Genetic Variation from chromosomes to single bases 1 Flashcards
What is the normal karyotype for humans?
46 XX/XY
What is the karyotype for a human with Down syndrome?
47 XX/XY + 21
Describe the structure of a chromosome from top to bottom.
- Telomere
- Short arm (p)
- Centromere
- Long arm (q)
- telomere
What are acrocentric chromosomes?
Chromosomes which have almost no short arm (p)
Give 2 examples of what acrocentric chromosomes can code for.
tRNA, satellite ribosomal genes etc.
What is a balanced chromosomal rearrangement?
When there is still all the genetic material present.
What is an unbalanced chromosomal rearrangement?
When there is either missing or extra chromosomal material (either 1 or 3 copies)
What does aneuploidy mean?
When there is whole extra or missing chromosome.
What does translocation mean?
rearrangement of sections of chromosomes.
What are deletions?
Missing genetic material from chromosome.
what are micro-deletions?
Small missing pieces of genetic material from chromosome.
What are robertsonian translocations?
When there is two acrocentric chromosomes stuck end to end. This creates a higher risk of trisomy.
How can X chromosome aneuploidy be tolerated?
X chromosome inactivation means an extra X could be inactivated.
What are examples of X chromosome aneuploidy disorders?
- 45X- turner syndrome (female)
- 47XXX- triple X (female)
- 47XXY-Klinefelter syndrome (male)
What are duplications?
Duplications of a section of a chromosome.
What are inversions?
When a section of a chromosome is inverted.
What are reciprocal translocations?
When two sections of two different chromosomes swap, normally (50% likelihood) producing a balanced chromosomal rearrangement.
What is FISH?
- Fluorescence in situ hybridisation
- can See 1 specific chromosome’s segment
Describe arrayCGH.
- The first line test for chromosomal imbalances
- it only detects unbalanced rearrangements
- detects polymorphisms
- detects tiny changes not visible through microscope
- genome wide
What is the difference between the exome and the genome?
Genome- all genetic material
Exome- all genetic material coding for RNA.
What are germ line mutations?
Mutations affecting germ cells, can be passed from mum or dad and mainly occur at gametogenesis
What is mosaicism?
When cells within the same person have a different genetic makeup. Could be a mosaic chromosome abnormality or mosaicism for a point mutation. This can be passed to children.
What is somatic mosaicism?
When body cells are showing as mosaic.
What does de-novo mean?
A new mutation, can occur at gametogenesis, could be post-zygotic or could have mosaic parents
What is PCR?
- Polymerase chain reaction
- amplifies a small sequence of DNA
What is Sanger sequencing?
It is the same as PCR but does it at a much smaller scale- smaller pieces amplified at a time.
What is Next generation sequencing (NGS)?
This can detect single base variations through alignment with a reference genome.
