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Definition
| An X chromosome that is randomly deactivated during the creation of a cell in the early stages of life in a female mammal. All cells that come from this cell will have this same x chromosome deactivated, but other cells can have a different X chromosome deactivated. |
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Definition
| A trait that is carried on either the X chromosome or the Y chromosome, but more often than not the X chromosome. Examples include cystic fibrosis, sickle cell, and Tay-Sachs disease. |
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Term
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Definition
| Genes that are very close to one another on a chromosome, and therefore are likely to stick together (for lack of a better word) during crossing over. If an organism has one of a pair of linked genes, they are likely to have the other as well. |
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Definition
| Offspring showing traits that are not exactly the same as either the parents: i.e. if one parent has AABB and another has aabb, the offspring would have Aabb or aaBb |
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Definition
| An abnormal number of chromosomes in an organism. It occurs as an error in mitosis; if the tetrads fail to seperate or the centromeres fail to uncouple one cell may have one more chromosome and the other one less. |
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Definition
| The term given to a chromosomal mutation during meiosis where tetrads fail to seperate or centromeres fail to uncouple |
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Definition
| A method of testing for genetic abnormalitieas; the liquid bathing the fetus is removed through a needle and tested. This can be done later than CVS, but carries a higher risk of miscarriage |
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Definition
| Also known as Chorionic villus sampling, this is a method of testing genetic abnormalities prior to birth. A sample of the placenta is removed and tested. This must be done early in the birth cycle. |
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Definition
| The breeding of an organism with another organism with a recessive trait to determine if the test organism is partially dominant (Aa) or fully dominant (AA) |
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Definition
| A term used to describe cells and organisms containing more than two paired (homologous) sets of chromosomes |
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Definition
| The location of a gene on a chromosome |
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Term
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Definition
| every individual possesses a pair of alleles for any particular trait and that each parent passes a randomly selected copy (allele) of only one of these to its offspring. |
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Term
| Law of Independent Assortment |
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Definition
| separate genes for separate traits are passed independently of one another from parents to offspring.Of course, with the discovery of linked traits, this is not completely true. |
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Definition
| The Law of Segregation and the Law of Independent assortment. This was discovered through a series of testcrosses of pea plants by, well, Gregor Mendel. |
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Term
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Definition
| (# of recombinants/total offspring)*100=__% frequency. This is used to determine the distance between traits on a chromosome. Genes that are close together on the chromosome have a much smaller recombination frequency. |
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Term
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Definition
| A genetic disorder created due to an extra copy (trisomy) of chromosome 21. |
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Term
| Chromosomal Mutation Types |
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Definition
| Deletion, duplication, inversion, and translocation |
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Term
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Definition
| Loss of a piece of a chromosomal segment. The impact of this varies depending on what segment was lost. |
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Term
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Definition
| Repeat of a chromosomal segment. The impact varies, but usually mild |
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Term
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Definition
| Reverse of a chromosomal segment within a chromosome. The impact can vary |
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Term
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Definition
| Crossing over in non homologous chromosomes. Usually very bad. |
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Term
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Definition
| A genetic phenomenon by which certain genes are expressed in a parent-of-origin-specific manner. For example, if a gene is inherited from a father, it might have one effect, and if that same gene is inherited from a mother, it might have a completely different effect. |
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Term
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Definition
| The stage in a cell's life cycle in which the cell begins to divide. It is composed of four stages: prophase, Prometaphase, metaphase, anaphase, and telophase. |
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Definition
| The stage in a cell's life cycle that the cell grows and copies DNA. It is the stage before mitosis, and comprises most of the cell's life cycle. |
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Definition
| The first phase of Mitosis. In this phase, the chromosomes of a cell condense, the nuclear envelope begins to break down, and the mitotic spindle begins to form. |
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Term
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Definition
| Also called "late prophase", this is the second phase of mitosis. In this phase, the chromosomes begin to migrate towards the cell equator, and two mitotic spindles, fully formed, arrive at the poles of the cell. |
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Term
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Definition
| "Packaging" filled with DNA molecules. Humans have 2 sets of 23 chromosomes, one from each parent. During mitosis, the chromosomes are joined at the center. This double-jointed form is also called a chromosome. |
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Term
