Chapter 7: Heredity Flashcards
Haploinsufficiency
one copy of the gene is lost or nonfunctional and the expression of the remaining copy is not sufficient to result in a normal phenotype
Haplosufficiency
the remaining copy of the gene is sufficient enough to result in a normal phenotype
proto-oncogenes
genes that can become oncogenes due to “gain-of-function” mutations. Normally involved in cell cycle control. Follow the “one hit hypothesis”
oncogenes
cancer-causing genes
Gain-of-function mutations
cause too much protein to be made or the production of an over-active protein. Causes cancerous growth.
One hit hypothesis
a gain-of-function mutation in one copy of the gene turns into an oncogene.
Tumor-suppressor genes
become cancerous as a result of “loss-of-function” mutations. They are normally needed to suppress cancerous growth. Follow the two hit hypothesis. Haplosufficient. (Ex. p53, p21, Retinoblastoma gene)
Two hit hypothesis
a loss-of-function mutation in both copies of the gene are needed to make it cause cancer.
Null alleles
come from mutations that cause the alleles to lack normal function.
p53
tumor-suppressor gene, it is upregulated to prevent cells from becoming cancerous.
p21
tumor-suppressor gene, inhibits phosphorylation activity to decrease rampant cell division.
Retinoblastoma gene (RB)
tumor-suppressor gene, codes for a retinoblastoma protein which prevents excessive cell growth during interphase.
Mendel’s Laws
- Law of dominance
- Law of segregation
- Law of independent assortment
Law of dominance
dominant alleles mask the expression of recessive alleles
Law of segregation
homologous gene copies separate during meiosis
