INTRODUCTION TO GENETICS BY MRS OZEMOKA H.J. AEB111 INTRODUCTION TO GENETICS BY MRS OZEMOKA H.J. INTRODUCTION TO GENETICS AEB 111 by MRS OZEMOKA H.J. is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.

INTENDED LEARNING OUTCOMES At the end of the week, the students are expected to know: what genetics entails the varoius areas of genetics Terminologies associated with genetics. Brief history of genetics. The laws of Mendelian genetics.

PRE VIEW QUESTIONS What is Genetics? State some terminologies associated with genetics. Differentiate between monohybrid cross and dihybrid cross. Differentiate between genotype and phenotype. State the Mendelian laws of inheritance.

WHAT IS GENETICS? A branch of science that deals with inheritance of Biological characteristics. It involves the study of the structure of the gene, the action and pattern of inheritance. Also referred to as the scientific study of heredity and variations in living organisms.

HEREDITY It can also be called inheritance and it is known as the transmission and expression of characters or traits in living organisms from parents to offspring. VARIATION: It is defined as the differences which exist between parents and offsprings as well as among offsprings.

AREAS OF GENETICS There are three areas of Genetics namely: Classical genetics: Molecular genetics: Evolutionary genetics

Classical genetics: It is also called Modern genetics. It refers to Mendelian genetics of inheritance.

MOLECULAR GENETICS It is the study of genetic materials (DNA and RNA), chemical structure, replication, change and function.

EVOLUTIONARY GENETICS It is the study of the mechanism of evolutionary change on a genetic level. It includes the interaction of the genes and the environment to produce phenotype population genetics.

HISTORY OF GENETICS. Study of genetics dates back to several years in man’s curiosity to unravel the mechanism behind the transmission of traits from parents to offspring. A breeder called Kilreuter worked with tobacco plants about 1770. He made crosses with variety of plants and produced hybrids. He also recognized that parental characters were transmitted by pollen and ovule.

HISTORY OF GENETICS CONTD: However, studies of heredity before 1866 were inconclusive and yielded little explanation as regards manner of transmission of inheritable features from one generation to another. In 1886, an Australian monk called Gegor Mendel, who lived in the monastry published two small treatise on the laws of heredity based on his experiments with pea plants.

HISTORY OF GENETICS CONTD: From his work, he came up with two principles known as Mendel’s principles of inheritance. It was in 1900 that the work of Mendel was fully understood and appreciated after the death of the Father of Genetics. New informations on cell allowed scientists to realize that Mendel’s factors of inheritance were genes.

MENDELIAN’S FIRST LAW OF INHERITANCE. Known as the law of segregation of genes.” It states that genes are responsible for the development of an individual and that they are independently transferred from one generation to another without going through alteration”. It should be noted that during gamete formation, alleles for each gene segregate from each other so that each gamete carry only one allele for each gene. This law illustrates monohybrid inheritance.

Monohydrid inheritance illustration.

MENDEL’S SECOND LAW OF INHERITANCE. It is known as law of independent assotment of genes. It states that each character behaves as a separate unit and is inherited independently of any other character.

Dihybrid illustration.

MENDELIAN’S THIRD LAW OF INHERITANCE. It is regarded as the law of dorminance and it states that recessive alleles will always be masked by dominant alleles. Therefore, a cross between a homozygous dominant and a homozygous recessive will express the dominant phenotype.

TERMINOLOGIES ASSOCIATED WITH GENETICS. ALLELES: Different versions of the same gene. The alleles for a trait occupy the same locus or position of homologous chromosome and governs the same trait. However, because they are different, their action may result in different expressions of that trait.

TERMINOLOGIES CONTINUES: MUTATION: An altered version of a gene. AUTOSOMES: Any chromosomes except sex chromosomes. GENES: Unit of inheritance which are responsible for hereditary characteristics. Genotype: The genetic make up of an individual. X- LINKED: It refers to a gene that is carried by the X- chromosome.

TERMINOLOGIES CONTINUES: V. CENTRIOLE: Small, dense bodies which are outside of a cell nucleus which contracts and becomes more visible early in mitosis and meiosis. It gives rise to spindle fibers when the nuclear membrane breaks.

TERMINOLOGIES CONTINUES: CHROMOSOMES: They are threadlike bodies which are found in the nucleus. They are composed primarily of DNA and protein. Visible only under magnification during cell division.

TERMINOLOGIES CONTINUES: CONDON: A sequence of three nucleotide bases in DNA or RNA molecule that codes for specific type of amino acid which will be used for protein synthesis.

TERMINOLOGIES CONTINUES: CROSSING OVER: The exchange of genetic materials (DNA) between the homologous chromosomes at the beginning of meiosis. It results in the production of sperm and ova with greater genetic diversity due to recombination of genes. Specifically, a portion of the end of a chromosome is broken and reattached to another chromosome.

TERMINOLOGIES CONTINUES: GAMETES: Reproductive cells which take part in sexual reproduction. Gametes are produced by meiosis and have haploid number of chromosomes.

TERMINOLOGIES CONTINUES: SRY gene: Sex determing region on Y gene. It is a gene on the Y chromosome which if present and functioning, causes the undifferentiated sex organs of an animal embryo to become testes. The testes then produces testosterone hormone which initiates the development of the male characteristics.

SUMMARY. Genetics is the scientific study of heredity and variation. Genetics could be classic, evolutionary or molecular. The father of Modern genetics is Gregor Mendel who came up with principles of genetics based on his experiments with Pisum sativum. Some terms of genetics are alleles, mutation, gene, condon, gametes e.t.c.

ASSIGNMENT Write on other terms associated with genetics which are not included in this lecture note. Write on the application of genetics with regards to sexual and asexual reproduction. 3 In a study of monohybrid inheritance, a pure breeding tall pea plant was crossed with a dwarf plant. Represent this diagrammatically and state the genotype and phenotype ratio of the first and second filial generation.

ANNOUNCEMENT Get your drawings books ready for your Thursday practical class

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