Introduction to Genetics - Genetic variation and heredity
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The document provides an overview of genetics, focusing on heredity, DNA, chromatin, and chromosome structure, alongside key genetic concepts such as alleles, genotype, and phenotype. It explains how traits are inherited and emphasizes the importance of understanding genetics for health and disease prevention. Additionally, it covers ploidy types, the human chromosome count, and fundamental genetics terms and principles.
Introduction to Genetics - Genetic variation and heredity
- 1. Dr. G. Shanmugavel, Assistant Professor of Biology , Department of HSS, Puducherry Technological University Email : shanmugavel.g@ptuniv.edu.in
- 2. Introduction to Genetics • Genetics is a branch of biology that deals with the genetic variation and heredity in living organisms. • The passing of traits from parents to offspring is known as heredity. • The term Genetics was firstly introduced by “William Bateson” in 1906. • It has been derived from the Greek word Gene - which means "to become" or "to grow into". • Understanding the concept of genetics and associated disorder is important in learning more about promoting health and preventing disease.
- 3. Introduction to Genetics • Genetics is built around molecules called Deoxyribonucleic acid (DNA). • DNA molecules hold all the genetic information for an organism. It provides cells with the information they need to perform tasks that allow an organism to grow, survive and reproduce. • A gene is one particular section of a DNA molecule that controls a cell to perform one specific task. • During reproduction, DNA is replicated and passed from a parent to their offspring. This inheritance of genetic material by offspring influences the appearance and behavior of the offspring. • The environment that an organism lives in can also influence how genes are expressed.
- 4. Genetic material, chromatin, chromosome, DNA, Gene
- 5. Chromatin, chromosome, chromatid • Chromatin is a mass of genetic material composed of DNA and proteins that condense to form chromosomes during eukaryotic cell division. Chromatin is located in the nucleus of our cells. • Chromosomes are single-stranded groupings of condensed chromatin. During the cell division processes of mitosis and meiosis, chromosomes replicate to ensure that each new daughter cell receives the correct number of chromosomes. A duplicated chromosome is double-stranded and has the familiar X shape. The two strands are identical and connected in a central region called the centromere. • A chromatid is either of the two strands of a replicated chromosome. Chromatids connected by a centromere are called sister chromatids. At the end of cell division, sister chromatids separate, becoming daughter chromosomes in the newly formed daughter cells.
- 6. Chromatin and condensed chromosome structure
- 7. DNA vs Gene DNA Gene DNA is a long chain polynucleotide which stores the genetic information of an organism Genes are the segment of DNA which are encoded for different proteins DNA composed of two chains which coil around each other to form a double helix Gene made up of either DNA or RNA DNA determines many functions such as gene regulation, expression etc. Gene determines the traits of an organism
- 8. What is ploidy? • Ploidy is the number of complete sets of chromosomes in a cell. Monoploidy – One complete set of chromosomes Diploidy – Two complete set of chromosomes Polyploidy – Three or more complete set of chromosomes Monoploidy Diploidy Polyploidy Triploidy Teraploidy
- 9. How many chromosomes do we have? • Humans are diploid organisms, carrying two complete sets of chromosomes in their somatic cells: one set of 23 chromosomes from their father and one set of 23 chromosomes from their mother. The two sets combined provide a full complement of 46 chromosomes. • When a human germ cell undergoes meiosis, the diploid 46-chromosome complement is split in half to form haploid gametes (1 set of 23 chromosomes). • After fusion of a male and a female gamete during fertilization, the resulting zygote again has the full complement of 46 chromosomes: 2 sets of 23 chromosomes. 23 pairs of homologous chromosomes presence in human cell
- 16. Genetics terms you need to know: • Gene: a unit of heredity; a section of DNA sequence encoding a single protein. • Genome: the entire set of genes in an organism. • Traits: a characteristics, e.g. height, colour etc • Alleles: Alternative form of gene or traits. Two genes that occupy the same position on homologous chromosomes and that cover the same trait.
- 17. • Locus – a fixed location on a strand of DNA where a gene or one of its alleles is located. • Homozygous – having identical genes (one from each parent) for a particular characteristic. • Heterozygous – having two different genes for a particular characteristic. • Dominant – the allele of a gene that masks or suppresses the expression of an alternate allele; the trait appears in the heterozygous condition. • Recessive – an allele that is masked by a dominant allele; does not appear in the heterozygous condition, only in homozygous.
- 18. Genotype and Phenotype • Genotype: Genetic makeup of an organism. It is determined by the alleles present for each trait. It can be represented by symbols, e.g. BB, Bb, bb • Phenotype: Physical appearance of an organism. It is the expression of the genotype. E.g. height of stem, color of flower.
- 19. Genotype and Phenotype A – dominant allele, a recessive allele
- 20. • True breeding: When the plants self-pollinate, all their offspring are of the same variety. • Hybridization: Mating, or crossing, of two varieties. • Monohybrid cross: a genetic cross involving a single pair of genes (one trait); parents differ by a single trait. – P = Parental generation – F1 = First filial generation; offspring from a genetic cross. – F2 = Second filial generation of a genetic cross
- 21. References: • Concepts of Genetics (9th ed.), W. S. Klug, M. R. Cummings, C. Spencer, C. A. Spencer, and M. A. Palladino, Pearson, 2008. • Molecular Genetics (Second edition), Stent, G. S.; and Calender, R. W.H. Freeman and company, Distributed by Satish Kumar Jain for CBS Publisher. • Human genetics : concepts and applications. Lewis, Ricki. (2007). Boston :McGraw-Hill Higher Education. • Genetics (9th ed.), Verma PS and Agarwal VK (2010). Publisher: S Chand & Co Ltd. • Textbook of PUBLIC HEALTH AND HYGIENE, G Shanmugavel and Binu George (2021). Publisher: Darshan Publishers. • Textbook of BIOLOGY FOR ENGINEERS, G Shanmugavel (2024). Publisher: Lambert academic publishing.