L5 - Meiosis and Recombination PDF

Summary Genetic variety and diversity homologous recombinations independent assortment: each alleles lines up how they want random fertilization: depending on which sperm fertilizers which egg makes unique zygote Mitosis: one division Two daughter cells Identical cells 2 sets of uniqu...

Summary Genetic variety and diversity homologous recombinations independent assortment: each alleles lines up how they want random fertilization: depending on which sperm fertilizers which egg makes unique zygote Mitosis: one division Two daughter cells Identical cells 2 sets of unique chromosomes Occurs in body cells Meiosis: Two division event four cells non genetically identical I set of uniques chromosomes occurs in ovaries and testes Meiosis I - reductional Meiosis I - equational Recombination = new combinations of alleles Linked genes if on same chromosome more likely to be inherited together high chance of cross-over Aneuploidy unequal number of allel division: some chromosomal mutations can lead to abnormal numbers of in chromosones present in gametes after meiosis more chromosomes - n + 1 not enough - n-1 meiosis I - all chromosoug are aneuploidy meiosis I - better because we will end up with Two normal gametes Trisomy 21 - downsyndrome Double y - super male Nondisjunctional combinations: better than getting an extra or not enough chromosomes can live normal with changes in X and y most the time reproductive organs are targeted for mutations Cycle 2 Meiosis and Recombination Genetic variety and diversity Homologous recombinations Independent assortment: each alleles lines up how the want to random fertilization: which egg get fertilized but which sperm  2n - diploid N - haploid One division event & 2n Two daughter cells Identical cells 2 sets of unique Two division event chromosomes (2n - diploid ) Four cells Occurs in Non genetically identical 2n 1 set of unique chromosomes (n - haploid) Occurs in the ovaries and testes (sex MI 2n organs) contain gem cells that become haploid gamete N Zu 2n M U  Meiosis I is reductional Polity is reduced from 2 to 1 Centroment Independent assortment ⑧J-chromosomeChr. Haploid (n) (sister)maid Diploid (2n) 2 4 D B Cb R 2 Site of recombination Prophase I Metaphase I Anaphase I Telophase I + cytokinesis  Meiosis II is equational Haploid stays a haploid - we need to divide to get on genome in each cell In in Prophase II Metaphase II Anaphase II Telophase II + cytokinesis Recombination creates new combinations of alleles. Red and red wont cross Blue and blue wont cross All genetically different due to cross over Creates haploid cell with different alleles All sister chromatids have the ability to cross over but not all them will  Linked Genes During cross over all genes can go whatever way Which two genes are more likely to be inherited together? Linked - inherited together But not linked to gene C High chance of crossover happening here If on different gene chromosomes not inherited together Chiasma If closer high possibility of being inherited together Gene A 1 Gene B 2 3 4 Gene C  SimuText Simulation Results of random crossing over in 20 pairs of chromosomes: Chance that gene A and C alleles inherited together = 53% Chance that gene A and B alleles inherited together = 93%  Independent Assortment is Unpredictable 1. If lined up this way you get these gametes 2.  Random Fertilization Zygotes bring DNA from two different parents into the same cell. Depending on which haploid cell is picked with haploid make a unique combination of zygote (n) haploid Diploid (n) (2n)  Aneuploidy Some chromosomal mutations can lead to abnormal numbers of chromosomes present in gametes after meiosis. More chromorosomes - one extra n + 1 Not enough - N-1 Non-disjunction during the 1st meiotic division When chromosome Eu-equal number of alleles ends up in wrong all gemeted are aneuploidy (meisis 1) but if it happens in meiosis 2 it is better because we will have two normal  Aneuploidy Some chromosomal mutations can lead to abnormal numbers of chromosomes present in gametes after meiosis. Non-disjunction during the 2nd meiotic division When chromosome ends up in wrong all gemeted are aneuploidy (meisis 1) but if it happens in meiosis 2 it is better because we will have two normal gametes  Down Syndrome: Trisomy 21 During metaphasae - line up chromosomes and take a picture When females age is past 35 there start to become an abnormal life of chromosomes they start to get out of place As age of mother increases chance of downsindrome is increased Trisomy 13 (Patau Syndrome): Chromosomal disorder that causes serious problems with brain and extra fingers and toes, cleft palate and lip, and other defects. Most infants with trisomy 13 die within the first year of life. Trisomy 18 (Edwards Syndrome): Chromosomal disorder that causes severe intellectual disability and serious physical problems such as a small head, heart defects, and deafness. Most of those affected with trisomy 18 die before birth or within the first month of life. This is better than getting extra or not enough chromosomes in mitosis Can leave normal with changes in X’s and Y’s Most of the time reproductive organs are targeted for mutations or extra or not enough chromosomes. 1 in 5000 Go through life without knowing you have 1 in 2000 klinefelters 1 in 1000 Super Male: Double-Y Chromosome  Animal Life Cycle Read in textbook - will be on exam MITOSIS Gametes arise by meiosis. The zygote divides by mitosis Plant and most Fungi Life Cycle MITOSIS Gametes arise by mitosis. MITOSIS MITOSIS Spores are formed by meiosis. Some Fungi and Algae Life Cycle Gametes arise by MITOSIS mitosis. MITOSIS The zygote divides by meiosis.