QUESTION: 1. If a diploid animal cell has 4 different chromosome types, then how many total DNA molecules are in this cell at Prophase I? In this cell, how many total DNA molecules would there be at Telophase I? How many DNA molecules would be in each of the daughter cells?
2. How many copies of a gene are in a single cell in Prophase I of Meiosis? How many copies of a gene are in a single cell in Telophase I? How many copies of a gene are in each of the daughter cells?
ANSWER: Hi Chantal.
1. I cannot answer this question for the following reasons
You are confusing chromosomes and molecules of DNA. Chromosomes are made up of genes containing thousands of DNA molecules. I can tee you that the amount of DNA in Prophase is doubled in Telophase as the chromosomes have duplicated.
2. The number of genes are different in the chromosomes so I cannot give a gene number. I can tell you that the chromosomes separate in mitosis l so the number is halved
---------- FOLLOW-UP ----------
QUESTION: Thank you for your quick reply. These questions were addressed in a review (not graded) for an upcoming test. I'm confused about the wording though.
For question 1, my understanding is that human somatic cells have 46 chromosomes (or 23 chromosome pairs, and each chromosome has 2 chromatids (DNA molecules)= 46 x 2 = 92 DNA molecules in prophase I of meiosis. From this, would the answer be 16 DNA molecules in prophase I(4 different chromosome types = 4 different chromosome pairs = 8 chromosomes x 2 chromatids per chromosomes = 16 DNA molecules) and 8 DNA molecules in Telophase I and 4 DNA molecules in each of the daughter cells?
In regards to copies of genes in a single cell, I believe that each daughter cell would be diploid with 1 gene copy from the mother and 1 from the father. But would the answer be 1 then if it is asking how many copies, instead of how many genes?
I guess that I was confusing with my answer and I was mixing up the DNA molecules and the hailstone proteins. I would like to refer you to web sites that explain this better so go to goggle and search Chromosomes and DNA molecules. You will find sites with diagrams.
With respect to the genes you are correct in that during meiosis the genetic number is halved in the gametes and haploid when fertilization occurs