E9 Basic genetics Flashcards
where does the evidence for importance of genetics in disease come from?
- studying identical and non-identical twins
- studies of identical twins separated at birth
how are genetic diseases becoming both preventable and treatable?
preventable
- human embryos have been edited to stop genetic disease
- gremlin editing isn’t allowed in the UK due to moral beliefs
treatable
- Nusinersen is an antisense oligonucleotide drug for spinal muscular atrophy
define trait
- inheritable characteristics
- eg. height (complex trait), hair colour (less complex, especially for red hair)
define phenotype
- variant of characteristic in individual
- eg. for hair colour, the phenotypes are brown, black, red, blonde etc.
define mutation
change in a gene
define allele
one of the different variants of a gene
define polymorphism
- the specific differences in the DNA sequence between alleles
- eg. deletion of a C base
define genotype
- combination of alleles in the DNA sequences of an individual
- although formally harmful mutations are also polymorphisms, the term is usually used for normal variation
- a lot of genetic variation has no detectable consequences eg. silent mutations or mutations in introns
what are people with Aa genotype called?
carriers
why do recessive alleles on the X chromosome affect men more than women?
women have 2 X chromosomes so they must be homozygous recessive to have condition but men only need one copy of recessive allele to have condition
where are mitochondrial mutations inherited from?
the mother only
describe Huntington’s disease genetics
- autosomal dominant
- mutated allele is always expressed if it is present
describe cystic fibrosis genetics
- autosomal recessive
- need to be homozygous recessive to be expressed
describe Duchenne muscular dystrophy genetics
- X-linked recessive
- males need one copy of Duchenne’s allele to be affected
- females need 2 copies (homozygous)
describe mitochondrial genetics
- most mitochondrial proteins are encoded in the nucleus
- mitochondria have a small genome on a circular chromosome of their own
- multiple mitochondrial genomes are inherited from the mother in the egg
how do Mendelian genetics and human genetics differ?
- Mendelian makes things look pretty simple in principle
- human genetics have many complicating factors in reality
what is incomplete penetrance?
- having a particular gene variant makes it more likely but not certain that you’ll have the disease
state a disease that involves complete penetrance
cystic fibrosis
what is meiotic recombination and what does it do?
- reshuffles gene variants
- this is due to crossing over in meiosis I
- the closer 2 genes are together on their chromosome, the less likely it is that they will be separated because it’s less likely that the chiasmata will be between the 2 genes
what happens in genetic mapping?
- an inherited trait is attributed to a certain gene
- based on linkage, polymorphisms are more likely to be inherited together if they’re located close to eachother
what is Next Generation Sequencing doing?
- speeding up the process of genome sequencing enormously
- bringing down the cost of whole genome sequencing
what are the 2 bottlenecks making the genomic revolution slower than advertised?
- obtaining enough DNA samples
- analysis
describe the bottleneck slowing down the genomic revolution of obtaining enough DNA samples
- need enough DNA samples with good clinical data and patient permission
blood tests
GDPR etc
describe the bottleneck slowing down the genomic revolution of analysis
- need to analyse the huge amount of data
