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Recessive/Dominant defects (1 Viewer)

abdog

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How do we know whether if a defect is recessive/dominant? Also, if you can, please explain the difference between trisomy and polyploidy to me. Thanks!
 

madharris

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Not really sure about your first question however
Trisomy: Diploids that have one extra chromosome e.g. downsyndrome is a trisomy on chromosome 21, which means there are 3 chromosomes instead of 2 on chromosome 21
Polyploidy: The presence of a whole extra set of chromosomes- this is common and beneficial in plants (larger leaves, fruits, etc) however is detrimental in animals
 
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abdog

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OK, so in other words, trisomy is an extra chromosome on any of the 23 sets of chromosomes? Also, when you say "extra set of chromosomes", does it mean a pair of chromosomes?
 

madharris

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OK, so in other words, trisomy is an extra chromosome on any of the 23 sets of chromosomes? Also, when you say "extra set of chromosomes", does it mean a pair of chromosomes?
yeah an extra pair

EDIT: I remember reading something a while ago however i'm pretty sure you don't need to know it for the hsc

I think recessive mutations inactivate the affected gene and lead to a loss of function. e.g. recessive mutations may remove part of or all the gene from the chromosome, disrupt expression of the gene, or alter the structure of the encoded protein, thereby altering its function.

Dominant mutations often lead to a gain of function. For example, dominant mutations may increase the activity of a given gene product, give a new activity on the gene product, or lead to its inappropriate spatial and temporal expression.
 

abdog

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I get what trisomy is now. But can you explain polyploidy with more detail? I'm still unsure of what it is. About the dominant/recessive question, I was asking about defects, not mutations. Haha.
 

madharris

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I get what trisomy is now. But can you explain polyploidy with more detail? I'm still unsure of what it is. About the dominant/recessive question, I was asking about defects, not mutations. Haha.
polyploidy in an organism means that twice the number haploid number of chromosomes e.g. An organisms that possess two sets of each chromosome. For instance, a human has twenty three pairs of chromosomes, the pair meaning that humans are diploid. This doubles our chromosome compliment to forty six.

For defects sorry (didn't completely register the question), you have to look at pedigrees to figure out if it is dominant or recessive

wow I haven't thought about biology in so long >.>
 

abdog

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So polyploidy means an extra SET/PAIR of chromosomes in ALL 23 sets of chromosomes?
 

madharris

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yeah, there is an extra copy of an entire set of chromosomes.
 

abdog

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So technically, trisomy is polyploidy in one set of chromosome?
 

madharris

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So technically, trisomy is polyploidy in one set of chromosome?
no

Polyploidy refers to the whole set of chromosomes.
Our cells have 2 of each (diploidy), except eggs and sperm (monoploid)..

Trisomy means having 3 (instead of 2) of 1 specifiic chromosome.
The most common example is trisomy 21, having 3 of number 21 - which produces Down syndrome.
 

abdog

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so polyploidy is like having 3 or more chromosomes for all 23 sets of chromosomes?
 
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jamesischool

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so polyploidy is like having 3 or more chromosomes for all 23 sets of chromosomes?
yes. in normal humans there are 2 pairs of each of the 23 chromosomes making 46 all up. polyploidy is where there is more than 2 copies of every single chromosome. e.g. 3 lots of every chromosome totaling in 69 chromosomes.
going back to answer how you know whether a defect is recessive or dominant you need to look at a pedigree. through analysis of the pedigree you can see if the trait is recessive/dominant and sex linked/autosomal. e.g. 2 unaffected parents produce an affected offspring - the trait must be recessive as the parents are unaffected and the trait is hidden by a dominant one in the parents
 

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