Unit 2: Genetics Lesson 1: The Nature of Heredity Nelson Biology 11: Section 4.1

Learning Goals All students will: Understand and explain what genetic material is Explain the benefits of sexual and asexual reproduction

Nature of Heredity Multicellular organisms use cell division and reproduction for growth and repair Unicellular organisms use it for reproduction Heredity – the passing of traits from parents to offspring (through chromosomes from parent cells to daughter cells)

Genetic Material Genetics – the scientific study of heredity and variation of inherited characteristics In a chromosome, genetic information is contained in a molecules of DNA (deoxyribonucleic acid) Gene – segment of a DNA molecule that codes for a particular trait: found at a specific location on a chromosome

Genetic Material Continued Locus (loci pleural) – the location of a gene on a chromosome

Chromosomes Chromosomes are found in the nucleus of all eukaryotic cells but vary in size, shape and number between different species Most multicellular organisms have less than 100 chromosomes In most multicellular organisms, chromosomes occur in sets – Diploid cells have two sets of chromosomes – Haploid cells have half the normal number of chromosomes – Polyploids are cells with three or more sets of chromosomes (a lot of plants!)

Species Chromosomes

Asexual Reproduction Asexual Reproduction – the production of offspring from a single parent; the genetic makeup of the offspring is identical to that of the parent Advantages of asexual reproduction: – Parent organism doesn’t have to find a mate, perform mating behaviours or possess specialized anatomy – Results in heredity that is direct and invariable – Quicker process, allows for exploitation of environment

Sexual Reproduction Sexual Reproduction – the production of the offspring from the fusion of two sex cells (usually from two different parents); the genetic makeup of the offspring is different from that of either parent Disadvantages of Sexual Reproduction – Must have specialized organs to produce sex cells – May inherit bad genes that make you weak and unable to survive – Sex is costly and risky! Animals, producing mating calls or being brightly coloured can help attract a mate but also predators Plants, producing flowers attracts pollinators but requires the production of nectar

Why Sexual Reproduction? If individuals were to rely on asexual reproduction only, their descendants would remain almost genetically identical over countless generations – Only beneficial if the parent is well adapted to the environment and environment is unchanging Sexual Reproduction creates variable offspring which allows for flexibility or insurance if the environment changes

To Do: Complete questions 1-10 on page 141