Patterns of inheritance

What’re pedigrees?

• Graphic representation of a family’s health history and genetic relationships

• Uses standardized symbols

• For, fast, accurate communication of medical and family history

What’re the instructions of a pedigree?

Understand these symbols

Understand all these common symbols

Understand the following slides of lines and pregnancy

Explain degree of relation

Explain the concept of cousins removed

Explain relatedness and consanguinity

• Ex: Lady Mary (Downtown Abbey)

What’re the 3 things used to evaluate a pedigree?

• Transmission: Vertical (multiple generations), Horizontal (siblings in single generations)

• Sex difference: Affected males to females, Difference in severity between sexes

• Segregation: Male-male transmission, transmitted through parents of which sex, transmitted to children of which sex and in what proportion

What are the 2 general modes of inheritance?

• Mendelian (i.e, monogenic, single-gene)

• Non-Mendelia

What’re the different types of Mendelian inheritance?

• Autosomal dominant

• Autosomal recessive

• X-linked dominant

• X-linked recessive

• Y-linked

What’re the different types of non-Mendelian inheritance?

• Imprinting

• Mitochondrial

• Multifactorial

• Sporadic

• Contiguous gene syndromes

What’re some complicating factors in inheritance?

What kind of transmission is in autosomal dominant?

• Vertical: Multiple generations affected

What’re the sex differences in autosomal dominant?

• Usually none

Whats the segregation in autosomal dominant?

• No specific segregation, could be inherited by male to male transmission

• Parent of any sex could transmit to children of any sex

• Any child of an affected parent has a 50% chance of being affected

Whats an important note about autosomal dominant?

• Unless otherwise specified, assume these are rare diseases: Spouses unlikely to have the same rare condition

Explain Neurofibromatosis Type 1

Understand the slides of COL1A1/2 Osteogenesis imperfecta

Whats mosaicism

• 2 or more cell lines with different genetic makeup due to post-zygotic event

Explain mosaicism in placental, somatic, and germline?

• Placental: placental cell lines may not match genetic makeup of fetus

• Somatic: 2 or more cell lines within an individual, which may or may not include germline

• Germline/ gonadal: Confined to the germline - precursors to egg or sperm

Explain myotonic dystrophy type 1

Explain BRCA1/2 Hereditary Breast and Ovarian Cancer Syndrome

Explain knudsons 2 hit hypothesis of cancer