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Autosomal recessives

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Nialllovespie:
What is the difference between autosomal recessive and recessive?

Thanks in advanced

Nia!

DalvinT:
Hi Nia!
Recessive is when a specific trait is not expressed within the  phenotype. For example, Tall is expressed but short gene isn't. Therefore the short gene is the recessive.

Autosomal recessive is one of the mode of inheritance and is not sex linked (X-linked). This means that the characteristic inherited from the parent(s) can be any of the 22 chromosomes (excluded the 23rd as it is X-linked).

Now, this mode of inheritance means that the recessive trait is PASS down and most likely expressed in the offspring if the parent(s) (dad and/or mum) are AFFECTED.
It can affect both sexes and it may skip generations.
For example, Generation 1 Dad (AA) and Mum (aa) has any evidence of the recessive trait being expressed in the Genotype . Generation 2 (son (aa) has recessive expressed phenotypic and daughter(Aa) will have recessive expressed in the genotype. Generation 3 (son (aa) marries affected Woman (aa)) therefore their son(s) and/or daughter(s) are bound to obtain the recessive trait unless a new mutation occurs.
An example of a genetic disease that occurs in an autosomal manner - familial hypercholesterolemia.

(THAT WAS A VERY SIMPLE, NOT SCIENTIFIC EXAMPLE. Take it with a grain of salt... just understand it so you get the gist of it).


I hope I explain it right haha!
If you are confused about something, ASK!  or if anyone notices that I may have explained something wrong. Be free to correct me!!

Nonetheless, I hope this helps :)

Nialllovespie:
Ohhhhhhhh yes that makes sense!!  Thanks so much for your help!! I really appreciate it!

Nialllovespie:
Also, how would I know if the trait is dominant or recessive when I look at a pedigree chart?

DalvinT:

--- Quote from: Nialllovespie on March 07, 2017, 11:18:15 am ---Also, how would I know if the trait is dominant or recessive when I look at a pedigree chart?

--- End quote ---


Hey! I didn't see your reply until now!! I'm so sorry!!
But it really depends on the question and what they give you...

Let's look at the photo attached... excuse my poor drawing haha.

So the question is:

What is the mode of inheritance?

To find this, I firstly think. "What gender is affecting more?"
If it's affecting more of the one gender than the other, then it's most likely sex-linked. If both genders are affected, then autosomal.
then I ask, "Is it skipping any generations?" [/i]
In this case,  yes, which means it is recessive. Why? Because, as you know, from the diagram (Gen 1, 1) is unaffected and (Gen 1, 2) is affected. Therefore, their children in Generation two would be heterozyous, regardless of gender.
Looking at (Gen 2,1) its male partner produces 3 unaffected and 1 affected. Again because the affected, inherited the recessive trait from the mum. (Son always herits X gene from mum).

I know this is really confusing, because I'm just poop at explaining . But please, ask if you're still unsure!

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