Lesson 6: Introduction to Genetics PDF

LESSON 6: INTRODUCTION TO GENETICS  Let’s review... copyright cmassengale What makes you unique? 4 ▪He is an Austrian botanist, teacher, and an Augustinian prelate ▪He studied the inheritance of traits in pea plants Gregor Johann...

LESSON 6: INTRODUCTION TO GENETICS  Let’s review... copyright cmassengale What makes you unique? 4 ▪He is an Austrian botanist, teacher, and an Augustinian prelate ▪He studied the inheritance of traits in pea plants Gregor Johann Mendel 5 ▪The genetic experiments Mendel did with pea plants took him eight years (1856- 1863) and he published his results in 1865. copyright cmassengale 6 ▪ During this time, Mendel grew over 10, 000 pea plants, keeping track of progeny number and type. copyright cmassengale 7 Site of Gregor Mendel’s experimental garden in the Czech Republic copyright cmassengale He developed the laws of inheritance: a. Law of Segregation b. Law of Independent Assortment c. Law of Dominance 9 He is considered to be the Gregor Johann Father of Genetics. Mendel copyright cmassengale (1822-1884) Mendel’s Pea Plant Experiments 10 copyright cmassengale  Why peas, Pisum sativum? ▪ It can be grown in a small area ▪ It produces pure plants when allowed to self-pollinate several generations ▪ It has a lots of offspring ▪It can be artificially cross-pollinated copyright cmassengale 11  Reproduction in Flowering Plants Pollen contains sperm ○Produced by the stamen Ovary contains eggs ○Found inside the flower Pollen carries sperm to the eggs for fertilization Self-fertilization can occur in the same flower Cross-fertilization can occur between flowers copyright cmassengale 12  13 copyright cmassengale  14 copyright cmassengale Before the discovery of chromosomes and DNA.. ▪Mendel stated that physical traits are inherited as “particles” ▪Mendel did not know that the “particles” were actually Chromosomes & DNA copyright cmassengale  What is Genetics? Genetics is a field of biology that studies how traits are passed from parents to their offspring. The passing of traits from parents to offspring is known as heredity, therefore, genetics is the study of heredity. copyright cmassengale  What is Genetics? Genetics is built around molecules called DNA. DNA molecules hold all the genetic information for an organism. A gene is one particular section of a DNA molecule that tells a cell to perform one specific task. copyright cmassengale GENETIC TERMINOLOGY Allele - a specific variation of gene (e.g. blue eyes, green eyes, Type A blood, brown skin) - every organism possesses two alleles for every gene copyright cmassengale 19  Genetic Terminology Trait - any physical characteristic that can be passed from parent to offspring copyright cmassengale 20  Genetic Terminology Dominant Allele - It is a trait being expressed / show off in an organism. Example: Black hair is dominant allele; one parent contributes for black hair, and the other is brown hair, the child will have a BLACK HAIR. In Punnett Square: It is represented by a CAPITAL letter (e.g. B – black hair) copyright cmassengale 21  Genetic Terminology ▪ Recessive Allele - It is a trait that is masked/ hidden by a dominant trait. Example: Brown hair is recessive allele; one parent contributes for black hair, and the other is light brown hair, the child has black hair, because the BROWN hair is hidden / masked. In Punnett Square: It is represented by a small letter (e.g. b – brown hair) copyright cmassengale 22  Genetic Terminology ▪ Homozygous Alleles (or PURE) - pair of alleles that produce a characteristic which is the same. Example: Allele B – black hair b- brown hair BB or bb Homozygous Homozygous Dominant Recessive 23  Genetic Terminology ▪ Heterozygous Alleles (or HYBRID) - pair of alleles that produce a characteristic which is different Example: Allele B – black hair b- brown hair (e.g. Bb) Heterozygous 24  Types of Genetic Crosses ▪Monohybrid cross - cross involving a single trait e.g. flower color ▪Dihybrid cross - cross involving two traits e.g. flower color & plant height copyright cmassengale 25  Genetic Terminology Genotypes - The genetic make-up of an organism, or an individual that contributes to its phenotype Example: B – black hair b- brown hair (e.g. Bb, BB, or bb) 26  Genetic Terminology Phenotypes - the physical feature resulting from a genotype Alleles: B – black hair b- brown hair GENOTYPES: PHENOTYPES: Bb Black hair BB Black hair bb brown hair 27  Genotype & Phenotype in Flowers Genotype of alleles: R = red flower r = yellow flower All genes occur in pairs, so two alleles affect a characteristic Possible combinations are: 28 Genotypes RR Rr rr Phenotypes RED RED copyright cmassengale YELLOW Punnett Square a square diagram that is used to predict the genotypes of a particular cross or breeding experiment. The diagram is used by biologists to determine the probability of an offspring having a particular genotype. In Summary, 30