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Objectives - at the end of this lecture you should be able to:. Identify dominant and recessive Mendelian modes of inheritanceDescribe reasons why some genetic diseases seem to depart from Mendelian expectations. Mendel's laws. 0.Genes are particulate and come in different forms known as alleles.
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1. Modes of Inheritance Jonathan Wolfe
Wolfson House, room 109
http://www.ucl.ac.uk/~ucbhjow/
2. Objectives - at the end of this lecture you should be able to: Identify dominant and recessive Mendelian modes of inheritance
Describe reasons why some genetic diseases seem to depart from Mendelian expectations
3. Mendel’s laws 0. Genes are particulate and come in different forms known as alleles.
Organisms (peas or humans!) have two copies of each gene but transmit only one to each offspring. Which one is transmitted is chosen at random. i.e. if you are heterozygous for two different alleles, the alleles will segregate from each other in your offspring.
Where alleles of more than one gene are segregating, segregation at each gene occurs independently of the others.
4. Autosomal dominant inheritance All affected individuals should have an affected parent
Both sexes should be equally affected
Roughly 50% of the offspring of an affected individual should also be affected
Huntington’s disease, Achondroplastic dysplasia, Neurofibromatosis.
5. A large autosomal dominant pedigree!
6. Autosomal Recessive Inheritance Usually there is no previous family history
The most likely place to find a second affected child is a sibling of the first
7. Autosomal recessive Inbreeding increases the chance of observing an autosomal recessive condition
E.g. Cystic fibrosis, sickle cell disease, Tay Sachs disease.
8. Exceptions to clear cut Mendelian inheritance Lethal alleles
9. Exceptions to clear cut Mendelian inheritance Lethal alleles
Incomplete dominance
10. Exceptions to clear cut Mendelian inheritance Lethal alleles
Incomplete dominance
Codominance
Silent alleles
11. Exceptions to clear cut Mendelian inheritance Lethal alleles
Incomplete dominance
Codominance
Silent alleles
Epistasis
12. Exceptions to clear cut Mendelian inheritance Lethal alleles
Incomplete dominance
Codominance
Silent alleles
Epistasis
13. Exceptions to clear cut Mendelian inheritance Lethal alleles
Incomplete dominance
Codominance
Silent alleles
Epistasis
Pleiotropy
genetic heterogeneity
14. Exceptions to clear cut Mendelian inheritance Lethal alleles
Incomplete dominance
Codominance
Silent alleles
Epistasis
Pleiotropy
genetic heterogeneity
variable expressivity
incomplete penetrance
15. Exceptions to clear cut Mendelian inheritance Lethal alleles
Incomplete dominance
Codominance
Silent alleles
Epistasis
Pleiotropy
genetic heterogeneity
variable expressivity
incomplete penetrance
16. Mitochondrial inheritance
17. Exceptions to clear cut Mendelian inheritance Lethal alleles
Incomplete dominance
Codominance
Silent alleles
Epistasis
Pleiotropy
genetic heterogeneity
variable expressivity
incomplete penetrance