Extra x chromosome disorder

Inherited Genetic Disorders | Genetics | Biology | FuseSchool

Inherited Genetic Disorders | Genetics | Biology | FuseSchool18 Jun. 2019
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Animation &


Animation & Design: Chloe Fyvie Adams

Narration: Dale Bennet

Script: Gemma Young

This girl has six fingers on her left hand. She has a condition called polydactyly, which causes extra fingers or toes. Her father and grandmother as well as some of her cousins also have the condition. This should give you a clue about how she came to have it... any ideas?

Well, polydactyly is an example of a genetic disorder - it is inherited.

You inherit genes from your parents, and you have two copies of each gene - one from your mother and one from your father.

Genes come in different forms, called alleles. Alleles may be recessive or dominant.

So going back to Polydactyly…

Polydactyly is caused by a dominant allele, shown as a capital P. You only have to have one copy of this allele to have the condition. So in an example the father has a copy of this allele, but the mother does not…

Offspring with one dominant allele big P, and one recessive allele little p will also have the condition.

Whereas these offspring won’t have the condition. Can you see what their genotype must be...?

Little p, little p - so two copies of the recessive allele.

Another example of an inherited disorder is cystic fibrosis. If you want to discover more about cystic fibrosis, and how it affects the body then watch this video [insert link to ‘cystic fibrosis’ video].

Cystic fibrosis is inherited in a different way to polydactyly. Take a look at this genetic diagram and see if you can figure out how it is different.

To have cystic fibrosis, you have to inherit two recessive alleles. The parents in the diagram are both carriers of the recessive allele, little f. They do not have the disorder themselves but they could both pass the recessive allele to their children.

Quite often, people do not know they are carriers of cystic fibrosis until they have a child with the disorder. This can be very upsetting, as it is a serious condition.

Parents are able to make sure they do not have another child with the disorder using embryo screening.

Let’s finish off with a little discussion about what embryo screening is.

Embryo screening can be used to ensure embryo’s do not suffer from inherited genetic disorders.

To do this, the parents would use in-vitro fertilisation, which is also known as IVF.

IVF is where eggs and sperm are mixed in a dish in a lab outside of the body. Each fertilised egg would be left to grow until it reached a few cells big, and then one cell from each embryo is removed and its genes tested to see if it has the genetic disorder. Only unaffected embryos - a maximum of two - would be placed back into the mother’s uterus to grow and hopefully develop into a healthy baby.

There are many issues surrounding embryo screening. One ethical issue is that the unused embryos, potential lives, are destroyed. Also, there are social concerns - IVF is not always successful and this can be upsetting for the parents and their family. Finally there are also economic issues because IVF is an expensive process.

So there we have a few examples of inherited genetic disorders. These are inherited from your parents, resulting from certain alleles your parents have been carriers of.

Sometimes genetic disorders are caused by dominant alleles - like polydactyly so it can be inherited from one parent - and others are caused by recessive alleles - like cystic fibrosis - so both parents need to carry the allele.

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Comments (18)
najd al.m

thank you so much for the video!!


The girl in the beginning is the author of the journals...

kayla andrew

i think im gonna ace my test tommorow ヾ(•ω•`)o




You guys' work is appreciated! Thanks!


Where there are so many problems in the world? Whyyyyyyy?

Vas Honda


Simon White

I don't want to be rude or anything, but the diagrams are wrong, because according to it, the mother is able to create a fetus using both halves of her genes (the rightmost one).
Otherwise, really helpful

Jono Clark

Off Topic:
So in Gravity Falls Stanford had Polydactyly as a birth defect.
It all makes sense now.
Well, if at least ONE of his parents had the defect aswell.

noor hamadi

your videos are so helpful !!! thank u for working so hard to let the people understand !!! please can u upload a video about lenses in physics !!!!

Habib Sanchez


lachique resimento

Thanks for this video...very helpful....

jaydin chichester

How about sickle cell


This is how many people came here from school




can't concentrate with this music


any info on Stickler syndrome?

Sgt Wingman

The big P and the small P are gonna have playdactyly?

X Chromosome Disorders Prevention & Developmental Implications in the Early Years

X Chromosome Disorders Prevention & Developmental Implications in the Early Years23 Mar. 2015
EITP IllinoisSubscribe 438 721

Presented by Katie

Presented by Katie Kastner and Melissa Zolecki, this recorded webinar reviews the major X chromosome disorders, including Fragile X Syndrome and Turner’s Syndrome. Discussions include syndrome presentation, diagnosis, associated medical conditions, developmental trajectory, and implications for supporting families in early intervention. This information is paired with a parent’s first-hand perspective of raising a child with Fragile X Syndrome.


1. Review the genetic basis and diagnosis of major X chromosome disorders, including Fragile X Syndrome and Turner’s syndrome

2. Discuss common medical co-morbidities of Fragile X Syndrome and Turner’s Syndrome and their management.

3. Review developmental impacts of Fragile X Syndrome and Turner’s Syndrome

4. Discuss resources and supports available for families and children impacted by Fragile X Syndrome and Turner’s Syndrome.

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