1. The gene OCA2 on chromosome 15 confers eye color in humans. The most common
phenotype is brown eyes (BB). A recessive allele of the OCA2 results in blue eyes (bb). Wilson
has brown eyes and Mia has blue eyes. What is the probability that Wilson and Mia’s child will
have blue eyes?
2- Emma finds a small lump in her breast and goes to her physician, who takes a medical and
family history. She mentions that her father died of brain cancer, a cousin had leukemia, and her
older sister was just diagnosed with a tumor of connective tissue. The doctor assures her that the
family cancer history doesn’t raise the risk that her breast lump is cancerous, because the other
cancers were not in the breast. Is the doctor correct?
3- . In X-linked inheritance disorders the females are usually the carriers whereas the males are
the affected. Give your reason
4- Explain the connection between cancer and control of cell cycle
Solution
1. The gene OCA2 on chromosome 15 confers eye color in humans. The most common
phenotype is brown eyes (BB). A recessive allele of the OCA2 results in blue eyes (bb). Wilson
has brown eyes and Mia has blue eyes.
The probability that Wilson and Mia’s child will have blue eyes is 1:4
2. The doctor is not correct in saying that because the other cancers were not breast cancers, her
breast lump is not cancerous.
The genes are inherited from parents in gametes and combine in the zygote. Single zygote divide
and differentiate to form a complete individual and the DNA is constant is each and every cell.
Thus, each cell carries the mutation in tumor suppressor gene or the oncogenes and each cell is
equally susceptible to be cancerous.
3. In X-linked inheritance disorders, the females are usually the carriers whereas the males are
the affected. The humans have heterogametic males and homogametic females i.e., female
carries two X-chromosomes and male have only one X-chromosome. In the case of X-linked
recessive disorders, the other X-chromosome carrying dominant gene mask the expression of the
mutant allele on the other X-chromosome and thus, the disease do not manifest. However, in
males the mutant allele on the X-chromosome of the heterogametic male results in the diseased
male.
4. The connection between cancer and control of cell cycle:
Cancer cells exhibit uncontrolled growth due to lack of contact inhibition. The uncontrolled
growth is a result of lack of control of the cell cycle..
1. The gene OCA2 on chromosome 15 confers eye color in humans. The m.pdf
1. 1. The gene OCA2 on chromosome 15 confers eye color in humans. The most common
phenotype is brown eyes (BB). A recessive allele of the OCA2 results in blue eyes (bb). Wilson
has brown eyes and Mia has blue eyes. What is the probability that Wilson and Mia’s child will
have blue eyes?
2- Emma finds a small lump in her breast and goes to her physician, who takes a medical and
family history. She mentions that her father died of brain cancer, a cousin had leukemia, and her
older sister was just diagnosed with a tumor of connective tissue. The doctor assures her that the
family cancer history doesn’t raise the risk that her breast lump is cancerous, because the other
cancers were not in the breast. Is the doctor correct?
3- . In X-linked inheritance disorders the females are usually the carriers whereas the males are
the affected. Give your reason
4- Explain the connection between cancer and control of cell cycle
Solution
1. The gene OCA2 on chromosome 15 confers eye color in humans. The most common
phenotype is brown eyes (BB). A recessive allele of the OCA2 results in blue eyes (bb). Wilson
has brown eyes and Mia has blue eyes.
The probability that Wilson and Mia’s child will have blue eyes is 1:4
2. The doctor is not correct in saying that because the other cancers were not breast cancers, her
breast lump is not cancerous.
The genes are inherited from parents in gametes and combine in the zygote. Single zygote divide
and differentiate to form a complete individual and the DNA is constant is each and every cell.
Thus, each cell carries the mutation in tumor suppressor gene or the oncogenes and each cell is
equally susceptible to be cancerous.
3. In X-linked inheritance disorders, the females are usually the carriers whereas the males are
the affected. The humans have heterogametic males and homogametic females i.e., female
carries two X-chromosomes and male have only one X-chromosome. In the case of X-linked
recessive disorders, the other X-chromosome carrying dominant gene mask the expression of the
mutant allele on the other X-chromosome and thus, the disease do not manifest. However, in
males the mutant allele on the X-chromosome of the heterogametic male results in the diseased
male.
4. The connection between cancer and control of cell cycle:
Cancer cells exhibit uncontrolled growth due to lack of contact inhibition. The uncontrolled
growth is a result of lack of control of the cell cycle.
