Hello and welcome to the Zero to Finals podcast. My name is Tom and in this episode I'm going to be talking to you about Mendalian inheritance of single gene disorders.

And this is how conditions are inherited in an autosomal dominant and autosomal recessive way.

And if you want to follow along with written notes on this topic,

you can follow along at zero definals.com slash inheritance or in the genetic section of

the zero de finals pediatrics book. So let's get straight in. Many genetic conditions exhibit

a simple inheritance pattern called mandalian inheritance. This type of inheritance only occurs where

the disease is caused by a single abnormal gene on one of the non-sex chromosomes. And remember,

the sex chromosomes are the X and Y chromosomes. These non-sex chromosomes are called autosomes,

which is why the conditions are autosomal, dominant or recessive.

Two examples of diseases that are caused by a single inherited gene are Huntington's career and cystic fibrosis.

The difference between these two conditions is that the gene for Huntington's career is a dominant gene

and the gene for cystic fibrosis is a recessive gene. This means that to have the phenotype

or to have the physical disease for Huntington's career, then you need to have only a single

abnormal copy of the gene. Huntington's career is

autosomal dominant. To have the phenotype for cystic fibrosis, meaning to have the actual

disease, two copies of the gene for that disease must be abnormal. Where there's one abnormal copy of the gene, the patient is a carrier. This means they

carry the gene for the disease and can pass it onto their offspring, but they don't have the

disease itself. The normal copy of the gene overrides the abnormal gene, and cystic fibrosis is

autosomal recessive. Let's talk about calculating therosis is autosomal recessive.

Let's talk about calculating the risk of an autosomal recessive condition.

A very common exam scenario tests your ability to calculate the risk of passing a genetic

condition onto a child. By calculating the four possible outcomes for each scenario, you should be able to

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