Week 10 Lecture Notes
Week 10 Lecture Notes EBIO 1210-001
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This 4 page Class Notes was uploaded by Tatiana Tabares on Thursday November 12, 2015. The Class Notes belongs to EBIO 1210-001 at University of Colorado taught by Dr. Barbara Demmig-Adams in Fall 2015. Since its upload, it has received 24 views. For similar materials see General Biology 1 in Biology at University of Colorado.
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Date Created: 11/12/15
Week 10 Lecture Notes Meiosis amp Genetic Variation iClicker Question 3 chromosomes were inherited from the child39s mom and 3 from the child39s dads Which of the following best describes a pair of homologous chromosomes Answer C Two chromosomes one inherited from each parent that have the same genes as each other Homologous chromosomes carry genes for the same inherited characters traits of an organism 2 Sexual reproduction BFertilization and Meiosis alternate Fertilization is when we go from haploid to diploid nn2n o gametes only have 23 chromosomes and are haploid My toes do mitosis my ovaries do meiosis Meiosis the division of a diploid cell leading to the eventual production of iClicker Question Answer True Meiosis halves the number of chromosomes fertilization restores the diploid number 3 A detailed look at meiosis First Cell Division Meiosis 1 We separate homologous chromosomes 2 cells with 2 sister chromosomes stuck together Looks very different to Mitosis 2nd Cell Division Meiosis 2 Sister chromatids are separated iClicker Question A cell at the very beginning of meiosis has a total of 4 chromatids What is quotnquot for the cell Answer 1 iClicker Question Week 10 Lecture Notes Meiosis amp Genetic Variation At the very beginning of meiosis a cell in your ovarytestis has 46 chromosomes At the end of meiosis 1 but before meiosis 2 this cell will have given rise to two cells that are each and each have chromosomes and chromotatids Answer Haploid 2346 Early in Meiosis l Homologous chromosomes loosely pair up alighed gene by gene In crossing over nonsister chromatids exchange homologous DNA segments 0 Importance will become apparent soon Middle of Meiosis l Pairs of homologous chromosomes line up in the middle of the cell with one chromosome facing each poe Spindle attaches to chromosomes What is MAJORLY different here from what you saw mitosis Prophase o Lined up 2 by 2 because the chromosomes are still in pairs o In mitosis they are lined up 1 by 1 because they are no longer in pairs of chromosomes 0 The way that they line up does not affect the way the next one line up example red on top blue on bottom blue on top red on bottom Anaphase o The chromosomes are being separated o Chromatids are NOT being separated sister chromatids remain a ached Meiosis II is very similar to mitosis at the end 4 daughter cells a haploid a genetically different Week 10 Lecture Notes Meiosis amp Genetic Variation Question Mitosis Meiosis Preceded by replication of Yes Yes chromosomes of rounds of cell division 1 2 of daughter cells 2 4 of chromosomes in daughter cells Same Half compared to parent cell daughter cells genetically identical to Yes No parent cell sister cells thus produced identical Yes No to one another happens in diploid cells haploid both depending diploid because you need 2 cells both or neither on organism chromosomes to split them crossing over No Yes p 200 figure 10 Summary of diff and similarities of Mitosis and Meiosis 4 Sources of genetic variation Same gene different Alleles The behavior of chromosomes during meiosis and fertilization reshuffles alleles and chromosomes ever generation Four mechanisms contribute to genetic variation in offspring of sexual reproduction o Mutations change in DNA sequence 0 Independent assortment of chromosomes Each possibility is equally likely Homologous pairs of chromosomes orient randomly during Meiosis l o Crossing over early in Meiosis l homologous chromosomes pair up gene by gene and exchange homologous segments This combines alleles that originated from two parents into a single chromosome Week 10 Lecture Notes Meiosis amp Genetic Variation 2quotn rulequot A single crossing over event gt each daughter cell is genetically unique 0 Random Fertilization 84 million possible gametes per person 70 trillion possible offspring per couple endless possibilities the number of possible chromosome sorting combos 2quotn n is the haploid number Blending inheritance traits of offspring will be an average of the traits of the parents
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