Please click on the link below to download the Mitosis and Meiosis Lab. Complete the assignment electronically (save the file using your name for the title) or by printing it off, completing it by hand, and scanning it into a computer (or taking pictures of each page). Finally, upload the assignment (or scan, or pictures) to this drop box. Be sure the file types are either word documents, pdfs, jpegs, etc
The ability to reproduce is one of the special characteristics that define life. For more than 3 billion years, living things have been reproducing themselves, generation after generation. Throughout history, people have wondered how biological information is transmitted by the parent to its young. Why do cats have kittens, dogs have puppies, and hens have chicks? Why do you resemble your father and mother? We now know that DNA carries the inherited information, but how is the complete genome transmitted from parents to offspring? In every case, this process happens at the cellular level. Reproduction occurs through cell division.
Cell division is also a key process in the growth and maintenance of multicellular organisms. As you read this lab, your body is changing at a dazzling rate. Certain cells are being created, others are dying, and still others are being changed. Your body is literally different now than it was when you started this paragraph. Cells divide, passing along virtually identical information to the two daughter cells. Some cells divide at an incredibly rapid pace (such as those on your palms), while others (such as most nerve cells) do not divide at all. Cell division allows for growth, development, and the replacement of old or damaged cells.
Mitosis is nuclear division. In mitosis, genetic material is very precisely divided to ensure that each daughter cell has DNA that is identical to that of the parent cell from which it arose. Mitosis occurs in body cells, or somatic cells, of multicellular organisms. Mitosis (division of the nucleus) is followed by cytoplasmic division, which fully separates the cytoplasm and organelles of the two daughter cells.
Meiosis is a highly specialized nuclear division process that reduces the chromosome number by half. Meiosis occurs in reproductive structures to produce cells called gametes (egg and sperm cells). Egg and sperm unite in a process called fertilization, resulting in a newly formed cell (zygote) that contains a full complement of DNA. Each zygote contains a unique combination of genetic information, half from the mother and half from the father. The zygote grows and develops by mitosis, completing a sexual life cycle.
Today’s lab will give you the opportunity to see for yourself how cells reproduce and how DNA is stored and passed from a cell to its offspring. You will undoubtedly find yourself confusing mitosis and meiosis. The two processes have much in common, but they also have crucial differences. As you review them in the lab today, make sure you note these differences and understand their importance.
We will be revisiting microscope slides in this lab. Please click on the links to see the different stages of plant and animal mitosis.
Interphase Prophase Metaphase
Label: nuclear membrane Label: chromosomes Label: chromosomes
Label: chromatids Label: cell plate
QUESTIONS about plant mitosis. Look very carefully at your examples and research the phases of mitosis in your textbook before answering.
(1) Is the nuclear membrane intact or breaking down during interphase? What about in prophase?
(2) Chromatin is the DNA and associated proteins that are found in the nucleus. Is the chromatin uncondensed and stringy or condensed during interphase? What about prophase?
(3) From the cells seen on the slide, where are the chromosomes in a cell in metaphase?
(4) From the cells seen on the slide, what is happening to the sister chromatids in a cell in anaphase?
(5) As telophase finishes dividing the nucleus contents equally, new nuclei form. Now that the nucleus is divided; what must happen to finish the process of cell division (give the name and describe the process)? How is this achieved in plant cells?
|Stages of cell cycle||Interphase||Prophase||Metaphase||Anaphase||Telophase|
|Total number of cells counted for each stage|
|Percent of cells in each stage (Assuming the total number of cells counted 200)|
|Time in minutes for each stage|
The average time for onion root tip cells to complete the cell cycle is 24 hours = 1440 minutes. To calculate the time for each stage:
% of cells in the stage × 1440 minutes = number of minutes in the stage
Interphase Prophase Metaphase
Question: Most cells appear to be in what phase?
Mitosis and meiosis have similar names and are both forms of cell division. However, they occur in different types of cells and have different functions. Answer the questions below to improve your understanding of these two processes. In each case assume that nuclear division (mitosis or meiosis) is followed by cytoplasmic division to fully separate the daughter cells. Also, do not assume that answers will always be different for the two processes: they are similar in some ways, but are very different in others.
(1) Provide one reason why mitosis occurs in you.
(2) Provide one reason why meiosis occurs in you.
(3) Does the parent cell at the beginning of mitosis have a diploid or haploid number of chromosomes?
(4) Do daughter cells formed from mitosis have a diploid or haploid number of chromosomes?
(5) Are daughter cells formed through mitosis genetically identical to or genetically different from the parent cell?
(6) Does the parent cell at the beginning of meiosis have a diploid or haploid number of chromosomes?
(7) Do daughter cells formed from meiosis (complete process, meiosis I and meiosis II) have a diploid or haploid number of chromosomes?
(8) Are daughter cells formed through meiosis genetically identical to or genetically different from the parent cell?
(9) Where does mitosis occur in your body?
(10) Where does meiosis occur (where is it completed) in a female body? In a male body?
(11) The events of anaphase of mitosis are most similar to events occurring in which phase of meiosis? Include both the division (I or II) and the specific phase.
(12) If a single cell divides by mitosis, how many daughter cells are produced?
(13) If a single cell completes the full process of meiosis, how many daughter cells are produced?
(14) If a parent cell with a diploid number of 12 (12 total chromosomes in six pairs) were to divide by mitosis, the two daughter cells would each have __________ chromosomes.
(15) If a parent cell with a diploid number of 12 were to divide by meiosis, each daughter cell would have __________ chromosomes.
(16) Crossing over occurs in (circle one: mitosis only / meiosis only / both mitosis and meiosis)
(17) When (specifically) does crossing over occur and why is it important?
(18) Do cancer cells divide by mitosis or meiosis?
(19) Fertilization (union of egg and sperm) creates the first cell of a new individual, called a zygote. Would this zygote divide by mitosis or meiosis to become two cells?