Genetics_1st-Semester-AY-2024-2025_Lecture2a-2b (1).pdf
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1 Semester AY 2024-2025 st Important Dates Term Duration: August 12 to December 15, 2024 Start of Class: August 12, 2024 Last Day for Dropping of Subjects: September 25, 2024 Midterm Examination: October 8-12, 2024 (Graduating and Non- graduating students) BU Olympics: October 21-25, 2024 Midterm...
1 Semester AY 2024-2025 st Important Dates Term Duration: August 12 to December 15, 2024 Start of Class: August 12, 2024 Last Day for Dropping of Subjects: September 25, 2024 Midterm Examination: October 8-12, 2024 (Graduating and Non- graduating students) BU Olympics: October 21-25, 2024 Midterm Interlude: October 28 to November 03, 2024 Final Examination: December 10-14, 2024 End of Class: December 15, 2024 (Start of Semestral Break) Agri 13 Principles of Genetics Second Year BSA (II-BSA) Bicol University Guinobatan Department of Agricultural Sciences Mr. Roy R. Boten, Lic. Agr. Course Instructor Agri 13: Principles of Genetics Credit Units: 3.0 (Lecture – 2 units & Laboratory – 1 unit) Second Year BSA (II-BSA) Schedule: Lecture: Mon, 1-3PM; Laboratory: Wed, 7-10AM Lecture: Mr. Roy R. Boten, L. Agr. Laboratory: Prof. Andrian Sola Grading System and Requirements Lecture Components (50%) - Attendance and Class Participation (10%) - Short and Long Quizzes (15%) - Lecture Activities/Guide Questions (30%) - Two Examinations (45%) Total = 100% Topics for the whole semester Unit I – Introduction to Genetics Unit II – Chromosomal Basis of Heredity Unit III – Gene Segregation and Interaction Unit IV – Linkage and Recombination Unit V – The DNA: Chemical Basis of Heredity Unit VI – Gene Functions Unit VII – Developmental Genetics Unit VIII – Epigenetics and Mutations Unit IX – Delayed Chromosomal and Extrachromosomal Inheritance Unit X – Quantitative and Population Genetics Unit XI – Human Genetics Week Number Lecture Topics/Activities Week 1 (August 12-16) Course Orientation and Introduction Week 2 (August 19-23) Unit I – Introduction to Genetics Week 3 (August 27-30) Unit II – Chromosomal Basis of Heredity Week 4 (September 2-6) Unit II – Chromosomal Basis of Heredity Week 5 (September 9-13) Unit III – Gene Segregation and Interaction Week 6 (September 16-20) Unit III – Gene Segregation and Interaction Week 7 (September 23-27) Unit IV – Linkage and Recombination Week 8 (September 30 to October 04) Unit V – The DNA: Chemical Basis of Heredity Week 9 (October 7-11) Midterm Examination Week Number Lecture Topics/Activities Week 10 (October 14-18) Unit VI – Gene Functions Week 11 (October 21-25) BU Olympics (Developmental Genetics) Week 12 (October 28-31) Midterm Interlude Week 13 (November 4-8) Unit VII – Developmental Genetics Unit VIII – Epigenetics and Mutations Week 14 (November 11-15) Unit IX – Delayed Chromosomal and Extrachromosomal Inheritance Week 15 (November 18-22) Unit X - Quantitative and Population Genetics Week 16 (November 25-29) Unit XI – Human Genetics Week 17 (December 2-6) Integration Period/Review Week Week 18 (December 9-13) Final Examination Genetics: The Science of Heredity and Variation - Genetics was derived from the Greek word “gen”, meaning to become or to grow into something. The term was coined by William Bateson in 1906. Beginning of Genetics - Began with the works of Austrian monk, Gregor Mendel (1822-1884). - In 1866, he discovered that hereditary characteristics were determined by elementary factors that are transmitted between generations in a uniform, predictable fashion. Reference: Ramirez, D.A., Mendioro, M.S., & Laude, R.P. (2013). Lectures in Genetics. 10th Edition. Genetics and Molecular Biology Division, Institute of Biological Sciences, University of the Philippines – Los Baños Major Attributes of a Gene - Inherited from generation to generation in a fashion that each progeny has a physical copy of this material. - Provides information regarding the structure, function, and other biological properties of the characteristics or traits it controls. Reference: Ramirez, D.A., Mendioro, M.S., & Laude, R.P. (2013). Lectures in Genetics. 10th Edition. Genetics and Molecular Biology Division, Institute of Biological Sciences, University of the Philippines – Los Baños Theory of Pangenesis - formulated by Aristotle in the 19th century - proposed that semen was formed everywhere in a man’s body and such semen reflected the characteristics of the body part where it was formed - It was accepted by many biologists including Charles Darwin (1809- 1882). Darwin suggested that all parts of the parents could contribute to the evolution and development of the offspring. Reference: Ramirez, D.A., Mendioro, M.S., & Laude, R.P. (2013). Lectures in Genetics. 