All of the following cells, shown in various stages of...

Name: Problem 28, Chapter 2: Genetics: A Conceptual Approach
Uploaded: 2021-01-28T19:58:26-08:00
Duration: 4 min 32 s
Channel: Jennifer Hudspeth
Description: All of the following cells, shown in various stages of mitosis and meiosis, come from the same rare species of plant. a. What is the diploid number of chromosomes in this plant? b. Give the names of each stage of mitosis or meiosis shown. c. Give the number of chromosomes and number of DNA molecules per cell present at each stage. (FIGURE CAN'T COPY)

All of the following cells, shown in various stages of mitosis and meiosis, come from the same rare species of plant. a. What is the diploid number of chromosomes in this plant? b. Give the names of each stage of mitosis or meiosis shown. c. Give the number of chromosomes and number of DNA molecules per cell present at each stage. (FIGURE CAN'T COPY)

All of the following cells, shown in various stages of mitosis and meiosis, come from the same rare species of plant.
a. What is the diploid number of chromosomes in this plant?
b. Give the names of each stage of mitosis or meiosis shown.
c. Give the number of chromosomes and number of DNA molecules per cell present at each stage.
(FIGURE CAN'T COPY)

Key Concepts

Diploid Number

The diploid number refers to the total number of chromosomes found in a typical somatic (non-reproductive) cell of an organism. It represents the paired nature of the chromosomes in a species, with one set inherited from each parent. In questions involving cell division stages, knowing the diploid number is crucial because it provides the baseline for understanding how the number of chromosomes and the DNA content change during processes like mitosis and meiosis.

Mitosis

Mitosis is the process of cell division that produces two genetically identical daughter cells from a single parent cell. It involves a series of well-defined phases—prophase, metaphase, anaphase, and telophase—each characterized by specific structural and molecular changes. A key point in mitosis is that while the number of chromosomes remains constant throughout, the number of individual DNA molecules (sister chromatids) temporarily doubles after DNA replication and then is separated equally into the daughter cells.

Meiosis

Meiosis is a specialized type of cell division that reduces the chromosome number by half, creating gametes for sexual reproduction. It consists of two sequential divisions: meiosis I and meiosis II. In meiosis I, homologous chromosomes are separated, resulting in two cells with halves of the original diploid set, while in meiosis II, the sister chromatids are separated. This reductional division and subsequent equational division ensure genetic diversity through recombination and the proper halving of DNA content in the gametes.

Chromosomes versus DNA Molecules

Understanding the difference between chromosomes and DNA molecules is essential in cell division. A chromosome is a long, organized structure of DNA and proteins that contains many genes, while a DNA molecule in this context typically refers to a single, continuous double-stranded DNA segment. Following DNA replication, each chromosome consists of two identical DNA molecules (sister chromatids), which are later separated during cell division. Keeping track of both the chromosome number and the number of DNA molecules is critical for analyzing the outcomes of mitotic and meiotic divisions.

Transcript

00:02 Hi there.

00:03 Let's look at these stages, these three pictures we have, of mitosis or meiosis in a rare species of plant.

00:14 So the first question asks us what the diploid number of this is.

00:19 In other words, what is the 2n for this particular plant? so looking at these three slides, and we'll come back and talk about this as we look at questions b and c, but it appears that the 2n number is six chromosomes.

00:34 There are three pairs of chromosomes for a total of a 2n or diploid number of 6.

00:41 For part b, i would like to put b and c together and make a little table.

00:49 So i want to do stage down the left side.

00:57 I want to do number of chromosomes from part c, and number of dna molecules, also from part c.

01:17 So stage is part b, and a number of chromosomes, and number of dna molecules are both for part c.

01:27 And then i am just going to my table.

01:29 I am just going to have the first slide there, the first picture, the second picture, and the third picture.

01:39 All right, so a little table.

01:41 Here we go.

01:41 So looking at the first one, the stage that it is in, we see that the chromosome number is going to soon be cut in half as soon as the two halves of that are complete.

01:55 So if the chromosome number is going to be cut in half, this is myosis.

02:02 And the stage that we are viewing here is the first anaphase, anaphase 1.

02:10 Because then in anapase 2, the sister chromatids would separate.

02:15 And ultimately we would end up with four cells that have the haploid number of three in each of them...

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