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ap bio unit 5 part 1
mitosis/meiosis
| Term | Definition |
|---|---|
| centromere | attaches two chromosomes together |
| a single-chromatid chromosome | produced at the end of mitosis when double chromatid chromosomes separate and during the second division of meiosis |
| when replication is completed.... | each double helix is composed of an old parental strand and a new strand; each double helix is identical to the other one (semi-conservative replication) |
| cell life is not linear but rather ________ | cyclical |
| not all cells divide ex: | nerve and muscle cells in adults |
| cells divide at different _______ | rates |
| if a cell is going to divide into two daughter cells, the cell must contain... | complete sets of the original DNA |
| interphase includes the | G1, S, and G2 phases; when semi-conservative replication takes place |
| mitotic phase includes: | prophase, metaphase, anaphase, and telophase |
| G1: | "normal" phase the growing cell is performing normal functions chromosomes are extended genes are being transcribed |
| S (synthesis): | if the cell is going to divide it is in this phase where DNA replicates |
| G2: | the chromosomes begin to condense |
| interphase is NOT technically part of ________ | mitosis |
| prophase (early) | centrioles begin to move apart chromosomes begin to appear as condensed threads nucleolus begins to disappear |
| prophase (middle) | centrioles move farther apart spindle fibers form between centrioles/centromeres |
| prophase (late) | centrioles go to opposite sides of nucleus spindle fibers form across chromosomes |
| metaphase | nuclear membrane disappears chromosomes line up in center of cell (metaphase plate) |
| anaphase | centromeres split and begin moving to opposite poles cytokinesis begins |
| telophase | nuclear membrane appears chromosomes begin to extend nucleolus appears mitosis is complete |
| cytokinesis | the division of cytoplasm animal cells: cleavage furrow plant cells: cell plate forms |
| sometimes in algae, fungi and some plants cytokinesis does NOT follow mitosis | results in cells with many nuclei |
| meiosis has how many divisions? | 2 |
| zygote = | fertilized egg |
| in order to form gametes, ________ must take place | meiosis |
| meiosis occurs in the ______ | gonads (testicles/ovaries) |
| meiosis first begins... | at puberty (women)/at birth |
| when does meiosis stop? | menopause (women) death (men) |
| prophase I: | homologous chromosomes synapse (pair up and become shorter/thicker) after they pair up they are called a tetrad |
| metaphase I: | homologous chromosomes move to the equatorial plane as a unit |
| anaphase I: | double-stranded chromosomes move apart to opposite poles |
| telophase I: | two daughter cells are formed (each with 23 chromosomes |
| interkinesis: | NO replication of genetic material |
| prophase II: | chromosomes condense |
| metaphase II: | chromosomes move to equatorial plane centromeres attach to spindle fibers |
| anaphase II: | spindle fibers pull chromosomes apart |
| telophase II: | final product = four daughter cells each with 23 single chromatid chromosomes |
| crossing over occurs... | during prophase I of meiosis |
| crossing over: | -chromosomes shorten/thicken -homologous chromosomes begin moving toward each other -axial protein gather the DNA of chromatids into organized loops and holds the chromatids together - homologous chromosomes synapse -recombinant nodules appear/clip |
| crossing over increases _____ ____________ | genetic variability |
| homologous chromosomes: | contain the same genes but maybe different alleles |
| allele: | different versions of a gene |
| human cells have... | 23 pairs of homologous chromosomes |
| autosomes | 22 pairs of chromosomes that code for genes that are non sex determining factors |
| sex chromosomes | 1 pair that determine a person's sex (XY) |
| diploid (2n) | homologous chromosomes are still in the SAME cell |
| haploid (1n) | homologous chromosome pair are NOT in the same cell |
| only cells that undergo meiosis become haploid | true |
| all body cells (somatic cells) are diploid | true |
| once cells are haploid.... | they remain haploid until they die (unless they are the lucky ones that fertilize) |
| first division of meiosis | separates the homologous pairs, reducing the number of chromosomes in each cell by half |
| 2nd division of meiosis | separates the chromosomes; chromatids are split into each cell (similar to mitosis) |
| polar microtubules appear in | prophase |
| chromosomes migrate to the poles in | anaphase |
| centromeres divide in | anaphase |
| centrioles move to poles in | prophase |
| chromosomes reach the poles in | telophase |
| G1, S, and G2 stages occur in | interphase |
| nuclear membrane and nucleoli disappear in | prophase |
| chromosomal replication occurs in | interphase |
| twin-chromatid chromosomes move to the poles | 1st division of meiosis |
| cells genetically identical to the parent cell are produced only in | mitosis |
| centromeres DO NOT divide during meiosis I | true |
| centrioles are not essential for cell division | true |
| S stage = | DNA replication |
| if there are 12 single-chromatid chromosomes in G1 what is the diploid # of chromosomes? | 12 |
| cytokinesis | occurs in animal cells by a pinching in of the plasma membrane |
| if there are 12 chromosomes in a cell that has just completed meiosis, what is the diploid number of chromosomes? | 24 |
| from each primary oocyte that undergoes meiosis, the number of functional egg cells produced in | 1 |
| genetic recombination occurs during | first division of meiosis, crossing over |
| each centromere sends kinetochore microtubules toward both poles during | mitosis, and the second division of meiosis |
| zygote = | fertilized egg |
| unfertilized egg and sperm cells | have no genes turned on; do not divide |
Created by:
tpolinsky24
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