9. Human genetics(1) Flashcards
What percentage of embryos have chromosomal defects?
50%
What percentage of newborn babies have a congenital disorder?
5%
what percentage of clinical conceptions terminate due to chromosomal abnormalities?
8%
What percentage of live births display a chromosomal abnormally?
0.1%
How does a mitochondrial disorder come about?
Mutations within mtDNA result in a number of mitochondrial disorders
(mutation disorder don’t follow mendelian patterns of inheritance)
Describe single gene disorders in terms of :
No of genes: Pattern of inheritance: Rarity: Penetrance: Tests:
No of genes - Disease allele at a single gene
Pattern of inheritance - Mendelian
Rarity: Individually rare - but collectively common
Penetrance - High
Tests - Tests are predictive
Describe complex gene disorders in terms of :
No of genes : Pattern of inheritance: Rarity: Tests: Environmental influence:
No of genes - Risk alleles are at multiple genes (polygenic)
Pattern of inheritance - No simple pattern of inheritance, but runs in families
Rarity - Conditions are common
Tests - No reliable tests
Environmental influence - Influenced by the environment
How many base pairs in the human genome?
3.2Gb (3x10^9) base pairs
What percentage of the human genome is “coding”
1.1% (20,500 coding genes)
What are coding and non coding regions of the genome called?
- Exons - coding
* Introns - non-coding
What happens to the introns in pre-mRNA?
Introns removed in splicing
What is ENCODE?
The Encyclopedia of DNA Elements (ENCODE) Consortium is an international research collaboration
Describe whole genome sequencing? (3)
- Sequencing the entire genome
- Enormous amount of data
- More expensive
What is whole exome sequencing?
• Targeted sequencing of only the protein encoding region of genome (1%)
Where are mutations identified in single gene disorders?
Coding sequence
Where are disease variants found in complex diseases?
Outside of the coding sequence
What does NGS (next generation sequencing) enable
NGS enables the routine sequencing of whole genomes/exomes
(A human genome can be sequenced in 24 hours and costs in the region of $1000)
Technology - Illumina Average Length of sequence read - 36 Average number of reads -35 000 000 Total amount of sequence - 1.3Gb Cost/Mb - $6
Technology - Sanger Average Length of sequence read - 800 Average number of reads - 384 Total amount of sequence - 300Kb Cost/Mb - $600
What is an example of :
Autosomal dominant disease
Autosomal recessive disease
X-chromosome linked disease
Huntington’s disease
Cystic fibrosis
Duschenes Muscular Dystrophy
