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