Chromosomal abnormalities Flashcards
What is cytogenetics?
Study of genetic makeup of cells through imaging of chromosomes
Why is cytogenetics done?
Accurate diagnosis
Future reproductive risks
Prenatal diagnosis
What are some examples as to why somebody may be referred to cytogenetics?
Birth defects
Infertility
Frequent miscarriages
Cancers
What are some examples of birth defects?
Congenital malformations
Mental retardaton
Developmental delay
How are chromosomes assessed on a visual karyotype?
Look at banding pattern
What is the genetic cause of Down syndrome?
Trisomy 21
What is the genetic cause of Edward syndrome?
Trisomy 18
What is the genetic cause of Patau syndrome?
Trisomy 13
What is the genetic cause of Turner syndrome?
45, X
Why do people with Turner syndrome manage to survive?
Because even in normal females, one X chromosome is inactivated, only one is active
What is polyploidy?
Gaining a whole haploid set of chromosomes
How many chromosomes are there altogether in polyploidy?
69
What is the main cause of polyploidy?
Polyspermy
What is polyspermy?
When one egg is fertilised by more than one sperm
What is anaphase lag?
Refers to how chromosome can be left behind at anaphase stage of cell division
What are the causes of anaphase lag?
Defects in spindle attachment to chromosomes
Defects in spindle function
What happens to the lagging chromosome in anaphase lag?
Lost entirely
What are some of the symptoms and signs of Down syndrome +21?
Characteristic facial features
Heart defects
Hypotonia
Intellectual disablity
What are some of the symptoms and signs of Edwards syndrome +18?
Overlapping fingers
Rocker bottom feet
Prominent occipit
Small lower jaw
Low-set ears
Is Edwards syndrome more common in male or females?
Females
What is the lifespan of a baby with Edwards syndrome?
Approx. 2 weeks
What are some of the symptoms and signs of Patau syndrome +13?
Polydactyly
What is the lifespan of a baby with Patau syndrome?
Most die as newborns
Why does having only one X chromosome cause problems in Turner syndrome?
Some genes are not inactivated in the second X chromosome
Individuals with Turner syndrome lack these genes
What are the signs and symptoms of Turner syndrome?
Short stature
Neck webbing
Puffy feet
Infertility
What is a reciprocal translocation?
Small part of two chromosomes broken off
swapped over
How are the gametes of somebody with a reciprocal translocation affected?
May be balanced
May be unbalanced
What is meant by balanced?
All genetic material is present
What is meant by unbalanced?
Some genetic material is extra or missing
What is a Robertsonian translocation?
Two acrocentric chromosomes fused together
How many chromosomes do people with a Robertsonian translocation have?
45
What is formed in meiosis in people with a Robertsonian translocation?
Trivalent - three chomrosomes
gives risk of aneuploidy
What will the phenotype of the unbalanced gamete depend on?
Which regions show monosomy and trisomy
What are the different types of FISH probes?
Gene specific probes
Centromere probes
Telomere probes
Whole chromosome paints
What are gene specific FISH probes used for?
Identify microdeletions
What are centromere FISH probes used for?
Identify chromosome of origin
What are whole chromosome paints in FISH used for?
Identify chromosomal rearrangement
What can microarray comparative genomic hybridisation not detect?
Balanced rearrangements
What is formed in prophase 1 of meiosis in people with Reciprocal translocations?
Quadrivalent - four chromosomes
