Human Genome Flashcards
The human genome project, begun in 1990, aimed to:
- identify all human genes, and their roles
- analyse genetic variation between humans
- sequence the genomes of server all model organisms used in genetics
- develop new sequencing techniques and computational analyses
- to share genome information with scientists and the general public as fast as possible
Define a genome
-a complete set of DNA of an organism, including all its genes
Genomics:
The study of genomes
Nuclear DNA vs Mitochondrial DNA
Nuclear DNA:
22 autosomes, X,Y
6 billion base pairs
Half from each parent
<20,000 genes
Mitochondrial DNA
Single,circular
16,569 base pairs
All from mother
37 genes
Key findings of the human genome
- there are fewer genes then expected
- less then 2% of our genome codes for proteins
- the genome is dynamic
- still don’t know what many of out protein coding genes do
- most human genes are related to those of other animals
- all humans are 99.9% similar at sequence level
- <2% coding (exons)
- 20% introns
- 20% of genes still have an unknown function
What are our genomes 0.1% different - what causes variation in the human genome?
- channels range form single base to chromosome rearrangements
- single nucleotide polymorphisms ‘SNPs” are sites in the DNA that commonly vary within populations
- 1.9 million SNPs?
SNPs
- single nucleotide polymorphisms ‘SNPs’ are common single base pair changes or variants
- are common, 1 every 300 nucleotides
- mostly from patents
- each genome sequenced adds to the variation on record
- diversity in a genome sequence adds to knowledge of variation
- many SNPs don’t do anything - they are just inherited variations - but doesn’t mean they’re not useful
What analysing common variants (genotyping) can tell you:
- relations
- where ancestors are from (some)
- disease risk / association
- if you will lose your hair
- muscle type
- how you’d respond to drugs
- Crime solving
Variation in the human genome (STRs)
- short tandem repeats (STRs) and DNA profiling
- STRs are repeats of 2-5 nucleotides, found in specific regions of genomes
- each person inherits 2 alleles, one from each each biological parent- which can be different lengths
- they can be used to create genetic profiles or “DNA fingerprints”
8 repeaters of CAG from biological mother + 3 repeates of CAG from biological father = the individual is 3,8 and STR1
Variation in the human genome: InDels
InDels: small insertions or deletions
- second most common variant type in human genome
- one of the most common genetic diseases, cystic fibrosis is caused by CFTR deltaF508, which is a 3 nucleotide deletion
- this can cause “frame shift” - a change in the way DNA is read, if in protein-coding regions
Insertion of one letter
Deletion of two letters
Structural variants
CNVs - copy number variants: chunks of DNA> 500bp that are present at different amounts or ‘copy numbers’ relative to a reference genome
- can be deleted or duplicated
- can span multiple genes
- humans have 10,000 CNVs, found within sensory perception and immunity (e.g smell)
