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Introduction To Genetics- Chapter 11. 11-1 The Work of Gregor Mendel. I. The work of Gregor Mendel. A. Gregor Mendel was born in 1822 and after becoming a priest; Mendel was a math teacher for 14 years and a monastery. Mendel was also in charge of the monastery garden.
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11-1 The Work of Gregor Mendel I. The work of Gregor Mendel A. Gregor Mendel was born in 1822 and after becoming a priest; Mendel was a math teacher for 14 years and a monastery. Mendel was also in charge of the monastery garden.
11-1 The Work of Gregor Mendel I. The work of Gregor Mendel 1. Mendel carried out his work with garden peas
11-1 The Work of Gregor Mendel I. The work of Gregor Mendel 2. Fertilization is the fusion of an egg and a sperm. 3. True breeding plants are plants that were allowed to self-pollinate and the offspring would be exactly like the parent.
11-1 The Work of Gregor Mendel I. The work of Gregor Mendel
11-1 The Work of Gregor Mendel Mendel’s experiments • The first thing Mendel did was create a “pure” generation or true-breeding generation. • He made sure that certain pea plants were only able to self pollinate, eliminating unwanted traits. • He did this by cutting away the stamen, or male part of each flower
11-1 The Work of Gregor Mendel Figure 11-3 Mendel’s Seven F1 Crosses on Pea Plants Section 11-1 Mendel’s experiments Seed Shape Seed Color Seed Coat Color Pod Shape Pod Color Flower Position Plant Height Round Yellow Gray Smooth Green Axial Tall Wrinkled Green White Constricted Yellow Terminal Short Round Yellow Gray Smooth Green Axial Tall *Flower color – purple (P) vs. white (p) Seed coat color and flower color are often put in for one another – thus, the EIGHT traits!!! Go to Section:
11-1 The Work of Gregor Mendel Genes and dominance • Trait : a characteristic • Mendel studied seven of these traits • After Mendel ensured that his true-breeding generation was pure, he then crossed plants showing contrasting traits. • He called the offspring the F1 generation or first filial.
11-1 The Work of Gregor Mendel What will happen when pure yellow peas are crossed with pure green peas? • Allof the offspring were yellow. • Hybrids = the offspring of crosses between parents with contrasting traits
11-1 The Work of Gregor Mendel What did Mendel conclude? • Inheritance is determined by factors passed on from one generation to another. • Mendel knew nothing about chromosomes, genes, or DNA. Why? • These terms hadn’t yet been defined.
11-1 The Work of Gregor Mendel What were Mendel’s “factors” • The ‘factors” that Mendel mentioned were the genes. • Each gene has different forms called alleles • Mendel’s second principle stated that some alleles are dominant and some are recessive.
11-1 The Work of Gregor Mendel Mendel’s second cross • He allowed the F1 generation to self-pollinate thus producing the F2 generation. • Did the recessive allele completely disappear? • What happened when he crossed two yellow pea hybrid (F1) plants?
11-1 The Work of Gregor Mendel Results: • ¾ of the peas were yellow, ¼ of the peas were green. • During the formation of the sex cells or gametes, the alleles separated or segregated to different gametes. (pollen and egg)
11-2 Probability and Punnett Squares Punnett square example
11-2 Probability and Punnett Squares Reading Punnett squares • Gametes are placed above and to the left of the square • Offspring are placed in the square. • Capital letters (Y) represent dominant alleles. • Lower case letters (y) represent recessive alleles.
Genotype The genetic makeup Symbolized with letters Tt or TT Phenotype Physical appearance of the organism Expression of the trait Short, tall, yellow, smooth, etc. 11-2 Probability and Punnett Squares Phenotype vs genotype
11-2 Probability and Punnett Squares Genes and Dominance 1. The different forms of a gene is called and an alleles. 2. The principal of dominance states that some alleles are dominant and others are recessive.
11-2 Probability and Punnett Squares • Genes and Dominance Pinky Finger Traits At Paris Gibson Ed Center we tested dominant and recessive traits in our school population. We tested pinky finger traits, whereby, the bent finger is dominant and the straight finger is recessive.
11-2 Probability and Punnett Squares C. Segregation 1. Each trait has two genes, one from the mother and one from the father. 2. Traits can be either dominant or recessive. 3. A dominant trait only needs one gene in order to be expressed.
