Professor Dr. Basim Zwain gave a lecture on patterns of inheritance at the Faculty of Medicine, Jabir ibn Hayyan Medical University. The lecture described the main patterns of inheritance including autosomal dominant, autosomal recessive, X-linked dominant and recessive, codominant, and mitochondrial inheritance. Examples of genetic disorders that follow each pattern of inheritance were provided.

1. BASIM ZWAIN LECTURES
MEDICAL PHYSIOLOGY
PATTERNS OF INHERITANCE
Professor Dr. Basim Zwain
Faculty of Medicine
Jabir ibn Hayyan Medical University
basimzwain@jmu.edu.iq

2. PATTERNS OF INHERITANCE
Inheritance pattern Description Examples
Autosomal dominant One mutated copy of the gene in each cell
is sufficient for a person to be affected by
an autosomal dominant disorder. Each
affected person usually has one affected
parent . Autosomal dominant disorders
tend to occur in every generation of an
affected family.
Huntington
disease,neurofibro
matosis type 1
Autosomal recessive Two mutated copies of the gene are
present in each cell when a person has an
autosomal recessive disorder. An affected
person usually has unaffected parents who
each carry a single copy of the mutated
gene (and are referred to as carriers) .
Autosomal recessive disorders are typically
not seen in every generation of an affected
family.
cystic fibrosis,
sickle cell anemia

3. PATTERNS OF INHERITANCE
Inheritance pattern Description Examples
X-linked dominant X-linked dominant disorders are caused by
mutations in genes on the X chromosome. Females
are more frequently affected than males, and the
chance of passing on an X-linked dominant disorder
differs between men and women . Families with an
X-linked dominant disorder often have both
affected males and affected females in each
generation. A characteristic of X-linked inheritance
is that fathers cannot pass X-linked traits to their
sons (no male-to-male transmission).
fragile X syndrome
X-linked recessive X-linked recessive disorders are also caused by
mutations in genes on the X chromosome. Males
are more frequently affected than females, and the
chance of passing on the disorder differs between
men and women . Families with an X-linked
recessive disorder often have affected males, but
rarely affected females, in each generation. A
characteristic of X-linked inheritance is that fathers
cannot pass X-linked traits to their sons (no male-to-
male transmission).
Hemophilia,
Fabry disease

4. PATTERNS OF INHERITANCE
Inheritance
pattern Description Examples
Codominant In codominant inheritance, two different versions
(alleles) of a gene can be expressed, and each
version makes a slightly different protein . Both
alleles influence the genetic trait or determine the
characteristics of the genetic condition.
ABO blood group,
alpha-1 antitrypsin
deficiency
Mitochondrial This type of inheritance, also known as maternal
inheritance, applies to genes in mitochondrial
DNA. Mitochondria, which are structures in each
cell that convert molecules into energy, each
contain a small amount of DNA. Because only egg
cells contribute mitochondria to the developing
embryo, only females can pass on mitochondrial
mutations to their children . Disorders resulting
from mutations in mitochondrial DNA can appear
in every generation of a family and can affect both
males and females, but fathers do not pass these
disorders to their children.
Leber hereditary
optic neuropathy
(LHON)