Genetics – Study of heredity Top – Madonna and her daughter Lourdes Left – Judy Garland (Dorothy – Wizard 0f Oz) and her daughter Liza Minnelli

Cell division in diploid cells that results in haploid cells; reduction division Homologous chromosomes – a pair of chromosomes having the same size and shape chromosomes having the same size and shape and carrying information (alleles) for the same and carrying information (alleles) for the same traits (Fig ) traits (Fig )

Diploid – 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?

During meiosis the chromosomes replicate once, but the cell divides twice – Fig Meiosis results in two haploid daughter cells with half the number of chromosomes as the original cell

Prophase I Homologous chromosomes pair (synapsis) to form a tetrad form a tetrad

Prophase I Crossing over – exchange of segments exchange of segments between nonsister between nonsister chromatids; chromatids; **increases genetic **increases genetic variation** variation**

Metaphase I Tetrads line up on equatorial plane

Anaphase I Disjunction occurs - homologous chromosomes from each tetrad separate from each tetrad separate Cytokinesis begins during late anaphase/early Cytokinesis begins during late anaphase/early telophase telophase

Telophase I End of first meiotic division coach/meiosis/mei1ani.html coach/meiosis/mei1ani.html

Prophase II

Metaphase II

Anaphase II

Telophase II coach/meiosis/mei2ani.html coach/meiosis/mei2ani.html

Overview m/meiosis.html m/meiosis.html

h/meiosis/quiz.html iz/mitosis.htm THIS SLIDE ENDS PART ONE

Gregor Mendel – “father” of modern genetics

Fertilization – the union of a female and male gamete (specialized sex cell formed during meiosis)

Pea plants are: - easy to grow - easy to grow - matured quickly - matured quickly - show contrasting - show contrasting traits traits - control pollination - 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

Gene – a distinct unit of hereditary material found in chromosomes; a sequence of nucleotides in DNA

Allele – the different forms of the gene for a trait

Principle of Dominance states that some alleles are dominant and others are recessive Homozygous – having two identical alleles alleles TT – homozygous dominant tt - homozygous recessive Heterozygous – having two different forms of a gene - Tt forms of a gene - Tt

Principle of Dominance states that some alleles are dominant and others are recessive

Principle of Segregation – factors that occur in pairs are separated from each other during gamete formation and recombined at fertilization ( Fig. – 11-5)

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

Punnett Square – a diagram used to show the results of a cross – Fig Phenotype – physical trait that appears as a result of genetic makeup Genotype – the genetic makeup of an organism; total set of genes