Crossing Over Manipulative & Lab Crossing Over SHOULD ONLY occur between Homologous Chomosomes during Meiosis Oogenesis - the creation of an egg/ovum Spermatogenesis - the creation of sperm

Chromosomes Chromosome #1 mom dad Preparing to divide Homologous chromosomes 2 pairs of sister chromatids = a tetrad Crossing over A mixing of genetic traits Karyotype of chromosomes With fluorescent markers at gene sites In Mitosis, homologous chromsoomes are present, but do NOT pair up

4 genetically unique cells 1 egg 3 smaller polar bodies 4 genetically unique sperm Synapsis - pairing of homologous chromosomes Chiasma - point where crossing over occurs Haploid (n) or Diploid (2N)? Meiosis - production of gametes Interphase Prophase I Metaphase I Anaphase I Prophase II Metaphase II Anaphase II Telophase II Telophase I No Interphase between Meiosis I and Meiosis II, means that G 1, S, and G 2 do not occur. What is the end result in terms Of the chromosome number? What 3 things happen here?

Gene loci centromere Hair color Eye color ethnicity height Artistic hand Music IQ personality Athletic ability Hair type Hair color Eye color ethnicity height Artistic hand Music IQ personality Athletic ability Hair type Describing YOUR traits! Artist Amateur Doodlist Musician Amateur Listener Brilliant Smart Average Olympian Jock Spectator Genes - genetic instruction determining traits/characteristics turned on (expressed) or turned off Shy, outgoing, friendly, introverted, extroverted, quiet, bubbly, funny, intellectual, secretive, stoic, silly, charming, energetic, kind, loyal, reliable, moody, sociable, thoughtful, witty, stubborn, vain, gullible, impulsive, domineering

Homologous Chromosomes IQ Hair color Eye color ethnicity height Artistic hand music personality Athletic ability Hair type Hair color Eye color ethnicity height Artistic hand music IQ personality Athletic ability Hair type Hair color Eye color ethnicity height Artistic hand music IQ personality Athletic ability Hair type Hair color Eye color ethnicity height Artistic hand music IQ personality Athletic ability Hair type Each tetrad provides information about the same trait

Homologous Chromosomes Crossing Over IQ Hair color Eye color ethnicity height Artistic hand music personality Athletic ability Hair type Hair color Eye color ethnicity height Artistic hand music IQ personality Athletic ability Hair type Hair color Eye color ethnicity height Artistic hand music IQ personality Athletic ability Hair type Hair color Eye color ethnicity height Artistic hand music IQ personality Athletic ability Hair type Each tetrad provides information about the same trait

Mom Dad Are the gametes genetically the same as each other or unique? Separate the gamete’s tetrad, draw them down & id person Hair color Eye color ethnicity height Artistic hand music IQ personality Athletic ability Hair type IQ Hair color Eye color ethnicity height Artistic hand music personality Athletic ability Hair type Crossing Over Hair color Eye color ethnicity height Artistic hand music IQ personality Athletic ability Hair type Hair color Eye color ethnicity height Artistic hand music IQ personality Athletic ability Hair type

Crossing Over “Mixing the Gene Pool!” Separating & Exchanging Genes

A b c d E F G h i J k A b c d E F G h i J k a b c D E f g h i j K a b c D E f g h i j K Identical sister chromatids Chromosome 1 Chromosome Genes Loci Traits Alleles Dominant Recessive Homozygous Heterozygous Hybrid A b c d E F G h i J k E F G h a b c D E f g h i j K a b c D E f g h i j K A b c d i J k

Non-Disjunction Chromosomal Errors Down Syndrome (21) Junction - come together Disjunction - don’t come together Non-Disjunction - come together even when you’re not supposed to? Philadelphia Chromosomes During Meioisis, Crossing Over between Homologous Chromosomes but not at the same place = missing info and extra info Shows up in EVERY Cell of the person During Mitosis, Translocation between Non-Homologous Chromosomes shows up only in the cells that have undergone the error during mitosis

And more variation… Crossing over Typically cross overs per chromosome creates completely new combinations of traits in next generation 2 23 = 8.4 million possible chromosomal combinations due to independent assortment

Random fertilization Any 2 parents will produce a zygote with (2 23 x 2 23 ) = over 70 trillion diploid combinations

Sexual reproduction creates variability Sexual reproduction allows us to maintain both genetic similarity & differences. Baldwin brothers Martin & Charlie Sheen, Emilio Estevez Kirk & Michael Douglas

Meryl Streep & Mamie Gummer Kate Hudson & Goldie Hawn Jamie Lee Curtis & Janet Leigh Melanie Griffith & Tippi Hedren The Judds Venus & Serena Williams