Chapter9 -Cell Cycle

What is the cell cycle?

The sequence of events from one cell division to the next.

What is cell division?

The process in which one cell divides into new cells.

What is cellular reproduction?

The production of new cells or organisms.

What is asexual reproduction?

Reproduction without the fusion of gametes.

What is binary fission?

A prokaryotic cell copies its DNA and divides into two cells.

What is mitosis?

Division of the nucleus that separates chromosomes.

What is cytokinesis?

Division of the cytoplasm into two daughter cells.

What is a somatic cell?

A body cell that is not a reproductive cell.

What are daughter cells?

The cells produced when a parent cell divides.

What is one function of mitosis?

Growth, development, cell replacement, and repair.

What is a chromosome?

A structure made of DNA and associated proteins.

What is chromatin?

The complex of DNA and proteins in the nucleus.

What are histones?

Proteins around which DNA wraps.

What is a nucleosome?

DNA wrapped around a core of histone proteins.

What does diploid (2n) mean?

Having two sets of chromosomes.

What does haploid (n) mean?

Having one set of chromosomes.

How many chromosomes are in a typical human somatic cell?

46 chromosomes, arranged in 23 pairs.

What is a karyotype?

An image of chromosomes arranged by size and shape.

What are homologous chromosomes?

A pair with the same genes; one came from each parent.

What is a gene?

A DNA sequence that contains genetic information.

What is an allele?

An alternative version of a gene.

What is DNA replication?

The process of copying DNA.

What are sister chromatids?

Two identical DNA copies of a replicated chromosome.

What is the centromere?

The chromosome region where sister chromatids are joined.

What does cohesin do?

It holds sister chromatids together.

What does condensin do?

It helps chromosomes become more compact.

What is the centrosome?

A structure that organizes microtubules and helps form the spindle.

What is the spindle apparatus?

A structure that moves and separates chromosomes.

What are microtubules?

Protein fibers that help form the spindle and move chromosomes.

What is a kinetochore?

A protein structure where spindle microtubules attach to a chromosome.

What is interphase?

The part of the cell cycle that includes G1, S, and G2.

What happens during G1 phase?

The cell grows and makes more cell components.

What happens during S phase?

DNA is replicated, producing sister chromatids.

What happens during G2 phase?

The cell prepares for division by making needed components.

What is M phase?

The phase that includes mitosis and cytokinesis.

What happens during prophase?

Chromosomes condense and the spindle begins to form.

What happens during prometaphase?

The nuclear envelope breaks down and spindle fibers attach to kinetochores.

What happens during metaphase?

Chromosomes line up in the center of the cell.

What is the metaphase plate?

The imaginary plane at the cell center where chromosomes line up.

What happens during anaphase?

Sister chromatids separate and move toward opposite poles.

What happens during telophase?

New nuclear envelopes form and chromosomes begin to uncoil.

What is a cleavage furrow?

An inward groove that forms as an animal cell divides.

What is a cell plate?

A structure that forms between two new plant daughter cells.

What do actin filaments do during cytokinesis?

They help constrict the cleavage furrow in animal cells.

What is the role of the Golgi apparatus in plant cytokinesis?

It supplies vesicles that help form the cell plate.

What is a cell cycle checkpoint?

A control point that checks progress and may pause the cycle.

What does the G1 checkpoint assess?

Whether conditions are suitable for the cell to continue dividing.

What does the G2 checkpoint assess?

Whether DNA replication is complete and the cell is ready for mitosis.

What does the M checkpoint assess?

Whether chromosomes are properly attached to the spindle.

What are cyclins?

Regulatory proteins whose levels help control the cell cycle.

What are growth factors?

External signals that can stimulate cell growth or division.

What is the role of the p53 gene?

It can pause the cell cycle after DNA damage and help trigger repair or cell death.

What is a tumor suppressor gene?

A gene that helps limit abnormal cell growth.

What is apoptosis?

Regulated, programmed cell death.

What are caspases?

Enzymes that help carry out apoptosis.

What is homeostasis?

The maintenance of relatively stable internal conditions.

What are stem cells?

Cells that can produce other cell types.

What are embryonic stem cells?

Stem cells that can develop into many different cell types.

What is reproductive cloning?

Cloning intended to produce a new organism.

What is therapeutic cloning?

Cloning intended to produce cells or tissues for treatment or research.

What are prokaryotes?

Organisms whose cells lack a membrane-bound nucleus.

What are eukaryotes?

Organisms whose cells have a membrane-bound nucleus.

What is the nucleoid?

The region containing chromosome DNA in a prokaryotic cell.

What is the origin of replication?

The site where DNA replication begins.

What is a termination site?

A site where DNA replication ends.

What is a septum in binary fission?

A partition that forms as a prokaryotic cell divides.

What does genetically identical mean?

Having the same genetic information.

What happens during S phase?

DNA is copied, so each chromosome has two sister chromatids.

Which phase aligns chromosomes at the cell center?

Metaphase.

Which phase separates sister chromatids?

Anaphase.

What happens during cytokinesis?

The cytoplasm divides, forming two separate daughter cells.

How does cytokinesis differ in animal and plant cells?

Animal cells form a cleavage furrow; plant cells form a cell plate.

Which cell cycle stage takes up most of the cycle in the lecture?

Interphase, approximately 90%.

What is the order of interphase stages?

G1 → S → G2.

What is the order of mitosis phases in this lecture?

Prophase → Prometaphase → Metaphase → Anaphase → Telophase.

What may happen if damaged DNA cannot be repaired?

p53 may help trigger apoptosis.

What does the M checkpoint verify?

That chromosomes are properly attached to the spindle before separation.

How do binary fission and mitosis differ?

Binary fission divides prokaryotic cells; mitosis divides a eukaryotic nucleus.

Do chromosome number and DNA amount change identically during replication?

No. DNA amount doubles, while chromosome count is usually still counted as 46 in humans.

What are the two major parts of M phase?

Mitosis and cytokinesis.

What is the function of mitosis in multicellular organisms?

Growth, development, cell replacement, and repair.

What happens to cohesin during anaphase?

It is removed or cleaved so sister chromatids can separate.

What happens to the nuclear envelope during telophase?

New nuclear envelopes form around the two sets of chromosomes.

What is the difference between a centromere and a kinetochore?

The centromere is a chromosome region; the kinetochore is a protein structure where spindle fibers attach.

What is the difference between chromatin and a condensed chromosome?

Chromatin is DNA-protein material; a condensed chromosome is its compact form.

What is the difference between diploid and haploid cells?

Diploid cells have two chromosome sets; haploid cells have one.

What do homologous chromosomes have in common?

They carry the same kinds of genes at corresponding locations, but alleles may differ.

What is one key difference between prokaryotic and eukaryotic cells?

Prokaryotes lack a membrane-bound nucleus; eukaryotes have one.

What is the general sequence of binary fission?

DNA replicates, the cell elongates, and the cell divides into two.

How do reproductive and therapeutic cloning differ?

Reproductive cloning aims to produce an organism; therapeutic cloning aims to produce cells or tissues.