Genetics Flashcards
Penetrance
The proportion of people with the relevant genotype who show the character
i.e. is the phenotype expressed or not (binary)
Expressivity
Affected people show only some of the feature, or may show a certain feature to different degrees
i.e. sliding scale
Genetic Herogeneity results from
Allelic heterogeneity and Locus Hertogeneiety
Allelic Heterogeneity
situation where a clinical condition can be caused by any of several different mutations within a SINGULAR gene
i.e CF
Locus Heterogeneity
situation where a clinical condition can be caused by any of several mutations on multiple genes
Compound Heterozygote
A person with a recessive condition who has 2 different mutant versions of a gene
CGH requires
Comparative Genome Hybridization
Reference DNA
CGH detects
Trisomy, gross chromosome imblanace
Small deletions or duplications below the resolution of conventional cytogenetics
FISH
detects DNA sequence without breaking up the cells
used for deletions greater than 100-500kb
Souther Blot hybridization
uses digested cellular DNA with restriction enzymes
1-20kb
Oligonucleotide hybridization (dot blot)
Detects single base changes
Need to know SNP you are looking for
(single nucleotide)
Microarrays
Detect specific DNA sequences
single nucleotide to 500kb
PCR
Detects size and sequence of DNA
Direct Sequencing
detects the exact nucleotide sequence
Epigenetics
Refers to how DNA is packaged that in chromatin rather than of changes in DNA sequence
X inactivation
In females, extra X chromosome is turned off
N-1 rule
DNA methylation
Inhibits DNA from being read by winding DNA tightly
Histone Acetylation
Promotes DNA being read by unwinding
Genomic Imprinting
Only one allele, either paternal or maternal is expressed in the relevant tissue
Prader Willi
lack of paternal 15q11-q13
Angelman Syndrome
lack of maternal 15q11-q13
Can also be a lack of gene UBE3A
Rules for HW
Pop is large Allele frequency is constant over time No rate of new mutations No immigration Random mating
Factors that Ruin HW
Stratification: population contain subgroups
Assortative mating: choosing a mate who is genetically similar to ones self.
Consanguinity and inbreeding: problem when carriers with AR disorders mate
Migration and Gene Flow: migration can change allele frequency.
Founder Affect
Small group of people who start a population have higher likely hood of certain traits
Heterozygote Advantage
Alleles where heterozygotes may show increased fitness.
Relative Risk
prevalence of disease in relatives / prevalence of disease in general pop
Concordance
When related individuals have the same disease (good for twin studies)
Heritability
V(DZ)-V(Mz) / V(Dz)
Haplotype
A set of closely linked alleles on a single chromosome that is normally inherited as a block
Complete disequilibrium
Two alleles are closely linked together and do no separate over many generations
Complete equilibrium
Two alleles are far apart and thus have a great high recombination frequency and will separate over few generations.
tagSNP
A collection of SNPs within a haplotype block that can be used to identify the haplotype block.
Phenylalanine to tyrosine is done by
phenylalanine hydroxylase (PAH) A deficiency leads to PKU
Congenital
Present at birth
Major Anomaly
severe enough to require intervention
Possibly life threatening
May result in life long morbidity / disability
Minor Anomaly
Generally does not require intervention or easily corrected
Types of morphogenic abnormalities
Malformation
Deformation
Disruption
Dysplasia
Malformation
congential
usually occurs by 8-10 weeks gestation
Malformation Syndrome
pattern of features often involving multiple organ systems
Unifying underlying cause
Association
Non random occurence of anomalies where the etiology is unknown
Deformation
Compression or mechanical distortion of an already normally formed body part
Usually occurs after 8-10 weeks
Disruption
destruction of a tissue that was previously normal or in the process of forming normally
Dysplasia
abnormal cellular organization within a tissue resulting in structural changes
Marfan Syndrome
Autosomal Dominant
Duchenne Muscular Dystophy
X linked Recessive
Rett Syndrome
X linked dominant
Cystic Fibrosis
Autosomal Recessive
Disease Incidence
q^2
Myotonic Dystrophy
Unstable repeat expansion
