Term
|
Definition
| A cross between two heterozygous organisms. Contains the information for only one allele. |
|
|
Term
|
Definition
| When a prokaryotic cell reproduces, the circular chormosome of the bacerium replicates and the cell divides in a process called binary fission. |
|
|
Term
|
Definition
| Has a compartmentalized cell structure with components bounded by intracellular membranes; can be either unicellular or multicellular. |
|
|
Term
|
Definition
| A Eukaryote has a nuclear envelope, which surrounds the genetic material to form a nucleus and separates the DNA from the other cellular content. |
|
|
Term
|
Definition
| DNA is closely associated with this special class of proteins to form tightly packed chromosomes. This complex of DNA and histone proteins is termed chromatin. |
|
|
Term
|
Definition
| In most eukaryotic cells, there are two sets of chromosomes. This is a consequence of sexual reproduciton. Each chromosome in one set has a corresponding chromosome in the other set, together constituting a homologous pair. The two chromosomes of a homologous pair are usually alike in structure and size, and each carries genetic information for the same set of hereditary characteristics (Sex chromosomes are an exception) |
|
|
Term
|
Definition
| Cells that carry two sets of genetic information |
|
|
Term
|
Definition
| A cell with a single set of chromosomes. A haploid cell has only onen copy of each gene. |
|
|
Term
|
Definition
| The natural ends, the tips, of a whole linear chromosome. They protect and stabilize the chromosome ends. |
|
|
Term
|
Definition
| Sites where DNA synthesis begins; not easily observed by microscopy |
|
|
Term
|
Definition
| In preparation for cell division, each chromosome replicates, making a copy of itself. These two initially identical copies, are called sister chromatids. They are held together at the centromere. Each sister chromatid consists of a single molecule of DNA. |
|
|
Term
|
Definition
| Patau Syndrome. Extreme malformation of organ systems. Survival less than 3 months. |
|
|
Term
|
Definition
| The life story of a cell, the stages through which it passes from one division to the next. This process is critical to genetics because, through the cell cycle, the gentic instructions for all characterisitcs are passed from parent to daughter cell. A new cycle begins after a cell has divided and produced two new cells. Each new cell metabolizes, grows, and develops. At the end of its cycle, the cell divides to produce two cells, which can then undergo additional cell cycles. Progression through the cell cycle is regulated at key transitions points called checkpoints |
|
|
Term
Interphase
(What is it? What are the stages of interphase?) |
|
Definition
First stage of cell cylce. The period between cell divisions, in which teh cell grows, develops, and functions. In interphase, critical events necessary for cell division take place.
DNA is being synthesized, RNA and proteins are being produced, and hundreds of biochemical reactions necessary for cellular functions are taking place. Interphase includes several checkpoints. These checkpoints insure that all cellular components are present and in good working order before the cell proceeds to the next stage.
1. G1
2. S Phase
3. G2 |
|
|
Term
|
Definition
| Occurs during interphase. Gap 1, the cell grows and the proteins necessary for cell division are synthesized. At the end of G1 a critical point called the G1/S checkpoint holds the cell in G1 until the cell has all of the enzymes necessary for replication of DNA. Before reaching teh G1/S checkpoint, cells may exit fromteh active cycle in response to regulatory signals and pass into a non-dividing phase called G0. |
|
|
Term
|
Definition
| Occurs during interphase. DNA synthesis occurs. Each chromosome duplicates. After the S Phase, each chromosome is composed of two chromatids. |
|
|
Term
|
Definition
| Occurs during Interphase. Gap 2, several additional biochemical events necessary for cell division take place. The important G2/M checkpoint is reached near the end of G2. This checkpoint is passed only if the cell's DNA is undamaged. |
|
|
Term
M-Phase
(What is it? What are the stages?) |
|
Definition
The Mitotic Phase. The period of active cell division. Includes mitosis and Cytokinesis, or cytoplasmic division.
Stagese include: Prophase, Metaphase, Anaphase, Telophase (cytokinesis) |
|
|
Term
|
Definition
| Division of the cytoplasm of the two daughter cells after mitosis. Sometimes occurs simultaneously with Telophase. |
|
|
Term
|
Definition
| Occurs during Prophase I. The chromosomes continue to condense; homologous chromosomes pair up and bein synapsis, a very close pairing association. Each homologous pair of synapsed chromosomes consists of four chromatids called a tetrad or bivalent. |
|
|
Term
|
Definition
| Takes place in Prophase I and refers to the exchange of genes between nonsister chromatids. After crossing over takes place teh sister chromatids may no longer be identical. |
|
|
Term
|
Definition
| A protein that holds the chromatids together (in homologous chromosomes). Cohesion can be broken by the enzyme separase. In anaphase I, cohesion along the chromosome arms is broken, allowing the two homologs to separate. However, cohesion at the centromere is protected by a protein called shugoshin, this prevents the separation of teh two sister chromatids (until Anaphase II). |
|
|
Term
|
Definition
Production of gametes in a male animal, this takes place in the testes. Their diploid primordial germ cells divide mitotically to produce diploid cells called spermatogenia. Each spermatogenium can undergo repeated rounds of mitosis, giving rise to numerous additional spermatogonia. Alternatively, a spermatogonium can initiate meiosis and enter into prophase I. Now called a Primary Spermatocyte, each Primary spermatocyte completes meiosis I, giving rise to two haploid secondary spermatocytes that then undergo meiosis II with each producing two haploid spermatids. Thus, each primary spermatocyte produces a total of four haploid spermatids, which mature and develop into sperm.
