Lecture 3 Flashcards
what is the purpose of genetic testing
- diagnostic testing
- carrier testing
- pre-symptomatic and predictive testing
- prenatal testing
- preimplantation testing
what is diagnostic testing
testing to confirm a suspected diagnosis or to aid diagnosis
explain carrier testing
testing someone who is usually healthy but may be a carrier of a recessive or X linked genetic condition
what is the importance of a correct diagnosis
- effective and timely treatment
- access to healthcare support
- may result in lifestyle changes for patient
- may inform life planning and reproductive decision making
- emotional impact of “not knowing “
why might someone undergo carrier testing
- individuals who have a family history of a genetic disorder
- people in certain ethnic groups with an increased risk of specific genetic conditions
- primarily used to guide and inform for reproductive choices
predictive testing
can identify mutations that increase a persons risk of developing disorders with a genetic basis
- eg. Bracca 1 gene testing
prenatal testing
used to detect changes in genes or chromosomes before birth
(used to look for specific conditions)
harmony test
a test the screens for chromosomal abnormalities
- a prenatal test
- at the moment is a private test
preimplantation genetic diagnosis
used to detect genetic changes in embryos created using IVF
pre-symptomatic testing
can determine whether a person will develop a genetic disorder before signs or symptoms
molecular diagnostics
a range of diagnostic tests that detect variants (mutations) in DNA
cytogenetic diagnostics
the examination of chromosomes to determine genetic abnormalities
sources of DNA when testing
blood
saliva
tissue samples
bone
amniotic fluid
CVS
where does the DNA sample come from in prenatal testing
he developing fetus
a thin needle is put through the mothers abdominal wall with ultrasound guidance
what are three different techniques used in cytogenetics
- karyotype (G banding)
- Fluorescence in situ hybridization FISH
- Array CGH
explain karyotype preparation with G banding
- obtain a blood sample
- colcemid is added to prevent spindle from forming therefore keeping cells in metaphase
- cells are collected
- treated with hypotonic solution to swell the cells
- cells fixed onto slides
- stained with Giemsa
- banding patterns are analyzed
- karyotype is made by arranging chromosomes into pairs
what type of syndrome does the karyotype appear normal
microdeletion syndromes
FISH
lab technique for detecting a specific DNA sequence on a chromosome, relies on exposing chromosome to a probe that is fluorescently labelled
what is a limitation of array CGH
it can only tell us if there is loses and gains in chromosomes, not if there is any structural changes
what is a limitation of G-banding
time consuming
low resolution
what is a limitation of FISH
targeted analysis
what is PCR
polymerase chain reaction
- a powerful laboratory technique used in genetics to amplify a specific segment of DNA. allows researchers to make millions of copies of a particular DNA sequence, making it easier to study and analyze.
what are the key steps in PCR
- denature the DNA
- temperature is increased to make it single stranded
- primer then needed to anneal the DNA at different temperatures depending on the components
- DNA polymerase expands the DNA by adding nucleotides
Huntington disease
- genetic disorder that affects the brain
- ## caused be abnormal increase in CAG repeats
how would you design your primers for fragment sizing
- CAG is the variable part
- if you design your primers to flank either side of the CAG repeat so then you can measure and tell someone how long their CAG repeat is
