Genetic Variation and Disease I Flashcards
What can help to recognise a chromosome?
Length, position of centromere and banding pattern with specific stains
What are the structures of a chromosome?
Telomere, short arm (p), centromere, long arm (q), telomere
What is different about acrocentric chromosomes?
The short arm doesn’t matter - satellite ribosomal genes, tRNAs etc
What is a balanced chromosome rearrangement?
All the chromosomal material is present
What is an unbalanced chromosome rearrangement?
Extra or missing chromosomal material, usually 1 or 3 copies of the genome rather than 2
What is aneuploidy?
Whole extra or missing chromosome
What is translocation?
Rearrangement of chromosomes, ie sections of different chromosomes switched out
What are insertions/ deletions?
Missing or duplicated genetic material
What is Robertsonian translocation?
Two acrocentric chromosomes stuck end to end. An increased risk of trisomy in pregnancy
Why is X chromosome aneuploidy better tolerated?
X inactivation
What is reciprocal translocation?
When the translocation occurs over two chromosomes from different pairs
What are the reproductive risks of reciprocal translocation?
50% will have normal chromosomes or the translocation will be balanced. Unbalanced (50%) products mainly result in miscarriage or sometimes dysmorphic delayed child.
What are the pros and cons or molecular cytogenetics?
You don’t need to see chromosomes to count them - quick, cheaper and more sensitive. However, you will only detect imbalance, and can detect tiny changes - some of which are polymorphisms
What is Array CGH?
DNA based technique that is genomewide and also finds lots of polymorphisms. Can detect any size of imbalance but does not detect balanced rearrangements
Where do New mutations occur?
In gametogenesis
What is mosaicism?
One human who has different cells with different genetic constitution.
Where does somatic mosaicism exist?
At meiosis and mitosis - for one chromosomal abnormality is one genetic change that contributes to cancer)
What could chromosome changes lead to?
Oncogene activation or deletion of a tumour supressor (stops cell division from being able to continue)
What does PCR allow?
The selection of one small piece of the human genome (100-10,000 bases) and amplify it
What does Next Generation Sequencing allow?
A whole genome to be sequenced (in a day) or the sequencing of all known exons - all quite cheaply!
If only a small section of the genome is exons, what does the rest do?
Regulation of genes, spaces genes out (insulates genes from promotors) and provides substrate to expand genome (add genes)
