Nuclear Structure and the Cell Cycle Overview

What is the function of the nucleus in eukaryotic cells?

The nucleus is a membrane-bound organelle that contains DNA and regulates gene expression.

What form does DNA take in its relaxed state?

DNA takes the form of chromatin, which is loose and unwound.

What is the role of the nucleolus?

The nucleolus builds the components that make ribosomes.

What is the significance of mRNA in relation to the nucleus?

mRNA leaves the nucleus through pores during protein synthesis.

What is the historical belief about genetic material before DNA was identified?

It was believed that genes were controlled by complex molecules like proteins.

What are chromosomes?

Chromosomes are packages that bundle genetic information.

What is a nucleosome?

A nucleosome is the DNA-histone complex that helps organize DNA into chromosomes.

What are the two arms of a chromatid called?

The upper arm is called the p arm, and the lower arm is called the q arm.

What are telomeres and why are they important?

Telomeres are protective tips of noncoding DNA that prevent chromosome degradation.

What are the three main sections of the cell cycle?

The three main sections are interphase, mitosis, and cytokinesis.

What percentage of its life does a cell spend in interphase?

A cell spends about 70-80% of its life in interphase.

What occurs during the G1 phase of interphase?

The cell grows and carries out its normal functions.

What happens during the S phase of interphase?

The cell copies its DNA in preparation for division.

What is the purpose of checkpoints in the cell cycle?

Checkpoints ensure there are no mistakes in the DNA or cell before division.

What are the four phases of mitosis?

The four phases are prophase, metaphase, anaphase, and telophase.

What occurs during prophase?

The nucleus begins to break down, and chromatin condenses into visible chromosomes.

What happens during metaphase?

Chromosomes line up in the center of the cell, and spindle fibers attach to their centromeres.

What occurs during anaphase?

Spindle fibers pull the chromosomes apart to opposite sides of the cell.

What happens during telophase?

Two new nuclei form around the chromosomes, which begin to uncoil back into chromatin.

What is cytokinesis?

Cytokinesis is the final stage where the cytoplasm splits to create two identical daughter cells.

How does cytokinesis differ in animal and plant cells?

In animal cells, a cleavage furrow forms, while in plant cells, a cell plate forms.

What is the mitotic index?

The mitotic index is the ratio of cells in mitosis to the total number of cells, expressed as a percentage.

What does a high mitotic index indicate?

A high mitotic index indicates uncontrolled cell growth, which can be a sign of cancer.