Chapter 7 Summary
Key Takeaways
- The Genome: All cells have a genome, complete DNA instructions. Eukaryotic DNA is stored in chromosomes inside a nucleus, while prokaryotic DNA forms a single circular loop.
- Chromosomes and Genes: Human body cells have 46 chromosomes (23 pairs), including autosomes and sex chromosomes. Genes on these chromosomes code for proteins and are inherited in pairs (diploid), except in gametes (haploid).
- The Cell Cycle: The cell cycle includes phases for growth (G1, G2), DNA replication (S), and Mitotic (M phase). Checkpoints regulate the cycle to prevent errors; uncontrolled growth can lead to cancer.
- Mitosis: Mitosis produces two identical diploid cells, used for growth, repair, and asexual reproduction. It involves four phases: prophase, metaphase, anaphase, and telophase, followed by cytokinesis.
- Meiosis and Sexual Reproduction: Meiosis creates four unique haploid gametes for sexual reproduction. It includes two divisions and increases genetic diversity through crossing over, independent assortment, and random fertilization.
- Errors in Meiosis: Mistakes like nondisjunction can result in extra or missing chromosomes, potentially causing genetic disorders such as Down syndrome.
OpenAI. (2025). ChatGPT. [Large language model]. https://chat.openai.com/chat
Prompt: Summarize the following content into six key takeaways.
Flash Cards
Text Description
- Genome: The complete genetic material (DNA) set in an organism
- Chromatin: DNA and associated proteins loosely packed within the nucleus; condenses to form chromosomes during cell division
- Chromosomes: Structures of tightly coiled DNA and proteins that carry genetic information in cells
- Genes: Segments of DNA encoding specific proteins, determining inherited characteristics
- Sister chromatids: Identical copies of a chromosome joined together after DNA replication; separate during cell division
- Centromere: Region where sister chromatids are attached, essential for their proper separation during cell division
- Somatic cells: Non-reproductive cells of an organism’s body, typically diploid
- Diploid: A cell containing a two complete sets of chromosomes (2n), one from each parent
- Homologous chromosomes: Pairs of chromosomes (one from each parent) carrying genes for the same traits in similar positions
- Gametes: Sex cells (sperm and egg) containing half the genetic material of somatic cells; involved in reproduction
- Haploid: A cell containing a single set of chromosomes (n), such as gametes
- Autosomes: Chromosomes that do not determine sex; humans have 22 pairs of autosomes
- Sex chromosomes: Chromosomes determine biological sex; Females (XX) and males (XY)
- Cell cycle: Series of stages that cells go through to grow and divide, consisting of interphase (G1, S, and G2 phases) and mitotic phase (mitosis and cytokinesis)
- Interphase: Phase of the cell cycle during which the cell grows, duplicates its DNA, and prepares for mitosis; Consists of three stages – G1, S, G2
- Gap 1: First stage of interphase in the cell cycle; cell grows rapidly while performing routine metabolic processes
- Synthesis: Second stage of interphase in the cell cycle; DNA replication occurs to prepare for the mitotic phase
- Gap 2: Final stage of interphase; makes final preparations to divide
- Cancer: Disease of the cell cycle where the cells do not respond properly to the cell cycle control system; Cancerous cells divide faster than normal cells and may form a tumour
- Cell division: Process in which a parent cell divides to form two daughter cells
- Parent cell: The original cell that divides to produce new cells during cell division
- Daughter cells: New cells produced after a cell divides; genetically identical after mitosis, varied after meiosis
- Binary fission: A form of asexual reproduction in prokaryotes where one cell divides into two identical daughter cells
- Mitotic phase: Stage of the cell cycle when the cell is dividing; Consists of mitosis and cytokinesis
- Mitosis: Cell division producing genetically identical daughter cells; essential for growth, repair, and asexual reproduction
- Cytokinesis: Process during cell division where the cytoplasm of a parent cell is divided into two daughter cells
- Cleavage furrow: Indentation that forms during cytokinesis in animal cells; Caused by a contractile ring that tightens and pinches the cell into two daughter cells
- Cell plate: Structure that forms during cytokinesis in plant cells; Vesicles fuse in the centre of the cell and expand outward dividing the cell into two daughter cells
- Reproduction: The biological process by which organisms produce new offspring
- Sexual reproduction: Reproduction involving two parents, combining genetic material through gamete fusion to create genetically unique offspring
- Gametes: Reproductive cells (sperm in males and eggs in females); Haploid (n); Unite during fertilization to form a new organism
- Fertilization: Fusion of two gametes (sperm and egg), forming a zygote
- Zygote: Diploid (2n) cell formed when two gametes fuse; first cell of a new organism
- Meiosis: Type of cell division producing haploid gametes; reduces chromosome number by half, creating genetic diversity
- Crossing-over: Exchange of genetic material between homologous chromosomes during meiosis; Increases genetic variation in the offspring
- Independent assortment: The random distribution of homologous chromosomes into gametes during meiosis; Contributes to genetic variation in the offspring
- Random fertilization: The two gametes that unite to produce an offspring is a matter of chance; Contributes to genetic variation in the offspring
- Nondisjunction: Failure of chromosomes to separate properly during meiosis, leading to an abnormal number of chromosomes in the daughter cells
- Two types of chromosomes: Autosomes and sex chromosomes
- Stages in the Cell Cycle: Interphase – G1, S, G2, Mitotic Phase – Mitosis (Prophase, Metaphase, Anaphase, Telophase) and Cytokinesis
- Checkpoints in Cell Cycle: Cell Growth Checkpoint, DNA Synthesis Checkpoint, Mitosis Checkpoint
- Functions of Mitosis: Growth, repair and asexual reproduction (in some organisms)
- Steps in Prophase: Chromatin condenses into chromosomes. Nuclear envelope disintegrates. Centrosomes migrate to opposite poles. Spindle fibers form and connect to chromosomes.
- Steps in Metaphase: Spindle fibers “tug of war”. Chromosomes line up at metaphase plate.
- Steps in Anaphase: Sister chromatids pulled apart. Chromosomes pulled to opposite poles as spindles shorten. Spindles not attached to chromosomes lengthen and elongate cell
- Steps in Telophase: Spindle fibers disassemble. Nuclear envelope re-forms. Chromosomes decondense back into chromatin (reverse of prophase).
- Types of cytokinesis: Cleavage furrow (animal cells) and cell plate (plant cells)
- Life cycle of sexually reproducing organisms: Adult (2n) > Sperm and egg (n) produced by meiosis > Zygote (formed through fertilization) > Growth using mitosis (from zygote to fetus, infant, adolescent, adult)
- Function of meiosis: Produce gametes for sexual reproduction; Reduce the chromosome number by half
- Key differences between Mitosis and Meiosis I:
Mitosis: chromosomes line up along the metaphase plate individually (or “single file”).
Meiosis I: homologous chromosome pairs line up along the metaphase plate in tetrads (or “double file”) which allows number of chromosomes to get cut in half in daughter cells; crossing over also occurs which increases genetic variation. - Three causes of genetic variation in sexual reproduction: Crossing over, independent assortment, random fertilization
OpenAI. (2025). ChatGPT. [Large language model]. https://chat.openai.com/chat
Prompt: Can you give me brief summaries of these key terms.
