Question

Explanation and answer to both please and thank you!

You are doing the Meselson and Stahl experiment to test the type of replication you are having in a newly identified species. You start with labeled HH and are only able to analyze generation 4. You find that your DNA is 1/8th HL and 7/8th LL. You conclude that replication is: Dispersive Semi-conservative O Conservative Cannot tell Question 18 3 pts At what point during meiosis of human cells do the daughter cells become haploid? After meiosis After S phase After meiosis II After mitosis

Answer 1

Ans:

Semi-conservative

Explanation: In semiconservative replication, DNA replication starts in N¹⁵ medium with Heavy DNA (HH). The cells are then transferred into N¹⁴ medium containing light (LL) DNA. After generation 1, the cells give all hybrid DNA (HL). If the cells continue to growing in N¹⁴ medium, 1/2 hybrid (HL) and 1/2 light DNA (LL) are produced after generation 2, 1/4 hybrid (HL) and 3/4 light DNA (LL) are produced after generation 3 and 1/8 hybrid (HL) and 7/8 light DNA (LL) are produced after generation 4. So, the replication is semiconservative. If it is conservative, 1/8 heavy (HH) and 7/8 light DNA (LL) are produced after generation 4, no hybrid DNA are produced. If it is dispersive, only hybrid DNA are produced after generation 4.

Question 18

Meiosis I

Explanation: In anaphase I of meiosis I, the homologous chromosomes are separated and each daughter cell consists haploid number of chromosomes after meiosis I. In meiosis II and mitosis, chromatids of each chromosome are separated and produces daughter cells with number of chromosomes. The four daugter cells of at the end of meiosis II are also haploid but haploid daughter cells are produced first at the end of meiosis I. In meiosis II, two haploid parent cells are produced four haploid daughter cells. In S phase DNA replication takes place. So, chromosomes are diploid after S phase.