Biology Unit 1: Cell Cycles

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Questions and Answers

What is a daughter cell?

A new cell formed by cell replication.

What is a zygote?

A diploid cell resulting from the fusion of an egg and sperm.

What is an embryo?

An early stage in the development of human, animal, or plant species.

What is mitosis?

<p>Division of a nucleus resulting in two cells that are genetically identical to the parent cell. (D)</p>
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What is cytokinesis?

<p>The division of the cell cytoplasm following mitosis or meiosis, where the cytoplasm divides and the cell splits into daughter cells.</p>
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In prokaryotes, the point at which the chromosome is attached to the plasma membrane is called the _____.

<p>origin</p>
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What is binary fission?

<p>A form of asexual reproduction in unicellular organisms involving the parent cell dividing into two approximately equal parts.</p>
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What constitutes the cell cycle?

<p>The events in the life of a cell, from its formation by cell division through its growth and function until it divides again.</p>
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Interphase is the phase in the cell cycle when the cell is actively undergoing mitosis.

<p>False (B)</p>
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What occurs during the G1 phase of the cell cycle?

<p>The G1 phase is the first growth phase of interphase, where the cell increases in size and synthesizes proteins and organelles.</p>
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What is the G0 phase?

<p>A resting phase where the cell has exited the cell cycle and is not actively preparing to divide.</p>
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The _____ phase of interphase is when chromosomes are replicated in the nucleus.

<p>S</p>
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What is a chromatid?

<p>One of the two identical copies of a chromosome formed during the S stage of interphase, joined together at the centromere.</p>
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What is the function of the centromere?

<p>It is the part of the chromosome that attaches to spindle fibres during mitosis and meiosis, and it is where the two sister chromatids of a double-stranded chromosome are joined.</p>
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The G2 phase is the first phase of interphase.

<p>False (B)</p>
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What characterizes prophase?

<p>Prophase is the first phase in mitosis where chromosomes condense and become visible, and the mitotic spindle begins to form.</p>
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What are centrioles?

<p>Barrel-shaped organelles found in animal cells that help organize cell division (formation of the mitotic spindle) and the production of cilia and flagella.</p>
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What is the mitotic spindle?

<p>A network of microtubule fibres formed during mitosis (primarily by centrioles in animal cells) that attaches to the centromeres of chromosomes to separate the sister chromatids.</p>
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During _____, the stage of mitosis between prophase and anaphase, chromosomes line up along the middle of the cell.

<p>metaphase</p>
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What key event occurs during anaphase?

<p>Sister chromatids separate and are pulled towards opposite poles of the cell by the shortening of the spindle fibres.</p>
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Telophase is the stage of mitosis that occurs immediately after prophase.

<p>False (B)</p>
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What is DNA replication?

<p>The process by which a double-stranded DNA molecule is copied to produce two identical double-stranded DNA molecules.</p>
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What are mutations?

<p>A permanent change in the base sequence of DNA.</p>
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What is the significance of the G1 checkpoint?

<p>The G1 checkpoint, occurring towards the end of the G1 phase, assesses cell size, nutrients, growth factors, and DNA damage before allowing the cell to proceed to the S phase.</p>
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_____ are protein molecules that act as biological catalysts to speed up biochemical reactions.

<p>Enzymes</p>
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What are apoptotic bodies?

<p>Structures formed during apoptosis when cellular components (like organelles and cytoplasm) are broken down and enclosed in membrane-bound vesicles as the cell's plasma membrane forms buds (blebs).</p>
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What is the role of phagocytic cells in the context of apoptosis?

<p>Phagocytic cells engulf and remove apoptotic bodies.</p>
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What is the mitochondrial pathway of apoptosis?

<p>One of the two main pathways initiating apoptosis, triggered by internal cell stress signals (like DNA damage), leading to the release of factors like cytochrome c from mitochondria.</p>
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What are caspases?

<p>A group of protease enzymes crucial for apoptosis, involved in cleaving specific proteins and DNA.</p>
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The death receptor pathway is the only pathway by which apoptosis can be initiated.

<p>False (B)</p>
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What are blebs in the context of apoptosis?

<p>Bulges or protrusions in the plasma membrane caused by the degradation of the cell's internal structure (cytoskeleton) during apoptosis.</p>
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What is tissue culture?

<p>The cultivation of plant or animal cells, tissues, or organs in vitro on a formulated nutrient medium under sterile conditions.</p>
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A region of repetitive DNA sequences found at the end of a chromosome is called a _____.

