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Aneuploidy and Related Biotechnologies

About 15% of all confirmed pregnancies result in miscarriage. Also, many miscarriages occur before a woman has missed her period and therefore may know that she is pregnant. Chromosome abnormalities within the embryo are the most common cause of miscarriage in early pregnancy.

Aneuploidy is the name given to the condition where there is variation from the expected number of chromosomes within a cell. For example in a human somatic cell, it is expected that there will be 2n or 46 chromosomes. If there are 45 or 47 chromosomes, this is aneuploidy. Aneuploidy is the most commonly identified chromosome abnormality in humans, occurring in at least 5% of all clinically recognised pregnancies (Hassold and Hunt, 2001). Because each chromosome contains a large number of genes, aneuploidy causes major disruptions, and in most cases will result in miscarriage at a very early stage in the pregnancy. However, some will survive to birth.

Aneuploidy occurs in 0.3% of live births and is the most common known cause of intellectual disability in humans. Aneuploidy is caused by the failure of chromosomes or chromatids to separate during cell division. This is called nondisjunction and can happen either during meiosis or mitosis.

Resources and challenge questions

Down Syndrome is caused by the presence of an extra copy of chromosome 21 (Fig 1c) and is the most common form of aneuploidy seen in humans. Many Down Syndrome pregnancies miscarry, so while in New Zealand Down Syndrome occurs in 1 in 400 pregnancies, it is only seen in 1 in 700 live births. The occurrence of Down Syndrome increases with increasing maternal age, rising from 1 in 1000 for 20-29 year old mothers to 1 in 90 for 40 years old mothers. There is no cure for Down Syndrome and it is not caused by any recognised environmental factor,

Aneuploidy and Related Biotechnologies seminar paper
Aneuploidy is a condition where there is variation from the expected number of chromosomes within a cell. (2.2 MB, PDF)
Pre-seminar discusion paper
For discussion in class before the seminar. (1.0 MB, PDF)
Seminar challenge questions
Post seminar challenge questions. (261.5 kB, PDF)
Seminar PowerPoint slides
Seminar slides excluding slide 74 that contains video content that exceeds server limits. (3.7 MB, PDF)