Question

1. The mitotic spindle and microtubules were not present in the mitosis models; describe their process throughout the steps of mitosis.

2. Are the chromosomes in mitosis a mixture of mother and father chromosomes? Explain your answer, comparing the process to meiosis.

3. Using your microscope images in Photo 12 and Photo 18, describe the difference in the telophase/cytokinesis step of mitosis between plants and animals.

4. Describe the similarities and differences between the microscopic images of the plant and animals.

5. Are the four daughter cells of meiosis genetically identical or different from one another? Explain your answer. Describe the daughter cells of your meiosis model; what color and how many of each color beads were present in each of the four daughter cells

6. Describe the similarities and differences between mitosis and meiosis.

7. Describe the similarities and differences between prophase I and prophase II.

Anything helps, thank you so much!!!

Answer 1

1. Mitosis has 4 steps- Prophase, Metaphase, Anaphase and Telophase

In early prophase, mitotic spindles start to form. Spindle is made up of microtubules which are strong fibres which can move chromosomes around, pull them and organize them. The spindles come out of centrosome which move to opposite parts of the cells. The spindles grow between them as they move apart.

In late prophase/prometaphase, the mitotic spindle starts growing and latching on to the chromosomes and organize them. Microtubules can bind to chromosomes at the kinetochore, a patch of protein found on the centromere of each sister chromatid. (Centromeres are the regions of DNA where the sister chromatids are most tightly connected.)

In metaphase, the mitotic spindle has latched on to every chromosome and has lined them up on the metaphase plate, or around the middle of the cell between in the two centrosomes. The centrosomes from each end has spindle fibres attached to all the chromosomes.

In anaphase, the spindle fibres pull on the sister chromatids ( chromosomes were divided into two sister chromatids which were joined at the centriole). Sister chromatids separate and go in opposite directions away from each other pulled by the spindle fibres which are contracting.

Microtubules not attached to chromosomes elongate and push apart, separating the poles and making the cell longer.

In telophase,the mitotic spindle is broken down into its building blocks.

2) No, mitosis is replication of a single cell which then yields two genetically identical cells. The cells duplicate their chromosomes, which leads to cells having two times the chromosome content. During division the chromosomes get separated into two cells which then restores the original chromosome content. i.e 4N becomes 2N or 2N become N depending on whether the cell is diploid or haploid respectively.

Mitosis is responsible for reproducing somatic cells and meiosis is responsible for reproducing germ cells.

Meiosis is a mixture of father and mother chromosomes. Meiosis involves two cell divisions.Meiosis leads to the production of germ cells, which are cells that give rise to gametes.Its goal is to make daughter cells with exactly half as many chromosomes as the starting cell. In meiosis, sister chromatid are separated but in addition to that it must also separate homologous chromosomes, the similar but nonidentical chromosome pairs an organism receives from its two parents. Exchange of DNA takes place between the homologues. And that is how mixture of father and mother chromosomes take place.

3) Animal cells furrows in between or forms a cleavage for the formation of daughter cells while plant cels do not form furrows but rather cell plate forms in centre of the dividing cells, and the two cells separate into two components.

4) Similarities between Plant and Animal cells

Both are eukaryotic cells, contain membrane bound organelles, both have a nucleus, cytoplasm, cell membrane.

Differences-

Plants have cell wall but animal cells do not.

Chloroplasts are specialized organelles which are only present in plants and are responsible for photosynthesis.

Plant cells have a large central vacuole while animal cells have scattered small vacuoles.

5) Meiosis leads to genetic variation. All the four cells are genetically different from each other due to variations in crossing over when the homologous chromosomes are attached to each other. Different bits and pieces change places and DNA gets exchanged. New combinations of genetic material are present in each daughter cell.

6) Both mitosis and meiosis are cell division processes. Both have similar steps, and both need to duplicate their DNA and pull it apart into two sets using mitotic spindles. Mitosis and meiosis lead to fresh cells based on their parent cell/s.

Mitosis produces two cells from one parent using one division event. But meiosis produces four new child cells with two divisions, each of which has half the genetic material of its parent. Mitosis takes place all over the body, while meiosis only takes place in the sex organs and produces sex cells. Purpose of mitosis is cellular proliferation while the goal of meiosis is sexual reproduction. Meiosis leads to genetic variation while mitosis is meant to produce genetically identical daughter cells.

7) Prophase I and Prophase II similarities

- Centrosome is duplicated prior to both the stages

-Both are important phases of sexual reproduction and gamete formation.

Prophase I and Prophase II differences

-Prophase I follows a long interphase while Prophase II starts immediately after Telophase I

- In prophase I homologous chromosomes are involved while in prophase II individual chromosomes are involved.

-Prophase I occurs in diploid cell while prophase II occurs in haploid cells

- Genetic material crosses over and is exchanged in prophase I, while no recombination takes place in prophase II