<p>telomere</p>
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What is a neoplasm?

<p>An abnormal tissue growth, often referred to as a tumor, caused by unusually rapid and uncontrolled cell replication.</p>
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Define cancer.

<p>A group of diseases characterized by uncontrolled cell division and the ability of these cells to invade other tissues (metastasis).</p>
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What are oncogenes?

<p>Mutated versions of normal genes (proto-oncogenes) that promote cell division. Oncogenes contribute to cancer by promoting uncontrolled cell growth.</p>
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Proto-oncogenes are mutated genes that cause cancer.

<p>False (B)</p>
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What is the function of tumour-suppressor genes?

<p>Normal genes that slow down cell division, repair DNA mistakes, or induce apoptosis (programmed cell death) when necessary.</p>
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What are embryonic stem cells?

<p>Stem cells derived from the inner cell mass of a blastocyst (an early-stage embryo). They are pluripotent, meaning they can differentiate into any cell type of the body.</p>
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What are adult stem cells?

<p>Unspecialized or undifferentiated cells found in various tissues of the body after development. They are typically multipotent or unipotent.</p>
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What does 'potency' refer to in the context of stem cells?

<p>A cell's ability or potential to differentiate into different types of specialized cells.</p>
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A _____ cell is an isolated cell, like a zygote, that is capable of developing into a complete, fertile adult individual and all extraembryonic tissues.

<p>totipotent</p>
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What does it mean for a cell to be pluripotent?

<p>A pluripotent cell can differentiate into any of the cell types that make up the body (derived from the three primary germ layers), but not into extraembryonic tissues like the placenta.</p>
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What are germ layers?

<p>The primary layers of cells (ectoderm, mesoderm, and endoderm) that form during early embryonic development and give rise to all the different tissues and organs of the body.</p>
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What does it mean for a stem cell to be multipotent?

<p>Multipotent stem cells have the ability to differentiate into multiple, but a limited range of, cell types, usually within a specific tissue or lineage.</p>
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Unipotent stem cells are capable of developing into many different types of cells or tissues.

<p>False (B)</p>
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List the key steps involved in the process of apoptosis described.

<ol> <li>Activation of caspases. 2. Digestion of cell components. 3. Cell shrinkage. 4. Membrane blebbing. 5. Formation of apoptotic bodies and removal by phagocytic cells (macrophages).</li> </ol>
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Define embryo.

<p>An early stage in the development of human, animal or plant species</p>
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Define cytokinesis.

<p>The division of the cell following mitosis or meiosis, where the cytoplasm divides and the cell splits into daughter cells</p>
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In prokaryotes, what is the 'origin'?

<p>The point at which the chromosome is attached to the plasma membrane</p>
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Define the cell cycle.

<p>The series of events in the life of a cell, from its formation by cell division through its growth and function until it divides again</p>
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What is interphase?

<p>The phase in the cell cycle when the cell is not undergoing mitosis, during which it grows and replicates its DNA</p>
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What occurs during the S phase?

<p>The synthesis phase of interphase where chromosomes are replicated in the nucleus</p>
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Define chromatid.

<p>One of the two identical copies of a chromosome formed during the S stage of interphase</p>
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What is a centromere?

<p>A part of the chromosome that attaches to spindle fibres during mitosis and where the two sister chromatids of a double-stranded chromosome are joined</p>
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Define the mitotic spindle.

<p>A network of microtubule fibres, formed with the help of centrioles in animal cells, that attaches to the centromeres of chromosomes to separate the chromatids during mitosis</p>
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What happens during metaphase?

<p>The stage of mitosis where chromosomes line up along the middle (equator) of the cell and spindle fibres attach to the centromeres of chromosomes</p>
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What occurs during anaphase?

<p>The stage of mitosis after metaphase where sister chromatids separate and are pulled towards opposite poles of the cell by the spindle fibers.</p>
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Describe telophase.

<p>The final stage of mitosis where chromosomes arrive at opposite poles, decondense, and nuclear envelopes reform around them.</p>
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Define mutations.

<p>A permanent change in the base sequence of DNA</p>
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What is the G1 checkpoint?

<p>A critical control point in the cell cycle during the G1 phase that checks for cell size, nutrients, growth factors, and DNA damage before allowing entry into S phase.</p>
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What are enzymes?

