The Cell Cycle and DNA Replication

This section delves into the intricate process of the cell cycle, focusing on the stages of interphase and mitosis.

Definition: The cell cycle is the series of events that takes place in a cell leading to its division and duplication.

The interphase stage is broken down into three sub-phases:

1. G1 $Gap 1$: Cell growth and preparation for DNA synthesis
2. S $Synthesis$: DNA replication occurs
3. G2 $Gap 2$: Further cell growth and preparation for mitosis

Highlight: During the S phase, each of the 46 chromosomes is duplicated, resulting in 92 chromatids.

The guide also mentions the G0 $Zero Growth$ phase, where cells exit the cycle after specialization.

Vocabulary: Cytokinesis is the process where the cytoplasm and cell membranes divide to form two identical daughter cells.

The importance of mitosis in various biological processes is emphasized:

• Growth from a zygote to an adult
• Repair and replacement of damaged cells
• Asexual reproduction in some organisms

Example: In plants, mitosis is crucial for asexual reproduction, allowing new individuals to grow from a single parent cell.

The page concludes with a detailed diagram of the cell cycle, illustrating the relationship between interphase, mitosis, and cytokinesis.

Mitosis and Stem Cells

This page provides an in-depth look at the process of mitosis and introduces the concept of stem cells.

Definition: Mitosis is a type of cell division that produces genetically identical cells, also known as clones.

The guide presents a step-by-step breakdown of mitosis, from DNA replication during interphase to the final cytokinesis stage:

1. DNA replication during interphase
2. Chromosome condensation and alignment
3. Separation of sister chromatids
4. Cell division resulting in two identical daughter cells

Highlight: The end result of mitosis is two daughter cells that are genetically identical and diploid.

The role of spindle fibers in chromosome separation is explained, emphasizing their importance in ensuring accurate distribution of genetic material.

Vocabulary: Spindle fibers are special structures that pull chromosomes to opposite ends of the cell during mitosis.

The concept of stem cells is introduced, with a focus on their unique properties:

Definition: A stem cell is an undifferentiated cell capable of giving rise to many more cells of the same type and from which certain other specialized cells can arise through differentiation.

The guide touches on the development from gametes to zygote to embryo, introducing the term "blastocyst" and explaining the concept of totipotency.

Vocabulary: Totipotency refers to a cell's ability to differentiate into all specialized cell types.

This comprehensive overview of mitosis and stem cells provides students with a solid foundation for understanding cell division and differentiation in the context of GCSE Biology.

DNA Replication and Mitosis

This section details the process of DNA replication and subsequent mitosis. The process ensures genetic continuity through identical daughter cells.

Vocabulary: Sister chromatids - Identical copies of chromosomes formed during DNA replication.

Definition: Cytokinesis is the final stage of cell division where the cell physically splits into two.

Highlight: Spindle fibers play a crucial role in pulling chromosomes apart during division.

Adult Stem Cells

Adult stem cells are specialized cells with limited differentiation potential, found throughout the body.

Definition: Multipotent stem cells can develop into several but not all cell types.

Example: Bone marrow stem cells can form various blood cell types.

Highlight: Skin maintains a large reserve of stem cells for continuous regeneration.

Embryonic Stem Cells

This section covers the advantages and ethical considerations of embryonic stem cell research.

Definition: Totipotent stem cells can develop into any cell type.

Quote: "Embryonic stem cells provide potential treatments for various diseases."

Highlight: These cells can differentiate into various tissues including spinal cord, heart, and kidney cells.

Therapeutic Cloning

The process of therapeutic cloning involves creating patient-specific tissues using nuclear transfer techniques.

Definition: Therapeutic cloning creates patient-matched tissues for transplantation.

Example: A skin cell nucleus can be transferred to an empty egg cell to create matching tissue.

Highlight: The process must be terminated within 14 days of embryo formation.

Monoclonal Antibodies Introduction

This section introduces monoclonal antibodies and their production process.

Definition: Monoclonal antibodies are identical antibodies produced from a single clone of cells.

Highlight: These antibodies can target specific proteins or cells in the body.

Vocabulary: Lymphocytes - White blood cells that produce antibodies.

Medical Applications of Monoclonal Antibodies

The therapeutic applications and limitations of monoclonal antibodies in medicine are explored.

Example: Monoclonal antibodies can deliver targeted cancer treatments.

Highlight: They can carry toxic drugs or radioactive substances specifically to cancer cells.

Definition: Hybridoma - A cell created by fusing an antibody-producing lymphocyte with a tumor cell.

Genetic Material and Cell Structure

The human body is composed of cells, each containing a nucleus that houses genetic information. Within the nucleus, chromosomes carry genetic material that determines bodily functions and characteristics.

Definition: Chromosomes are thread-like structures made of DNA that carry genetic information.

Human body cells contain 46 chromosomes in 23 pairs. Each chromosome is composed of a long, coiled DNA strand containing numerous genes.

Vocabulary: Genes are sections of DNA that code for specific protein molecules, controlling individual characteristics.

The guide introduces key terms related to chromosomes and genetic material:

Highlight:

• Diploid: Cells with a full set of paired chromosomes $46 in humans$
• Haploid: Cells with half the number of chromosomes $23 in human gametes$
• Homologous chromosomes: Paired chromosomes carrying the same genes in the same positions

The process of fertilization is briefly explained, showing how haploid gametes $sperm and egg$ combine to form a diploid zygote.

Example: During sexual reproduction, a sperm cell $23 chromosomes$ fertilizes an egg cell $23 chromosomes$ to create a zygote with 46 chromosomes.

The page concludes with a detailed illustration of chromosome structure, including centromeres, chromatids, and the appearance of chromosomes during different stages of cell division.