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1. Deafness on Chromosome 14:
An Example of Dominant and Recessive Inheritance
Michael Hasson

2. The Condition

Prelingual deafness is a loss in hearing
before a child learns how to speak

3. Genes on Chromosome 14

There are two different genes on
chromosome 14 which can cause
prelingual deafness when mutated

ESRRB - Recessive

SIX1 - Dominant

4. How Are Traits Inherited?

Each parent has two copies of every
gene in their genome.

A child receives one copy of each
gene called an allele from each
parent.

Alleles are typically either recessive or
dominant.

The combination of alleles received
from the parents determines the traits
that are expressed.

5. Recessive Inheritance - ESRRB

The child will only become deaf if they inherit a mutated
copy of the gene from both parents.

A table showing the possible genotypes of children of two
parents who carry a mutated copy of ESRRB
Gene from
Parent 1 >
Parent 2 V
D(normal) d(mutant)
D DD – normal
hearing
Dd – normal
hearing
d Dd – normal
hearing
dd - deafness

6. Dominant Inheritance - SIX1

The child will become deaf if they inherit a mutated copy
of the gene from one parent.

A table showing the possible genotypes of children of two
parents who carry a mutated copy of ESRRB
Gene from
Parent 1 >
Parent 2 V
D(normal) d(mutant)
D DD – normal
hearing
Dd – deafness
d Dd – deafness dd - deafness

7. Exceptions

Not all traits follow the rules of dominant
and recessive alleles.

In the cases of codominance and
incomplete dominance two different
alleles can be expressed at once.

Genes on the X and Y chromosomes
behave differently because males only
receive one copy of each.

8. Resources

Information

http://omim.org/entry/608565

http://omim.org/entry/605192

Images

http://upload.wikimedia.org/wikipedia/commons/a/a3/International_Symbol_for_Deafness.jpg

http://www.wirelessbabymonitorsworld.com/wp-content/uploads/2013/01/Baby-Monitors-for-Deaf-
and-Hard-of-Hearing-2.jpg