|
|
|
Term
|
Definition
The production of gametes in a female animal. Within the ovaries, diploid primordial germ cells divide mitotically to produce oogonia. Like spermatogonia, oogonia can undergo repeated round so f mitosis or they can enter into meiosis. When they enter prophase I, these still-diploid cells are called primary oocytes. Each primary oocyte completes meiosis I and divides. In oogenesis cytokinesis is unequal: most of the cytoplasm is allocated to one of the two haploid cells, the secondary oocyte. The smaller cell, which contains half of the chromosomes but only a small part of the cytoplasm is called the first polar body; it may or may not divide further. The secondary oocyte completes meiosis II, and, again, cytokinesis is unequal—most of the cytoplasm passes into on the cells. The larger cell , which acquires most of the cytoplasm is the ovum, the mature female gamete. The smaller cell is the second polar body. Only the ovum is capable of being fertilized, and the polar bodies usually disintegrate. Oogenesis, then, produces a single mature games from each primary oocyte. |
|
|
Term
| What are the four types of Chromosomes based on Centromere position? |
|
Definition
1. Metacentric: Centromere is essentially midway between the sister chromatids. The p and q arms are basically equal in length.
2. Submetacentric: The centromere is slightly higher than on a metacetric chromosome. The p arm is slightly shorter than the q arm.
3. Acrocentric: The centromere is almost at the very top of the chromosome. The p arm is very short and the q arm is very long.
4. Telocentric: The centromere is at the very top of the chromosome, at the telomere. The p arm is basically nonexistent and the q arm is very long. |
|
|
Term
|
Definition
Process in which chromosomes of a eukaryotic cell divide to give rise to haploid reproductive cells. Consists of two division: meiosis I and meiosis II.
Meiosis I: First phase of meiosis. In meiosis I, chromosome number is reduced by half.
Meiosis II: Second phase of meiosis. Events in meiosis II are essentially those in mitosis. |
|
|
Term
|
Definition
| Fusion of gametes (sex cells) to form a zygote. |
|
|
Term
|
Definition
| Difference from the wild type in teh number or structure of one or more chromosomes; often affects many genes and has large phenotypic effects |
|
|
Term
|
Definition
| Change from the wild type in the structure of one or more chromosomes. |
|
|
Term
|
Definition
| Mutation that doubles a segment of a chromosome. |
|
|
Term
|
Definition
| Loss of a chromosome segment. |
|
|
Term
|
Definition
| Expression of a normallly recessive allele owing to a deletion on the homologous chromosome. |
|
|
Term
|
Definition
| Must be present in two copies for normal function. If one copy of teh gene is missing, a mutant phenotype is produced. |
|
|
Term
|
Definition
rearrangement in which a segment of a chromosome has been inverted 180 degrees.
Pericentric- Includes the centromere
Paracentric- Excludes the centromere |
|
|
Term
|
Definition
| Dependence of the expression of a gene on the gene's location in the genome. |
|
|
Term
|
Definition
| Movement of a chromosome segment to a nonhomologous chromosome or to a region within the same chromosome. Also, movement of a ribosome along mRNA in teh course of translation. |
|
|
Term
| Nonreciprocal translocation |
|
Definition
| Movement of a chromosome segment to a nonhomologous chromosome or region without any (or with unequal) reciprocal exchange of segments. |
|
|
Term
|
Definition
| Reciprocal exchange of segments between two nonhomologous chromosomes. |
|
|
Term
| Robertsonian Translocation |
|
Definition
| Translocation in which the long arms (q arms) of two acrocentric chromosomes become joined to a common centromere, resulting in a chromosome with two long arms and usually another chromosome with two short arms. |
|
|
Term
|
Definition
| Change from the wild type in the number of (individual) chromosomes; most often an increase or decrease of one or more chromosomes. |
|
|
Term
|
Definition
| Possesion of more than two haploid sets of chromosomes. |
|
|
Term
|
Definition
| Absence of both chromosomes in a homologous pair (2n-2) |
|
|
Term
|
Definition
| Absence of one of the chromosomes of a homologous pair |
|
|
Term
|
Definition
Presence of an additional copy of a chromosome (2n+1).
One additional member of a homologous pair. Almost always lethal. |
|
|
Term
|
Definition
| Possession of three haploid sets of chromosomes. (3n) |
|
|
Term
|
Definition
| Presence of two extra copies of a chromosome (2n+2) |
|
|
Term
|
Definition
| Possession of four haploid sets of a chromosome (4n) |
|
|
Term
|
Definition
Trisomy 21
Characterized by variable degrees of mental retardation, characteristic facial features, some retardation of growth and development, and an increased incidence of heart defects, leukemia, and other abnormalities; caused by teh duplication of all or part of chromosome 21 1/660 live births |
|
|
Term
|
Definition
| Individual organism heterozygous for a chromosome translocation. |
|
|
Term
|
Definition
| Human condition in which cells contain a single X chromosome and no Y chromosome (XO). Persons with Turner's Syndrome are female in appearance but do not undergo puberty and have poorly developed female secondary sex characteristics; most are sterile but have normal intelligence. |
|
|
Term
|
Definition
| Human condition in which cells contain one or more Y chromosomes along with multiple X chromosomes (most commonly XXY but may also be XXXY, XXXXY, or XXYY). Persons with klinefelter syndrome are male in appearance but frequently possess small testes, some breast enlargement, and reduced facial and pubic hair; often taller than normal and sterile, most have normal intelligence. |
|
|
Term
|
Definition
| Inheritance of both chromosomes of a homologous pair from a signle parent. |
|
|
Term
|
Definition
| Edward Syndrome. Lethal, 1/8000 live births. Slow growth and multiple abnormalities (i.e., Clefts, clutched fist, small face, small chest, low ears) Survival 2-4 months |
|
|
Term
|
Definition
| Only one X is in an active state; all others are inactive & condensed into Barr bodies |
|
|