10 th Edition. Genetics and Molecular Biology Division, Institute of Biological Sciences, University of the Philippines – Los Baños Theory of Inheritance of Acquired Characteristics - proposed by Jean Baptiste de Lamarck (1744-1829) - body modification acquired by use or disuse could be transmitted to the offspring because the semen formed reflected such modifications - based on the Theory of Pangenesis Key Difference: Use and Disuse focuses on how traits are developed or diminished during an organism's lifetime due to usage or lack thereof. Acquired Characteristics suggests that these traits, once developed, can be inherited by the next generation. Weismann’s Germplasm Theory - first who challenged the Theory of Pangenesis by conducting it on mice experiments (August Weismann 1834-1914) Main Findings: - Inheritance of the tail length does not depend on particles produced in the tails of parent mice. - Germplasm or the sex cells perpetuated themselves in reproduction generation after generation (which were not affected when the tails were cut) Reference: Ramirez, D.A., Mendioro, M.S., & Laude, R.P. (2013). Lectures in Genetics. 10 th Edition. Genetics and Molecular Biology Division, Institute of Biological Sciences, University of the Philippines – Los Baños Weismann’s Germplasm Theory Reference: Ramirez, D.A., Mendioro, M.S., & Laude, R.P. (2013). Lectures in Genetics. 10th Edition. Genetics and Molecular Biology Division, Institute of Biological Sciences, University of the Philippines – Los Baños Joseph Gottlieb Kolreuter (1733-1806) - observed that although hybrids between species might have shown uniform appearance, their fertile offspring would usually produce considerable diversity. - Gartner (1772-1850), Naudin (1815-1899), and Darwin reported similar observations Reference: Ramirez, D.A., Mendioro, M.S., & Laude, R.P. (2013). Lectures in Genetics. 10th Edition. Genetics and Molecular Biology Division, Institute of Biological Sciences, University of the Philippines – Los Baños Father of Genetics - while Gregor Mendel was not the first to study biological inheritance, he was nonetheless named the Father of Genetics - attributed mainly to his brilliant insights and methodologies on the garden peas experiment Reference: Ramirez, D.A., Mendioro, M.S., & Laude, R.P. (2013). Lectures in Genetics. 10th Edition. Genetics and Molecular Biology Division, Institute of Biological Sciences, University of the Philippines – Los Baños Question to Ponder! The work of Mendel was not considered important for almost 40 years? Why? The work of Mendel was not considered important for almost 40 years? Why? - Most mathematicians had little knowledge or interest in biology while biologists had little interest in Mathematics - He used hawkweed (Hieracium sp.), an apomictic species, and therefore, exhibited maternal inheritance. - For many years, his paper remained only a reference material for those conducting research Reference: Ramirez, D.A., Mendioro, M.S., & Laude, R.P. (2013). Lectures in Genetics. 10th Edition. Genetics and Molecular Biology Division, Institute of Biological Sciences, University of the Philippines – Los Baños Carl Correns (Germany), Erick Von Tschermak (Austria), and Hugo de Vries (Netherlands) (1900) - independently duplicated Mendel’s experiments on garden peas, maize, primroses, poppies, and many other flowering plants. - obtained the same ratios as those of Mendel - provided follow-up work that Mendel was not able to do - rediscoverers of Mendel William Bateson, Saunders, and Cuenot (1902) - shown that Mendel’s principles also applied to animals Walter S. Sutton (USA) and Theodor Boveri (Germany) (1903) - suggested the association of the Mendelian factors with the chromosomes Reference: Ramirez, D.A., Mendioro, M.S., & Laude, R.P. (2013). Lectures in Genetics. 10th Edition. Genetics and Molecular Biology Division, Institute of Biological Sciences, University of the Philippines – Los Baños Chromosome Theory of Inheritance - the discovery of the sex chromosomes and the demonstration of the association between specific genes and specific chromosomes - demonstrated that each chromosome contained not one but many genes - Thomas Hunt Morgan (1910) and Calvin B. Bridges (1916) Reference: Ramirez, D.A., Mendioro, M.S., & Laude, R.P. (2013). Lectures in Genetics. 