Living Organisms Some basic characteristics of life: Need H2O GAS EXCHANGE Need NUTRIENTS Made of CELLS REPRODUCE Living Organisms Some basic characteristics of life: All living things need H2O Living Organisms Some basic characteristics of life: Living things Need NUTRIENTS Living Organisms Some basic characteristics of life: Living things have a system for GAS EXCHANGE Living Organisms Some basic characteristics of life: Made of CELLS Living Organisms Some basic characteristics of life: All living things REPRODUCE ASEXUALLY SEXUALLY to create new individuals that are clones to create new individuals with a combination of traits ASEXUAL REPRODUCTION • Only one parent reproduces. • The same genetic material (DNA) is passed directly from parent to offspring. • All offspring are CLONES of the parent and have the exact same traits. Types of Asexual Reproduction • Fission Cell division by a parent cell splitting into two parts, each growing into a new exact copy of the parent cell. • Budding To develop as a growth on a parent, then break off and mature into a new exact copy of the parent. • Fragmentation and Regeneration Offspring can grow from a fragment (piece) of the parent, or the parent can re-generate the missing piece. FISSION FISSION BUDDING Planarians are flat worms that can be rapidly regenerate. Fragmentation They can be cut across or along their body. Regeneration SEXUAL REPRODUCTION • Two parents (of opposite sex) reproduce. • Two sex cells (one from each parent) combine during fertilization. • Parents combine genetic material (DNA) to form offspring that has a COMBINATION of parent’s traits. Sperm 23 x Egg 23 X zygote 46 X Female cell divides to produce eggs Contains half of the mother’s DNA Male cell divides to produce sperm Contains half of the father’s DNA Mothers half + fathers half = Full set of DNA Genes and Chromosomes GENES and CHROMOSOMES • Inside the cell nucleus are chromosomes. • Chromosomes are bundles of tightly coiled strands of long molecules called DNA. • A segment of DNA codes for a trait. • These segments are called GENES. A gene codes for a specific type of trait. Each trait is determined by a pair of GENES. A chromosome is a bundle of DNA. Segments of DNA are genes. Gregor Mendel -Austrian Monk -Gardener/Scientist -Worked with peas -Noticed patterns of traits in generations -Developed the main idea of heredity Gregor Mendel determined that… • Each trait is determined by a pair of genes – one from each parent. • Both parents contribute equally to your genes. • A gene is either dominant or recessive. • Three possible gene pairs for any trait: 2 dominant genes 2 recessive genes 1 dom and 1 rec gene Dominant Genes • Dominant genes are ‘stronger’ than recessive genes, and can cover them up. • If at least one gene in the gene pair is dominant, then the individual will ‘express’ the dominant form of the trait. • Represented with a CAPITAL letter… Usually the first letter of the trait. • Ex: Black fur is dominant, so B = a dominant gene. Recessive Genes • Recessive genes are weaker, and cannot cover up dominant genes. • ONLY if both genes in the gene pair are recessive, then the individual will ‘express’ the recessive form of the trait. • Represented with a lower case letter.. Usually the first letter of the trait. • Ex: Black fur is dominant, white fur is recessive, so b = a recessive gene. Genotypes and Phenotypes Possible gene combinations Genotype AA 2 dominant genes Purebred dominant 1 dominant gene and 1 recessive gene Aa Hybrid aa 2 recessive genes Purebred recessive Phenotype Dominant trait expressed Dominant trait expressed Recessive trait expressed Gregor Mendel studied many traits of pea plants, like seed color and shape, and the color of the petals. Traits in Humans Dominant • • • • • • • • • Brown eyes farsightedness normal vision normal vision normal vision Dimples unattached earlobes Freckles broad lips Recessive • • • • • • • • • Gray, blue, green, hazel normal vision Nearsightedness night blindness color blindness* no dimples attached earlobes no freckles thin lips Practice Questions DIMPLES ARE DOMINANT OVER DIMPLE-LESSNESS. What is the genotype of someone who has no dimples? dd What is the phenotype of someone who has a genotype of Dd? They have dimples. Practice Questions CURLY HAIR IS DOMINANT OVER STRAIT. What is the genotype of someone who has curly hair? CC or Cc What is the phenotype of someone who has a genotype of cc? They have straight hair. Practice Questions Which of the gene pairs are: Purebred dominant? Aa BB Cc dd Hybrid? Purebred recessive? ee FF Gg hh