SGFS/BU/CHAPTER 4 (2024) Cell Division Study Set

A comprehensive collection of flashcards based on the Chapter 4 Cell Division worksheet, covering the cell cycle, mitosis, meiosis, and DNA replication.

What are the three key roles of cell division?

The three key roles of cell division are reproduction, growth and development, and tissue repair.

How is the cell cycle defined?

The cell cycle is the life of a cell from the time it is first formed from a dividing parent cell until its own division into two daughter cells.

How many chromosomes are in a human somatic cell?

A human somatic cell contains $46$ chromosomes.

What are two types of somatic cells found in the body?

Examples of somatic cells include skin cells, muscle cells, or white blood cells (all body cells except reproductive cells).

What is the definition of gametes?

Gametes are reproductive cells, such as sperm and eggs, that contain half the number of chromosomes as somatic cells.

Identify the number of chromosomes present in a human white blood cell.

A human white blood cell, being a somatic cell, contains $46$ chromosomes.

Based on Diagram I, identify phases I, II, III, and IV of the cell cycle.

Phase I is $G_1$ phase, Phase II is $S$ phase, Phase III is $G_2$ phase (together forming interphase), and Phase IV is the $M$ phase (Mitosis).

What specific events occur during phase II ($S$ phase) of the cell cycle?

During phase II, DNA replication or synthesis occurs, resulting in the doubling of the amount of DNA in the cell.

Compare the amount of DNA in a cell at phase III ($G_2$) with the amount of DNA in a cell at phase I ($G_1$).

The amount of DNA in phase III is double ($2 \times$) the amount of DNA found in phase I because the DNA was replicated during the intervening $S$ phase.

How does the genetic composition of daughter cells produced by mitosis compare to the parent cell?

The daughter cells are genetically identical to the parent cell.

What will be the chromosomal number of daughter cells at the end of phase IV (mitotic division) in humans?

The chromosomal number will be the diploid number, which is $46$ chromosomes.

Explain why an increase in the amount of DNA is important in the cell cycle.

It ensures that when the cell divides, each daughter cell receives a complete and identical set of the genetic information.

Why is it misleading to describe interphase as the 'resting stage'?

It is not a 'resting stage' because the cell is metabolically active, performing intense activities such as protein synthesis, organelle production, and DNA replication.

In an epithelial tissue sample, why might some cells have $8.4$ units of DNA while others have only $4.2$ units?

Cells with $4.2$ units are in the $G_1$ phase (before DNA replication), while cells with $8.4$ units have completed the $S$ phase and are in the $G_2$ or early mitotic phase.

Name the structures labeled A, B, and C on a pair of homologous chromosomes during meiosis.

A refers to the centromere, B refers to the chromatids (or sister chromatids), and C refers to the chiasmata (site of crossing over).

What are the primary sources of variation in the process of meiosis?

The sources of variation are crossing over (during prophase I), independent assortment of chromosomes (during metaphase I), and random fertilization.

State two events that occur during Prophase I of meiosis.

During Prophase I, homologous chromosomes undergo synapsis to form bivalents (tetrads) and crossing over occurs at the chiasmata.

What is the difference between cytokinesis in animal cells and plant cells?

In animal cells, cytokinesis occurs through the formation of a cleavage furrow; in plant cells, it occurs through the formation of a cell plate.

What is the significance of mitosis?

Mitosis is significant for growth, replacement of damaged cells (repair), and asexual reproduction in some organisms, ensuring genetic stability across cell generations.