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Why do geneticists suspect that the extra chromosome seen in down syndrome usually comes from the egg rather than the sperm?
Wiki User
∙ 11y ago
Meiosis takes longer in the ovary, increasing
the likelihood of error.
Wiki User
∙ 11y ago
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Is it possible to have a XXY chromosome set for gender?
Yes. It is known as Klinefelter's syndrome. The extra X chromosome interferes with meiosis and usually prevents the affected males from reproducing.
What effect does Down syndrome have on the chromosomes?
Down syndrome is usually caused by a condition known as Trisomy 21, which means that a person has three copies of Chromosome 21, rather than the usual two copies. An extra chromosome is added. The normal amount is 46, but people with Down syndrome have 47.Occasionally, the condition is a result of part of Chromosome 21 becoming fused to the end of another chromosome.More info on Chromosome 21While Chromosome 21 isn't the shortest chromosome, it is the one that contains the fewest genes (other than the Y chromosome). This is because genes on Chromosome 22 are more closely spaced, and thus the chromosome contains more genes, despite its smaller size.
What is trisomy mutation?
A trisomy is when a person has 3 versions of a chromosome. 'Normal' humans will only have 2 of each chromosome. For example, having 3 versions of chromosome 21 is known as Trisomy 21 or Down Syndrome.
How rare is Rett Syndrome?
According to the International Rett Syndrome Foundation, it occurs in 1 out of every 10,000 to 23,000 female births. It is very rare, so the rate of occurrence is not known absolutely. Almost all of those alive with Rett Syndrome are female; males who have the genetic mutation do not have a second X chromosome to compensate for the defective gene so they usually die before birth or shortly thereafter. The males that survive almost always have an extra X chromosome (XXY).
What does chromosome 21 provide?
Usually humans have 46 chromosomes, divided into 23 pairs within each cell, one copied from each parent. Chromosome 21 is the smallest and the second human chromosome to be sequenced. Many genetic conditions are related to changes in particular genes on this chromosome including Cancers, Downs Syndrome and Alzheimer's Disease Changes in the structure in the number of copies of a chromosome may also cause problems with health and development. Cancer For example -translocation in chromosomes 12 and 21 have been linked to Lymphoblastic Leukemia whilst links between translocation of 8 and 21 Acute Myeloid leukemia. Downs Syndrome -a chromosomal condition that, in most cases is caused by trisomy 21 (each cell has 3 copies instead of the normal 2).
Down syndrome is usually caused by an extra copy of what chromosome?
Down syndrome occurs because of the extra chromosome on chromosome 21. If you go onto google images and type in karyotype of Down syndrome, you will find a picture of the extra chromosome. Instead of having two chromosomes on chromosome 21, there is an extra. Type your answer here...
How do you know you have Down syndrome?
a test is usually done in pregnancy which identifies the condition. people with Down syndrome have an extra chromosome. people with down syndrome usually have impaired cognitive ability and typical facial characteristics such as an oversized tongue and are usually small in stature
Is it possible to have a XXY chromosome set for gender?
Yes. It is known as Klinefelter's syndrome. The extra X chromosome interferes with meiosis and usually prevents the affected males from reproducing.
How many copies of Chromosome 21 are there in someone who has Down syndrome?
3 Pairs of Chromosome 21There are 47 chromosomes in someone with Down syndrome (most people have 46); the 21st pair has an extra chromosome. Down syndrome is also known as "Trisomy 21" - a reference to the fact that someone with Down syndrome has 3 pairs of chromosomes 21.
What causes prader wili syndrome?
PWS is usually not inherited in MOSt cases. It occur as random events and is caused by the deletion of chromosome 15.
Is Edwards syndrome autosomal or sex-linked?
Down Syndrome is a trisomy of the 21st chromosome as opposed to an allelic inheritance through the X chromosome. Trisomy is a somatic disorder caused by improper division during gametogenesis (usually of the ovum) that results in 3 copies of the 21st chromosome in the egg once it is fertilized.
How many chromosomes would the body of a women born with Turner's syndrome have?
45. 22 pairs plus one chromosome; the one X Turner's syndrome women usually posses.
What effect does Down syndrome have on the chromosomes?
Down syndrome is usually caused by a condition known as Trisomy 21, which means that a person has three copies of Chromosome 21, rather than the usual two copies. An extra chromosome is added. The normal amount is 46, but people with Down syndrome have 47.Occasionally, the condition is a result of part of Chromosome 21 becoming fused to the end of another chromosome.More info on Chromosome 21While Chromosome 21 isn't the shortest chromosome, it is the one that contains the fewest genes (other than the Y chromosome). This is because genes on Chromosome 22 are more closely spaced, and thus the chromosome contains more genes, despite its smaller size.
When did Russell Silver syndrome develop?
No one knows when Russell Silver Syndrome developed but it is caused by a copy of the seventh chromosome. People usually get the copy from their mother. Russel Silver syndrome is a TREATABLE form of dwarfism. This is treated with the write diet
Why are males more likely to have fragile X syndrome?
males have only one copy of the X chromosome. Males who inherit the full mutation are expected to have mental impairment. A female's normal X chromosome may compensate for her chromosome with the fragile X gene mutation
If a human gamete with an extra chromosome participated in fertilization with a normal human gamete what condition results?
A trisomy. Trisomies are usually fatal in all chromosome pairs except 5, 13, 21 (these cause Down syndrome), and 23 (The chromosome pair that determines gender)
What causes disorders such as klinefelter syndrome and turner syndrome?
Klinefelter syndrome is a chromosomal condition that only affects males and is characterized by a male having an additional X chromosome (XXY) in cells. This chromosome abnormality occurs when there is an error in cell division, resulting in an extra copy of the X chromosome.
