Cell Biology: DNA Replication and Cell Cycle
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Questions and Answers

What process results in the production of two new cells from one cell?

  • Fertilization
  • Mitosis (correct)
  • Apoptosis
  • Meiosis

Which type of reproduction is commonly used by unicellular organisms?

  • Mitosis
  • Budding
  • Binary fission (correct)
  • Sexual reproduction

What is the primary function of meiosis?

  • Generating new cells for growth
  • Facilitating genetic mutations
  • Producing gametes (correct)
  • Repairing damaged tissues

What term describes programmed cell death that shapes organisms?

<p>Apoptosis (D)</p> Signup and view all the answers

Which process occurs during the union of sperm and ova?

<p>Fertilization (A)</p> Signup and view all the answers

How do multicellular organisms primarily reproduce?

<p>Sexual reproduction via gamete exchange (A)</p> Signup and view all the answers

What occurs in the cell cycle from inception to the creation of two new cells?

<p>Cell division (B)</p> Signup and view all the answers

What is a key characteristic of life related to cell function?

<p>Life reproduces. (C)</p> Signup and view all the answers

What direction does DNA replication proceed in when new nucleotides are added?

<p>5’ to 3’ (A)</p> Signup and view all the answers

What role does helicase play in DNA replication?

<p>It unzips or opens up the DNA molecule. (A)</p> Signup and view all the answers

Which strand is continuously synthesized during DNA replication?

<p>Leading strand (C)</p> Signup and view all the answers

What are Okazaki fragments?

<p>Short DNA sequences synthesized on the lagging strand. (C)</p> Signup and view all the answers

Which enzyme adds a short RNA primer to facilitate DNA synthesis?

<p>Primase (D)</p> Signup and view all the answers

What happens to RNA primers placed by Primase during DNA replication?

<p>They are lost and do not remain in the final DNA strand. (D)</p> Signup and view all the answers

Which process is involved in reducing cell webbing between toes?

<p>Apoptosis (D)</p> Signup and view all the answers

What happens to DNA during replication?

<p>DNA is unzipped and new nucleotides are added. (B)</p> Signup and view all the answers

How are the two strands of DNA oriented in relation to each other?

<p>Antiparallel (B)</p> Signup and view all the answers

What is the role of binding proteins during DNA replication?

<p>To stabilize the separation of the two DNA strands. (A)</p> Signup and view all the answers

What is meant by the term 'antiparallel' in DNA structure?

<p>The strands are oriented in opposite directions. (A)</p> Signup and view all the answers

What are the two important steps for cell reproduction mentioned?

<p>DNA Replication and Movement of Replicated DNA (B)</p> Signup and view all the answers

Which component does not belong to the nucleotide structure?

<p>Amino acid (A)</p> Signup and view all the answers

What is the role of carbon atoms in the 5 Carbon sugar of DNA?

<p>They play a role in the formation of new DNA molecules. (A)</p> Signup and view all the answers

What occurs after DNA is replicated?

<p>Two new strands are formed, each with old and new material. (B)</p> Signup and view all the answers

Which component is specifically highlighted as cytosine in the nucleotide structure?

<p>Nitrogenous base (D)</p> Signup and view all the answers

What role does DNA ligase perform during DNA replication?

<p>It fixes gaps between Okazaki fragments. (B)</p> Signup and view all the answers

Which mutation involves the substitution of one nucleotide for another?

<p>Substitution mutation (C)</p> Signup and view all the answers

What is the average accuracy rate of DNA polymerase in nucleotide addition?

<p>One mistake for every billion nucleotides (B)</p> Signup and view all the answers

What is the primary structural organization unit of chromatin?

<p>Nucleosomes (B)</p> Signup and view all the answers

What typically happens to chromosomes after DNA replication?

<p>They begin to condense and are visible under a light microscope. (D)</p> Signup and view all the answers

Which of the following is NOT a type of mutation that DNA polymerase can make?

<p>Connection mutation (C)</p> Signup and view all the answers

How many chromosomes do most humans have?

<p>46 (B)</p> Signup and view all the answers

What is the purpose of histones in relation to DNA?

<p>They package and organize DNA into nucleosomes. (A)</p> Signup and view all the answers

What role does the p53 protein play in cell division?

