Patho LOs Exam 5

Question 1

Variable expressivity vs partial penetrance

Answer 1

50% penetrance= half the people with the variant show the traits associated with that variant

expressivity= penetrance + how much of the traits are being shown of that variant
-factors that affect expressivity include other genes, harmful chemicals/conditions, environment, age

Question 2

Type of genetic variants

Answer 2

Missense mutation- substitution of a single nucleotide that leads to a different amino acid than the normal one being produced
Nonsense mutation- substitution of a single nucleotide that leads to an amino acid added as a stop codon therefore ending the protein sequence
Insertion mutation- frameshift mutation that inserts one or more nucleotide that changes the amino acid sequence following it
Deletion nucleotide- frameshift nucleotide that has a deletion of one of more nucleotides that changes the amino acid sequence following it

Question 3

Gain-of-function vs loss-of-function

Answer 3

Gain-of-function is dominant, normal protein has a new function that is not the usual function
loss-of-function is recessive, normal protein loses its normal function

Question 4

chromosome nondisjunction

Answer 4

failure of the chromosomes to separate
-can lead to abnormal number of chromosomes in daughter cells
-leads to potential genetic diseases (down syndrome, turner syndrome)

Question 5

Carcinogenesis

Answer 5

fundamental principles of carcinogenesis
-Genetic changes (mutations) lie at the heart of carcinogenesis
-damage targets Oncogenes (genes that encode proteins that promote cancer)
Tumor suppressor genes (genes that encode proteins that inhibit cancer)
-carcinogenesis is a multistep process with multiple genes involved

Question 6

Oncogenes and tumor suppressor genes

Answer 6

-Oncogenes: alterations are dominant and occur at a single allele

Question 7

6 Hallmarks of cancer

Answer 7

1. Self-sufficiency in growth signals; Ras can be permanently switched “on” meaning there is no requirement for growth factor and a receptor
2. Resistance to growth inhibitory signals; cancer can arise through loss of expression (mutation) in the growth inhibitory proteins; PTEN-phiosphatase that reverses Pi3K kinase phosphorylation, NF1-inhibits Ras
3. Evade apoptosis- disrupts apoptotic pathways and prevents cell death (loss-of-function mutations)
4. Limitless replicative potential- overexpression of telomerase
5. Tumor cells trigger anigiogenesis- tumor cells produce VEGF which promote angiogenesis (growing blood cells)
6. Metastasize- breakdown ECM by proteins and go into bloodstream