Question

Describe the structure of DNA List the steps involved in DNA Replication What is crossing over? (Honors Only) What occurs during nondisjunction? What is a monosomy, and a trisomy? Give examples of disorders caused by each.

Answer 1

1. In 1953 first time watson and crick described the structure of the DNA double helix, DNA double helix is a polynucleotide contain deoxyribose sugar,phosphate and 4 different nitrogen base (Adenine,guanine,cytosine and thymine),Between nitrogen base form the hydrogen bond(A=T,G=_C).The two strand of DNA run opposite direction one is 5'-3' and other is 3'-5'.

2. The step of replication is Initiation, Elongation, and termination.

3.Crossing over is a reciprocal exchange of equal and corresponding segment between non sister chromatids in a pair of homologous chromosome.

4.During non disjunction aneuploidy condition occur in the cell.

5.Monosomy is 2n-1, example of monosomy disorder is turner's Syndrome. Trisomy is 2n+1,example of trisomy is Down's syndrome.