The Genetics of Cancer

Question 1

what is the name for a fertilized egg and sperm?

Answer 1

zygote

Question 2

Meiosis occurs in the …. and mitosis occurs in the ….

Answer 2

Germline

Soma

Question 3

what is mitosis?

Answer 3

the process by which a diploid cell replicates its chromosomes and then segregates them, producing two identical diploid cells

this process is what creates a human from zygote to adult - cell division is occurring

diploid - DNA replicates to homologous chromosomes and attaches to spindle machinery then the sister chromatids separate and forms diploid cells each with one chromosome copy from each parent

Question 4

if there is a mutation in the germline, what will that affect?

Answer 4

a mutation in the germline will affect the entire offspring - all the cells in an individual of next generation

why?
mutation of the gametes - either sperm or egg cells

mutation propagates into zygote, then each cell going forward would have this mutation in the body since zygote is basis before mitosis

Question 5

if you have a mutation in the soma (body cells) somatic mutation, what will this affect?

Answer 5

the somatic mutation will occur in a single cell in the body and will only affect cells produced from that single cell

• Somatic mutations affect only the progeny of the original mutated cell
• does not affect ALL cells - that is germline only

ex: tanning, UV light mutation in a skin cell, if that skin cell grows then could lead to skin cancer
* clone of cells that carry mutation

Question 6

a collection of diseases characterized by uncontrolled cell growth
* cells can divide rapidly, evade protective mechanisms that kill abnormal cells, and metastasize (migration to other parts of body)

Answer 6

cancer

Question 7

what kind of mutations lead to cancer?

Answer 7

Somatic mutations

• Cancer is caused by a series of somatic mutations that affect a clone of cells.

Question 8

what are the two major proteins that regulate cell division?

Answer 8

growth-promoting factors and growth inhibiting factors

Question 9

what are the genes that encode the growth promoting factors and growth inhibiting factors?

Answer 9

proto-oncogenes (promote)
tumor supressor genes (inhibit)

in cancer we get gain of function mutations in proto-oncogenes

Question 10

what kind of mutations could happen in cancer to either proto-oncogenes or tumor suppressor genes? and are they dominant/recessive?

Answer 10

in cancer we get gain of function mutations in our proto-oncogenes

• so this mutation would promote cell growth/division more than in normal cell
• it either increases expression of the gene or the activity of the protein
• tends to be dominant

we can get loss of function mutations in tumor suppressor genes

• so this mutation would cause the things that inhibit cell growth to be less active
• mutation tends to be recessive- AKA a two hit hypothesis meaning that you need o get two independent mutations for the cancer to progress one in each allele of gene

Question 11

DNA damage repair genes are type of tumor suppressor gene that works to suppress tumors/cancer when a mutation arises. But if there is a mutation in the DNA damage repair gene what happens?

Answer 11

mutation in DNA damage repair gene lead to unable to fix mutations - uncontrollable division - tumor/cancer

Question 12

Cancer is generally caused by the accumulation of 2-20 … mutations that occur over time and allow cancer to progress in some way. Whereas …. mutations, which do not contribute to cancer progression, also accumulate randomly over time.

Answer 12

driver mutations

passenger mutations

Question 13

cancer onset and progression can be influenced by what?

Answer 13

genetics (hereditary cancer- variant thru germline mutations) and environmental factors (exposure to carcinogens- smoking, UV)

Question 14

In cancer therapeutics, the major goal is to kill cancer cells with as few side effects as possible. What are the traditional approaches to treating cancer?

Answer 14

1. surgery - physically remove the tumor
2. radiation - induces DNA damage to kill cancer cells
3. chemotherapy - drug-based to target cancer cells to induce DNA damage or inhibit division

Question 15

New type of treatment for cancer that involves targeting the specific driver mutations in an individual tumor for a person-specific case

Answer 15

Precision medicine

• you identify driver mutations by comparing tumor gene to normal gene in individual
• once you identify drivers you can target with drug

*faces a number of challenges- could be multiple driver mutations, presence of many passenger mutations, classifying mutations, resistance to drugs