Genes and Inheritance [7]: Cystic Fibrosis (High band Biology)
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Genes and Inheritance [7]: Cystic Fibrosis (High band Biology)

A Level Biology: Genes and Inheritance 7 – Cystic
Fibrosis Hi! Welcome to my seventh video on the series
about Genes. Today, we are going to be looking at Cystic Fibrosis. Cystic Fibrosis is a disease
that affects thousands of people across the UK and it is an inherited disease so that
you receive the alleles from your parents. So in order to suffer from the disease, you
need to have both recessive alleles. You can also be a carrier of this disease. This is
where you posses one healthy allele and one cystic fibrosis allele. If we are to look
at an example of two people who are carriers, heterozygous for cystic fibrosis, we are going
to use F to represent the different alleles. F in this case would be the healthy allele
and the f will represent the cystic fibrosis allele. If we are going to look at this Punnett square,
these top boxes here, they represent the alleles contained within the sperm of the father.
So if you remember, the sperms can only carry half the genetic information of a normal cell
and so the sperm can either carry in this case: the healthy or non-cystic fibrosis allele
and the recessive, cystic fibrosis allele. The same is true with the mother. These represent
the alleles found within the eggs. In this case, the likelihood of the child
that actually suffers from cystic fibrosis is this individual here. There are ? chances
of that with these two heterozygous parents who are carriers. Cystic fibrosis, the disease itself, what
it actually does is it cause in the respiratory system and digestive system to produce excess
sticky mucus and what this can do in the case of the respiratory system is it can block
passageways in the lungs and the symptoms that you would expect to get are breathlessness
and certain respiratory diseases such as pneumonia. With the digestive system, it can block up
the tubes that lead towards the pancreas. This can basically prevent, because the pancreas
produces a huge number of digestive enzymes, it can slow down digestion. To review, what parts of the body does Cystic
fibrosis affect? Two, mainly the respiratory and digestive systems. Cystic fibrosis is caused by which parent
and why? Because you need to receive two alleles and
because it is recessive, therefore it is caused by both parents. If you receive the healthy
allele from one parent, it means that you would be the carrier. If two heterozygous parents breed, what is
the likelihood that the offspring will be a carrier? Draw a genetic diagram to help. Two heterozygous
parents mean that they’re carriers for the disease. That would be Ff. If you look here,
this would be the father. One of the sperm if F and the other one is f; the same with
the mother eggs, one with F and other one with f. Therefore, if we look here, this individual
would be homozygous and this individual would be homozygous as well. These two individuals
here would be heterozygous characters. So that would be 2/4 and so it is 50%. [end of audio – 3:34]
A Level Biology: Genes and Inheritance 7 – Cystic Fibrosis

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