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Biology - Chapter 3
Cell Division/Sexual Reproduction
| Term | Definition |
|---|---|
| Cell cycle | This is essentially the life of a cell. Occurs in 5 distinct stages and includes the processes of cell division. |
| G1 phase | Where ribosomes, enzymes and cell components, along with mRNA and tRNA are produced. A.K.A. "gap" or "growth". |
| S phase | Where DNA is replicated in the nucleus. A.K.A. "synthesis". |
| G2 phase | Where spindle fibers form and protein synthesis occurs. A.K.A. "gap" or "growth". |
| Interphase | G1, S and G2, collectively. |
| Mitosis | Where cell division and cytokinesis occur in 4 distinct stages. |
| G0 | A period of mitotic dormancy. The differentiation or specialization of cells occurs here (i.e. becoming muscle or nerve cells). |
| Prophase | Where the nucleolus, as well as the nuclear membrane disassemble. Chromatin coils, shortens and thickens to become chromosomes. Centrioles begin to move towards the cell poles. A.K.A. the first stage of mitosis. |
| Metaphase | Fully formed spindle fibres attach to the centromeres of chromosomes along the equatorial plane of the cell, and the centrioles have migrated to opposite poles. A.K.A. the second stage in mitosis. |
| Anaphase | Enzymes within the cell digest the centromeres of the chromosomes, and the individual halves (chromatids) begin to move along the spindle fibres towards the poles. A.K.A. the third stage in mitosis. |
| Telophase | The nuclear membrane reappears, enclosing the daughter chromosomes, and the nucleolus reforms. Spindle fibres disappear, and cytokinesis begins to occur. A.K.A. the final stage of mitosis. |
| Centrioles | Structures which assist in cell division. They are present in animal cells, but not in plant cells. |
| Chromosomes | Visible structures composed of DNA and protein which are organized into genes, and consist of two parallel threadlike parts. |
| Chromatids | The individual halves of chromosomes. They occur as parallel, threadlike structures and are joined together in the middle by a centromere. |
| Centromere | Found in the middle of a chromosome, and their function is to adjoin the two chromatids. |
| Spindles | Formed by assemblages of microtubules extending between the poles of the cell along the equatorial plane, and assist in the movement of chromosomes during cell division. |
| Equatorial plane | Spindle fibres will align in this area, which is located in the centre of the cell. |
| Daughter chromosomes | This is what chromatids are referred to once they separate. |
| Cytokinesis | Process of cell separation which happens during telophase. Occurs differently in plant and animal cells. Plants - Cell plate begins to form in the middle and moves outwards. Animals - Cell membrane pinches off at the middle (cleavage furrow). |
| Cleavage furrow | Occurs only in animal cell cytokinesis. Process by which the cell membrane begins to pinch off at the middle. |
| Cell plate | Occurs only in plant cell cytokinesis. Begins to form in the middle and moves outwards towards the cell membrane. |
| Meiosis | Form of specialized cell division that results in the formation of gametes, and occurs in the reproductive organs. Occurs in two main stages, which each consist of four steps. |
| Gamete | Individual sex cells are referred to as this. |
| Sexual reproduction | The formation of a new individual by the union of two gametes. Results in a shuffling of genetic information. |
| Gametogenesis | Another name for meiosis, or sex cell production. |
| Fertilization | The union of a sperm and an egg. A.K.A. formation of a zygote. |
| Zygote | Another name for an egg which has been fertilized. Cells begin to divide repeatedly by mitosis and form into a complete individual. |
| 46 | Chromosomes in a human cell. |
| Diploid | A complete "2n" set of chromosomes within a cell. |
| Haploid | An "n" set of chromosomes, found within a gamete. |
| 3n | An organism possessing this number of chromosomes will likely by sterile. |
| Homologous | Individual chromosomes (or together, referred to as a pair) in a diploid (2n) cell which possess similar genes appear throughout. |
| Ovaries | Appear in female animals, and are the organs which produce sex cells. |
| Testes | Appear in male animals, and are the organs which produce sex cells. |
| Pistle | Appear in female plants, and are the organs which produce sex cells. |
| Anther | Appear in male plants, and are the organs which produce sex cells. |
| Meiosis 1 | Occurs only in gamete formation. Consists of four separate stages; after which the reduction division occurs. |