<p>It promotes genes involved in DNA repair. (B)</p> Signup and view all the answers

What happens during the G1 checkpoint of the cell cycle?

<p>The cell evaluates if there is damaged DNA. (B)</p> Signup and view all the answers

How does a malignant tumor differ from a benign tumor?

<p>Malignant tumors invade adjacent tissues. (D)</p> Signup and view all the answers

At what checkpoint does the cell ensure the chromosomes are properly aligned?

<p>Metaphase checkpoint (C)</p> Signup and view all the answers

What can trigger apoptosis during the cell cycle?

<p>Misalignment of chromosomes. (B), Dysfunction of the p53 protein. (D)</p> Signup and view all the answers

What is the significance of telomeres in chromosomes?

<p>They shorten with each cell division. (A)</p> Signup and view all the answers

What is a common characteristic of cancer cells?

<p>They continue dividing without responding to checkpoints. (A)</p> Signup and view all the answers

What occurs if there are not enough nucleotides during the S phase of the cell cycle?

<p>The cell cycle may pause or stop. (B)</p> Signup and view all the answers

What happens to normal cells when their telomeres are lost?

<p>They stop dividing and enter apoptosis. (D)</p> Signup and view all the answers

Which of the following statements about telomerase is true?

<p>Telomerase helps to maintain telomere length. (A)</p> Signup and view all the answers

What is the effect of oncogenes when they are mutated?

<p>They speed up the rate of cell division. (D)</p> Signup and view all the answers

What role do tumor suppressor genes play in the body?

<p>They block the spread of cancer. (C)</p> Signup and view all the answers

How do cancer cells differ from normal cells in terms of growth?

<p>Cancer cells can grow piled on top of one another. (C)</p> Signup and view all the answers

Which of the following is NOT a known risk factor for cancer?

<p>Genetic predisposition solely (D)</p> Signup and view all the answers

What is contact inhibition?

<p>When cells stop growing upon touching each other. (A)</p> Signup and view all the answers

Which statement about cellular respiration and molecular oxygen is correct?

<p>Molecular oxygen is a carcinogen but also essential for respiration. (C)</p> Signup and view all the answers

Flashcards

Cell Cycle

The life cycle of a cell, from its formation to its division into two new cells.

Asexual Reproduction

Reproduction that involves only one parent.

Sexual Reproduction

Reproduction that involves two parents exchanging sex cells.

Mitosis

A process of cell division that results in two identical cells. Duplicated DNA is transferred.

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Meiosis

The process of forming sex cells (sperm and ova).

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Fertilization

The union of sperm and ovum, forming a zygote.

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Apoptosis

Programmed cell death, essential for development.

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Cell

The fundamental unit of life.

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Apoptosis

Programmed cell death, a crucial process for development and tissue maintenance.

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DNA Replication

The process where a DNA molecule is copied to produce two identical DNA molecules.

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Nucleotide

The basic building block of DNA, consisting of a sugar, a phosphate, and a nitrogenous base.

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Antiparallel Strands

DNA strands that run in opposite directions.

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DNA

Deoxyribonucleic acid; the molecule that carries the genetic instructions for life.

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Cell Reproduction

The process of creating new cells by duplication and division.

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Mitosis

A type of cell division where a single cell divides to produce two identical daughter cells (important for growth and repair).

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Replication Process

The opening or unzipping of DNA and the addition of new nucleotides to form two new strands.

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Okazaki Fragments

Short DNA fragments formed on the lagging strand during DNA replication.

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DNA Ligase

Enzyme that joins Okazaki fragments together by forming phosphodiester bonds, finishing DNA replication.

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Leading Strand

Strand of DNA replicated continuously during DNA replication.

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DNA Polymerase Proofreading

Error-checking mechanism of DNA polymerase that corrects mistakes during replication.

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Substitution Mutation

Mutation where one nucleotide is replaced with another.

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Chromosome

Long strand of DNA tightly wound around proteins (histones) forming a compact structure.

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Chromatin

Collective mass of DNA and associated proteins which collectively form chromosomes.

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Nucleosomes

Structural units of chromatin, composed of DNA wrapped around histone proteins.

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Antiparallel DNA Strands

The two DNA strands run in opposite directions, with one strand's 5' end facing opposite to the other strand's 3' end.

