Does Down syndrome affect phenotype?
Down syndrome (DS) is one of the most frequent congenital birth defects, and the most common genetic cause of mental retardation. In most cases, DS results from the presence of an extra copy of chromosome 21. DS has a complex phenotype, and a major goal of DS research is to identify genotype–phenotype correlations.
Why does Down syndrome affect the phenotype?
Down syndrome is an aneuploidy syndrome that is caused by trisomy for human chromosome 21. While the phenotype is most likely due to a subtle increase in gene dosage of only a small minority of the estimated 500–800 genes that are present on this chromosome, the molecular genetics of Down syndrome remains speculative.
What are the phenotypic characteristics of Down syndrome?
People with Down syndrome often have a characteristic facial appearance that includes a flattened appearance to the face, outside corners of the eyes that point upward (upslanting palpebral fissures ), small ears, a short neck , and a tongue that tends to stick out of the mouth.
What gene is affected by Down syndrome?
Down syndrome is a genetic disorder caused when abnormal cell division results in an extra full or partial copy of chromosome 21. This extra genetic material causes the developmental changes and physical features of Down syndrome.
Is 31 too old to have a baby?
Ages 31 to 35 In your early 30s, the chances you’ll be able to have a baby are still high. You still have a lot of high-quality eggs to offer, but your odds will start to decline steadily at this age. Your fecundity rate decreases gradually until age 32. At 37, it drops dramatically.
What age is the most fertile?
In general:
- women are most fertile before the age of 30.
- after 30, women’s fertility starts to decrease.
- after 35 fertility declines more significantly.
- by 40, a woman’s fertility is about half the level it was before she was 30.