Chapter 4- Inheritance

Question 1

Monogenic Single Gene Disorders

Answer 1

Can deduce probability of transmission
Determined by genetic testing
Follow Mendelian Inheritance

Question 2

Principle of Segregation

Answer 2

Each individual has two copies of a gene (paternal and maternal)
One copy is transmitted to offspring during meiosis
Copies remain intact and distinct during transmission

Question 3

Independent Assortment

Answer 3

Chromosomes segregate randomly
Inheritance of one gene does not impact another

Question 4

Dominant Genes

Answer 4

Gain of function mutations- Abnormal protein has a novel function
Dominant negative mutation- Abnormal protein interferes with normal protein function

Question 5

Recessive Genes

Answer 5

Loss of function mutations
Prevent production of normally functioning proteins

Question 6

Epistasis

Answer 6

Multiple genes interact to produce unique phenotypes

Question 7

Genes of Eye Color

Answer 7

OCA2- Control melanin synthesis
Dominant- Brown, recessive- blue
HERC2- Control OCA2 expression
Disruptions- Always blue

Question 8

Pedigree

Answer 8

Diagram showing familial relationships to analyze heredity

Question 9

Autosomal Dominant Pedigree

Answer 9

Produced by heterozygote carrier and normal parent
Equal across gender
No generation skipping
Vertical transmission pattern- For child to have condition, parent must have it
50% recurrence risk

Question 10

Autosomal Recessive Pedigree

Answer 10

Parents are usually heterozygous carriers without knowing
Seen in 1+ children without family history
Equal across gender
Horizontal transmission pattern- Multiple children but not parents
More common in consanguineous populations

Question 11

Inheritance Exceptions

Answer 11

De novo mutations
Germline mosiacism
Somatic mosiacism

Question 12

Inbreeding

Answer 12

Mating within a small population

Question 13

Consanguinity

Answer 13

Mating with blood relatives

Question 14

Achondroplasia

Answer 14

Defect in cartilage leading to human dwarfism
Autosomal dominant missense mutation in FGFR3
Gain of function growth repression
Short stature and limbs, bowed legs, macrocephaly, spinal stenosis

Question 15

Marfan Syndrome

Answer 15

Autosomal dominant disorder of connective tissue
Mutation of FBN1 gene that encodes fibrillin 1- component of microfibrils
Microfibrils supposed to bind growth factor beta to reduce growth
Infufficient fibrillin leads to excess growth ni ocular, skeletal, and cardiovascular systems
Tall skeleton, malformed sternum, mitral and aortic regurgitation, aortic aneurysm, and eye disruptions

Question 16

Neurofibromatosis-1 NF-1

Answer 16

Autosomal dominant mutation of NF-1 gene
Neurofibromin- Protein in microtubules and signal transduction
Mutation causes overactive RAS pathway, causes tumor growth
Neurologic problems and malignancies

Question 17

Cystic Fibrosis

Answer 17

Autosomal recessive mutation of CFTR gene
Abnormal folding of chloride channel causes many symptoms
Salty sweat
Increased sodium absorption in airway- thick mucus
Duct blockage in pancreas leads to insufficient digestive enzymes and auto-digestion
Persistent infections of airway