Mendelian inheritance.pptx
- 2. Gregor Mendel ? Gregor Mendel, through his work on pea plants, discovered the fundamental laws of inheritance. ? Gregor Mendel was a botanist, teacher, and Augustinian priest, the first person to lay the mathematical foundation of the science of genetics, in what came to be called Mendelism. ? Mendel chose to conduct his studies with the edible pea (Pisum sativum).
- 3. ? He was born in 1822, and at 21, he joined a monastery in Br¨¹nn (now in the Czech Republic). ? The monastery had a botanical garden and library and was a centre for science, religion and culture. ? In 1856, Mendel began a series of experiments at the monastery to find out how traits are passed from generation to generation. ? From 1854 to 1856, he tested 34 varieties for constancy of their traits.
- 5. Genetic Terminology ? Trait ; A trait, as related to genetics, is a specific characteristic of an individual. Traits can be determined by genes, environmental factors or by a combination of both. Traits can be qualitative (such as eye color) or quantitative (such as height or blood pressure). ? Monohybrid cross; A monohybrid cross is defined as the cross happening in the F1 generation offspring of parents differing in one trait only. ? Dihybrid cross; A dihybrid cross is a cross of F1 generation offsprings, differing in two traits.
- 6. ? Allele; An allele is one of two or more versions of DNA sequence (a single base or a segment of bases) at a given genomic location. ? Genotype; The genetic constitution of an individual organism. ? Phenotype; Phenotype refers to an individual's observable traits, such as height, eye color and blood type. A person's phenotype is determined by both their genomic makeup (genotype) and environmental factors. ? Homozygous; having two identical alleles of a particular gene or genes. ? Heterozygous; having two different alleles of a particular gene or genes. ? Genotype RR Rr rr ? Phenotype Red Red yellow
- 7. Punnett Square ? The Punnett square is a square diagram that is used to predict the genotypes of a particular cross or breeding experiment.
- 8. Why Pea? ? He chose peas because they had been used for similar studies, are easy to grow and can be sown each year. ? Pea flowers contain both male and female parts, called stamen and stigma, and usually self-pollinate. ? Self-pollination happens before the flowers open, so progeny are produced from a single plant. ? Pea plant has shortest life cycle.
- 9. Mendel¡¯s Experiment Method ? Mendel was interested in the offspring of two different parent plants, so he had to prevent self-pollination. ? He removed the anthers from the flowers of some of the plants in his experiments. ? Then he pollinated them with pollen from other parent plants of his choice.
- 10. Mendel¡¯s Law of Dominance ? Mendel's law of dominance states that: ¡°When parents with pure, contrasting traits are crossed together, only one form of trait appears in the next generation. ? The hybrid offspring's will exhibit only the dominant trait in the phenotype. ? Law of dominance is known as the first law of inheritance.
- 12. Mendel¡¯s Law of Segregation ? The law of segregation states that each individual that is a diploid has a pair of alleles (copy) for a particular trait. Each parent passes an allele at random to their offspring resulting in a diploid organism. The allele that contains the dominant trait determines the phenotype of the offspring.
- 13. Monohybrid Cross ? The cross between two monohybrid traits (TT and tt) is called a Monohybrid Cross. Monohybrid cross is responsible for the inheritance of one gene.
- 14. Mendel¡¯s Law of Independent Assortment ? Mendel's law of independent assortment states that the alleles of two (or more) different genes get sorted into gametes independently of one another. In other words, the allele a gamete receives for one gene does not influence the allele received for another gene.
- 15. Dihybrid Cross ? A dihybrid cross describes a mating experiment between two organisms that are identically hybrid for two traits. ? A hybrid organism is one that is heterozygous, which means that is carries two different alleles at a particular genetic position, or locus.
- 16. Test Cross ? The test cross is another fundamental tool devised by Gregor Mendel. ? In its simplest form, a test cross is an experimental cross of an individual organism of dominant phenotype but unknown genotype and an organism with a homozygous recessive genotype (and phenotype). ? A test cross is an experiment that is used to find out the genotype of a dominant plant of the F2 generation. ? It is performed by crossing the dominant offspring with the homozygous recessive parent. A tall plant (unknown genotype) is crossed with a dwarf plant (known genotype).
- 18. Back Cross ? The mating of a hybrid organism (offspring of genetically unlike parents) with one of its parents or with an organism genetically similar to the parent. ? The backcross is useful in genetics studies for isolating (separating out) certain characteristics in a related group of animals or plants. ? The purpose of a backcross is to recover elite genotypes and to produce offspring that are genetically similar or closer to parents.
- 19. Complete Dominance ? Complete dominance is a form of dominance wherein the dominant allele completely masks the effect of the recessive allele in heterozygous conditions. A gene (or allele) shows dominance when it suppresses the expression ¡ª or dominates the effects ¡ª of the recessive gene (or allele). ? An example of a simple phenotype, is flower color in Mendel's peas. One allele as a homozygote produces purple flowers, while the other allele as a homozygote produces white flowers.
- 20. Incomplete Dominance ? Incomplete dominance is a form of Gene interaction in which both alleles of a gene at a locus are partially expressed, often resulting in an intermediate or different phenotype. It is also known as partial dominance.
- 21. Codominance ? Codominance, as it relates to genetics, refers to a type of inheritance in which two versions (alleles) of the same gene are expressed separately to yield different traits in an individual.
- 22. THAN