1. Lecture 44 – Lecture 45 Basic Patterns of Human Inheritance Ozgur Unal
NIS - BIOLOGY
Lecture 44 – Lecture 45
Basic Patterns of Human Inheritance
Ozgur Unal

2. Basic Patterns of Human Inheritance
How does the animal in the picture look?
What is different in this animal from others of the same species?
Do you find it beautiful?
A genetic disorder is a disease that can pass from generation to generation.
The animals in the pictures have a genetic disorder called albinism.

3. Recessive Genetic Disorders
Remember recessive and dominant traits
Example: Yellow seed color, Y, is dominant over green seed color, y.
How about being homozygous and heterozygous for a trait?
Example: Yy  heterozygous for seed color
YY or yy  homozygous for seed color

4. Recessive Genetic Disorders
Some genetic disorders exhibit themselves only if the individual is homozygous for that genetic disorder  recessive genetic disorder
An individual who is heterozygous for a recessive disorder is called a carrier.
Example: Albinism (A and a alleles)
AA  Healthy individual
Aa  Healthy individual who is a carrier
aa  Albino

5. Recessive Genetic Disorders
There are various recessive genetic disorders:
Cystic Fibrosis
Albinism
Tay-Sachs Disease
Galactosemia
Cystic Fibrosis: Affects 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 the sweat.
Without sufficient Cl- in the cells, water does not diffuse from the cells  causes secretion of thick mucus that affects many areas in the body (pancreas, lung etc)
Treatment: Physical therapy, medication, special diet etc.

6. Recessive Genetic Disorders
Albinism:
Absence of skin pigment melanin in the hair and eyes.
A person with albinism has white hair, very pale skin, and pink pupils.
The absence of pigment in eyes cause vision problems.
Tay-Sachs Disease: Found on chromosome 15.
Identified by a cherry red spot on the back of the eye.
Seems to be predominant among Jews of the Eastern Europe descent.
Absence of enzymes breaking down
fatty acids called gangliosides.
These fatty acids accumulate in the brain and cause mental deterioration.

7. Recessive Genetic Disorders
Galactosemia:
Inability to digest galactose.
During the digestion of milk, lactose is broken down into glucose and galactose.
Galactose is later broken
into glucose by an enzyme
called GALT.
A person who lacks or
has defective GALT cannot
digest milk products.

8. Dominant Genetic Disorders
Some genetic disorders are caused by dominant alleles  Dominant genetic disorder
This means that those who do not have the disorder are homozygous for the recessive trait.
Example: Huntington’s Disease
Affects individuals between ages (1 out of 10,000 people in the US)
Symptoms include gradual loss of
brain function, uncontrollable
movements and emotional disturbances.
H and h alleles:
Hh and HH  Individuals that have the disease
hh  healthy individuals

9. Dominant Genetic Disorders
Another example of a dominant genetic disorder is achondroplasia  most common form of dwarfism
A person with achondroplasia has a small body size and limbs that are comparatively short.
Interestingly, 75 % of individuals with achondroplasia are born to parents with average size  indicates
that the condition occured because of a new
mutation ora genetic change.
Why are recessive genetic disorders
are more common than dominant
genetic disorders?

10. Pedigrees
A pedigree is a diagram that traces the inheritance of a particular trait through several generations.
A pedigree uses symbols to illustrate inheritance of the trait.
Males  squares
Females  circles
One who expresses the trait
being studied is represented
by a dark square/circle.
One who does not express
the trait is represented by an
unfilled square/circle

11. Pedigrees
A horizontal line between two symbols shows that these individuals are the parents of the offsprings listed below them.
Offsprings are listen in descending order from left to right.
A pedigree uses a numbering system:
Roman numerals  generations
Arabic numbers  individuals

12. Analyzing Pedigrees Check out and analyze Figure 11.2
Look at the figure below and analyze the phenotypes and genotypes.
Check out and analyze Figure 11.3