The Cellular Basis of Inheritance

Life Cycles of Sexually Reproducing Organisms

Fertilization: The term used to describe the fusion of haploid cells is fertilization, defined as the union of two haploid cells from different organisms.
Zygotic Meiosis Life-Cycle: This life cycle contains a unicellular haploid stage.
Ploidy in Daughter Cells:
- Mitosis: Produces 2 daughter cells with the same ploidy as the parent cell, meaning the chromosome number remains constant (e.g., diploid to diploid).
- Meiosis: Produces 4 daughter cells with half the ploidy of the parent cell, thereby reducing the chromosome number by half (e.g., diploid to haploid).
- Mitosis maintains ploidy, while meiosis halves it.
Cells Produced During Meiosis: Meiosis produces haploid cells.
Homologous Chromosomes: These are defined as pairs of chromosomes that have the same genes, with one chromosome contributed by each parent.
DNA/Chromosome Amount During Meiosis: The amount of DNA and the number of chromosomes are halved during meiosis.
Prior to Meiosis I: DNA replication occurs during the interphase before meiosis I.
Chromosome Number at End of Meiosis I: The chromosome number is halved at the conclusion of meiosis I.
Crossing Over: Occurs during meiosis, in which non-sister chromatids exchange genetic material.
Nondisjunction: This refers to the failure of synapsed homologs to separate during meiosis, potentially leading to gametes with abnormal chromosome numbers.
Anaphase I: In this phase, homologous chromosomes separate.
Anaphase II: In this phase, sister chromatids separate.
S Phase: The phase of the cell cycle in which DNA is replicated.
Cells Produced at End of Meiosis I: At the end of meiosis I, a total of 2 cells are produced.
Sister Chromatids Separation: Sister chromatids separate during anaphase II of meiosis.
Dividing Structures in Mitosis and Meiosis:
- Mitosis: The nucleus and then the cell divide.
- Meiosis: Homologous chromosomes first, then sister chromatids divide.
Spindle Fiber Microtubule Attachment: Microtubules attach to sister chromatids at the kinetochores.
Crossover Point Term: The term that describes the crossover point of non-sister chromatids during crossing over is called the chiasma.
Somatic Cells: These are the non-sex cells.
Spindle Microtubule Attachment in Meiosis: Spindle microtubules attach to kinetochores during prometaphase I and prometaphase II.
Chromosome Source in Sexually Reproducing Organisms: Organisms receive their two sets of chromosomes from each parent.
Genome: This term refers to the complete set of genetic material present in a cell or organism.

Alternation of Generations

Definition: A life cycle characteristic of plants and algae that contains distinct sexual haploid and asexual diploid phases.
Organisms Exhibiting Alternation of Generations: This process is exhibited by plants and algae.
Sporophyte Cell Division: The sporophyte utilizes meiosis to produce spores.
Haploid Gametes in Plants: Mitosis produces haploid gametes in plants.
Dominant Stage in Fungi Life Cycle: The dominant stage in the life cycle of fungi is the haploid stage.