Genetics Flashcards
What are mutations?
Alterations of bases in the code
What is the result of a mutation?
Protein is malformed
Phenotype
When acharacteristic coded for is physically presented
Genotype
The genetic code of a person
Aneuploidy:
More/fewer chromosomes that normal
Deletion:
Part of chromosome or DNA code is missing
Inversion:
A piece of chromosome breaks and turns around and then reattaches
Ring
The ends of a chromosome attach to each other, forming a ring
Translocation:
Segment of a chromosome separates and reattaches to another site on the chromosome or on a different chromosome entirely
Mosaicism:
2 or more sets of chromosomes in the cell with different genetic material
If some cells are affected, it will lead to a milder version of the condition
What is the group name for downs, edwards and pataus?
Trisomy
What chromosome is affected in Down’s syndrome?
21
What chromosome is affected in edwards syndrome?
18
What chromosome is affected in pataus syndrome?
13
Options of screening for trisomy conditions:
- none
- downs only
- e&p only
-all three
What is the Trisomy screening and when does it happen?
-between 11-14 weeks
- blood test and scan
- scan for the nuchal fold
- blood test measures levels of Papp-A and hCG
What measurement of the nuchal fold, Papp-A and hCG correlates to a trisomy condition?
-high nuchal fold measurements
-low Papp-A
-High hCG
What does the quadruple screening test for?
- Down’s syndrome only
-blood test between 14-20 weeks - tests for alpha-fetoprotien (AFP), hCG, estriol and inhibit A
What’s classed as a high/low result for trisomy?
High= 1 in 150 or less
Low= 1 in 151 or more
What is NIPT:
-Non-invasive prenatal testing
-follow on screening test when previous screening is high result
-takes maternal blood and screens for fetal DNA
Order of most reliable screening to least:
1) NIPT
2) Combined
3)Quadruple
What is sickle cell disease:
- autosomal recessive
- RBC are sickle shaped
-clump together causing inflammation
-RBC have a lower o2 carrying capacity
-mainly affects Afro-Caribbean ethnicities
What is thalassaemia:
-autosomal recessive
-RBC produce little/no haemoglobin
- anaemia
-affects south Asian, Middle Eastern ethnicities
Screening for thalassaemia:
- offered to all pregnant women
- blood tests
-If pregnant woman is a carrier than partner is screened - if both are carriers than diagnostic testing is offered
Screening for sickle cell disease:
- offered to women who live in areas of high prevalence
-family origin questionnaire may determine whether one needs screening
-if pregnant women is a carrier, partner is screened - if both are carriers, diagnostic testing is offered
What is chronic villus sampling:
-diagnostic testing
-needle inserted via abdomen/cervix to obtain sample of placental tissue to obtain fetal DNA
-between 11-14 weeks
- risk of miscarriage is 0.5%
What is Amniocentesis:
-fine needle is inserted to obtain a sample of amniotic fluid
-fetal DNA is obtained and screened
- between 15-20 weeks
Risk of miscarriage is 0.5%
What is a neural tube defect?
-Spinal cord doesn’t fuse
-caused by genetic and environmental factors
-screened for at the anomaly scan
