Cell Biology: Chromosome Structure & Cell Cycle

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Questions and Answers

What is the role of telomeres at the ends of chromosomes?

They assist in the replication of DNA.

They stabilize the chromosome structure. (correct)

They provide sites for sister chromatid attachment.

They facilitate spindle attachment during division.

What primarily regulates the movement of chromosomes during mitosis?

Cytokinesis readiness

Nuclear envelope integrity

Cell shape changes

Kinetochores (correct)

Which feature distinguishes diploid cells from haploid cells?

Diploid cells contain homologous pairs of chromosomes. (correct)

Haploid cells are found only in somatic tissues.

Diploid cells undergo binary fission.

Haploid cells have two complete sets of chromosomes.

Which process primarily occurs during interphase of the eukaryotic cell cycle?

Cell growth and DNA replication Signup and view all the answers

What distinguishes the cell cycle of prokaryotes from that of eukaryotes?

Eukaryotic cells replicate DNA in phases. Signup and view all the answers

Which cells typically divide the most frequently?

Bone marrow cells Signup and view all the answers

What is the primary outcome of the eukaryotic cell cycle?

Production of genetically identical daughter cells. Signup and view all the answers

What function does the centromere serve during cell division?

It provides an attachment site for sister chromatids. Signup and view all the answers

Which cell cycle phase is characterized by the growth and increase in cell size as well as metabolic activities?

First gap phase (G1) Signup and view all the answers

During which phase of mitosis do chromosomes align at the metaphase plate?

Metaphase Signup and view all the answers

What occurs during the anaphase stage of mitosis?

Sister chromatids separate Signup and view all the answers

What component is absent in plant cells that is present in animal cells, aiding in spindle organization during mitosis?

Centrioles Signup and view all the answers

Which cellular event occurs during the G2 phase before mitosis begins?

Protein synthesis Signup and view all the answers

What type of cell division produces two daughter cells with identical chromosomes to the parent cell?

Mitosis Signup and view all the answers

In plant cells, how is cytokinesis achieved given the rigidity of the cell wall?

Formation of a cell plate Signup and view all the answers

What is the primary function of the cell cycle's synthesis phase (S)?

Replicate DNA Signup and view all the answers

What is the primary outcome of meiosis in terms of chromosome number in daughter cells?

Daughter cells are haploid and contain half the chromosome number of the parent nucleus. Signup and view all the answers

During which stage of prophase I does crossing over occur?

Pachytene Signup and view all the answers

Which term describes the pair of homologous chromosomes formed during synapsis?

Bivalents Signup and view all the answers

What structural change occurs to the nucleolus during prophase I of meiosis?

The nucleolus disintegrates. Signup and view all the answers

What is the significance of chiasma during meiosis?

It indicates a region where non-sister chromatids are attached and crossing over occurs. Signup and view all the answers

Which of the following correctly describes the chromosome behavior during Metaphase I?

Spindle fibers are fully developed and homologous chromosomes align at the metaphase plate. Signup and view all the answers

How many times does the cell divide during meiosis?

Twice Signup and view all the answers

What is the genetic outcome of crossing over in Meiosis?

It results in genetic recombination and variation among daughter cells. Signup and view all the answers

What is the key difference between anaphase I of meiosis and anaphase of mitosis?

Homologous chromosomes remain intact in anaphase I. Signup and view all the answers

During which stage do chromosome numbers reduce, and the nuclear envelope reforms in meiosis?

Telophase I Signup and view all the answers

What aspect of crossing over is true?

It is exclusive to prophase I of meiosis. Signup and view all the answers

What happens in telophase II and cytokinesis II?

Cleavage furrow forms in animal cells. Signup and view all the answers

Which statement correctly describes the organization of chromosomes during metaphase?