10th Edition. Genetics and Molecular Biology Division, Institute of Biological Sciences, University of the Philippines – Los Baños Oswald T. Avery, Collin M. Macleod, and Maclyn McCarty (1940) - identified the deoxyribonucleic acid (DNA) as the hereditary material At King’s College London, Rosalind Franklin obtained images of DNA using X-ray crystallography, an idea first broached by Maurice Wilkins. Franklin’s images allowed James Watson and Francis Crick to create their famous two-strand, or double-helix, model. Reference: Ramirez, D.A., Mendioro, M.S., & Laude, R.P. (2013). Lectures in Genetics. 10th Edition. Genetics and Molecular Biology Division, Institute of Biological Sciences, University of the Philippines – Los Baños James Watson and Francis Crick with their DNA model at the Cavendish Laboratories in 1953. The Historic Photo 51 Agri 13 Principles of Genetics Laboratory Exercise 1 Understanding the Cell Cycle Mr. Roy R. Boten, L. Agr. Course Instructor Importance of Cell Division - crucial in the process of heredity and variation - cells in all organisms grow and reproduce by cell division - as long as the cell is growing and dividing, the physical and metabolic activities of the cells occur in a regular cycle and in a repetitive manner (cell cycle) INTERPHASE (Non-Dividing Phase) - nucleus is very distinct and enclosed by a definite nuclear membrane - presence of nucleoli and a granular network of darkly staining material called the chromatin Reference: Ramirez, D.A., Mendioro, M.S., & Laude, R.P. (2013). Lectures in Genetics. 10th Edition. Genetics and Molecular Biology Division, Institute of Biological Sciences, University of the Philippines – Los Baños G1 Phase. Nucleus and cytoplasm are enlarging toward mature size. Cell increases in volume by imbibing water and nutrients (building new protoplasm). S Phase. Active DNA synthesis (replication) and histones, components of the chromatin (2c = 4c after replication). G2 Phase. Active RNA and protein synthesis necessary for the chromosome. Double chromatin fiber is folded to form a chromosome. Parts of the Chromosome and its type (based on the location of the centromere) M or the Division Phase (Mitosis) - undergone by all somatic (body) and germ cells - means of increasing the number of cells and of replacing worn-out tissues the four stages of mitosis Reference: Ramirez, D.A., Mendioro, M.S., & Laude, R.P. (2013). Lectures in Genetics. 10th Edition. Genetics and Molecular Biology Division, Institute of Biological Sciences, University of the Philippines – Los Baños Prophase – chromosomes shorten, thicken, and become visible as thick rods Metaphase – chromosomes, which are maximally condensed and aligned at the equatorial plate Anaphase – the centromere becomes functionally double. Each member of the doubled chromosomes begins to move toward opposite poles. Telophase – the chromosomes regroup into two nuclear regions Relation to the study of heredity: The chromosome number remains constant through successive cell divisions. The chromosome makeup of the two daughter cells is the same as that of the parent cell, making mitosis an equational division. Meiosis - occurs during the process of gametogenesis (formation of gametes) - spermatogenesis (for male) & oogenesis (for female) - megasporogenesis (in higher plants) - consists of two consecutive divisions (Meiosis I and II) Meiosis I – Prophase I In Coleus, the somatic cells are diploid with 24 chromosomes. How many of each of the following is present in each cell at the stage of mitosis and meiosis indicated below: a. Kinetochores at prophase b. Chromosomes at anaphase c. Chromatids at metaphase I d. Chromosomes at telophase after cytokinesis e. Centromeres at anaphase f. Chromosomes at telophase II after cytokinesis g. Centromeres at anaphase I h. Chromatids at metaphase Agri 13 Principles of Genetics Lecture and Laboratory Exercise 2a Gene Segregation Mr. Roy R. Boten, L. Agr. Course Instructor Gene Segregation - through the works of Mendel on garden peas, he proposed two laws: (1) Law of independent segregation (2) Law of independent assortment - these laws described how the hereditary material is passed from parent to offspring as evidenced by the physical appearance of the offspring Terminologies: - alleles, gene pairs, genotype and phenotype Reference: Ramirez, D.A., Mendioro, M.S., & Laude, R.P. (2013). Lectures in Genetics. 