son
Oldest
Youngest
PEDIGREE CHARTS
A family history of a genetic
condition
© 2007 Paul Billiet ODWS
What is a pedigree chart?
Pedigree charts show a record of the
family of an individual
 They can be used to study the
transmission of a hereditary condition
 They are particularly useful when there
are large families and a good family
record over several generations.

© 2007 Paul Billiet ODWS
Symbols used in pedigree charts





Normal male
Affected male
Normal female
Affected female
Marriage
A marriage with five children, two
daughters and three sons. The 2nd
eldest son is affected by the condition.
Eldest child  Youngest child
© 2007 Paul Billiet ODWS
Organising the pedigree chart
– Generations are identified by Roman
numerals
I
II
III
IV
© 2007 Paul Billiet ODWS
Some History



Hemophilia has played an
important role in Europe's
history
The disease began to
crop up in Great Britain's
Queen Victoria’s children
It became known as the
"Royal disease" because
it spread to the royal
families of Europe
through Victoria's
descendants
How it Spread
it spread through the
Royal Houses of
Europe as monarchs
arranged marriages to
consolidate political
alliances.
 We can trace the
appearance of
hemophilia as it
popped up in Spain,
Russia, and Prussia by
looking at the family
tree.

The Royal Family Tree
Pedigree
Karyotype