Module 2 - Genetics and Inheritance

what percent of congenital hearing loss is genetic?

50 to 60%

what are the three areas that genetics influences for hearing loss?

onset

severity

progression

Genetics impacts what dimensions of hearing loss treatment?

diagnosis

counseling

management

prognosis

family planning

What is DNA?

the basic code of life that is in the nucleus of the cell

a blueprint that tells us what we are going to be

housed in the chromosomes

What are genes?

carry the instructions to produce protein

tells us what the protein is going to do?

we have about 20,000 genomes, or genes, and about 100+ are linked to hearing loss

Walk through the bakery metaphor for transcription and translation.

• DNA is the recipe book, and we have to make copies of the recipe

• RNA is the copies of the recipe, that then delivers the recipe to the genes

• genes use the recipe and create the protein

• protein is what makes the structures, who we are and what we have anatomically

what is missense?

one word is mistaken

what is nonsense?

recipe just stops

what is insertion/deletion?

delete one word

add one word

what is frameshift?

everything shifts over one space

what are the effects of variants and mutations?

no protein

altered protein

abnormal functions

how many chromosome pairs are there?

23

how many autosomal and sex chromosomes do humans have?

22 autosomal

1 sex

how many chromosomes do we inherit from each parent?

we inherit half from each parent

what is non-syndromic hearing loss?

only have hearing loss, no other comorbidities occurring

account for 70% of all genetic losses

examples: GJB2, SLC26A4

what is syndromic hearing loss?

hearing loss + other issues

account for 30% of all genetic losses

examples: Usher’s, Waardenburg

what are the kinds of inheritance patterns discussed in class?

autosomal dominant

autosomal recessive

x-linked dominant

x-linked recessive

mitochondrial

codominant

describe autosomal dominant inheritance

one mutation of each gene

one mutation from parent

disorders usually occur in every generation

one parent has the disorder

describe autosomal recessive inheritance

two mutations of the gene present

but parents are carriers, but unaffected

not seen in every generation

describe x-linked dominant inheritance

mutation is on the X chromosome

females are more common symptomatic than males

usually, each generation is affected

no male-to-male transmission

affected have 50% chance of passing on to child

less common than x-linked recessive

describe x-linked recessive inheritance

mutation is on the X chromosome

males more affected than females

affected males in each generation more than females in each generation

no male-to-male transmission

women are carriers, likely not affected

describe mitochondrial linked inheritance

trait embedded in the mitochondria

can affect male or female

always receive from maternal line

no male-to-male transmission

describe codominant inheritance

two different versions of genes expressed where each version makes a different protein

both influence trait and determine genetic condition

what pattern is hearing loss?

most, if not all inheritance patterns are possible

considerations for genetic hearing loss

gene testing, for both parents and siblings

counseling, to ensure families understand what gene mutation may mean and possible guilt from parents

intervention planning, to know what the path forward is

ethics and psychosocial factors

consent and privacy in genetic tesing

family planning implications

emotional impact of genetic results

equity and access to testing