Genetic disorders can be caused by mutations to genes or entire chromosomes. Gene defects affect a single gene and protein, while chromosomal defects impact many genes on an affected chromosome. Genetic disorders are inherited in autosomal dominant, autosomal recessive, or sex-linked patterns. Karyotyping allows detection of chromosomal mutations like monosomy, trisomy, deletions, and translocations that cause many genetic disorders by disrupting multiple genes.

2. Genetic Disorders
 A genetic disorder is caused by a mutation to a
gene, group of genes, or entire chromosome.
 Remember, genes carry instructions to build proteins.
 When these instructions are mutated, proteins can’t
get build correctly.
 Genetic disorders generally occur in two different
varieties.
a) Chromosomal defect (chromosomal mutations)
b) Gene defect (gene mutations)

3. Gene Defects
 Gene defects occur when an individual gene is
mutated on a chromosome.
 Since only one gene is affected, usually only one
protein is affected. Ex.) hemophilia
 Many gene defects can be inherited, however, many of
them can occur spontaneously (without being
inherited) through being exposed to mutagens like
chemicals or radiation.

4. Inheriting a Gene Defect
 There are generally three different patterns of
inheritance.
a) Autosomal recessive
b) Autosomal dominant
c) Sex linked recessive

5. Sex chromosomes

6. Autosomal Recessive Inheritance
 Ex.) Cystic Fibrosis
 Caused by a recessive allele on chromosome #7.
 FF – normal Ff – carrier (normal) ff – disease
 Two parents that are both carriers for CF, want to know
the chance of having a child with CF?
FF Ff
Ff ff
F
F f
f

7. Autosomal Dominant Inheritance
 Ex.) Huntington’s Disease
 Caused by a dominant allele on chromosome #12.
 HH – lethal in embryo
 Hh – Huntington’s disease
 hh – normal
 One member of a couple has Huntington’s, what is the chance of
their children having the disease?
Hh hh
Hh hh
H h
h
h

8. Sex Linked Recessive Inheritance
 Ex.) Hemophilia
 Caused by recessive allele on the X chromosome
 XHXH - Normal female
 XHXh - Carrier female
 XhXh - Hemophiliac female
 XHY - Normal male
 XhY - Hemophiliac male
 Cross a carrier female with a
normal male? What are the
possibilities in their children?
XHXH XHXh
XHY XhY
XH Xh
XH
Y

9. Chromosomal Defects
 Some genetic disorders are caused by defects to an
entire chromosome.
 Ex.) Monosomy – a chromosome is missing.
Trisomy – having an extra chromosome.
 Sometimes only pieces of chromosomes are affected.
 Ex.) Inversion, deletion, translocation.
 Chromosomal defects generally affect many proteins
because so many genes are affected on the
chromosome.
 Many of these defects lead to miscarriages.

11. How are chromosomal
mutations detected?
Karyotyping
A set of chromosomes
46 chromosomes in a human
karyotype (23 pairs).

12. What can be determined
from looking at a karyotype?
1. Sex of the individual.
2. Chromosomal mutations (abberations)
a) Monosomy (missing a chromosome)
b) Trisomy (extra chromosome)
c) Deletions (section of chromosome missing)
***Depending which chromosome has the
mutation, this determines the disorder…

13. Karyotype

14. Evaluate the Karyotype…

15. Evaluate the Karyotype…

16. Evaluate the Karyotype…

17. Evaluate the Karyotype…