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Definition
| A cell with only one copy of each chromosome. This is not us. |
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Term
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Definition
| A cell with two copy of each chromosome. This is us. |
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Term
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Definition
| Reproductive cells, produced in meiosis, with only 23 chromosomes. Also known as "sperm" and "egg" cells. |
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Term
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Definition
| The third phase of mitosis. In this phase, the chromosomes have assembled at the cell equator, the centromeres have reached the poles of the cells, and the chromosomes have attached to the mitotic spindle at their centromeres. |
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Term
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Definition
| The junction point of two chromosomes during mitosis and meiosis |
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Term
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Definition
| The main microtubule organizing center, creating the mitotic spindle in mitosis and meiosis. |
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Term
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Definition
| The fourth stage of mitosis. In this stage, the chromosomes are pulled apart from one another by the mitotic spindle, forming two seperate daughter chromosomes. The chromosomes are pulled to opposite poles of the cells. |
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Term
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Definition
| The "splitting point" of two cells in animal cells during cytokinesis of mitosis and meiosis |
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Term
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Definition
| The fifth and final stage of mitosis. In this stage, the fragments of a new nuclear envelope begin to form around the chromosomes, which in turn begin to decompress. |
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Term
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Definition
| While not technically a part of meiosis, this stage is nonetheless very important in cell division. It is in this phase that the cell officially splits into two (hopefully) genetically identical cells. |
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Term
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Definition
| Literally "division in half", this is a form of asexual reproduction in prokaryotes using only mitosis. |
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Term
| Cell cycle control system |
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Definition
| A series of "checkpoints" in a cell's life cycle that makes sure that there were no errors in any of the cell's growth. These are used to prevent cells with genetic disorders from reproducing. |
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Term
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Definition
| A kinase that prevents the cell from continuing its life cycle if it has not done what it's supposed to (see Cell cycle control system). These only work when attached to a protein cyclin (hence the name). |
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Term
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Definition
| A descriptor to describe a cancerous tumor that remains at its original site. |
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Term
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Definition
| A descriptor to describe a cancerous tumor that does not remain at its original site. These tumors can impair the functions of an organism, and even cause death. |
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Term
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Definition
| A term for the chromosomes used to determine gender; the X and Y chromosomes. |
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Term
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Definition
| A chromosome that is not a sex chromosome. |
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Term
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Definition
| Chromosome pairs of approximately the same length, centromere position, and staining pattern. |
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Term
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Definition
| The number and appearance of chromosomes in the nucleus of an eukaryotic cell. |
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Term
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Definition
| Any biological cell forming the body of an organism; that is, in a multicellular organism, any cell other than a gamete, germ cell, gametocyte or undifferentiated stem cell. |
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Term
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Definition
| The pairing of two homologous chromosomes during meiosis to form a tetrad |
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Term
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Definition
| Sometimes, a tetrad can condense so hard that the homologous chromosomes will lose a chromosome segment, which will be replaced by the homologoous segment of the other chromosome. THIS IS NORMAL, GOOD and helps to increase genetic variation. |
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Term
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Definition
| Four synapsed chromatids (two chromosomes) that become visible during prophase 1 of meiosis and seperate in anaphase 1 of meiosis. |
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Term
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Definition
| The site of crossing over in a tetrad during meiosis |
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Term
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Definition
| The first phase of meiosis. This phase is very similar to prophase of mitosis, but instead of forming regular chromosomes, the chromosomes form homologous pairs called tetrads |
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Term
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Definition
| The second phase of meiosis. In this phase, the tetrads line up at the equator and the microtubules attach to the centromere of the duplicated chromosomes, but not two to each (i.e. the chromosomes are not pulled apart, only the tetrad) |
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Term
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Definition
| The third phase of meiosis. In this phase the duplicated chromosomes move to the cell poles. the sister chromosomes remain attached, but the tetrad has broken up. |
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