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Meiosis basics

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kcurcin's version from 2017-04-03 16:13

Section 1

Question Answer
what are allelesdifferent versions of the same gene
what is a tetrada pair of homologous chromosomes
when does recombination occurin prophase 1, when the homologous chromosomes are paired
when does the cell become haploidafter the first meiotic division
are all gametes alleles identical?no, each has a different mix of alleles
when are homologous pairs of chromosomes replicatedpre meiotic interphase
what is gene linkagegenes that are close together so they are less likely to be separated during crossing over
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Section 2

Question Answer
what happens in prophase 1/pro-metaphase 1duplicated chromosomes condense, homologous chromosomes pair and exchange alleles while spindle fibres attach to each pair
what happens during metaphase 1each maternal chromosome (a pair of sister chromatids) and its paternal homologue align RANDOMLY at the spindle midpoint
what happens during anaphase 1homologous chromosomes, each as a pair of sister chromatids, separate and move to opposite poles
what happens during telophase 1two haploid (n) nuclei form
what happens during prophase 2/pro-metaphase 2each pair of sister chromatids attaches to a newly formed spindle
what happens during metaphase 2chromosomes line up individually at the spindle midpoint
what happens during anaphase 2sister chromatids of each chromosome are pulled apart to opposite poles
what happens during telophase 2four haploid (n) nuclei form, cytokinesis produces 4 haploid cells
memorize

Section 3

Question Answer
what is independent assortmentthe homologous chromosomes line up randomly in metaphase 1 (not one side is all paternal other is all maternal)
what is random segregationsister chromatids are also divided completely randomly and independent of one another
how many possible combinations are there2n organism has 2^n combinations, where n= the haploid chromosomes number
what are the female and male gametes calledegg and sperm
what is non-disjunction in meiosis 1when homologous chromosomes fail to separate during anaphase 1, result in 2 cells with n-1 and two cells with n+1
what is non-disjunctions in meiosis 2when sister chromatids don't pull apart during anaphase 2, results in 2 with normal n and one with n+1 and other with n-1
what is a euploid normal number of chromosomes
what is a aneuploidextra or missing chromosomes
what is polyploidextra sets of all chromosomes, spindle fails during mitosis in cells leading to germ cells
what is down syndromean aneuploidy with an extra 21 chromosome
how is polyploidy useful in plantssource of variability
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Section 4

Question Answer
what is deletion whole gene is gone and lost from chromosome
what is duplicationa duplicated segment is inserted into homologous chromosome
what is a beneficial trait that arose through duplicationcolour vision, there was a duplicated opsin
what is translocationa broken segment is attached to a non-homologous chromosome
what disease is linked to duplicationcertain leukemias
what is inversionorder is flipped resulting in a whole new set of codons
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