10.07 Genetic Diseases

Question 1

single gene

Answer 1

• autosomal dominant (dominant negative: Marfan syndrome)
• autosomal recessive (often polygenic
• sex-linked recessive (happens in males and skips generation)

Question 2

polygenic

Answer 2

co-recessive

• people are usually carriers of several recessive genetic diseases
• some genetic dz need more than one gene (need multiple recessive genes)
• only when several systems fail, the dz manifests

Question 3

polymorphism vs. pleomorphism

Answer 3

polymorphism: multiple genes for same phenotype (hair color)
pleomorphism: one gene with multiple functions (post-transcriptional modificaton)

Question 4

genetic heterogeneity

Answer 4

• one of many genes can mess up and all manifest as same dz (e.g., DNA repair system includes many steps/genes and if one fails, the system fails.
  *

Question 5

genetic heterogeneity assay

Answer 5

• when two cells from two people can’t do the same thing, you fuse the cells to make one cell (heterocarrion: one cell, two nuclei)
• if the heterocarrion can repair DNA (complementation), the defect was due to different mutations
• if the heterocarrion cannot repair DNA, both people had same mutation
• complementatoin group: a group of people who cannot complement each other
• if three or more people, you can make assay of different heterocarrions to determine the mutated genes

Question 6

Marfan syndrome

Answer 6

mutation in gene coding fibrilin, which is required for structural integrity of connective tissue

major tissue affected are the skeleton, eyes, and cardiovascular system

clinical features include tall stature, long fingers, aortic anuerysm, etc

Prez Lincoln prob had it

Question 7

familial hypercholesterolemia

Answer 7

autosomal dominant caused by mutation in the low-density lipoprotein (LDL) receptor gene

excessive cholesterol in blood (reduced catabolism + increased biosynthesis)

heterozygotes have high risk of atherosclerosis and coronary artery dz

homozygotes have even greater risk + cholesterol deposits along the tendon sheates: produce xanothomas

Question 8

phenylketonuria (PKU)

Answer 8

autosomal recessive caused by lack of the enzyme that metabolizes phenylalanine

severe mental regardation, seizures and decresaed skin pigmentation

can be avoided by restricting phenylalanine in diet

Question 9

storage disorder

• lysosomal
• glycogen

Answer 9

• lysosomal: instead of digesting things, lysosomes accumulate things
• glycogen: can’t breakdown glycogen for glucose and just store them

Question 10

storage disorder mechanism

Answer 10

enzymes are activated in series (A>>B>>C>>D) with feedback mechanism. if feedback is disrupted, more or less enzymes are synthesized.

Question 11

Pompe disease

Answer 11

• Pompe disease: both lysosomal and glycogen storage disese. affects heart

Question 12

Von Gierke disease

Answer 12

• Von Gierke disease: liver cells store glycogen

Question 13

lipid storage disease

Answer 13

• “cherry-red” spots in the eye for lipid storage disorder

Question 14

Barr hypothesis

Answer 14

in human female development, upto 40 cells, both X chrom work but after 40 cells, one X becomes “barr body” and gets precipitated in cytoplasm and not expressed.

X0 disorder: Turner syndrome (no barr body)

XXY disorder: Klinefelter syndrome. male with barr body (disjunction). infertile

Question 15

trisomy 23: Down Syndrome

Answer 15

advanced maternal age (greater than 35) is a risk factor

cardiac abnormalities in infant, high risk for M.leukimia in adolescent, high risk for Alzheimer in advanced age.

no cancer except for leukemia