Gametogenesis (genetic/congenital disorders)
Sample Solution
Non-disjunction is a failure of homologous chromosomes to separate properly during meiosis. This can lead to gametes with either too many or too few chromosomes. When a gamete with an extra chromosome fertilizes an egg, the resulting embryo will have an extra chromosome, also known as trisomy.Full Answer Section
The incidence of non-disjunction increases with age in females. This is because the oocytes (eggs) in a woman's ovaries have been arrested in meiosis I since she was born. As the woman ages, the oocytes become more susceptible to damage. This damage can make it more likely that the chromosomes will not separate properly during meiosis II, leading to non-disjunction.
2. Correlation between parental ages and genetic/congenital disorders
The risk of having a child with a genetic or congenital disorder increases with parental age. This is due to a number of factors, including:
- Increased risk of non-disjunction: As mentioned above, the risk of non-disjunction increases with age in females. This can lead to trisomies, such as Down syndrome, which are the most common genetic disorders.
- Sperm quality: Sperm quality decreases with age in males. This can increase the risk of chromosomal abnormalities in the sperm, which can lead to genetic disorders.
- Increased risk of mutations: Mutations can occur in DNA at any time, but the risk increases with age. This is because the DNA in our cells is constantly being damaged and repaired. As we age, the repair process becomes less efficient, which can lead to more mutations.
Some specific examples of genetic disorders that are more common in older parents include:
- Down syndrome
- Trisomy 18
- Trisomy 13
- Klinefelter syndrome
- Turner syndrome
- Fragile X syndrome
3. Teratocarcinoma
A teratocarcinoma is a type of germ cell tumor that can form in the ovaries, testes, or brain. It is made up of a variety of different cell types, including cells that can develop into different tissues and organs.
The cause of teratocarcinomas is not fully understood, but they are thought to be caused by mutations in germ cells. Germ cells are the cells that give rise to sperm and eggs.
Teratocarcinomas can be life-threatening, but they are often treatable with surgery, chemotherapy, and radiation therapy.
4. Embryonic stem cell lines and teratocarcinomas
Embryonic stem cells are pluripotent cells, meaning that they have the potential to develop into any type of cell in the body. Embryonic stem cells can be derived from blastocysts, which are early-stage embryos.
Teratocarcinomas can be used to derive embryonic stem cell lines. This is done by removing the pluripotent cells from the teratocarcinoma and growing them in culture.
Embryonic stem cells are used in research to study human development and to develop new treatments for diseases. They are also being investigated as potential therapies for a variety of diseases, including cancer, Parkinson's disease, and spinal cord injury.
Potential clinical use of embryonic stem cells
Embryonic stem cells have the potential to be used to treat a variety of diseases and conditions, including:
- Cancer: Embryonic stem cells can be used to generate new cells and tissues to replace those that have been damaged or destroyed by cancer.
- Neurological disorders: Embryonic stem cells can be used to generate new nerve cells to replace those that have been damaged by neurological disorders such as Parkinson's disease and spinal cord injury.
- Autoimmune diseases: Embryonic stem cells can be used to generate new cells and tissues to replace those that have been damaged by autoimmune diseases such as type 1 diabetes and multiple sclerosis.
- Other diseases: Embryonic stem cells are also being investigated as potential therapies for a variety of other diseases, such as heart disease, liver disease, and macular degeneration.
5. Karyotypes, common names, life expectancy, prevalence and major systems of the following abnormalities of chromosome number