Problems with meiosis may lead to genetic disorders or infertility.
Contributing Factors
• Disease• Environmental factors• Random errors
Non-disjunction
Homologous chromosomes fail to separate during meiosis.
One daughter cell has one extra chromosome. One daughter cell has one missing chromosome
Too much or too little protein is made.
trisomy
3 copies of a chromosomeExamples: trisomy 21-Down’s syndrome
trisomy 13-Patau’s syndrome
monosomy
1 copy of a chromosomeExample: 0X -Turner’s syndrome
Risk Factors Increase with Age
The risk of non-disjunction increases with age.1 in 800 children is born with Down Syndrome.
• A woman in her 20’s has a 1 in 1000 chance of delivering a child with Down Syndrome.
• A woman in her 40’s has a 1 in 40 chance of delivering a child with Down Syndrome
Karyotype
Prepared using white blood cells frozen in metaphase, photographed and sorted
Prenatal Testing
After age 35.At 8 weeks, the chorionic villus sampling (CVS) can remove cells from the outer membrane surrounding the embryoLater, amniocentesis can be doneBetween 15-20 weeks a multiple markerblood test can be done.
Infertility
10% of couples in Ontario are unable to produce children
-poor sperm or egg quality-blockages in the fallopian tube or vas deferens