Question

Question 2: The Atlas blue butterfly has 224 homologous pairs of chromosomes. Each pair consists of one chromosome from the butterfly's mother and one from its father. A. Assuming no crossing over, what is the probability that a sperm this butterfly makes has all of the chromosomes from the butterfly's own father? Why? (You do not need to calculate out this number- a number with an exponent is fine.) (roughly 3-4 sentences) B. How many chromosome 17's does this butterfly have in each of its cells? If the answer is more than 1, how are these chromosome 17's alike or different? Explain using the word allele. (roughly 1-3 sentences) C. In the space below, diagram the steps of DNA replication and two rounds of cell division for meiosis WITH crossing over for one pair of homologous chromosomes, say chromosome 17. from the starting cell below. The chromosome from the mother is marked M and the chromosome from the father is marked P. You do not need to include intermediate steps, but in your diagram you should: • Label the steps where DNA replication and cell division occur . Clearly label all instances of M and P DNA in each cell you draw (including after replication)

Answer 1

(A) Answer: (1/2) ^ 224

Each sperm has half a chance of inheriting the mother's chromosome and half a chance of inheriting the father's chromosome, FOR EACH CHROMOSOME NUMBER. So there are 224 homologous pairs which means n = 224, 2n = 448. There are 224 chromosomes, each having 2 options (mother, father). Using AND rule of probability, we multiply each 1/2 224 times.

(B)

There are 2 chromosome 17s in each cell. One from the mother, one from the father. They are alike in that they both carry alleles for the same set of traits, at the same loci. They are different in that they carry different alleles. For example both carry the gene for hair type at say locus 17q.17. But the mother's carries allele for curly, the father's carries allele for straight.

(C)

MITOSIS cell (1) Min M M P Replication, MP divides 2nX2 MEIOSISI MEIOSIS 2 MM M MP P nxa 2nX2 divides nxa CROSSING OVER in PROPHASEI MEIOSIS 2

(D)

In mitosis the daughter cells are diploid.

In the meiosis the daughter cells are haploid but but there are two sister chromatids.

Diploid means that there is a chromosome from both parents. Haploid means it's only from one parent. In meiosis 1 each cell has 2 chromosomes but they are from only one parent.

(E)

The daughter cells of meiosis are haploid, those of mitosis are diploid.

The daughter cells of mitosis have the complete genome of that organism, those of meiosis don't.

The daughter cells of mitosis can undergo mitosis, meiosis 1 and 2. Those of meiosis cannot. They can only fuse with another gamete to form a zygote.