Question

1. Given that a patient is a carrier of a genetic disease, why must this patient always be heterozygous and can never be homozygous?

2. Color blindness in a male is inherited only from his mother, but color blindness in a female is inherited from both of her parents. Explain.

3. Describe nondisjunction and identify why it is so genetically significant.

4. Identify three (3) genetic disorders caused by nondisjunction. Explain why.

5. Identify any one (1) genetic disorder not caused by nondisjunction. Explain why.

6). Given that Phenylketonuria (PKU) is inherited as a recessive trait. What is the chance for two heterozygous parents to have a phenylalanine-sensitive child? Explain.

7). Given a mating between a non-hemophiliac male & a heterozygous female what is the probability for a hemophiliac female child? Explain.

8). Given a mating between an albino male & a carrier female, what is the probability for a child who is a carrier for albinism? Explain.

9). Given that brown eyes are dominant, what is the probability for two heterozygous parents to have a blue-eyed child? Explain.

10). If a karyotype is to be constructed for a patient, would a cell in metaphase of the cell cycle be more useful than a cell in interphase of the cell cycle? Explain why.

11). Describe the procedural differences between mitosis & meiosis and why mitosis & meiosis are genetically important.

12). Describe some reasonable theories for the different functions of hair located in these diverse body regions:

- Eyebrows

- Eyelashes

- Scalp

13). How do merocrine & apocrine sweat glands differ in their structure and in their function? Explain.

14). It is important for the epidermis to be effective at screening UV radiation, but not to be too effective. Explain.

15). Your patient asks you which cell type in the skin is the most important cell and why? How would you reply? Explain.

16). Describe the stages of intramembranous ossification and name at least one (1) bone that is formed using this process.

17). Describe the stages of endochondral ossification and name at least one (1) bone that is formed using this process.

18). What effect does the hormone calcitonin have on blood calcium levels & how does it produce this effect? Explain.

19). What effect does parathyroid hormone have on blood calcium levels & how does it produce this effect? Explain.

20). How is vitamin D synthesized and what effect does vitamin D have on blood calcium concentrations? Explain.

- Nostrils

- Axilla

Answer 1

1. Given that a patient is a carrier of a genetic disease, why must this patient always be heterozygous and can never be homozygous?

A person is heterozygous when only one recessive allele is inherited whereas homozygous is when both allele are either dominant or recessive. Heterozygous usually does not display that trait or show symptoms of the disease and act as the heriditary carrier. When both recessive allele are inherited each from both the parents, the person will be homozygous and show disease symptoms.

2. Color blindness in a male is inherited only from his mother, but color blindness in a female is inherited from both of her parents. Explain.

Color blindness is genetic disorder and a sex linked trait which is carried on the X chromosome.

Male has XY genotype - X chromosome recieved from mother and Y recieved from father. This is the reason that color blindness for male is inherited only from his mother.

Female has XX genotype - recieves one X chromosome from each os the parents. Therefore, she can inherit the colorblindness from any of them.

3. Describe nondisjunction and identify why it is so genetically significant.

Nondisjunction is the condition when the paired chromosome failed to seperate during cell division which results in passage of both the chromosome to one daughter cell and none to the other. The three categories of diajunctions are:

• failure of a pair of homologous chromosomes to separate in meiosis I
• failure of sister chromatids to separate during meiosis II and
• failure of sister chromatids to separate during mitosis.

Nondisjunction results in aneuploidy.

4. Identify three (3) genetic disorders caused by nondisjunction. Explain why.

During cell division, seperation of apired chromosome is crucial to ensure that each daughter cell recieve one chromosome from mother cell. Failure of this leads to passage of both the chromosomes to only one daughter cell and none to the other. The above event is called as non-disjunction. Example of nondisjunctions are:

• Down syndrome or trisomy 21. A typical gamete has inherited only one copy of each chromosome
• Monosomy X or Turner syndrome - when there is loss of one chromosome. Disorder in which a female is born with only one X chromosome
• Klinefelter's syndrome or XXY males - can occur due to nondisjunction of X chromosomes during prophase of meiosis I in females.