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Introduction to Genetics – Part 1Genetics – Study of heredity
Top – Madonna and her daughter LourdesLeft – Judy Garland (Dorothy – Wizard 0f Oz) and her daughter Liza Minnelli
MeiosisCell division in diploid cells that results in haploid cells; reduction division
Homologous chromosomes – a pair of chromosomes having the same size and shape and carrying information (alleles) for the same traits (Fig. 11-14)
Diploid vs HaploidDiploid – having two sets of chromosomes, or all the homologous chromosomes that are characteristic of the species (2n)Haploid – having only one chromosome from each pair of homologous chromosomes (n)
How does a cell go from diploid to haploid?
Phases of MeiosisDuring meiosis the chromosomes replicate once, but the cell divides twice – Fig. 11-15
Meiosis results in two haploid daughter cells with half the number of chromosomes as the original cell
Phases of MeiosisProphase I
Homologous chromosomes pair (synapsis) to form a tetrad
Phases of MeiosisProphase I
Crossing over – exchange of segments between nonsister chromatids; **increases genetic variation**
Phases of MeiosisMetaphase I
Tetrads line up on equatorial plane
Phases of MeiosisAnaphase I
Disjunction occurs - homologous chromosomes from each tetrad separate Cytokinesis begins during late anaphase/early telophase
Phases of MeiosisTelophase I
End of first meiotic divisionhttp://www.phschool.com/science/biology_place/biocoach/meiosis/mei1ani.html
Phases of MeiosisProphase II
Phases of MeiosisMetaphase II
Phases of MeiosisAnaphase II
Phases of MeiosisTelophase II
http://www.phschool.com/science/biology_place/biocoach/meiosis/mei2ani.html
Phases of MeiosisOverview
http://www.johnkyrk.com/meiosis.html
Meiosis vs Mitosis
Meiosis Quizzes
http://biology.about.com/library/weekly/blmeios2a.htm
http://www.phschool.com/science/biology_place/biocoach/meiosis/quiz.html
http://www.cst.cmich.edu/users/benja1dw/bio101/tools/quiz/mitosis.htm
THIS SLIDE ENDS PART ONE
Introduction to Genetics – Part 2 Gregor Mendel – “father” of modern genetics
Gregor Mendel’s Peas
Introduction to Genetics – Part 2 Fertilization – the union of a female and male gamete (specialized sex cell formed during meiosis)
Introduction to Genetics – Part 2 Pea plants are: - easy to grow - matured quickly - show contrasting traits - control pollination True breeding – pure for a particular trait. If plants with yellow seeds were self pollinated for several generations they would always produce plants with yellow seeds
Genes and Dominance
Gene – a distinct unit of hereditary material found in chromosomes; a sequence of nucleotides in DNA
Genes and Dominance Allele – the different forms of the gene for a trait
Genes and Dominance Principle of Dominance states that some alleles are dominant and others are recessive
Homozygous – having two identical alleles
TT – homozygous dominanttt - homozygous recessive
Heterozygous – having two different forms of a gene - Tt
Genes and Dominance Principle of Dominance states that some alleles are dominant and others are recessive
Genes and Dominance Principle of Segregation – factors that occur in pairs are separated from each other during gamete formation and recombined at fertilization ( Fig. – 11-5)
Probability & Punnett Squares Probability – likelihood that a particular event will occur
Principle of Probability – if there are several possible event that might happen, and no one of them is more likely to happen than any other, then they will happen in equal numbers over a large number of trials
Example – Coin Toss – Fig. 11-7
Probability & Punnett Squares Punnett Square – a diagram used to show the results of a cross – Fig. 11-7
Phenotype – physical trait that appears as a result of genetic makeupGenotype – the genetic makeup of an organism; total set of genes