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Definition
Molecule that holds together the two sister chromatids of a chromosome together. The breakdown of cohesin at the centromeres enables the chromatids to separate in anaphase of mitosis and anaphase II of meiosis.
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Term
| homologous chromosome pair |
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Definition
| two chromosomes that are alike in structure and size and that carry genetic information for the same set of hereditary characteristics. One chromosome of the pair is inherited from the male parent and the other is inherited from the female parent. |
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Term
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Definition
| Mitosis is a cellular process that replicates chromosomes and produces two identical nuclei in preparation for cell division. Generally, mitosis is immediately followed by the equal division of the cell nuclei and other cell contents into two daughter cells. |
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| Meiosis is the formation of egg and sperm cells. In sexually reproducing organisms, body cells are diploid, meaning they contain two sets of chromosomes (one set from each parent). To maintain this state, the egg and sperm that unite during fertilization must be haploid, meaning they each contain a single set of chromosomes. During meiosis, diploid cells undergo DNA replication, followed by two rounds of cell division, producing four haploid sex cells. |
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Definition
| A chromatid is one of two identical halves of a replicated chromosome. During cell division, the chromosomes first replicate so that each daughter cell receives a complete set of chromosomes. Following DNA replication, the chromosome consists of two identical structures called sister chromatids, which are joined at the centromere. |
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Term
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Definition
| A centromere is a constricted region of a chromosome that separates it into a short arm (p) and a long arm (q). During cell division, the chromosomes first replicate so that each daughter cell receives a complete set of chromosomes. Following DNA replication, the chromosome consists of two identical structures called sister chromatids, which are joined at the centromere. |
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| A telomere is the end of a chromosome. Telomeres are made of repetitive sequences of non-coding DNA that protect the chromosome from damage. Each time a cell divides, the telomeres become shorter. Eventually, the telomeres become so short that the cell can no longer divide. |
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Definition
| site where DNA synthesis is initiated |
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Term
| homologous recombination (crossing over) |
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Definition
| Homologous recombination is a type of genetic recombination that occurs during meiosis (the formation of egg and sperm cells). Paired chromosomes from the male and female parent align so that similar DNA sequences from the paired chromosomes cross over each other. Crossing over results in a shuffling of genetic material and is an important cause of the genetic variation seen among offspring. |
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Term
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Definition
| A cell cycle is a series of events that takes place in a cell as it grows and divides. A cell spends most of its time in what is called interphase, and during this time it grows, replicates its chromosomes, and prepares for cell division. The cell then leaves interphase, undergoes mitosis, and completes its division. The resulting cells, known as daughter cells, each enter their own interphase and begin a new round of the cell cycle. |
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Term
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Definition
| Chromatin is a substance within a chromosome consisting of DNA and protein. The DNA carries the cell's genetic instructions. The major proteins in chromatin are histones, which help package the DNA in a compact form that fits in the cell nucleus. Changes in chromatin structure are associated with DNA replication and gene expression. |
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Definition
| A histone is a protein that provides structural support to a chromosome. In order for very long DNA molecules to fit into the cell nucleus, they wrap around complexes of histone proteins, giving the chromosome a more compact shape. Some variants of histones are associated with the regulation of gene expression. |
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| Diploid reproductive cell in the stamen of a plant; undergoes meiosis to produce four haploid microspores. |
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| Haploid product of meiosis in plants. |
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| In the ovary of a plant, a diploid reprodctuve cell that undergoes meiosis to produce haploid macrospores. |
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| One of four products of meiosis in plants. |
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| Haploid reproductive cell, sperm and egg. |
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| Final product of oogenesis |
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| Stage of mitosis. In prophase, the chromoses contract and become visible, the cytoskeleton breaks down, and the mitotic spindle begins to form. |
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Definition
| Stage of mitosis. In metaphase, chromosomes align in the center of the cell. |
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Definition
| Stage of mitosis in which chromatids separate and move toward the spindle poles. |
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| Stage of mitosis. In telophase, the chromosomes arrive at the spindle poles, the nuclear membrane reforms, and the chromosomes relax and lengthen. |
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Definition
| Process by which the cytoplasm of a cell divides. |
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