Question | Answer |
Chromatin | Complex of DNA with histone and nonhistone protein. Organized into discrete bodies called chromosomes |
Karyotype | Number, size, and morphology of the chromosome set of a cell |
Genome | Chromosomes in a haploid set, or all the chromosomes in a diploid nucleus |
Centromere positions, from the middle to the end | Metacentric, submetacentric, acrocentric or sub-telocentric, telocentric |
Fundamental difference between asexual and sexual reproduction | Sexual reproduction generates variation through genetic recombination |
Cytokinesis | Division of cytoplasm |
Cell cycle | Cycle of growth, mitosis, and cell division |
Two phases of somatic cell cycle | Interphase and mitotic or dividing phase |
What occurs during interphase? | DNA replication and synthesis of protein and nucleic acid components |
What are the three stages of interphase? | G1, S, and G2 |
S period | Synthesis or replication of DNA |
G1 period | Synthesis of RNA, functional protein, and enzymes and substrates for DNA replication |
G2 period | Synthesis of structural protein, and spindle and aster protein. High energy demand |
Uses of cell division | Growth, replacement of cells, and wound healing |
Five phases of mitosis | Prophase, prometaphase, metaphase, anaphase, telophase |
Prophase | Chromatin condenses and chromosomes become visible |
Prometaphase | Chromosomes continue condensing, nuclear membrane and nucleolus break down, centrioles migrate to poles of cell, spindle fibers extend |
Metaphase | Spindle fibers pull chromosomes into line along metaphase plate. Order is important, and each sister chromatid is attached by spindle fibers to opposite poles of cell |
Anaphase | Sister chromatids split and move to opposite poles of cell |
Telophase | Fibers from centrioles break down and nuclear envelope forms around each set of chromosomes. Chromatin decondenses and nucleolus reappears |
Spindle fibers | Microtubules consisting of proteins called tubulins. Form spindle between two pairs of centrioles |
Aster | Microtubules radiating outward from centrioles |
Kinetochore microtubules | Invade nuclear space and attach to kinetochores during prometaphase |
Polar microtubules | Push against each other to move centrosomes apart |
Kinetochore | Multiprotein disk located on the centromere that is specialized to interact with spindle fibers during mitosis |
When does crossing over occur? | Prophase I of meiosis I |
Synapsis | Two homologous chromosomes come into side-by-side contact to form a bivalent |
Bivalent | Pair of homologous chromosomes held together by a complex |
Tetrad | Two pairs of chromatids, so four future chromosomes |
What are the 5 stages of prophase I | Leptonema, zygonema, pachynema, diplonema, and diakinesis |
Leptonema | Chromosomes begin to coil. Pairing of homologous chromosomes |
Zygonema | Yolk-thread. Synapsis, or the formation of the synaptonemal complex |
Synaptonemal complex | Zipper-like structure along length of chromatids |
Pachynema | Thick-thread. Synapsis is complete, crossing over occurs. Synapsis disassembles |
Diplonema | Double-thread. Homologues begin to separate. Chiasma becomes apparent |
Chiasma | Cross-shaped structure that is physical evidence of crossing over |
Diakinesis | Across thread. Chiasmata often terminalize and tetrads become clearly visible |
What are PARs? | Pseudoautosomal regions. Found on each end of Y chromosomes and allow sex chromosomes to pair and cross over even though they are not homologous. |
What happens if the PAR is deleted from the short arm of the Y chromosome? | Pairing does not occur between X and Y chromosomes, so the male is fertile |
Metaphase I of meiosis I | Tetrads align at metaphase plate |
Anaphase I of meiosis I | Homologous chromosomes are pulled apart, but sister chromatids stay together |
What do the daughter cells of meiosis I contain? | One of each of the homologous chromosomes. Sister chromatids are not identical |
What does meiosis II result in? | Four unidentical haploid daughter cells |
What does spermatogenisis result in? | Four spermatids that develop into spermatozoa |
What does oogenisis result in? | One ovum and three polar bodies |
Gametophyte | Haploid plant stage in which gametes are produced by meiosis (sexual) |
Sporophyte | Diploid plant stage in which haploid spores are produced by mitosis (asexual) |
Pistil | Female part of a flower. Includes stigma, style, and ovary |
Stamen | Male part of a flower. Includes anther and filament |
Megasporogenisis | Meiosis in female part of the flower that produces a megaspore |
Megagametophyte | Cell with eight identical haploid nuclei in a common cytoplasm. Produced by megaspore undergoing three successive rounds of nuclear mitotic divisions |
Embryo sac | Entire seven-celled megagametophyte structure. One cell becomes the egg |
Microsporogenisis | Meiosis in male part of the flower that produces pollen grains |
Process of microsporogenisis | Anther>four pollen sacs>diploid microspore mother cells>four haploid microspores (pollen) |
Significance of sex | Generate genetic diversity through independent assortment, crossing over, and random fertilization |