Chromosomal Abnormailities Flashcards
What is the difference between a balanced and unbalanced genome?
Balanced - no genetic info lost
Unbalanced - genetic info lost
What is karyotyping?
The systematic sorting of chromosomes.
Aneuploidy?
The loss/gain of whole chromosomes.
What is polyploidy and what’s the most common reason for it?
Poly - gain of a whole haploid set of chromosomes.
Usually fertilisation of an egg from more than on sperm.
Non-disjunction?
Failure of one or more pairs of homologous chromosomes/ chromatids to separate during normal division.
What is anaphase lag?
When a chromosome gets ‘left behind’ in anaphase due to defects in the spindle. Can be lost entirely.
What chromosomal abnormality results in Down Syndrome and what are the symptoms?
Trisomy 21 (extra chromosome in 21) Characteristic face defects, intellectual disability, increased risk of leukaemia/alzheimars.
What is Edward’s Syndrome?
Trisomy 18 Maternal meiosis 2 error Small jaw, overlapping fingers, rocker bottom feet Pre-natal diagnosis 5-15 day life span
What is Turner syndrome?
Usually absent paternal X chromosome
Puffy feet
Extra skin at back of neck
What is mosaicsm?
Mosaicism is a condition in which cells within the same person have a different genetic makeup.
Starts from mitosis in a single fertilised egg.
What is a reciprocal translocation?
Exchange in material across non-homologous chromosomes
Usually harmless to the patient but can be dangerous for any offspring.
If a patient with a reciprocal translocation were to have a child, what is and what would be the consequence of:
A)Alternate segregation
B)Adjacent segregation
C)Adjacent segregation
A) Genotype would be either be normal or balanced - the right amount of genetic information on each chromosome
B and C) Unbalanced - there would be too much of one chromosome and too little of the other - not viable for life/high chance of birth defects
What is a Robertsonian translocation?
When two chromosomes for two different locations stick together to make one big chromosome.
E.g. Chromosome 13 and 14 - patient would have one normal chromosome 13, one normal chromosome 14, and one big 13/14 chromosome.
Patient healthy
If a patient with a Robertsonian translocation on chromsome 13 and 14 wanted to have a child, what are the four outcomes?
1) A healthy child with one normal 13 chromosome and one normal chromosome 14
2) A healthy child with the balanced 13/14 chromosome (still has all genetic info)
3) A child with one copy of normal chromosome 13 and one copy of the 13/14 chromosome
4) A child with one copy of normal chromosome 14 and one copy of the 13/14 chromosome
In cases 3 and 4, the child would not be viable for life.
If a patient has a Robertsonian translocation on their chromosome 21, what condition could they pass onto their child?
Down Syndrome
