Question

1.) Define autosome, monosomy, trisomy, aneuploidy, and meiotic nondisjunction. Describe the effects of these conditions and list the examples of the conditions (e.g. down syndrome, XXYY)

2.) What are induced pluripotent stem cells and what are thebadvantages and disadvantages of using induced pluripotent stem cells?

3.) what is the beneficience principle?

Answer 1

Ans 1) Autosome refers to all the chromosomes except X and Y (sex chromosomes) chromosomes in the case of Humans.

There are 23 pairs of chromosomes in Humans (Diploid or 2n = 46). Here "2" refers to two copies of chromosomes i.e each from mother and father.

There are 22 pairs of autosomes and 1 pair of allosome (sex chromosome) in humans which is equal to 44 + 2 (X and Y = 2 chromosomes) = 46 chromosomes (haploid or n ).

Monosomy - When the diploid organism lacks one chromosome from just one pair of chromosome is called as monosomy and it is represented by (2n -1 ). Turner syndrome can occur by monosomy (45,X) in females (Normally females have 2 X chromosomes.But due to monosomy, one of the X chromosome get deleted) and the effects will be Sterile female with retarded sexual development,webbing of skin in the neck part,etc.

Aneuploidy - Change in the number of chromosomes within a set by deletions or additions resulting in deviations from the normal diploid chromosome numbers (like we saw in monosomy which occurred due to deletion) is called as Aneuploidy. Effects are always deleterious because of such genetic imbalance which occurs.

Meiotic nondisjunction refers to improper separation of chromosome in each of the cell.Due to this, one cell may receive extra chromosome and other cell none of the chromosome and when such diploid gamete fuse with the haploid, polyploidy can occur. Example is Down syndrome. It leads to three copies of chromosome number 21 instead of 2 which occurs due to improper chromosome separation as we have discussed above.

Ans 2) Induced pluripotent stem cells (iPSC) are type of pluripotent cells that are produced from adult cells by genetic reprogramming to form Embryonic like stem cells (ES) which can give rise to any type of cell in the body. They arre created by inserting four transcription factors namely, Oct4,Sox2,Klf-4,c-Myc.

Advantages is that 1) They will not be rejected by immune system after introduction in the body to treat some conditions since they have been derived from our own body (from blood).

2) Like stem cells, it can divide indefinitely to produce required number of cells.

3) It can differentiate into almost any cell type (Just like embryonic stem cells).

4) No animals will be harmed to create them,since they are derived from our body only.

Disadvantages are that 1) since the IPSC cells are created using retroviruses, the risk of overexpression can lead of cancer (c-myc gene is transcription factor which when overexpressed can increase the cell division and thus leading to cancer).

2) In some non-dividing cell types, the rate of reprogramming to become IPSC is very low (approx 0.02%).

Ans 3) The principle of Beneficience is that the practice conducted by the medical practioners should do more good in every situation and they should possess high skill and knowledge to conduct such practice on the patient i.e to minimize risk and maximize the benefits of the procedure to the patient.