Down Syndrome

[Guest 100x]

I know that intercourse between relatives increases the chance of having a child with down syndrome, but when the relatives have no trace or any history of down syndrome, then the chance of having a child with down syndrome would simply depend on a mutation, not heredity, correct?

 

I know that a tribe in India interbreeds and it has no history of down syndrome, so interbreeding in this tribe doesnt affect the chance of down sydrome?

 

Can someone also explain to me how interbreeding affects the chance of having a son with down syndrome?

[SubJunk]

Downe's Syndrome (that's what it's called, Down Syndrome is what it is often wrongfully called, often even by doctors who don't specialise in Downe's Syndrome)

The mutation of the 26th chromosome (completely off the top of my head so I might have the number wrong) that causes this disorder has, interestingly enough, been linked to evolution. I read it earlier this year in the 2003 Comprehensive Oxford Science Journal, though can't remember the exact explanation. You might want to look it up.

I know inbreeding often causes people to have similar disorders to this but not sure if it actually affects the rate of actual Downe's Syndrome. I could be wrong though.

[Mokele]

The mutation of the 26th chromosome (completely off the top of my head so I might have the number wrong)

 

I vaguely recall it being the 21st, actually, but I'm not totally sure either.

 

I know inbreeding often causes people to have similar disorders to this but not sure if it actually affects the rate of actual Downe's Syndrome. I could be wrong though.

 

Inbreeding basically decreases the heterozygosity of a population, driving it toward being exclusively homozygotes (which might be good or bad for you, depending on what you're homozygous for) at all loci. So, if the population already has some Downes alleles, you'll get a lot more expression of them in an inbred population. If there's no alleles, it won't show up at all until mutation creates it (and, for small populations, that's not very likely).

 

Mokele

[muad'dib]

Down's syndrome is due to a malfunction of the 21st chromosome, called trisomy 21. What happens in most cases is that nondisjuntion occurs during meiosis I resulting in one gamete having an extra 21st chromosome. This means that when this gamete combines with another from the opposite sex the zygote has 47 chromosomes not 46. There is not Down's syndrome allele as far as I know.

[Auburngirl05]

Much like what muad'dib said, I don't think there's an allele for it, you can't inherit the nondisjunction that causes the triple 21st chromosome.

For some reason the risk of Down's (and other diseases resulting from aneuploidy) increases as the age of the mother increases, with the ratio rising from ages in the early-mid thirties onward. I'm fairly certain that it's one of the conditions tested for with an amniocentesis.

[Glider]

Both the above are right. Down's is the result of nondisjunction of chromosome 21.

 

This occurs because females are born with all the eggs they will ever have (unlike males who constantly produce sperm). The longer the amount of time before the egg undergoes meiosis, the harder it is for complete disjunction to take place. This is why the risk increases with the age of the female.

 

There is no allele for Down's. Down's is one of the conditions amniocentesis detects.

[Skye]

I know that intercourse between relatives increases the chance of having a child with down syndrome

Where did you learn this?

[Radical Edward]

Much like what muad'dib said' date=' I don't think there's an allele for it, you can't inherit the nondisjunction that causes the triple 21st chromosome.

[/quote']

 

you can if you have a downe's parent. they are not sterile.

[gene]

There is no allele for Down's. Down's is one of the conditions amniocentesis detects.

 

But, if there is a mutation in the gene, which causes Down's. Wouldn't that allele be passed on? As let's say one parent has a normal allele and the other parent has the allele for down's, the child would have down's symdrone as the child obtains one allele from one and second allele from the other parent? When it mates, it passes on to the child isn't it???

 

Although changes are that the person infected with Down's Sydrome would be unlike to reproduce. as he would probably die at young age.

[Glider]

It's not a mutation, it's a structural problem cause by the chromosomes not separating properly during meiosis. This may or may not happen, but the probability increases with the age of the cell. There is no allele for it, it is a congenital condition, not an hereditary one.

[Auburngirl05]

you can if you have a downe's parent. they are not sterile.

As several others in addition to me have stated, you can't inherit a nondisjunction, it's a "mechanical" error in DNA replication.

[_13eoWuLF__]

As a mother gets older it increases the chances for a Down's syndrom baby.

[_13eoWuLF__]

As a mother gets older it increases the chances for a Down's syndrom baby.

