Term
|
Definition
| the reproduction of a cell to produce two new cells, in eukaryotes, this process involves nuclear division (mitosis) and cytoplasmic division (cytokinesis). |
|
|
Term
|
Definition
| the division of the cytoplasm of a dividing cell (contrast with mitosis) |
|
|
Term
|
Definition
| the stages through which a cell passes between one mitotic division and the next. includes all stages of interphase and mitosis |
|
|
Term
|
Definition
| in bacteria and viruses, the DNA molecule that contains most or all of the genetic information of the cell or virus. In eukaryotes, a structure composed of DNA and proteins that bears part of the genetic information of the cell |
|
|
Term
|
Definition
| the nucleic-acid protein complex that makes up eukaryotic chromosomes |
|
|
Term
|
Definition
| the region where sister chromatids join |
|
|
Term
|
Definition
| a paired organelle that helps organize the microtubules in animal and protist cells during nuclear division |
|
|
Term
|
Definition
| genetically identical cells or organisms produced from a common ancestor by asexual means. to produce many identical copies of a DNA sequence by its introduction into and subsequent asexual production of a cell or organism |
|
|
Term
|
Definition
| an X shaped connection between paired homologous chromosomes in prophase I of meiosis a chiasma is the visible manifestation of crossing over between homologous chromosomes |
|
|
Term
|
Definition
| the mechanism by which linked genes undergo recombination. in general, the term refers tot he reciprocal exchange of corresponding segments between two homologous chromatids |
|
|
Term
|
Definition
| initiates cell division and may originate from either inside or outside the cell |
|
|
Term
|
Definition
| the duplication of genetic material |
|
|
Term
|
Definition
| Polar microtubules interdigitate at the spindle midzone and push the spindle poles apart via motor proteins. |
|
|
Term
|
Definition
| the first stage of nuclear division, during which chromosomes condense from diffuse, threadlike material to discrete compact bodies |
|
|
Term
|
Definition
| the phase of nuclear division that begins with the disintegration of the nuclear envelope |
|
|
Term
|
Definition
| Ploidy is the number of sets of chromosomes in a cell. Usually a gamete (sperm or egg, which fuse into a single cell during the fertilization phase of sexual reproduction) carries a full set of chromosomes that includes a single copy of each chromosome, as aneuploidy generally leads to severe genetic disease in the offspring. |
|
|
Term
|
Definition
| possessing more than two entire sets of chromosomes |
|
|
Term
|
Definition
| in genetics, the separation of alleles or of homologous chromosomes, from each other during meiosis so that each of the haploid daughter nuclei produced contains one or the other member of the pair found in the diploid parent cell, but never both. This principle was articulated by Mendel as his first law |
|
|
Term
|
Definition
| in the cell cycle, the stage of interphase during which DNA is replicated |
|
|
Term
|
Definition
| each of a pair of newly replicated chromatids |
|
|
Term
|
Definition
| array of microtubules emanating from both poles of a dividing cell during mitosis and playing a role in the movement of chromosomes at nuclear division |
|
|
Term
|
Definition
| reproduction involving the union of two gametes |
|
|
Term
|
Definition
| the highly specific parallel alignment (pairing) of homologous chromosomes during the first division of meiosis. s the pairing of two homologous chromosomes that occurs during meiosis. It allows matching-up of homologous pairs prior to their segregation, and possible chromosomal crossover between them. Synapsis takes place during prophase I of meiosis. When homologous chromosomes synapse, their ends are first attached to the nuclear envelope. |
|
|
Term
|
Definition
| reproduction of a prokaryote by division of a cell into two comparable progeny cells |
|
|
Term
|
Definition
| division of a diploid nucleus to produce four haploid daughter cells. the process consists of two successive nuclear divisions with only one cycle of chromosome replication. In meiosis I homologous chromosomes separate but retain their chromatids. The second division meiosis II, is similar to mitosis, in which chromatids separate. |
|
|
Term
|
Definition
| nuclear division in eukaryotes leading to the formation of two daughter nuclei, each with a chromosome complement identical to that of the original nucleus. |
|
|
Term
|
Definition
| s a form of aneuploidy (odd number of chromosomes in a cell) with the presence of only one chromosome from a pair. monosomy occurs when only a portion of the chromosome has one copy, while the rest has two copies. |
|
|
Term
|
Definition
| segregates homologous chromosomes, which are joined as tetrads (2n, 4c), producing two haploid cells (n chromosomes, 23 in humans) which each contain chromatid pairs (1n, 2c). Because the ploidy is reduced from diploid to haploid, meiosis I is referred to as a reductional division. |
|
|
Term
|
Definition
| usually involves equational segregation, or separation of sister chromatids. Mechanically, the process is similar to mitosis, though its genetic results are fundamentally different. The end result is production of four haploid cells (n chromosomes, 23 in humans) from the two haploid cells (with n chromosomes, each consisting of two sister chromatids) produced in meiosis I. The four main steps of Meiosis II are: Prophase II, Metaphase II, Anaphase II, and Telophase II. |
|
|
Term
|
Definition
| there is a stereotyped series of consecutive events as the nucleus prepares for the division and apportionment of its replicated chromosomes. The chromosomes become visibly discernible under a light microscope; their distribution and movement define the progressive phases of mitosis. |
|
|
Term
|
Definition