<p>Protein molecules that act as biological catalysts to speed up biochemical reactions</p>
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Define apoptosis.

<p>A regulated process of programmed cell death characterized by a specific series of steps leading to cell elimination without inflammation.</p>
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What are phagocytic cells?

<p>Cells that protect the body by ingesting harmful foreign particles, bacteria, and dead or dying cells (like apoptotic bodies) through a process called phagocytosis.</p>
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Describe the mitochondrial pathway of apoptosis.

<p>An intrinsic pathway of apoptosis initiated by internal cellular stress signals (like DNA damage), leading to the release of cytochrome c from mitochondria and subsequent activation of caspases.</p>
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Describe the death receptor pathway of apoptosis.

<p>An extrinsic pathway of apoptosis initiated by the binding of external signaling molecules (ligands like TNF or Fas ligand) to death receptors on the cell surface, leading directly to the activation of caspases.</p>
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What are blebs in the context of cell biology?

<p>Bulges or protrusions of the plasma membrane that occur when the cell's cytoskeleton breaks down, characteristic of apoptosis.</p>
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Define tissue culture.

<p>The technique of growing plant or animal cells, tissues, or organs in a sterile laboratory environment on an artificial nutrient medium.</p>
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What are proto-oncogenes?

<p>Normal genes that play essential roles in regulating cell growth, division, and differentiation.</p>
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What are tumour-suppressor genes?

<p>Normal genes that slow down cell division, repair DNA mistakes, or trigger apoptosis (programmed cell death).</p>
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What does potency refer to in cell biology?

<p>A stem cell's ability or potential to differentiate into different specialized cell types.</p>
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Define totipotent.

<p>The ability of a single cell (like a zygote) to divide and differentiate to form the entire organism, including extraembryonic tissues like the placenta.</p>
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List the key morphological steps in the process of apoptosis.

<p>Key steps include: 1. Activation of caspases, 2. Digestion of cellular components (proteins, DNA), 3. Cell shrinkage and chromatin condensation, 4. Membrane blebbing (forming bulges), 5. Formation of apoptotic bodies which are then engulfed by phagocytic cells (like macrophages).</p>
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Which process involves the division of a nucleus resulting in two cells that are genetically identical to the parent cell?

<p>Mitosis (A)</p>
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Which process involves the division of the nucleus resulting in one copy of each homologous chromosome and one sex chromosome in each daughter cell?

<p>Meiosis (D)</p>
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What term describes the sequence of events in the life of a cell, from its formation by cell division through its growth and function until it divides again?

<p>Cell cycle (A)</p>
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What is interphase in the cell cycle?

<p>The phase in the cell cycle when the cell is not undergoing mitosis.</p>
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What is the term for the programmed process of cell death involving a characteristic series of steps?

<p>Apoptosis (A)</p>
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What is the mitochondrial pathway in relation to apoptosis?

<p>One of the two main pathways initiating apoptosis, often triggered by internal cell stress signals like DNA damage. It involves the release of pro-apoptotic molecules from the mitochondria.</p>
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What is the death receptor pathway in relation to apoptosis?

<p>One of the two main pathways initiating apoptosis, triggered by external signals binding to death receptors on the cell surface.</p>
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What are blebs in the context of cell death?

<p>Bulges or protrusions in the plasma membrane caused by the degradation of the internal cellular structure, particularly the cytoskeleton, during apoptosis.</p>
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What term describes a cell's ability to differentiate into other cell types?

<p>Potency (B)</p>
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A cell that is able to produce a complete, fertile adult individual is described as:

<p>Totipotent (A)</p>
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A cell that can develop into many different types of cells or tissues derived from any of the three germ layers (ectoderm, mesoderm, endoderm) is described as:

<p>Pluripotent (A)</p>
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What does multipotent mean?

<p>The ability of stem cells to differentiate into multiple, but limited, cell types within a specific lineage or germ layer.</p>
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List the key steps in the process of apoptosis.

<ol> <li>Caspase activation. 2. Digestion of cell contents (proteins, DNA). 3. Cell shrinkage. 4. Membrane blebbing. 5. Formation of apoptotic bodies which are then engulfed by phagocytic cells (macrophages).</li> </ol>
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Flashcards

Daughter Cells

New cells formed by cell replication.

Zygote

Diploid cell resulting from the fusion of an egg and sperm.

Embryo

Early stage in the development of a human, animal, or plant species.

Mitosis

Division of a nucleus resulting in two cells that are genetically identical to the parent cell.

