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
Law of independent assortment
homologous chromosomes line up independently during metaphase 1 of meiosis and separate randomly.