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DNA Helicase

Enzyme that unwinds the DNA double helix by breaking the hydrogen bonds between base pairs.

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Leading Strand

The DNA strand that is replicated continuously in the 5' to 3' direction, in the same direction as the replication fork.

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Lagging Strand

The DNA strand that is synthesized discontinuously in short fragments, known as Okazaki fragments, which are later joined.

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Okazaki Fragments

Short fragments of DNA that are synthesized on the lagging strand during DNA replication.

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DNA Primase

Enzyme that creates short RNA primers on the DNA template strand to initiate DNA synthesis.

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DNA Polymerase

Enzyme that synthesizes new DNA by adding nucleotides to the 3' end of the existing DNA strand.

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5' to 3' DNA synthesis

The direction in which DNA polymerases add nucleotides during DNA replication and repair.

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Cell Cycle Checkpoints

Control points that ensure cells divide correctly, preventing uncontrolled growth.

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p53 Protein's Role

A protein that triggers DNA repair or apoptosis if DNA damage is severe.

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Benign Tumor

A non-cancerous tumor that grows slowly and doesn't spread.

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Malignant Tumor

A cancerous tumor that invades surrounding tissues and may metastasize.

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Metastasis

The spread of cancer cells from one part of the body to another.

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Cancer Cell Division

Cancer cells divide uncontrollably, escaping normal cell cycle checkpoints.

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G2 Checkpoint

Final checkpoint before cell division; checks for complete sets of DNA and proper spindle apparatus.

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Telomeres

Non-coding DNA sequences at the ends of chromosomes; protect them from damage and fusion.

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Telomeres

Protective caps at the ends of chromosomes that shorten with each cell division, eventually halting cell division.

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Telomerase

An enzyme that rebuilds telomeres, allowing cells to divide beyond the limit imposed by telomere shortening.

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Cancer Cells (growth)

Cancer cells continue to grow even when normal cells stop growing, and often ignore signals that tell them to stop dividing.

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Growth Factors

Proteins that stimulate cell division.

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Contact Inhibition

Cells stopping growth when they touch each other, preventing overcrowding and uncontrolled growth.

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Oncogenes

Mutated genes that speed up cell division, potentially leading to cancer.

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Tumor Suppressor Genes

Genes that normally prevent uncontrolled cell growth and cancer development.

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Environmental Cancer Risk

Environmental factors, including UV light, chemicals, radiation, and viruses, can increase the chances of cancer.

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Study Notes

DNA Replication, Mitosis, and Cell Cycle

  • Cells are the fundamental unit of life and life consists of one or more cells.
  • Life reproduces because life dies.
  • Cells reproduce and are replaced by other cells through cell reproduction.
  • Cell cycle is the process from a cell's inception to the moment it produces two new cells.
  • Bacteria reproduce asexually with binary fission.

Multicellular Reproduction

  • Simple unicellular organisms reproduce asexually.
  • Multicellular organisms reproduce sexually with two parents exchanging gametes (sex cells).
  • Meiosis forms gametes (sperm and ova).
  • Fertilization is the union of sperm and ova.
  • Mitosis results in duplicated DNA transferred from one cell to two.

Death is a Part of Life

  • Development from a single cell includes cell division, resulting in two identical cells.
  • Development also includes apoptosis (programmed cell death).
  • Cell death shapes organisms in a similar way that chiseling shapes rocks.
  • Life is a balance between cell death and cell reproduction.

DNA Replication

  • Two important steps in cell reproduction are DNA replication and moving the replicated DNA to each cell.
  • DNA replication occurs when DNA is opened or unzipped.
  • New nucleotides are added to each old strand of DNA.
  • One piece of DNA becomes two, each with a copy of the old and new material.

Nucleotide Structure

  • Nucleotides have a nitrogenous base (cytosine is mentioned).
  • A 5-carbon sugar.
  • A phosphate.

DNA Structure

  • The two strands of DNA are antiparallel.
  • The 5' carbon point upwards on the right strand.
  • The 3' carbon point upwards on the left strand.

How DNA Replicates

  • Helicase unzips the DNA molecule.
  • Binding proteins stabilize separation.
  • Primase adds short RNA primers to the template DNA.
  • DNA polymerase adds new nucleotides to the old strand.