10th Edition. Genetics and Molecular Biology Division, Institute of Biological Sciences, University of the Philippines – Los Baños Law of Independent Segregation - states that the alleles of a gene pair separate completely and cleanly from each other during meiosis. Terminologies: - locus, homozygous, and heterozygous Reference: Ramirez, D.A., Mendioro, M.S., & Laude, R.P. (2013). Lectures in Genetics. 10th Edition. Genetics and Molecular Biology Division, Institute of Biological Sciences, University of the Philippines – Los Baños Law of Independent Assortment - states that the alleles of the different gene pairs separate completely and cleanly from each other and randomly combine during meiosis. Reference: Ramirez, D.A., Mendioro, M.S., & Laude, R.P. (2013). Lectures in Genetics. 10th Edition. Genetics and Molecular Biology Division, Institute of Biological Sciences, University of the Philippines – Los Baños Monohybrid Cross - cross between homozygous individuals that are different from each other at one gene locus. Reference: Ramirez, D.A., Mendioro, M.S., & Laude, R.P. (2013). Lectures in Genetics. 10th Edition. Genetics and Molecular Biology Division, Institute of Biological Sciences, University of the Philippines – Los Baños Monohybrid Cross - cross between homozygous individuals that are different from each other at one gene locus. Terminologies: - complete dominance and Punnett Square (Checkerboard Method) Reference: Ramirez, D.A., Mendioro, M.S., & Laude, R.P. (2013). Lectures in Genetics. 10th Edition. Genetics and Molecular Biology Division, Institute of Biological Sciences, University of the Philippines – Los Baños Dihybrid Cross - cross between two homozygous individuals that are different from each other at two gene loci. - branching method (dichotomous branching) - TEGI and TEPI Agri 13 Principles of Genetics Lecture and Laboratory Exercise 2b Gene Interaction Mr. Roy R. Boten, L. Agr. Course Instructor Gene Interaction - may result in modified phenotypic ratios deviating from those expected of independently assorting genes exhibiting complete dominance. Allelic Interactions – only one gene controls a trait Overdominance Codominance Lethal Genes (Dominant Lethal) – are genes whose lethal effects occur when a dominant allele is present in a homozygous or heterozygous condition. Lethal Genes (Recessive Lethal) – are those that are lethal when in the homozygous recessive condition. Non-Allelic Interactions – two genes are controlling one trait Epistasis – an allele of a gene masks the effect of the allele of the other gene Dominant Epistasis a. Complete dominance at both gene pairs, but one gene, when dominant, is epistatic to the other. (A is dominant to a; B is dominant to b; A is epistatic to B and bb). Dominant Epistasis a. Complete dominance at both gene pairs, but one gene, when dominant, is epistatic to the second. The second gene, when homozygous recessive, is epistatic to the first. (A is dominant to a; B is dominant to b; A is epistatic to B and bb; bb is epistatic to aa; A and bb has the same expression) The green colour of plants is governed by the gene I, which is dominant over the purple colour. The purple colour is controlled by a dominant gene P. When a cross was made between green (Iipp) and purple (iiPP) colour plants, the F1 was green. Inter-mating of F1 plants produced green and purple plants in a 13 : 3 ratio in F2. Recessive Epistasis - Complete dominance at both gene pairs, but one gene, when homozygous recessive is epistatic or masks the effect of the other gene. - (A is dominant to a; B is dominant to b; aa is epistatic to B and bb). Duplicate Genes (Duplicate Dominant Epistasis) - Complete dominance at both gene pairs, but either gene, when dominant is epistatic to the recessive of the other. (A is dominant to a; B is dominant to b; A is epistatic to bb; B is epistatic to aa). Complementary Genes (Duplicate Recessive Epistasis) - Complete dominance at both gene pairs, but either gene, when homozygous recessive, is epistatic to the effects of the dominant allele for the other gene. (A is dominant to a; aa is epistatic to B; B is dominant to b; bb is epistatic to A) Gene Assignment: Novel Phenotypes R __ Rose is dominant to non-rose (rr) - Complete dominance at P __ Pea is dominant to non-pea (pp) both gene pairs. New RRpp (rose) x rrPP (pea) phenotypes are produced F1 – RrPp (walnut) from the interaction between dominants and between both homozygous recessives. (A is dominant to a; B is dominant to b; A interacts with B producing new phenotype; aa interacts with bb to produce new phenotype)
