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Genetics

Genetics. Chapter 10. Gregor Mendel. Father of genetics – the branch of biology that studies heredity. Mendel did his experiments on pea plants. Mendels Experiments. Mendel carried out the first important studies of heredity (the passing on of characteristics from parent to offspring)

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Genetics

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  1. Genetics Chapter 10

  2. Gregor Mendel • Father of genetics – the branch of biology that studies heredity. • Mendel did his experiments on pea plants

  3. Mendels Experiments Mendel carried out the first important studies of heredity (the passing on of characteristics from parent to offspring) Mendel controlled the pollination of the pea plants in his experiments. Characteristics that are inherited are called traits.

  4. Mendel Chose Seven Traits

  5. The rule of unit factors Each organism has two factors that control each of its traits. These factors are called genes. Genes exist in alternate forms called alleles (you have two alleles for each of your traits – one coming from your mom and one from your dad)

  6. The rule of dominance Dominant – the observed trait (represented by a capital letter) Recessive – the trait that disappeared (represented by a lower case letter) Ex. Tall plant (T) short plant (t)

  7. The rule of dominance The dominant trait always wins out and is the trait to show up if it is present. An uppercase letter represents dominant traits Ex. Tall plant (T) TT = ? short plant (t) Tt = ? tt = ?

  8. Phenotypes and Genotypes The appearance of an organism is called its phenotype (ex. Tall plant, brown hair) The gene combination of an organism is called its genotype (ex. TT, Tt, tt) You cant always know an organism’s genotype by looking at its phenotype.

  9. If both alleles for a trait are the same then the organism is homozygous. ex. TT = homozygous dominant tt = homozygous recessive An organism is heterozygous for a trait if its two alleles are different. ex. Tt

  10. Monohybrid Crosses Crosses involving only “one” trait P generation = parents F1 generation = first filial generation F2 generation = second filial generation

  11. Monohybrid Crosses • Cross two parents to get the F1 generation • Cross two F1 to get the F2 generation • Put the alleles for each parent on the outside of the box.

  12. Meiosis Chapter 10.2

  13. Diploid and Haploid Cells In the body cells of animals and most plants, chromosomes occur in pairs. One chromosome came from the male parent, and the other came from the female parent. A cell with two of each kind of chromosome is called a diploid (2n) cell.

  14. This pairing supports Mendel’s conclusion that organisms have two factors – alleles – for each trait. Organisms produce gametes (sperm and egg) that contain one of each kind of chromosome. A cell with one of each kind of chromosome is called a haploid (n) cell.

  15. Human diploid cells have 46 chromosomes (23 from mom and 23 from dad) Human haploid cells have 23 chromosomes If a dogs diploid cells had 78 chromosomes, how many chromosomes would its haploid cells have?

  16. Why meiosis? Meiosis is the division of diploid cells to produce gametes containing half the number of chromosomes (haploid). If meiosis didn’t occur, then the offspring would have twice as many chromosomes as the parents. 23 chromomes (sperm) + 23 chromosomes (egg) = 46 chromosomes (zygote)

  17. Meiosis Consists of two separate divisions known as Meiosis I and Meiosis II. Meiosis starts with one diploid cell and ends with 4 haploid cells. Everything happens the same in the stages just like mitosis, but what happens to the chromosomes is different.

  18. Crossing Over The exchange of genetic material between chromosomes. Crossing over can occur at any location on a chromosome (happens randomly) Crossing over results in new combinations of alleles on a chromosome

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