Arch Genetics Exam answers Flashcards
Turners cause and karyotype (1 mark)
Turner syndrome is caused by partial or complete loss (monosomy) of the second sex chromosome. (45XO)
- Name 2 pathologies due to Turners (2 marks)
genetic female with low oestrogen, no breasts, amenorrhea
- What treatments can reduce the physiological consequences of Turners (2 marks)
Most girls with Turner syndrome need to start estrogen and related hormone therapy in order to begin puberty. Often, estrogen therapy is started around age 11 or 12 years. Estrogen helps to promote breast development and improve the size (volume) of the uterus.
- Screening methods of Turners in utero (2 marks)
Karyotyping is a test that involves analysing the 23 pairs of chromosomes. It’s often used when Turner syndrome is suspected. The test can either be carried out while the baby is inside the womb – by taking a sample of amniotic fluid (amniocentesis) – or after birth by taking a sample of the baby’s blood.
What is the role of genetic counselling (3 marks)
The role of a genetic counsellor allows individuals to make informed decisions about their health. Genetic counsellors are trained in both medical genetics and counselling to interpret family history information and genetic test results and present complex information to families in a way that is meaningful to them.
Mother refused screening for Turners when she was pregs, give 2 reasons why she may have refused (1 mark)
It’s against the mother’s religious beliefs/termination is not an option
Doesn’t want to take on any increased risk of miscarriage or believes the baby will get harmed by the procedure
Klinefelters cause and karyotype (1 mark)
Chromosomal abnormality (similar to trisomy) →47 XXY
Name 4 Klinefelters pathologies (4 marks)
small, firm testes,
a small penis,
sparse pubic, armpit and facial hair,
enlarged breasts (called gynecomastia),
tall stature,
abnormal body proportions (long legs, short trunk).
Why would the DNA similarities between two 3yo monozygotic twins living together differ from two 60yo monozygotic twins living separately with their own families (4 marks)
Monozygotic twins share the same DNA so any differences to DNA must be caused by external factors → epigenetics →
One example of an epigenetic change is DNA methylation — the addition of a methyl group, or a “chemical cap,” to part of the DNA molecule, which prevents certain genes from being expressed.
Another example is histone modification. Histones are proteins that DNA wraps around. (Without histones, DNA would be too long to fit inside cells.) If histones squeeze DNA tightly, the DNA cannot be “read” by the cell. Modifications that relax the histones can make the DNA accessible to proteins that “read” genes. Environmental factors therefore allow genes to be turned or off.
Ethical justifications for disclosing bad news to parents (Guthrie test came positive for PKU in their 2 year old)
There are four main principles of ethics: autonomy, beneficence, justice, and non-maleficence. Each patient has the right to make their own decisions based on their own beliefs and values.
Function of the Guthrie test and what does it measure in PKU
Heel prick test that screens for 25 conditions including PKU, Galactosaemia, CF, amino acid disorders → done on a guthrie card. In PKU it measures phenylalanine in the blood.
Prognosis and treatment of PKU
If PKU is confirmed, treatment will be given straight away to reduce the risk of serious complications. Treatment includes a special diet and regular blood tests. With early diagnosis and the correct treatment, most children with PKU are able to live healthy lives.
Molecular process of CF
CF disease is due to the defect of the CFTR gene located on chromosome 7.
Mutation results in a defective CFTR transport protein which regulates movement of chloride ions out of mucous epithelial cells, results in dysfunction of several organs
lungs: thick mucus that narrows airways and cannot be cleared, chronic bacterial infection, inflammation, fibrosis
pancreas: thick mucus blocks pancreatic ducts → pancreatitis and malabsorption
male reproductive tract: absence of vas deferens causing male infertility
sweat glands: high chloride and sodium in sweat, basis of sweat test
