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genetics chapter 3
chromosomes and inheritance
| Question | Answer |
|---|---|
| chromosomes | dense, threadlike bodies that contain DNA |
| homologs/homologous chromosomes | chromosomes that match in size, shape, and banding patterns |
| chromatids | rod of a chromosome |
| chromatin | complex of DNA and proteins in eukaryotic cells |
| centromeres | region of a chromosome that links 2 sister chromatids together |
| mitosis | somatic cell division that results in 2 daughter cells containing the same number and type of chromosomes as the parent cell |
| meiosis | cell division that generates egg/sperm cells and contains half the number of chromosomes found in somatic cells |
| zygote | fertilized egg cell, diploid |
| haploid | n; cell containing 23 chromosomes |
| diploid | 2n; cell containing 46 chromosomes, 23 pairs |
| somatic cells | diploid body cells |
| gametes | mature haploid germ cell |
| germ-line cells | cells that produce sperm and egg |
| karyotype | micrographs of stained chromosomes in homologous pairs of decreasing size |
| metacentric chromosomes | centromere is more or less in the middle |
| acrocentric chromosomes | centromere is close to one end |
| what are sex chromosomes? | pair of chromosomes that determine an individual's biological sex |
| how do sex chromosomes differ between different species? | they can differ in number, combination, and sex they determine |
| what are autosomes? | 44 chromosomes in matching pairs (non-sex chromosomes) |
| does the number in autosomes differ between different species? | yes. each species has a different number of chromosomes but it does not determine the complexity or size of the organism |
| what is the cell cycle? | repeated pattern of cell growth followed by division |
| different phases of the cell cycle | Interphase (G1, S, G2) and mitosis |
| G1 phase | it is a period where chromosomes are neither duplicating nor dividing; most of the cell's growth occurs in this phase |
| S phase | the cell duplicates its genetic material by synthesizing its DNA; each chromosome doubles to produce two identical sister chromatids joined together |
| G2 phase | interval between chromosome duplication and mitosis, growth may occur but proteins essential for mitosis are synthesized |
| what also occurs during interphase? | an array of microtubules become visible outside the nucleus; those microtubules radiate out into the cytoplasm from the centrosome located near the nucleus |
| phases of mitosis | prophase, prometaphase, metaphase, anaphase, and telophase |
| prophase | condensation of chromosomes from chromatin initiates prophase; darkly staining nucleoli breaks down/ disappears and ribosome manufacture ceases; replicated chromosomes move apart, propelled by forces exerted from microtubules |
| prometaphase | begins with the breakdown of the nuclear envelope, which allows microtubules to invade the nucleus; chromosomes attach to microtubules through the kinetichore; three different types of microtubule fibers together form the mitotic spindle |
| metaphase | chromosomes move towards an imaginary equator |
| anaphase | begins with nearly simultaneous severing of the centromeric connections between sister chromatids of all chromosomes; kinetichore microtubules shorten; |
| telophase | spindle fibers disperse; nuclear envelope forms around each group of chromatids; nucleoli reappear; chromosomes decondense into chromatin |
| cytokinesis | parent cell separates into 2 daughter cells with identical nuclei; cytoplasmic division |
| microtubules | hollow rigid tubes in eukaryotic cells that form the mitotic spindle and radiate from the centrosome |
| kinetochore | structure in the centromere region that connects to the microtubules of the spindle |
| polar microtubules | microtubules from the centrosome that are directed towards the middle of the cell |
| astral microtubules | microtubules that extend out from the centrosome towards the cell's periphery |
| how is mitosis regulated and controlled? | enzymes at regulatory checkpoints that evaluate the results of the previous steps and determine if the cell is good to proceed to the next |
| what is the difference between meiosis I, meiosis II, and mitosis? | mitosis results in two identical diploid daughter cells, mitosis I results in 2 haploid cells, and meiosis II results in 4 haploid daughter cells |
| overview of meiosis I | sister chromatids remain together throughout meiosis I; homologous chromosomes pair together and go through recombination, then are pulled apart into 2 separate daughter cells |
| overview of meiosis II | chromosome count is reduced by half than in meiosis I; chromosomes line up at center and the sister chromatids are then pulled apart to opposite ends of the cell, to which the cells divide and form 4 daughter cells. |
| crossing over | process in which genetic material is crossed over between homologous chromosomes at the chiasma in meiosis I |
| recombination | exchange of genetic material between molecules that results in new combinations of alleles |
| chiasmata | intervals along the length of homologous chromosomes that represent where crossing over occurred |
| how is genetic diversity accomplished in meiosis? | chance governs which parental homologs travel to different poles of the cell during meiosis I, different gametes carry different mix of maternal and paternal chromosomes; reshuffling of genetic material in meiosis I |
| how does meiosis explain Mendel's observations? | each cell contains two copies of each chromosome; law of independent assortment |
Created by:
angievelasco