| begins with the disappearance of the nuclear membrane, though sometimes this is included as the last event of prophase. The spindle, which has up until now existed in the cytoplasm can now interact with the chromosomes. Consequently, each chromatid is individually anchored to the spindle by its kinetochore. |
|
|
Term
|
Definition
| the first substage of interphase, it is the first gap ,the cell prepares for the ensuing replication of chromosomes |
|
|
Term
|
Definition
| substage of interphase, the post replication phase during which the cell readies for the upcoming mitotic events. |
|
|
Term
|
Definition
| substage of interphase, is the DNA synthesis stage of the cell cycle |
|
|
Term
|
Definition
| or 'resting phase' is a period in the cell cycle in which cells exist in a quiescent state. G0 phase is viewed as either an extended G1 phase, where the cell is neither dividing nor preparing to divide, or a distinct quiescent stage that occurs outside of the cell cycle. |
|
|
Term
|
Definition
| The G1/S transition is a stage in the cell cycle at the boundary between the G1 phase, in which the cell grows, and the S phase, during which DNA is replicated |
|
|
Term
|
Definition
| A growth factor is a naturally occurring substance capable of stimulating cellular growth, proliferation, healing, and cellular differentiation. Usually it is a protein or a steroid hormone. Growth factors are important for regulating a variety of cellular processes |
|
|
Term
|
Definition
| highly alkaline proteins found in eukaryotic cell nuclei that package and order the DNA into structural units called nucleosomes. They are the chief protein components of chromatin, acting as spools around which DNA winds, and playing a role in gene regulation. Without histones, the unwound DNA in chromosomes would be very long |
|
|
Term
|
Definition
| A nucleosome is a basic unit of DNA packaging in eukaryotes, consisting of a segment of DNA wound in sequence around eight histone protein cores. This structure is often compared to thread wrapped around a spool |
|
|
Term
|
Definition
| is a protein structure on chromatids where the spindle fibers attach during cell division to pull sister chromatids apart. Their proteins help to hold the sister chromatids together and also play a role in chromosome editing |
|
|
Term
|
Definition
| Any of the spindle microtubules that attach to the kinetochores of chromosomes by their plus ends, and maneuver the chromosomes during mitotic or meiotic chromosome segregation. |
|
|
Term
|
Definition
| s the stage of mitosis when replicated chromosomes are split and the daughter chromatids are moved to opposite poles of the cell. Chromosomes also reach their overall maximum condensation in late anaphase, to help chromosome segregation and the re-formation of the nucleus. |
|
|
Term
|
Definition
| is the final stage in both meiosis and mitosis in a eukaryotic cell. During telophase, the effects of prophase and prometaphase (the nuclear membrane and nucleolus disintegrating) are reversed. |
|
|
Term
|
Definition
| type of reproduction by which offspring arise from a single organism, and inherit the genes of that parent only; it does not involve the fusion of gametes and almost never changes the number of chromosomes. Asexual reproduction is the primary form of reproduction for single-celled organisms such as the archaebacteria, eubacteria, and protists. |
|
|
Term
|
Definition
| a mature haploid male or female germ cell that is able to unite with another of the opposite sex in sexual reproduction to form a zygote. |
|
|
Term
|
Definition
| s 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. |
|
|
Term
|
Definition
| s a pair of chromosomes that exist in diploid cells. One of the pair you inherit from your father, the other from your mother. |
|
|
Term
|
Definition
| is the existence of shared ancestry between a pair of structures, or genes, in different taxa. |
|
|
Term
|
Definition
| cells that have half the number of chromosomes (n) as diploid - i.e. a haploid cell contains only one complete set of chromosomes. |
|
|
Term
|
Definition
| contain two complete sets (2n) of chromosomes. |
|
|
Term
|
Definition
| the action or process of fertilizing an egg, female animal, or plant, involving the fusion of male and female gametes to form a zygote. |
|
|
Term
|
Definition
| is a eukaryotic cell formed by a fertilization event between two gametes. The zygote's genome is a combination of the DNA in each gamete, and contains all of the genetic information necessary to form a new individual. In multicellular organisms, the zygote is the earliest developmental stage. |
|
|
Term
|
Definition
| four homologous chromatids or 2 homologous chromosomes |
|
|
Term
|
Definition
| is a copy of another chromosome that differ just slightly. It is called recombinant since it is a form of artificial creation. |
|
|
Term
|
Definition
| principle states that the alleles for a trait separate when gametes are formed. These allele pairs are then randomly united at fertilization. |
|
|
Term
|
Definition
| is the failure of homologous chromosomes or sister chromatids to separate properly during cell division. There are three forms of nondisjunction: failure of a pair of homologous chromosomes to separate in meiosis I, failure of sister chromatids to separate during meiosis II, and failure of sister chromatids to separate during mitosis. |
|
|
Term
|
Definition
| is the presence of an abnormal number of chromosomes in a cell, for example a human cell having 45 or 47 chromosomes instead of the usual 46. It does not include a difference of one or more complete sets of chromosomes, which is called euploidy. |
|
|
Term
|
Definition
| a condition in which an extra copy of a chromosome is present in the cell nuclei, causing developmental abnormalities. |
|
|
Term
|
Definition
| (of a cell or nucleus) containing more than two homologous sets of chromosomes. |
|
|
Term
|
Definition
| is the number and appearance of chromosomes in the nucleus of a eukaryotic cell. The term is also used for the complete set of chromosomes in a species, or an individual organism. |
|
|
