Cell Biology: Mitosis and Chromosomes

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Questions and Answers

What is the primary purpose of mitosis in eukaryotic cells?

To decrease the number of chromosomes in the cell

To facilitate genetic recombination

To increase cellular diversity

To produce two identical daughter cells (correct)

During which phase of the cell cycle does DNA replication occur?

M phase

G2 phase

G1 phase

S phase (correct)

Which of the following correctly describes homologous chromosomes?

They consist of one maternal and one paternal chromosome (correct)

They consist only of sister chromatids

They are formed during cytokinesis

They contain identical genetic information

What is the role of the centromere in cell division?

It holds sister chromatids together Signup and view all the answers

What characterizes eukaryotic chromosomes compared to prokaryotic chromosomes?

Eukaryotic chromosomes consist of linear DNA and associated proteins Signup and view all the answers

In which phase does the mitotic spindle apparatus begin to form?

Prophase Signup and view all the answers

Which type of chromatin is condensed and does not exhibit gene expression?

Heterochromatin Signup and view all the answers

What is the end result of cytokinesis in animal cells?

Two daughter cells that are completely separate Signup and view all the answers

What characterizes a somatic cell in terms of chromosome count?

Diploid with 46 chromosomes Signup and view all the answers

What happens during the G1 phase of the cell cycle?

Cell growth occurs Signup and view all the answers

Which of the following statements about homologous chromosomes is true?

They are pairs of chromosomes that contain the same genes. Signup and view all the answers

During which stage of mitosis do the sister chromatids separate?

Anaphase Signup and view all the answers

What is a key feature of heterochromatin?

It is condensed and does not express genes. Signup and view all the answers

What is the result of cytokinesis in animal cells?

Two distinct daughter cells separate completely. Signup and view all the answers

Which statement is true regarding the DNA composition of chromatin?

It consists of 40% DNA and 60% proteins. Signup and view all the answers

What is the main role of apoptosis in the cell cycle?

To remove unwanted or damaged cells. Signup and view all the answers

Study Notes

Cell Division

Cell division is essential for development, growth, and health.
Cell death, known as apoptosis, is a programmed process.
Mitosis is a type of cell division where two identical daughter cells are formed from a single parent cell.

The Cell Cycle

The cell cycle is the period of growth and division of somatic cells.
Stages of the cell cycle are:
- G1: first growth phase.
- S: DNA synthesis (replication) phase.
- G2: second growth phase, preparation for cell division
- M: mitosis (nuclear division).
- C: cytokinesis (cytoplasm division).

Cell Division in Eukaryotes

Eukaryotic cells have a nucleus that contains a large and complex genome.
DNA is organized into linear chromosomes.
The number of chromosomes varies between species.

Chromosomes in Different Species

Number of chromosomes in different species:
- Human: 46
- Gorilla: 48
- Mouse: 40
- Maize: 10
- Garden pea: 14
- Drosophila: 8
- E.coli: 1

Homologous Chromosomes and Sister Chromatids

Homologous chromosomes are pairs of the same chromosome.
Each chromosome homologue is composed of two sister chromatids.
Sister chromatids are held together by a centromere.

Chromosome Makeup

Chromatin is composed of 40% DNA and 60% protein.
DNA double helix coils around histone proteins forming a nucleosome.
The chromatin fibre is further coiled into supercoils.
Heterochromatin is condensed and does not express genes.
Euchromatin is uncoiled and expresses genes.

Number of Chromosomes per Cell

Somatic cells are diploid (2n).
Diploid cells have two homologues for each chromosome, one maternal and one paternal.
Gametes are haploid (n).
Haploid cells have a single copy of each chromosome, either maternal or paternal.

Cell Division in Somatic Cells - Mitosis

Stages of mitosis:
- Prophase: formation of the mitotic spindle apparatus.
- Metaphase: chromosomes align at the metaphase plate.
- Anaphase: sister chromatids separate and move to opposite poles.
- Telophase: nuclear envelope reforms, chromosomes decondense, and cytokinesis begins.
- Cytokinesis: division of the cytoplasm.

Cytokinesis (Animal Cells)

Cleavage furrow forms, pinching off the two new cells.
The two daughter cells remain joined by a thin band of cytoplasm.

Cell Growth Checkpoint

The cell cycle is controlled by checkpoints that ensure proper growth and division.
The cell cycle checkpoints regulate how often a cell divides.

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Description

Test your understanding of the processes involved in mitosis and the structure of chromosomes in eukaryotic cells. This quiz covers key concepts such as DNA replication, homologous chromosomes, and the role of the centromere. Perfect for students studying cell biology!