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Explore Gregor Mendel's groundbreaking work with pea plants, covering topics like fertilization, traits passing to offspring, segregation probability, Punnett squares, two-factor cross, and Mendel's genetic principles. Learn about genes, alleles, gametes, and genetic inheritance patterns in this engaging introduction to genetics.
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Chapter 11 Intro to Genetics
Gregor Mendel and His Peas • Fertilization in pea plants: • asexual reproduction vs. sexual reproduction • True –breeding vs. crossbreeding • Identical traits vs. hybrid traits
Passing of Traits to Offspring • Genes control traits and are passed from parent to offspring • Alleles are different forms of genes (describe genotype, dominant or recessive) • Gametes – sex cells that contain the DNA /genes/traits that are passed to offspring
Probability and Punnett Squares • Flip a coin three times. What is the probability it will land heads up each time? • ½ x ½ x ½ = 1/8 • Cross a heterozygous tall (Tt) plant with a heterozygous tall (Tt) plant. • In the F1 generation what is the probability of getting a tall allele and getting a short allele? • In the F2 generation what is the probability of getting a tall offspring and short offspring?
Two Factor Cross and Independent Assortment • Mendel was able to study two different genes at the same time by observing two different traits. • Seed color and seed shape Mendel crossed round yellow seeds with wrinkled green seeds. • Make a Punnett square showing the two factor cross using the genotypes RRYY and rryy • This cross showed that the alleles segregated independently of each other. • Examples of one-factor cross and two-factor cross on TB pg 268.
Summary of Mendel’s Principles • Biological characteristics are inherited through units called genes. Genes are passed from parents to offspring. • Sometimes there are two or more forms (alleles) of a gene for a single trait. Some forms of a gene may be dominant and others may be recessive. • In most sexually reproducing organisms, each adult has two copies of each gene. Organisms get one copy from each parent. These alleles segregate from each other when gametes are made. • Alleles for different genes usually segregate independently of each other.