Genetics Flashcards
What are the four kinds of genetic disorders?
- Single gene disorders: sex-linked, autosomal
- Mitochondrial diseases
- Chromosomal abnormalities
- Multifactorial disorders: congenital malformations, adulthood diseases
Define the law of dominance
Gene expression is separated into dominant and recessive alleles that have complete expression of one or the other. Not both.
Define the law of segregation.
States that paired genes must separate into different gametes so that offspring have equal chance of getting either gene.
Define the law of independent assortment
Genes (except for those that are close together) don’t influence where other genes end up. They all have the same odds of being combined in any order regardless of prior gene placement.
What is the coefficient of the relationship?
The proportion of shared genes
What are the mode of non-mendelian transmission with one or two examples?
Pleiotropy: Gene influences more than one physiological or anatomical function
-Marfans syndrome, cystic fibrosis
Codominance: Alleles each express their phenotype
-AB bloodtype
Multiple Alleles: More than two alleles in inheritance in diploid organisms
-ABO blood typing
Incomplete dominance: expression of heterozygous alleles is somewhere in between the expression of completely dominant or recessive
-Hypercholesterolemia
Polygenic Inheritance: expression caused by a combination of genes (mutations of those genes)
-Height, eye color, skin color, weight
Epistasis: The effects of one gene are modified by one or many other genes.
-Many
Linked Genes: Genes are located close to each other on chromosomes and are more likely to be inherited together.
-Sex-linked diseases
Define “New Mutations” are what are its associated disorders?
A new mutation in a line “de novo”
-Achondroplasia: shortening of the limbs compared to the rest of the body.
Define “Mosaicism” and state related disorders?
Mutation in either the somatic or germline cells that can affect daughter cells depending on its timing.
- Osteogenesis Imperfecta
- Chondroplasia
- Neurofibromatosis type 1
- Duchenne Muscular Dystrophy
- Hemophilia A
Define “Penetrance” name associated disorders
Two types, age dependent and incomplete (reduced):
Age dependent are mutations that are in the genome that may not express until adulthood.
-Huntington’s
-Alzheimer’s
-Inherited cancers
-Hemachromatosis: autosomal recessive iron storage deficiency
Incomplete (reduced): Carrier of the disease without expressing the phenotype.
- Retinoblastoma
- Breast Cancer
Define “Locus Heterogeneity” and list disorders.
A mutation at different loci in different genes can cause the same disease.
- Adult poly cystic disease: Autosomal Dominant
- Progressive accumulation of Renal cysts
Define “variable expression” and list corresponding disorders.
A disease phenotype with varying degrees of severity.
-Neurofibromatosis type 1 (NF1, Recklinghausen disease) Autosomal Dominant
-characterized by multiple neurofibromas and Lisch Nodules: small
hamartomas of the iris.
SOMATIC MOSAICISM
Name 4 different broad changes that genetic testing can find.
Single gene disorders
Mitochondrial disorders
Multifactoral disorders
Chromosomal disorders
What tests can be done for single gene disorders?
PCR Southern Blotting Northern Blotting Restriction Fragment Analysis Microarray Analysis High Throughput DNA Sequencing
What tests can be done for Mulitfactorial Testing?
ELISA
Western Blotting/Electrophoresis
Enzyme Activity Essay
What tests can be done for Chromosomal Abnormalities?
FISH (Fluorescence in Situ Hybridization)
CGH (Comparative Genomic Hybridization)
High Resolution Banding
What is a great mutation analysis technique and why?
PCR because it uses primers and the original DNA to make lots of copies of DNA to use for testing.
Explain Multifactorial (complex) Disorders
They do not follow regular patterns and are affected by exogenous (environmental) cause and are polygenic.
Congenital Malformations and many Adult diseases are Mulifactorial.
- Cleft Lip
- Alzheimers
What are two kinds of special chromosomes?
Ring Chromosomes: When the two end are lost and the sticky ends join together in a ring
Isochromosomes: Instead of dividing along its usual axis, the chromosome splits so that one has only long arms and one only has short arms.
What are the two kinds of inversions?
Pericentric: Genes on a chromosome swap across the centromere: usually
Paracentric: The inversion segment only involves one arm of the chromosome.
What are translocations
Where parts of chromosomes are broken off and moved to form different chromosomes.
Reciprocal: involves breaks at two chromosomes in the arms, that are then switched between each other.
Robertsonian: Involves breaks near the centromere that then can adjoin and form two chromosomes, half from one, and half from the other.
What are 5 kinds of structural Chromosomal Abnormalities?
Insertion or deletion
Duplication
Inversion
Translocation
What are some example of Numerical Chromosomal Abnormalities?
Trisomy 21: Down Syndrome XXY: Klinefelter Syndrome Trisomy 13: Patau Syndrome Trisomy 18: Edwards Syndrome Turner Syndrome: Monosomy X
What is Aneuploid?
An error in the number of chromosomes. Monosomy or Trisomy
What is Anticipation?
The phenomenon of a disease that becomes progressively worse or presents earlier in adulthood the more times it is passed on.
Trinucleotide repeats: They increase as it is passed on (Myotonic Dystrophy)
