A protein, called PHD (protein for retinoblastoma) a synthesized by a gene (Rb) on chromosome
13 in humans. When mutant or absent in the homozygous state in a retinal cell, there is a high
likelihood of developing a cancerous condition of the eye called retinoblastoma. Nonmutant pRb
binds with and temporarily inactivates E2F, a transcription factor that stimulates genes to
produce proteins that initiate S phase of the mitotic cell cycle (thus, Rb is a negative regulator of
cell division). When phosphorylated in response to a variety of normal stimuli, pRb normally
releases E2F and cell division is stimulated. Thus, Rb is a tumor suppressor gene. (For a recent
review, see H. Liu et al. (2004). \'Novel functions of the RB tumor suppressor.\" Current
Opinions in Genetics and Development 14: 55-64. When retinoblastoma occurs in fannies, the
disease tends to have an early onset and express bilaterally (both eyes). When sporadic
(spontaneous, not inherited), it tends to show later onset and be unilateral (one eye only).
Individuals who inherit a predisposition for the disease are Rb +/Rb- and may got retinoblastoma
by having a mutation in the Rb+ allele Assume that two heterozygous parents have children. One
would expect the Rb-/Rb- genotypic combination in a zygote (one-cell stage of an individual) to
be characterized as: lethal (in viable or lasting a relatively short time) completely normal having
a very low likelihood of developing retinoblastoma having unilateral retinoblastoma only
Solution
3. Having a very low likelihood of developing retinoblastoma
although, Rb-/Rb- is a normal genotype, but here while answering we would keep the possibility
of somatic mutations alive. Children born with the normal gene can have some spontaneous
mutations such that the function of Rb- with be mutated or lost resulting in loss of the function of
the pRb protein resulting in uncontrolled cell growth..
A protein, called PHD (protein for retinoblastoma) a synthesized by a.pdf
1. A protein, called PHD (protein for retinoblastoma) a synthesized by a gene (Rb) on chromosome
13 in humans. When mutant or absent in the homozygous state in a retinal cell, there is a high
likelihood of developing a cancerous condition of the eye called retinoblastoma. Nonmutant pRb
binds with and temporarily inactivates E2F, a transcription factor that stimulates genes to
produce proteins that initiate S phase of the mitotic cell cycle (thus, Rb is a negative regulator of
cell division). When phosphorylated in response to a variety of normal stimuli, pRb normally
releases E2F and cell division is stimulated. Thus, Rb is a tumor suppressor gene. (For a recent
review, see H. Liu et al. (2004). 'Novel functions of the RB tumor suppressor." Current
Opinions in Genetics and Development 14: 55-64. When retinoblastoma occurs in fannies, the
disease tends to have an early onset and express bilaterally (both eyes). When sporadic
(spontaneous, not inherited), it tends to show later onset and be unilateral (one eye only).
Individuals who inherit a predisposition for the disease are Rb +/Rb- and may got retinoblastoma
by having a mutation in the Rb+ allele Assume that two heterozygous parents have children. One
would expect the Rb-/Rb- genotypic combination in a zygote (one-cell stage of an individual) to
be characterized as: lethal (in viable or lasting a relatively short time) completely normal having
a very low likelihood of developing retinoblastoma having unilateral retinoblastoma only
Solution
3. Having a very low likelihood of developing retinoblastoma
although, Rb-/Rb- is a normal genotype, but here while answering we would keep the possibility
of somatic mutations alive. Children born with the normal gene can have some spontaneous
mutations such that the function of Rb- with be mutated or lost resulting in loss of the function of
the pRb protein resulting in uncontrolled cell growth.