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Cytokinesis

The division of cell cytoplasm following mitosis or meiosis, resulting in two daughter cells.

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Meiosis

Division of the nucleus resulting in daughter cells with one copy of each homologous chromosome and one sex chromosome.

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Origin

In prokaryotes, the point at which the chromosome is attached to the plasma membrane.

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Binary Fission

A form of asexual reproduction in unicellular organisms, parent cell divides into two approximately equal parts.

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Cell Cycle

The events in the life of a cell, from its formation by cell division through its growth and function until it divides again.

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Interphase

The phase in the cell cycle when the cell is not undergoing mitosis.

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G1 Phase

A checkpoint that occurs towards the end of G1 in interphase.

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G0 Phase

A phase of interphase in the cell cycle, cell is not actively preparing to divide.

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S Phase

The synthesis phase of interphase where chromosomes are replicated in the nucleus.

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Chromatid

One of the two copies of a chromosome formed during the S stage of interphase.

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Centromere

A part of the chromosome that attaches to spindle fibers during mitosis, where sister chromatids are joined.

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G2 Phase

The last phase of interphase before mitosis.

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Prophase

The first phase in mitosis in which chromosomes condense and become visible.

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Centrioles

Barrel-shaped organelles that help organize cell division and the production of cilia.

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Mitotic Spindle

A network of fibers formed by the centrioles to attach the centromere of chromosomes to separate the strands during mitosis.

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Metaphase

The stage of mitosis where chromosomes line up along the middle of the cell and spindle fibres attach to the centromeres.

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Anaphase

The stage of mitosis after metaphase and before telophase, sister chromatids separate.

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Telophase

The final stage of mitosis between anaphase and cytokinesis, two new nuclei form.

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DNA Replication

The process of a double-stranded DNA being copied to produce an identical double-stranded DNA.

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Mutations

A permanent change in the base sequence of DNA.

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G1 Checkpoint

A checkpoint that occurs towards the G1 in interphase.

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G2 Checkpoint

A checkpoint that occurs towards the end of G2 in interphase.

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M Checkpoint

Checkpoint that occurs towards the end of metaphase.

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Enzymes

A protein molecule that speeds up biochemical reactions.

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Apoptosis

A process of cell death that involves a characteristic series of steps.

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Apoptotic Bodies

A structure formed during apoptosis when cellular components are broken down and the cell's plasma membrane forms a bud.

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Phagocytic Cells

A process by which a solid particle in the extracellular fluid is taken into a cell.

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Mitochondrial Pathway

One of the two pathways by which apoptosis can be initiated.

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Caspases

A group of enzymes involved in protein and DNA cleavage.

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Death Receptor Pathway

One of two pathways by which apoptosis can be initiated.

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Blebs

A bulge in the plasma membrane caused by the degradation of the internal structure of the cell.

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Tissue Culture

Cultivation of plant cells, tissues, or organs on formulated nutrient media.

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Telomeres

A region of repetitive DNA sequences at the end of a chromosome.

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Neoplasm

Abnormal tissue growth, caused by unusually rapid cell replication.

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Cancers

A group of diseases characterized by uncontrolled cell division.

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Oncogenes

A group of genetic mutations that may cause cancer.

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Proto-oncogenes

Normal genes which affect normal cell growth.

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Tumour-suppressor Genes

A normal gene that slows down cell division or tells cells to die at the right time.

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Mutagens

Anything that causes a mutation (change in the DNA of the cell).

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Embryonic Stem Cells

A stem cell that can be obtained from a blastocyst.

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Adult Stem Cells

Unspecialized or undifferentiated cells found in the body.

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Potency

A cell's ability to differentiate into another cell type.

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Totipotent

An isolated cell that is able to produce a fertile adult individual.

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Pluripotent

A cell that is able to develop into many different types of cells or tissues in the body.

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Germ Layers

A group of cells in an embryo that interacts with each other as the embryo develops.

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Multipotent

The ability of stem cells to differentiate into multiple but limited cell types.

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Unipotent

Capable of developing into only one type of cell or tissue.

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Study Notes

  • Study notes on Biology Unit 1, Chapter 3: Cell Cycles

Daughter Cells

  • New cells formed through cell replication.

Zygote

  • A diploid cell created by the fusion of an egg and sperm.

Embryo

  • The early stage in the development of humans, animals, or plants.

Mitosis

  • The division of a nucleus, resulting in two cells genetically identical to the parent cell.