11-2 Probability and Punnett Squares C. Segregation 4. A recessive trait needs two genes in order to be expressed.
11-2 Probability and Punnett Squares C. Segregation 5. Egg and sperm are sex cells called gametes. 6. Segregation is the separation of alleles during gamete formation.
11-2 Probability and Punnett Squares II. Probability and Punnett Squares A. Genetics and Probability 1. The likelihood that a particular event will occur is called probability. 2. The principals of probability can be used to predict the outcome of genetic crosses.
11-2 Probability and Punnett Squares II. Probability and Punnett Squares
11-2 Probability and Punnett Squares B. Punnett Squares 1. The gene combination that might result from a genetic cross can be determined by drawing a diagram known as a Punnett square. 2. Punnett squares can be used to predict and compare the genetic variations that will result from a cross.
11-2 Probability and Punnett Squares B. Punnett Squares 3. Each trait has two genes- one from the mother and one from the father. 4. Alleles can be homozygous – having the same traits. 5. Alleles can be heterozygous- having different traits.
11-2 Probability and Punnett Squares B. Punnett Squares
11-2 Probability and Punnett Squares B. Punnett Squares 6. Physical characteristics are called the phenotype. 7. Genetic make up is the genotype.
11-3 Exploring Mendelian Genetics III. Exploring Mendalian Genetics A. Independent assortment 1. Genes segregate independently.
11-3 Exploring Mendelian Genetics III. Exploring Mendalian Genetics 2. The principle of independent assortment states that genes for different traits can segregate independently during the formation of gametes. 3. Independent assortment helps account for the many genetic variations observed in plants, animals and other organisms.
11-3 Exploring Mendelian Genetics The dihybrid cross • Punnett square on board:
11-3 Exploring Mendelian Genetics B. A summary of Mendel’s Principals 1. Genes are passed from parent to offspring. 2. Some forms of a gene may be dominant and others recessive.
11-3 Exploring Mendelian Genetics B. A summary of Mendel’s Principals 3. In most sexually producing organisms, each adult has two copies of each gene- one from each parent. These genes are segregated from each other when gametes are formed. 4. The alleles for different genes usually segregate independently of one another.
11-3 Exploring Mendelian Genetics C. Beyond Dominance and Recessive alleles 1. Some alleles are neither dominant nor recessive, and many traits are controlled by multiple alleles or multiple genes. 2. Cases in which one allele is not completely dominant over another are called incomplete dominance.
11-3 Exploring Mendelian Genetics Incomplete dominance • A situation in which neither allele is dominant. • When both alleles are present a “new” phenotype appears that is a blend of each allele. • Alleles will be represented by capital letters only.
11-3 Exploring Mendelian Genetics Incomplete dominance Example: White (W) and Red (R) is both dominate. If WW X RR the F1 generation would be WR= pink.
11-3 Exploring Mendelian Genetics What happens when a red flower is crossed with a white flower? • According to Mendel either some white and some red or all offspring either red or white. • All are pink
11-3 Exploring Mendelian Genetics C. Beyond Dominance and Recessive alleles 3. Codominance is when both alleles contribute to the phenotype. Example: Feather colors
11-3 Exploring Mendelian Genetics C. Beyond Dominance and Recessive alleles 4. Many genes have more than two alleles and are referred to have multiple alleles. a. This means that more than two possible alleles exist in a population. Example: colors of rabbits see page 273.
11-3 Exploring Mendelian Genetics C. Beyond Dominance and Recessive alleles
11-3 Exploring Mendelian Genetics C. Beyond Dominance and Recessive alleles 5. Traits that are controlled by two or more genes are said to be polygenic traits, which means, “having many genes.” a. Example: eye color has many different genes.
Meiosis Division of Sex Cells
11-4 Meiosis The Point of Meiosis Meiosis is a process of reduction division in which the number of chromosomes per cell is cut in half through the separation of homologous chromosomes in a diploid cell.
11-4 Meiosis 2 types: Spermatogeneis & Oogenesis
11-4 Meiosis Meiosis • Diploid– 2 sets of chromosomes • Haploid– 1 set of chromosomes • Homologous– chromosomes that each have a corresponding chromosome from the opposite sex parent