| Reduction division | Occurs after meiosis 1. Homologous pairs of chromosomes are separated into two complete sets in two daughter cells. |
| Meiosis 2 | Occurs only in gamete formation. Consists of four separate stages; following immediately after reduction division. |
| Prophase 1 | Where the nucleolus, as well as the nuclear membrane disassemble. Chromatin coils, shortens and thickens to become chromosomes. Synapsis then occurs. Centrioles begin to move to the poles of the cell. |
| Metaphase 1 | Fully formed spindle fibres attach to the centromeres of homologous pairs along the equatorial plane of the cell, and the centrioles have migrated to opposite poles. The chromosomes from both parents are intermingled. |
| Anaphase 1 | Reduction of the number of chromosomes from diploid to haploid occurs here. The centromeres from each homologous pair attach to the spindle fibres, and each individual from each pair moves to opposite poles. |
| Telophase 1 | Nuclear membranes and nucleoli reappear; and chromosomes uncoil to become chromatin. Cytokinesis separates the cell into two daughter cells, which each have a haploid number of chromosomes. |
| Prophase 2 | The nucleolus and the nuclear membrane disassemble. Chromatin coils, shortens and thickens to become chromosomes (haploid number). Centrioles begin to move towards the cell poles. |
| Metaphase 2 | The fully formed spindle fibres attach to the centromeres of the chromosomes along the equatorial plane of the cell, and the centrioles have completely migrated to opposite poles. No intermingling occurs. |
| Anaphase 2 | Centromeres divide and form 2 daughter chromosomes from the individual chromatids, which then begin to move along the spindle fibres towards the poles of the cell. |
| Telophase 2 | The nuclear membranes and nucleoli reappear; and the chromosomes uncoil to become chromatin. Cytokinesis separates the cells into two more daughter cells, bringing the total daughter cells to four; each with a haploid number of chromosomes. |
| Synapsis | Occurs during prophase 1, and is the process of homologous chromosomes pairing/lining up. |
| Crossing over | Occurs during synapsis, and is the process by which sections of DNA from each member of the homologous pair are exchanged. This ensures genetic variability. |
| Genetics | First studied by Gregor Mendel (an Augustinian monk), and is a term referring to the study of genes. |
| Gene | A portion of DNA which determines a physical characteristic in an organism. |
| Pea plants | Studied by Gregor Mendel (an Augustinian monk) in order to determine how characteristic traits are passed from one generation to the next (genetics). |
| Alleles | A specific version or form of a gene for a particular trait. |
| Locus | Refers to the physical location along the chromosome where a specific allele is found. |
| Genome | The list of all the genes that express the characteristics of a specific organism. |
| Genotype | List of the genes present in an organism, although some of these genes may not be physically expressed. |
| Phenotype | The physical, behavioural or chemical expression of genes. |
| Dominant alleles | Express or display traits, and can mask or hide the presence of another trait. Represented by an uppercase letter. |
| Recessive alleles | Must be present in a homozygous condition (identical genes from both parents) in order to be displayed in an organism. |
| Pure line | Refers to a self-reproducing line of organisms which are homozygous for the vast majority of traits. |
| Punnett square | A common way to predict single genetic crosses, which is presented as a table. |
| Mendel's Laws of Heredity | Set of universal constants which dictate how characteristics are passed from one generation to the next. |
| Law of Dominance | When an organism possesses two different alleles for the same trait, one of those alleles will obscure the other. This leads to the preeminent gene being expressed. |
| Law of Segregation | When gametes are formed, the two alleles for a trait from the parent cell are separated between them which ensures differentiation. |
| Law of Independent Assortment | Members of one gene pair separate independently of the members of another gene pair; meaning that all traits will always be expressed in one form or another. |
| 3 | Amount of different genotypes there can be for a particular trait. |
| Homozygous | Term referring to two genes for a particular trait which are identical. |
| Heterozygous | Refers to two genes for a particular trait which are not identical. |
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davidsnarr
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