Cytokinesis

  • The division of the cell following mitosis or meiosis, where the cytoplasm divides, and the cell splits into daughter cells.

Meiosis

  • The division of the nucleus that results in daughter cells having one copy of each homologous chromosome and one sex chromosome.

Origin

  • In prokaryotes, the point where the chromosome attaches to the plasma membrane.

Binary Fission

  • A form of asexual reproduction in unicellular organisms where the parent cell divides into two approximately equal parts.

Cell Cycle

  • The events in the life of a cell, from its formation by cell division through its growth and function until it divides again.

Interphase

  • The phase in the cell cycle when the cell is not undergoing mitosis.

G1 Phase

  • A checkpoint that occurs towards the end of G1 in interphase.

G0 Phase

  • One of the phases of interphase in the cell cycle.

S Phase

  • The synthesis phase of interphase where chromosomes are replicated in the nucleus.

Chromatid

  • One of the two copies of a chromosome formed during the S stage of interphase.

Centromere

  • The part of the chromosome that attaches to spindle fibers during mitosis and where the two sister chromatids of a double-stranded chromosome are joined.

G2 Phase

  • The last phase of interphase before mitosis.

Prophase

  • The first phase in mitosis in which chromosomes condense and become visible.

Centrioles

  • Barrel-shaped organelles that help organize cell division and the production of cilia.

Mitotic Spindle

  • A network of fibers formed by the centrioles to attach the centromere of chromosomes to separate the strands during mitosis.

Metaphase

  • The stage of mitosis where chromosomes line up along the middle of the cell, and spindle fibers attach to the centromeres of chromosomes.

Anaphase

  • The stage of mitosis after metaphase and before telophase.

Telophase

  • The final stage of mitosis between anaphase and cytokinesis.

DNA Replication

  • The process of copying a double-stranded DNA to produce an identical double-stranded DNA.

Mutations

  • Permanent changes in the base sequence of DNA.

G1 Checkpoint

  • A checkpoint that occurs towards the end of G1 in interphase.

G2 Checkpoint

  • A checkpoint that occurs towards the end of G2 in interphase.

M Checkpoint

  • A checkpoint that occurs towards the end of metaphase.

Enzymes

  • Protein molecules that speed up biochemical reactions.

Apoptosis

  • A process of cell death that involves a characteristic series of steps.

Apoptotic Bodies

  • Structures formed during apoptosis when cellular components are broken down and the cell's plasma membrane forms a bud.

Phagocytic Cells

  • Cells that engulf and digest particles or debris in the extracellular fluid.

Mitochondrial Pathway

  • One of the two pathways by which apoptosis can be initiated.

Caspases

  • Enzymes involved in protein and DNA cleavage during apoptosis.

Death Receptor Pathway

  • One of the two pathways by which apoptosis can be initiated, triggered by signals from outside the cell.

Blebs

  • A bulge in the plasma membrane caused by the degradation of the internal structure of the cell.

Tissue Culture

  • The cultivation of plant cells, tissues, or organs on formulated nutrient media.

Telomeres

  • Regions of repetitive DNA sequences at the end of a chromosome.

Neoplasm

  • Abnormal tissue growth, caused by unusually rapid cell replication.

Cancers

  • A group of diseases characterized by uncontrolled cell division.

Oncogenes

  • Genetic mutations that may cause cancer.

Proto-oncogenes

  • Normal genes which affect regular cell growth, but can become oncogenes if mutated.

Tumor-Suppressor Genes

  • Normal genes that slow down cell division or tell cells to die at the appropriate time.

Mutagens

  • Anything that causes a mutation (change in the DNA of the cell).

Embryonic Stem Cells

  • Stem cells that can be obtained from a blastocyst.

Adult Stem Cells

  • Unspecialized or undifferentiated cells found in differentiated tissues.

Potency

  • A cell's ability to differentiate into other cell types.

Totipotent

  • An isolated cell that can produce a fertile adult individual.

Pluripotent

  • A cell that can develop into many different types of cells or tissues in the body.

Germ Layers

  • Groups of cells in an embryo that interact during development.

Multipotent

  • The ability of stem cells to differentiate into multiple but limited cell types.

Unipotent

  • Capable of developing into only one type of cell or tissue.

Process of Apoptosis

  • Involves: Activation of caspases, digestion of cell components, cell shrinkage, blebbing, and engulfment by phagocytic cells.

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