BIOL 1st Edition Lecture 20 Outline of Last Lecture I DNA and Cell Activities II Transcription III Translation Outline of Current Lecture I The Cell Cycle II Meiosis and Sexual Cell Cycles III Mendel and Chromosomes IV The Molecular Basis of Inheritance Current Lecture Exam 3 Review I The Cell Cycle Terms genome chromatin nuclear envelope centromere kinetochore spindle replicated chromosome sister chromatid metaphase plate o Matching draw replicated chromosome What is cytokinesis o Division of cytoplasm Be able to draw a cell in metaphase and label sister chromatids kinetochore and spindle o Sister chromatids are held tightly together at centromere kinetochore is the protein complex that the spindle apparatus attaches to Possible discussion question How do cancer cells differ from normal cells with regard to cell cycle control will be on exam o 3 basic ways normal cells will divide a certain number of times 30 50 times and then it will get old and die cancer cells are mortal they divide forever in tissue culture a normal cell will grow until they touch one another contact inhibition and then they stop dividing cancer cells keep dividing and pile up on each other no contact inhibition cancer cells USUALLY don t stop dividing but when they do they stop at the wrong point and have the wrong amount of DNA II Meiosis and Sexual Life Cycles What are the two major kinds of reproduction and how do they differ from each other with regard to the offspring produced o 2 ways asexual one parent genetically identical to offspring and parent basically cell division not the best way to reproduce sexual 2 parents offspring are genetically unique Terms to know gamete zygote chromosome homologous chromosomes also called homologs or homologous chromosome pairs o Matching section most likely zygote is diploid 1st cell chromosomes come in pairs in body cells haploid versus diploid several questions cover this concept ex If diploid number of an organism is 10 how many chromosomes are in the sperm cell Or the body cells Etc o body cells are diploid cells CHROMOSOMES COME IN PAIRS gametes egg sperm are haploid cells have HALF AS MANY CHROMOSOMES humans have 46 chromosomes in body cells 23 PAIRS one from egg one from sperm if diploid number is 10 there are 5 chromosomes in sperm egg o LOOK ONLINE FOR SCANNED QUIZ WITH EXAMPLES What is meiosis What is the purpose of meiosis What kind of cell undergoes meiosis a germline cell undergoes meiosis In humans these are only found in the ovaries and testes o Meiosis produces eggs and sperm only Germline cells undergo meiosis only job is to make gametes Given the diploid 2n or haploid n number of an organism be able to draw a cell of that organism in metaphase of mitosis meiosis I and meiosis II WILL BE ON EXAM o 2N 6 1N 3 mitosis all 6 chromosomes lined up single file on metaphase plate meiosis I 3 pairs of 2 chromosomes line up 2 by 2 on the metaphase plate meiosis II replicated chromosomes line up 1 by 1 on the on metaphase plate but only have 3 chromosomes o 2N 8 1N 4 mitosis 8 chromosomes single file meiosis I 4 pairs of 2 lined up 2 by 2 meiosis II 4 chromosomes line up 1 by 1 Name three sources of genetic variation in sexual reproduction independent assortment of chromosomes during meiosis crossing over random fertilization multiple choice fill in the blank o Independent assortment Maternal and paternal homologs line up randomly with no effect on any other pairs o Crossing over 1 in 8 million possible combinations in egg AND sperm 1 in 64 trillion possible combos o Random fertilization Given the 2n or n of an organism be able to figure out the of possible combinations of maternal and paternal homologs in the gametes of possible combinations 2n where n haploid o 2N 6 then 1N 3 and then 23 8 possible combos 1N 8 million 2N 64 million then 223 64 trillion What is crossing over When does it occur What is a meiotic tetrad o 2 replicated chromosomes then in meiosis they get close together and exchange DNA tetrad 4 pieces of DNA from the 2 replicated pieces of DNA occurs in meiosis III Mendel and Chromosomes Terms true breeding allele dominant recessive homozygous heterozygous o matching or fill in the blank true breeding monohybrid crosses with 2 pea plants that differed from one another by only one SINGLE trait allele alternative form of a gene protein located along a piece of DNA dominant expressed recessive unexpressed must have 2 recessive to have it expressed homozygous both copies are the same heterozygous one of each Mendel s Law of Independent assortment be able to give the possible combinations of alleles in the gametes of an individual who is heterozygous for TWO traits located on DIFFERENT chromosomes think of foiling ex GgRr GR Gr gR gr o Traits only assort independently if they are on different chromosomes gametes each get one of the homologous pairs Genetic disorders in humans recessive disorders cystic fibrosis sickle cell anemia dominant disorders dwarfism Huntington s matching multiple choice What does it mean to be a carrier of a recessive allele o Definitely matching Possible discussion Why is the sickle cell trait so common in the African American population o Almost definitely on exam this trait occurs with an advantage resistance to malaria so in Africa it was desired because if you carried it you were resistant to malaria keeping it at a high level in population Complications of Mendelian genetics incomplete dominance also called intermediate inheritance multiple alleles epistasis pleiotrophy environmental factors o matching multiple choice X Y system of sex determination know the terms homogametic sex and heterogametic sex Which determines the sex of the offspring o Homogametic sex X gametes female XX heterogametic sex X and Y gametes male XY behave as though they are homologous chromosome pairs but they don t share many alleles Know differences between X and Y chromosomes multiple choice Possible discussion questions 1 Are any genes on the Y chromosome required for life Why or why not 2 What does the term Xlinked mean o No impossible because women have XX and no Y chromosome x linked gene carries on x chromosomes much bigger and has a lot of genes that are irrelevant to being a female or male y linked strictly for sex determination Be able to work simple sex linked genetic problems o Father can t pass x linked genes to his SONS because he passes on the Y chromosome sons ONLY get x linked traits from mother because she donates the x