Individual chromosomes align at the metaphase plate in mitosis. Signup and view all the answers

Study Notes

Chromosome Structure

The centromere is the attachment site of sister chromatids.
Telomeres are repeated nucleotide sequences at the ends of chromosomes, essential for stability.
Kinetochores mediate spindle microtubule attachment and control chromosomal movement during mitosis and meiosis.

Cell Cycle

The cell cycle refers to the series of events in a cell resulting in growth, DNA replication, and division.
Somatic cells are diploid (2n) with two complete sets of chromosomes.
Gametes are haploid (n) with one set of unpaired chromosomes.

Prokaryotic Cell Cycle

Prokaryotes reproduce asexually through binary fission.
DNA replication occurs continuously, not in phases.
The process involves cell elongation, plasma membrane growth inward, and septum formation.

Eukaryotic Cell Cycle

Eukaryotic cells divide through mitosis and meiosis, depending on factors like cell type and signals.
Bone marrow and skin cells divide frequently, while nerve and muscle cells stop dividing after maturation.

Interphase

The longest stage of the cell cycle, accounting for over 90% of the time.
Includes the first gap phase (G1), synthesis phase (S), and the second gap phase (G2).
During G1, cells grow, increase in size, and produce ribosomes and RNA.
The S phase involves DNA synthesis and replication.
G2 is characterized by intensive cellular synthesis, protein production, and continued cell growth.

Mitosis

Division of the nucleus and cytoplasm, resulting in two daughter cells with identical chromosomes to the parent cell.
Essential for repair and replacement of dead cells.
In animal cells, centrosomes containing centrioles and asters organize spindle microtubules.
In plant cells, spindle fibers are organized by enzymes, and a cell plate forms from vesicles for cell wall formation.

Stages of Mitosis

Prophase: Chromosomes condense, nucleoli disappear, nuclear envelope breaks down, and spindle fibers form.
Metaphase: Chromosomes align at the metaphase plate, perpendicular to spindle fibers.
Anaphase: Sister chromatids separate as daughter chromosomes move to opposite poles of the cell.
Telophase: Chromatin uncoils, nuclear envelopes form, and cleavage furrow forms in animal cells, while a cell plate forms in plant cells.
Cytokinesis: Division of cytoplasm and organelles, resulting in two daughter cells.

Meiosis

Division of the nucleus resulting in four daughter cells, each haploid (n) and genetically different from the parent cell.
Important for producing sex cells and maintaining species.

Stages of Meiosis I

Prophase I: Chromosomes condense, homologous chromosomes pair up (synapsis) forming bivalents, crossing over occurs (exchange of genetic material), and the nuclear envelope disintegrates.
Metaphase I: Bivalents align across the metaphase plate, with each pointing to one pole.
Anaphase I: Homologous chromosomes separate, moving to opposite poles.
Telophase I & Cytokinesis: Chromosomes are partitioned into two nuclei, and cytoplasm divides.

Stages of Meiosis II

Prophase II: New spindle fibers form.
Metaphase II: Chromosomes align at the metaphase plate.
Anaphase II: Centromeres split, and chromatids move to opposite poles.
Telophase II & Cytokinesis II: Nuclei reform, chromatin uncoils, and cytoplasm divides, resulting in four haploid daughter cells.

Key Differences Between Mitosis and Meiosis

Mitosis produces two diploid daughter cells, while meiosis produces four haploid daughter cells.
DNA replicates only once during interphase before mitosis and meiosis I, but not before meiosis II.
Crossing over occurs only in prophase I of meiosis, not in mitosis or meiosis II.
Homologous chromosomes align at the metaphase plate in meiosis I, while individual chromosomes align in mitosis.
Centromeres remain intact in anaphase I of meiosis, while sister chromatids separate in mitosis.

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Description

This quiz covers essential concepts in cell biology, including chromosome structure, the cell cycle, and reproduction methods in prokaryotic and eukaryotic cells. Explore topics like centromeres, telomeres, and the differences between somatic cells and gametes. Test your understanding of mitosis, meiosis, and prokaryotic binary fission.