DNA Built in 5' to 3' Direction

  • New nucleotides are added by DNA polymerase to the 5' side.
  • This creates a leading strand and a lagging strand.

Okazaki Fragments

  • RNA primers are lost, creating fragments.
  • Fragments on lagging strand are Okazaki Fragments.
  • Gaps between fragments are fixed by ligase.
  • DNA molecule construction is finalized.

Mutations

  • DNA polymerase is very accurate but can make mistakes.
  • Mistakes include substitutions (purine/pyrimidine), deletions, and insertions.

DNA in the Nucleus

  • Chromosomes are a polymer of DNA and associated proteins.
  • Humans have 46 chromosomes, while others vary.
  • Chromatin is DNA and proteins.
  • DNA is packaged into nucleosomes and further organized.

Chromosomes Condense After Replication

  • Nucleosomes condense after DNA replication.
  • Duplicated chromosomes become visible in a light microscope.
  • Identical pieces of DNA are called sister chromatids.
  • Sister chromatids join at the centromere.

Mitotic Division Creates Identical Cells

  • Mitosis is part of the cell cycle and redistributes sister chromatids.
  • The cell cycle comprises Interphase, Mitosis, and Cytokinesis.
  • Interphase is a period of growth, metabolism, and protein synthesis.
  • Mitosis involves splitting of the cell's cytoplasm into two.

Interphase

  • 90% of cell divisions are spent in interphase.
  • It's a period of growth, metabolism, and protein synthesis.
  • Interphase is split into three gap phases (G1, Go, and G2).
  • Chromatin is very diffuse during interphase and thus not visible.

Normal Cell Metabolism

  • During G1 phase the cell grows, carries out basic metabolic functions like glycolysis, makes molecules for organelles.
  • G0 phase cells are fully grown and don't divide or replicate.
  • Most body cells are in G0 phase.

Preparation of Cell Division

  • DNA replicates in the S phase.
  • The cell makes proteins necessary for division in the G2 phase.

Mitosis

  • Mitosis is the separation of sister chromatids and consists of Prophase, Prometaphase, Metaphase, Anaphase, and Telophase.
  • Mitosis functions in asexual reproduction, growth and development, and repair.

Prophase and Prometaphase

  • DNA condenses, forming chromosomes visible with a light microscope.
  • Spindle fibers form, and the nuclear envelope breaks down.
  • Spindle fibers attach to kinetochores on the centromere.

Metaphase and Anaphase

  • Duplicated chromosomes line up along the cell's equator.
  • Once tension is even, the cell enters anaphase.
  • Chromatids move towards opposite ends of the cell.

Telophase and Cytokinesis

  • New nuclear envelopes and nucleoli form.
  • Cytoplasm divides into two daughter cells.

Plant and Animal Cytokinesis

  • Animal cytokinesis involves a cleavage furrow (indentation).
  • Plant cytokinesis forms a cell plate.

Cells Out of Control

  • Cancer is the result of cells dividing out of control.
  • Cells normally have checkpoints (G1, p53) to control division.

Further Checkpoints

  • G2 checkpoints ensure DNA integrity and spindle formation.
  • Metaphase checkpoints ensure proper chromosome alignment.

Cancer

  • Cancer cells divide uncontrollably.
  • Benign tumors grow slowly, don't invade other tissues.
  • Malignant tumors spread to other tissues (metastasis).

Cell Fuses

  • Telomeres are DNA sequences at the ends of chromosomes.
  • Telomeres shorten with each cell division.
  • Telomerase is an enzyme that maintains telomere length.
  • Cancer cells often have active telomerase, allowing unlimited division.

Cell Growth

  • Cancer cells continue to grow, often with high growth factors.
  • Normal cells have contact inhibition, stopping growth when contact is made with other cells.
  • Cancer cells grow unchecked on top of each other.

Genes That Affect Cancer

  • Oncogenes are mutated proto-oncogenes, accelerating cell division.
  • Tumor suppressor genes (e.g., p53) block cancer.
  • Mutated tumor suppressor genes lead to uncontrolled cell division.

Environment

  • Factors like UV exposure, chemicals, and radiation can affect cancer risk.
  • Molecular oxygen is essential for cells but is also a carcinogen.

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