[rakuenso]

read up on oogenesis and nondysjunction

[rakuenso]

read up on oogenesis and nondysjunction

[_13eoWuLF__]

some stats - There is a direct relationship between a mother's age and having a baby with Down syndrome. For women under 30 the chance is less than one in 1000, but at age 35 the chance is 1 in 400; at age 40 the chance is 1 in 105; and at age 44 the chance is 1 in 35.

 

When either parent has had a child with a chromosomal abnormality, there are at least 1 or 2 chances in 100 that a subsequent child will have severe birth defects associated with chromosomal abnormalities. For some specific types of chromosomal abnormalities the risk is even higher.

 

We are having our second child and sometimes I think about this subject. There are so many other genetic defects that are worse than downs. No matter what we are keeping the baby even if we knew it would be a downs baby.

 

Can you imagine what kind of genetic sceince will be going on in say 200 years?

[_13eoWuLF__]

some stats - There is a direct relationship between a mother's age and having a baby with Down syndrome. For women under 30 the chance is less than one in 1000, but at age 35 the chance is 1 in 400; at age 40 the chance is 1 in 105; and at age 44 the chance is 1 in 35.

 

When either parent has had a child with a chromosomal abnormality, there are at least 1 or 2 chances in 100 that a subsequent child will have severe birth defects associated with chromosomal abnormalities. For some specific types of chromosomal abnormalities the risk is even higher.

 

We are having our second child and sometimes I think about this subject. There are so many other genetic defects that are worse than downs. No matter what we are keeping the baby even if we knew it would be a downs baby.

 

Can you imagine what kind of genetic sceince will be going on in say 200 years?

[Guest 100x]

I think Im partially wrong about the "I know that intercourse between relatives increases the chance of having a child with downe syndrome", thats what my friend told me.

 

Interbreeding among relatives only increases the chance of downe syndrome if there is a history of it right?

[Guest 100x]

I think Im partially wrong about the "I know that intercourse between relatives increases the chance of having a child with downe syndrome", thats what my friend told me.

 

Interbreeding among relatives only increases the chance of downe syndrome if there is a history of it right?

[Auburngirl05]

 

Interbreeding among relatives only increases the chance of downe syndrome if there is a history of it right?

No' date=' the triple chromosome #21 that causes the disease results from an operational error, it is not a mutation of the chromosome like some other chromosomal disorders that [i']can [/i] cause birth defects.

To answer your question directly, the chance increases with inbreeding only if your interbreeding relatives include elderly women, but that applies to any breeding population. You can't inherit a nondisjunction. Do some reading on the meiosis process, it will explain aneuploidy.

[Auburngirl05]

 

Interbreeding among relatives only increases the chance of downe syndrome if there is a history of it right?

No' date=' the triple chromosome #21 that causes the disease results from an operational error, it is not a mutation of the chromosome like some other chromosomal disorders that [i']can [/i] cause birth defects.

To answer your question directly, the chance increases with inbreeding only if your interbreeding relatives include elderly women, but that applies to any breeding population. You can't inherit a nondisjunction. Do some reading on the meiosis process, it will explain aneuploidy.

[_13eoWuLF__]

Yeah I'm thinking it may increase other problems that would be linked to recessive genes not downs. But hey if you marry your sister or brother you prob aren't worried much about that.

 

You know on that topic there are alot of famous familys that have had alot of intrabreeding say between cousins and it didn't seem to hurt them. Seems I read an article in Discover about this.

[_13eoWuLF__]

Yeah I'm thinking it may increase other problems that would be linked to recessive genes not downs. But hey if you marry your sister or brother you prob aren't worried much about that.

 

You know on that topic there are alot of famous familys that have had alot of intrabreeding say between cousins and it didn't seem to hurt them. Seems I read an article in Discover about this.

[Skye]

As a hypothetical, if members of a family contained faulty alleles that were responsible for the segregation of chromosomes then inbreeding is likely to concentrate that allele in certain individuals, and could lead to a greater chance of Down syndrome occuring.

 

This wouldn't be likely create much difference in the chance of a baby being born with Down syndrome, as any large increase in errors in chromosome assortment is likely to be severely debilitating.

[Skye]

As a hypothetical, if members of a family contained faulty alleles that were responsible for the segregation of chromosomes then inbreeding is likely to concentrate that allele in certain individuals, and could lead to a greater chance of Down syndrome occuring.

 

This wouldn't be likely create much difference in the chance of a baby being born with Down syndrome, as any large increase in errors in chromosome assortment is likely to be severely debilitating.