Question

During meiosis I, assuming no crossing over, what chromatid combination(s) will be present at the completion of prophase? Draw all possible alignments of chromatids as migration begins during early anaphase.

Short answer

Answer: Assuming two homologous pairs and no crossing over, there are four possible chromatid combinations at the end of Prophase I: 1. [M1, M2], [P1, P2] 2. [M1, P2], [P1, M2] 3. [P1, M2], [M1, P2] 4. [P1, P2], [M1, M2] During early Anaphase I, these combinations will start migrating towards opposite poles of the cell, maintaining their respective alignments.

Step-by-step solution

Understand Meiosis I and the events of Prophase

During meiosis I, a diploid cell divides into two haploid cells. This process involves two main stages: Prophase I and Anaphase I. In Prophase I, chromosomes replicate and condense, and homologous pairs (a set of one maternal and one paternal chromosome) associate with each other. Since there is no crossing over in this case, the chromatids remain identical. In Anaphase I, homologous pairs separate and migrate towards opposite poles of the cell.

Determine the number of possible chromatid combinations at the end of Prophase I

As no crossing over occurs, each homologous pair remains distinct from each other. Considering that there are 2^n possible orientations for homologous pairs at the end of prophase I, where n is the number of homologous pairs, we can calculate the number of possible chromatid combinations. However, since the exact number of chromosomes is not given in this exercise, we will assume a hypothetical situation with two homologous pairs. Therefore, we can compute the possible chromatid combinations as: 2^2 = 4.

Draw the possible chromatid combinations at the end of Prophase I

Assuming two homologous pairs, we'll have four possible combinations at the end of Prophase I. Denoting maternal chromosomes as M1 and M2 and paternal chromosomes as P1 and P2, the combinations will be: 1. [M1, M2], [P1, P2] 2. [M1, P2], [P1, M2] 3. [P1, M2], [M1, P2] 4. [P1, P2], [M1, M2]

Understand the events during early Anaphase I

In early Anaphase I, the homologous pairs separate and migrate towards opposite poles of the cell. The chromatids do not separate during Anaphase I, which happens in Anaphase II.

Draw all possible alignments of chromatids as migration begins during early Anaphase I

Based on the possible chromatid combinations in Step 3, the possible alignments as migration begins during early Anaphase I will be as follows: 1. [M1, M2] [P1, P2] | | v v 2. [M1, P2] [P1, M2] | | v v 3. [P1, M2] [M1, P2] | | v v 4. [P1, P2] [M1, M2] | | v v In each of these four alignments, the chromatids start migrating towards opposite poles of the cell during early Anaphase I.