Question

5. The Supreme Court has heard a case in which one company, Myriad, had the patent rights to two genetic markers, BRCA 1 and BRCA 2. What are these markers to and why are they important in cancer diagnosis?

6. What are the major differences between mitosis and meiosis? Between prophase I (in meiosis I) and prophase II (in meiosis II)?

Answer 1

5 BRCA 1 and BRCA 2 are Breast Cancer type 1 susceptibility protein and Breast cancer type 2 Susceptibility protein.BRCA 1 is a part of complex that repairs double stranded breaks in DNA .Certain variations in BRCA1 and BRCA2 gene leads to an increased risk for breast cancer .Females with abnormal BRCA 1 and BRCA2 are more susceptible to undergo neoplastic transformation of the breast cells there is an 80 percent increased chance fro breast cancer.These mutation may result from change in simal number of DNA base pairs .Thus these mutated BRCA 1 gene causes production of a protein that functions abnormally and this abnormal protein causes damage t the DNA repair mechanism leading to abnormal DNA repair which in turn leads to mutation .BRCA 1 gene mutations can also result in ovarian cancer and cancer of prostate gland..Thus the early identification of abnormal BRCA1 and BRCA2 gene helps in early diagnosis of cancers of the breast ovary ets.Thus the markers BRCA 1 and BRCA2 gene are important in early diagnosis of breast cancer.

6

	MITOSIS	MEIOSIS
Definition	A process of asexual reproduction in which cell divides into 2 producing replica with equal number of chromosome	type of cellular reproduction in which the number of chromosomes are reduced to half producing two haploid cells
occurrence	all organisms	reproductive cells of human animals and plants and fungi
type of reproduction	asexual	sexual
Genetic	produces identical cells	different cells
pairing of homologous chromosome	absent	present
number of division	1	2
number of daughter cell produced	2dipolid cell	4 haploid cell

PROPHASE I	PROPHASE II
Initial step of meiosis I	Initial phase of meiosis II
Presence of long interphase	presence of telophase I
Centrosome duplicated prior to this stage	centrosome is duplicated during this stage
Homologous chromosomes are involved	Individual chromosomes are involved
Occurs in diploid cells	Occurs in haploid cell
Presence of crossover and chiasmata formation	Absence of crossover and chiasmata formation
Exchange of genetic material by crossing over leads to recombination	Absence of recombination