This document discusses human genetics and inheritance through three main topics: genetic disorders, types of recessive genetic disorders (including cystic fibrosis, albinism, and Tay-Sachs disease), and dominant genetic disorders (including Huntington's disease and achondroplasia). It also covers pedigrees, which are diagrams used to track the inheritance of traits through generations using symbolic representations of individuals and their genetic statuses. Key points are that recessive traits only appear if homozygous, while dominants can be inherited heterozygous or homozygous, and conditions like cystic fibrosis and Huntington's disease are caused by genetic defects on specific chromosomes.

1. Chapter 11
Complex Inheritance and Human
Heredity

2. 11.1 Basic Patterns of Human
Inheritance
 The inheritance of a trait over several
generations can be shown in a pedigree
 Pedigrees can help us to track and
understand genetic disorders

3. Genetic Disorders
 Review:
HH= homozygous dominant
Hh= heterozygous
hh= homozygous recessive
A recessive trait is only expressed if it is
homozygous recessive
If an individual is heterozygous for a recessive
disorder, they are called a carrier.

4. Types of Recessive Genetic
Disorders:
Cystic Fibrosis
 Affects the mucus-producing glands,
digestive enzymes, and sweat glands
 Chloride ions are not absorbed into the
cells of a person with cystic fibrosis but
are excreted in sweat
 Without sufficient chloride ions in the
cells, a thick mucus is secreted

5. Location of the
CF gene on
chromosome 7

6. Breathing Treatment for CF

7. Albinism
 Caused by altered genes, resulting in
the absence of pigment in the skin and
eyes
 White hair
 Very pale skin
 Pink iris

8. Tay-Sachs Disease
 Caused by the absence of the enzyme
responsible for breaking down fatty
acids called gangliosides
 Gangliosides accumulate in the brain,
inflating brain nerve cells and causing
mental deterioration.

9. Dominant Genetic Disorders
You can be either heterozygous
or homozygous dominant to
inherit a dominant genetic
disorder.

10. Huntington’s disease
Affects the nervous system
 Caused by a genetic defect on
chromosome 4
– Section of DNA repeats too many times
– As the gene is passed down from one
generation to the next, the number of
repeats gets larger
– This means that the symptoms develop at
younger and younger ages.

11. Achondroplasia
Genetic
condition that
causes small
body size and
limbs that are
comparatively
short

12. Pedigrees
 A diagram that traces the inheritance of
a particular trait through several
generations

13. Pedigree Symbols
 Normal Female
 Female that expresses the trait
 Female carrier (half shaded)
 Normal male
 Male that expresses the trait
 Male who is a carrier for the trait

14. Pedigree Symbols
Roman Numerals (I, II, III, etc.)
= Generation number
Arabic numbers (1,2,3, etc) =
individuals in a particular
generation

15. Pedigree
I
II
III