1. Chapter 11 Intro. to Genetics

2. Chap. 11-4 Meiosis Mitosis – division of body cells (somatic cells) End result - 2 cells identical to starting cell w/same number of chromosomes Meiosis – production of sex cells (sperm & egg) (gametes) End result – 4 cells with ½ the chromosome number as starting cell

3. Karyotype A picture of one’s chromosomes arranged in pairs Each pair are alike in that they carry genes for the same traits Are called homologous chromosomes

4. Homologous Pair

5. Chromosome Number Gametes – called haploid b/c they contain only half the number of chromosomes Called the n number (n refers to number of chromosomes in gametes) Gametes have only one member of each homologous pair

6. Chromosome Number Somatic cells – called diploid b/c they contain two of each chromosome or 23 pairs (in humans) Each pair – called a homologous pair Because each pair forms a 4-stranded group, they are also called a tetrad Come together in Prophase I in a process called synapsis

7. Divisions of Meiosis Meiosis occurs in 2 major divisions: 1st division – Meiosis I - separates homologous pairs of chromosomes (reduction phase) 2nd division – Meiosis II - separates chromatids of each chromosome (division phase) & is similar to mitosis

8. Meiosis

9. Important events to remember: Synapsis & crossing over – Prophase I Separation of homologous chromosomes – Anaphase I Division of chromatids – Anaphase II

10. Importance of Meiosis Causes variation in chromosomes by: 1. Crossing over - when homologous chromosomes exchange genes

11. Importance of Meiosis 2. Usually results in random segregation (separation) of chromo- somes Both result in new genetic combin- ations in the off- spring

12. Mitosis vs. Meiosis MitosisMeiosis 1 division2 divisions Produces 2 genetically identical cells Produces 4 genetically different cells Cells are diploidCells are haploid Produces body (somatic) cells Produces sex cells (gametes)

13. Meiosis in Males

14. Meiosis in Females

16. CHAP. 11-1 & 11-2 Mendel’s Laws of Heredity Genetics – study of heredity Heredity – passing of traits from parent to offspring Traits transmitted by genes located on chromosomes Most traits determined by a pair of genes located on paired chromosomes (homologous)

17. Mendel’s Laws of Heredity Gregor Mendel – “Father of Genetics” Studied garden pea plants; 2 reasons: 1.Have 7 contrast- ing traits ex. – tall vs. short, green pod vs. yellow, etc.

18. Mendel 2. Easy to cross-pollinate - (the transfer of male pollen grains from one plant to the female organ of another plant) (usually pea plants self- pollinate

19. Genetics Vocab. Genotype – genetic makeup of an organism (Tt) Phenotype – physical makeup of an organism (tall) Homozygous (pure) – when 2 genes for a trait are the same (TT or tt) Heterozygous (hybrid) – when 2 genes for a trait are different (Tt) Monohybrid cross – one with only 1 trait crossed Alleles – different forms of a gene (T or t)

20. Mendel’s Experiments Mendel first crossed pure tall plant with pure short plant To work a genetics problem: Step 1- Pick symbols: T - tall, t - short Step 2 - Diagram the cross: TT x tt (Parents or P generation)

21. Mendel’s Experiments Step 3 – Do the Punnett square: TT x tt offspring are called 1 st filial or F 1 generation) one trait shows up (tallness) & one disappears (shortness)

22. Mendel’s Experiments Step 4 – List ratios: Genotypic ratio – Phenotypic ratio -

23. Mendel’s Experiments Next Mendel did a second generation cross (cross 2 plants from the 1 st generation) F 2 cross = Tt x Tt Now the tall trait appears Offspring are called F 2 generation

24. Monohybrid Crosses

25. Mendel’s Laws Law of Dominance – in an organism w/contrasting alleles (different forms of a gene), one gene shows up & the other disappears Gene that shows up – dominant Gene that disappears – recessive Law of Segregation – pairs of genes separate when gametes are formed in meiosis (shown in the Punnett square

26. Ch. 11-3 Mendel’s Laws Law of Independent Assortment – pairs of genes separate independently of each other Dihybrid cross – one with 2 different traits

27. Dihybrid Cross – used to show Mendel’s Law of Independent Assortment F-o-i-l (first – outside – inside - last) In guinea pigs, black fur is dominant over white. Rough coat is also dominant over smooth. Cross a homozygous black, rough guinea pig with a heterozygous black, rough guinea pig.

29. Incomplete Dominance Incomplete dominance – when 1 gene is not completely dominant over the other; a blending of traits occurs Problem - In some flowers, red is incompletely dominant over white. The heterozygous condition produces pink flowers. Pick symbols: R – red, R′ - white Possible genotypes: RR- red R′R′ - white RR′ - pink

30. Codominance Codominance – when neither gene is dominant; both genes in a pair are expressed In cattle, red hair is codominant with white. The heterozygous condition produces a roan (mix of red & white) offspring. Pick symbols – R-red; W-white R Possible genotypes: RR – red WW – white RW - roan

31. Bio. Bingo Mendelallelesgametes Independent assortmentsegregationhyrbid HeterozygousF 2 fertilization Genotypeself-pollinationprobabilityb Phenotypedominant Geneticsmonohybrid Heredityincomplete dominance Recessivecodominance 1 st filial1:2:1 Homozygouscross pollination Peasdominance Traitsdihybrid Genesdominant Punnett square3:1