So I am confused with how I end up with 23 chromosomes per sister cell on the la

Question

So I am confused with how I end up with 23 chromosomes per sister cell on the last slide.

Although mitosis and meiosis share similarities, they are different processes and create very different results. In this experiment, you will follow the movement of chromosomes through mitosis to create somatic daughter cells. Materials 2 Sets of Different Colored Pop-it8 Beads (32 of each -these may be any color) (8) 5-Holed Pop-it Beads (used as centromeres) Procedure Genetic content is replicated during interphase. DNA exists as loose molecular strands called chromatin it has not condensed to form chromosomes yet. Sister chromatids begin coiling into chromosomes during prophase. Begin your experiment here 1. Build a pair of replicated, homologous chromosomes. Use ten beads to create each individual sister chromatid (20 beads per chromosome pair). Two five-holed beads represent each centromere. To do this: a. Start with 20 beads of one color to create your first sister chromatid pair. Five beads must be snapped together for each of the four different strands. Two strands create the first chromatid, and strands create the second chromatid. Figure 5: Beod ser-up. The blue beods represent ane pair of sister chromatids and the black beads represent a second pair of sister chromatids. The black and biue poir are homologous second b. Place one five-holed bead flat on a ed bead flat on work surface with the node positioned up. Then, snap two of the four strands into the bead to create an I-shaped sister chromatid. Repeat this step with the other two strands and anotherfive-holed bead. Once both sister chromatids are constructed, connect them by their five- holed beads, creating an"X" shape. c. d. Repeat this process using 20 new beads (of a different color) to create the second sister chromatid pair. See Figure 5 for reference. Assemble a second pair of replicated sister chromatids. This time, use 12 beads per pair (sik beads per each complete sister chromatid strand). 2. Repeat this process using 12 new beads (of a different color) to create the second set of sister chromatids. See Figure 6 for 3. 4. Configure the chromosomes as they would appear in each stage of the cell cycle (prophase, metaphase, anaphase, telophase, and cytokinesis). Diagram the images for each stage the number of chromosomes present in each cell during each phase. each stage. Be sure to indicate Figure 6: second set of replicoed ch sion: Mitosis Beads Prophase Metaphase Anaphase

Explanation / Answer

The experiment you are conducting of mitosis is essentially correct. The mistake you are making is in the understanding of DNA replication during the S-phase of the cell cycle and how it is incorporated in the mitosis. Each diploid cell has 2n chromosomes. In humans, this number would correspond to 2 x 23 = 46 chromosomes, 22 pairs of autosomes and 1 "pair" of sex chromosomes.

Now, as for the DNA replication in S-phase, you have to understand that replication generates identical copies of all of the DNA molecules present in G1 of the cell cycle, but without increasing the total number of chromosomes. Thus, in a human cell, there are 46 chromosomes, each containing 2 sister chromatids at the prophase stage. In metaphase stage, 46 chromosomes line up at the equator of the metaphasic spindle. At anaphase, the 2 chromatids of each chromosome is pulled apart. So, in telophase and subsequently cytokinesis, the daughter cells on each slide will have 46 chromosomes, with no demarkation of sister chromatids. Only 46 individual threads of chromatic will be present on each slide. The crux of the matter here is that DNA replication generates sisters not homologs. After DNA replication, each member of a homologous chromosome pair consists of two sister chromatids. The sister chromatids are actually just one chromosome, not a homolog pair of chromosmes. Thus, your last slides will also have 46 chromosomes in each daughter cells.

Related Questions

Navigate

• Browse (All)
• Browse S
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.