Genetics and Genomics Flashcards
What is a haplotype?
=an individuals set of alleles at a locus or cluster or loci on a chromosome
What are single gene disorders?
- these disorders are determined primarily by the alleles at a SINGLE locus
- recurrence risk describes the likelihood of passing on the gene
Mendelian Genetics… what is it concerned with?
-monogenetic traits aka single gene traits
Independent assortment
is one gene locus is independently transmitted from a gene on a different locus
Autosomal dominant disease
seen in every generation
M=F
-structural genes are often seen in this inheritance pattern
-no skipping generations unless new mutation!
-probability to inherit=50%
ex. achondroplasia
Achondroplastics are…
rizomyere???
their limbs (humerus and femur) are short but their tib/fib and radius/ulna are normal length
What is the danger with 2 people who have an AD disease mating?
-they have more problems in those who will become homozygotes much more severe issues
Autosomal Recessive
-rare
-often seen in metabolic disorders
-this is sometimes seen in those who are relatives who mate CONSANGUINITY
-those that are heterozygotes may have reduced enzyme activity and then combine to make no activity
M=F
-probability to inherit from heterozygote parents 25%
Ex.
-Hurler/Hunter
What is hurler syndrome?
- AR disease
- skeletal abnormalities
- similar to hunter
Cystic fibrosis
- mutation to CTFR gene
- Cl transporter mutation
- pleiotropic: effects more than one organ
Remember that dominant and recessive refer to ___ not ___
traits not genes!
Sex linked inheritance
types:
X linked dominant
X linked recessive
Y linked
x chromosome: larger so more mutations
-common in men
y linked: much smaller contains less genes
X linked recessive
M > F–bc males usually only ones affected
-SONS of heterozygote mothers have 50% chance of being affected
X linked dominant
M and F can be affected
-all female offspring of affected father will be affected
Y linked
only father to son transmission
Mitochondrial Inheritance
- only given from mother
- all offspring of affected females show signs of disease
- not all mitochondria congregate in specific organs… so they effect organs different =heteroplasmy
New mutations
- this can complicate the “normal” pattern of inheritance
- the gene transmitted undergoes a mutation from the normal allele
Achondroplasia and risks and what they have!
- most cases are due to new mutations
- only 1/8 are transmitted from dwarf parents
- distinguish this by taking a family hx
remember they are: Rhizomelic—> refers to either a disproportion of the length of the proximal limb, such as the shortened limbs of achondroplasia, or some other disorder of the hip or shoulder.
What is gremlin mosaicism?
- when 2 or more offspring present with an AD disease with no familial hx
- this is when all parts of the germline cells are affected by the same mutation
- mutation occurs during the parents embryonic development of the germ cells
Age Dependent Penetrance
aka delayed age onset
- ex. of this is BRCA gene
- this is when the disease does not present until AFTER patients reach reproductive age or adulthood
- this can cause a difficulty in detecting the mode of inheritance
other ex.
huntingtons
polycystic kidney disease
alzheimers
Reduced penetrance
-this is when those that have the genotype fail to express the appropriate phenotype although they pass it to the next generation
penetrance is the general idea that a phenotype expression is dependent upon the predisposing genotype
ex. retinoblastoma
Variable expression
a trait in which the same genotype can produce phenotypes of varying severity or expression
- penetrance=complete
- severity is what varies
- a parent with midl expression may pass on the disease
ex. neurofibroblastoma
What are some causes for variable expression?
- environmental factors
- modifier genes
- allelic heterogeneity
What is pleiotropy?
-genes that affect multiple aspects of physio or anatomy
ex. sickle cell
OI
CF
