AP Biology Chapter 13: Meiosis and Sexual Life Cycles – Flashcards
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heredity
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the transmission of traits from one generation to the next
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variation
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offspring differ somewhat in appearance from parents and siblings
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genetics
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the study of heredity and heredity variation
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genes
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parents endow their offspring with this coded information in the form of heredity units
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gametes
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these reproductive cells are the vehicles that transmit genes from one generation to the next. unite and pass on during fertilization
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locus
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a gene's specific location along the length of a chromosome
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asexual reproduction
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produce exact copies of themselves this way. a single individual is the sole parent and passes copies of all its genes to its offspring
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clone
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an individual that reproduces asexually creates a group of genetically identical individuals
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sexual reproduction
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two parents give rise to offspring that have unique combinations of genes inherited from the two parents. variations on a common theme of family inheritance
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karyotype
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the picture of chromosomes arranged in pairs, starting with the longest chromosomes
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homologous chromosomes
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the two chromosomes composing a pair that have the same length, centromere position, and staining pattern
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sex chromosomes
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X and Y, determine the sex
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autosomes
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non sex chromosomes
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diploid cell
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cells with two chromosome sets, in humans the total is 46
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haploid cell
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cell with one chromosome set, in humans 23
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fertilization
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the union of gametes, the egg and sperm
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zygote
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the resulting fertilized egg
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animal life cycle
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gametes are only haploid cells. meiosis occurs during the production of gametes, which undergo no further cell division prior to fertilization. the diploid zygote divides by mitosis producing a mulitcellular organism that is diploid
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alternation of generations
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exhibited by plants and some species of algae. includes both diploid and haploid multicellular stages. multicellular diploid stage is the sporophyte. meiosis in the sporophyte produces the haploid spores which gives rise to a haploid gametophyte
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sporophyte
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the multicellular diploid stage of the alternation of generations. goes through meiosis to produce spores
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spores
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haploid cells that give rise to mulitcellular individual without fusing with another cell. divides mitotically to generate a multicellular haploid stage called gametophyte
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gametophyte
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haploid, comes from spores, makes gametes by mitosis. fertilization here results in the zygote
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fungi and protist life cycle
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gametes fuse and form a diploid zygote, meiosis occurs without a diploid offspring developing. meiosis produces not gametes but haploid cells that then divide by mitosis and give rise to a haploid multicellular adult. the haploid adult carries out mitosis producing cells that develop into gametes.
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meiosis I
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first consecutive cell division
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meiosis II
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second consecutive cell division
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interphase
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-chromosomes duplicate during S phase but remain uncondensed. -each replicated chromosome consists of two genetically identical sister chromatids connected at the centromere. -the centrosome replicates, forming two centromeres
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prophase I
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-90 percent of the time for meiosis. -chromosomes begin to condense. -homologous chromosomes loosely pair along their lengths, precicely aligned gene by gene. -in crossing over. the DNA molecules in nonsi
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prophase I
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-in crossing over the DNA molecules in nonsister chromatids break at corresponding places and then rejoin to the other's DNA
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prophase I
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-in synapsis, a protein structure called thje synaptonemal complex forms between homologues, holding them together tightly along their lengths
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prophase I
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-the synaptonemal complex disassembles in the late part of this stage, and each chromosome pair becomes visible in the microscope of as a tetrad, a group of four chromatids.
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prophase I
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-each tetrad has one or more chiasmata holding the homologues together until anaphase I
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chiasmata
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criss crossed regions where crossing over has occured.
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prophase I
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-the movement of centrosomes, formation of spindle microtubules, breakdown of the nuclear envelope, and dispersal of nucleoli occur as in mitosis
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prophase I
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-late in this stage the kinetochores of each homologue attach to microtubules from one pole or the other. the homologous pairs then move toward the metaphase plate.
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metaphase I
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-the pairs of homologous chromosomes, in the form of tetrads, are now arranged on the metaphase plate, with one chromosome of each pair facing each pole, with one chromosome of each pair facing each pole
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metaphase I
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-both chromatids of a homologue are attached to kinetochore microtubules from one pole; those of the other homologoue are attached to microtubules of the other pole
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anaphase I
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-the chromosomes move toward the poles, guided by the spindle apparatus
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anaphase I
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-sister chromatids remain attached at the centromere and move as a single unit toward the same pole
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anaphase I
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-homologous chromosomes, each composed of two sister chromatids, move toward opposite poles.
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telophase I
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-at the beginning of this stage, each half of the cell has a complete haploid set of chromosomes, but each chromosome is still composed of two sister chromatids
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cytokinesis
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-this forms in conjunction with telophase I, forming two haploid daughter cells
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cytokinesis
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-in animal cells a cleavage furrow forms, in plant cells, a cell wall
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cytokinesis
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in some species the chromosomes decondense, and the nuclear envelope reforms
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prophase II
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-a spindle apparatus forms
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prophase II
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-late in this phase, chromosomes each still composed of 2 chromatids, move toward the metaphase II plate
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metaphase II
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-the chromosomes are positioned on the metaphase plate as in mitosis
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metaphase II
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-because of crossing over in meiosis I, the two sister chromatids of each chromosome are not genetically identical
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metaphase II
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-the kinetochores of sister chromatids are attached to microtubules extending from opposite poles
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anaphase II
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-the centromeres of each chromosome finally separate, and the sister chromatids fall apart
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anaphase II
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the sister chromatids of each chromosome now move as two individual chromosomes toward opposite poles
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telophase II
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-nuclei form, the chromosomes begin decondensing, and cytokinesis begins
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cytokinesis
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-the meiotic division of one parent cell produces four daughters, each with a haploid set of chromosomes
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cytokinesis
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-each of the 4 daughter cells is genetically distinct from the other daughter cells and from the parent cell
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synapsis
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duplicated homologous chromosomes line up and become physically connected along their lengths by a zipperlike protein structure
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crossing over
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genetic rearrangement between nonsister chromatids, swap parts
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tetrad
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the four chromatids of a homologous pair are visible in the light microscope as this. FOUR
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recombiant chromosomes
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produced by crossing over, individual chromosomes that carry genes derived from two different parents
