A cell in G1 of interphase has 12 chromosomes. How many...

Key Concepts

Meiosis

Meiosis is a specialized form of cell division that produces gametes (sex cells) with half the number of chromosomes of the original cell. It comprises two successive rounds of division (meiosis I and meiosis II). In meiosis I, homologous chromosomes pair up and segregate, reducing the chromosome number by half, while in meiosis II, the sister chromatids separate, similar to mitosis, further refining the genetic content.

Cytokinesis

Cytokinesis is the process in which the cytoplasm of a parent cell is divided between two daughter cells at the end of cell division. It is the final physical separation step following nuclear division. The outcome of cytokinesis varies with the type of division; in mitosis, it results in two identical cells, whereas in meiosis it can lead to cells with different chromosome complements, particularly in the formation of gametes.

Mitosis

Mitosis is a type of cell division that results in two genetically identical daughter cells. It follows interphase and includes stages such as prophase, metaphase, anaphase, and telophase. During mitosis, sister chromatids are separated into two new nuclei, ensuring that each daughter cell receives an identical set of chromosomes.

DNA Replication

DNA replication occurs during the S phase of interphase and is the process by which a cell makes an identical copy of its DNA. This results in each chromosome being composed of two identical sister chromatids, effectively doubling the number of DNA molecules while the number of chromosomes remains the same until chromatid separation.

Interphase

Interphase is the period of the cell cycle during which the cell prepares for division. It consists of the G1 phase (cell growth), the S phase (DNA replication), and the G2 phase (further growth and preparation for division). The events of interphase determine how many chromosomes and DNA molecules the cell will have before entering the division phases.

Cell Cycle

The cell cycle is the complete sequence of events a cell goes through from one division to the next. It includes phases of growth, DNA replication, and division, ensuring that each daughter cell receives the correct genetic material. This overarching process is essential for both growth and reproduction in living organisms.

Chromosome Number versus DNA Molecules

It is important to distinguish between chromosome number and the number of DNA molecules. Chromosome number refers to the count of distinct chromosomes, while each chromosome may consist of one or two DNA molecules (sister chromatids) depending on the stage of the cell cycle. After replication, a single chromosome is made up of two DNA molecules, which later separate during cell division.

Transcript

00:03 So when we're considering how many chromosomes and dna molecules are going to be found in each of the different listed cell cycle stages, we first need to consider how many chromosomes and dna molecules we're starting with.

00:19 And so the question gives us the answer to that.

00:21 We know that we're in g1 of interface with 12 chromosomes.

00:28 So we have 12 chromosomes, and we know that if we're in g1 of interface, this means that we're in g1 of interface, this means.

00:33 That we have not gone through s phase where the dna duplicates.

00:37 And so we have one copy, which means that we have 12 dna molecules.

00:45 So next, the question asks us, how many chromosomes in dna molecules do we have in g2 of interphase? and so in g2, we know that this comes after s phase.

00:58 And so our dna has duplicated.

01:00 And so we have sister chromatids now.

01:02 And so that means that we still have 12 chromosomes.

01:07 However, now, since our dna is duplicated, we have 24 dna molecules.

01:16 So next, we need to know how many are in metaphase 1 of myosis.

01:22 And so we can use this diagram over here.

01:26 And you can see here, metaphase 1, we have not yet split cells and we have not split chromosomes.

01:32 And so this means that we're still going to have the same number.

01:37 12 chromosomes, 24 dna molecules.

01:43 And in c, we need to know prophase of mitosis.

01:48 And so we can still use this diagram because prophase 1 of myosis is essentially the same thing as prophase 1 of mitosis.

01:56 And you can see we're in the same stage, not stage, but we're in the same kind of position as metaphase 1, where our spindles are attaching, but our cells have not split yet, and our chromosomes have not split.

02:10 And so we still have 12 chromosomes, 24 dna molecules.

02:21 And so in d, they're asking for anaphase 1 of myosis.

02:25 And so that's over here.

02:27 And again, we have not split chromosomes.

02:29 We're only moving them to opposite sides of the cell.

02:32 And this is still one cell.

02:34 So we still have all of our chromosomes in the same cell and all of the dna molecules in the same cell.

02:40 And so again, the answer is 12 chromosomes, 24 dna molecules.

02:47 And in e, they're asking for anaphyse 2 of myiosis...