1 / 18

Genetics and DNA

Genetics and DNA. Contents. Genes Alleles Clones Tissue Culture Animal Cloning Evolution Mutation Evidence for Evolution Layout of Fossils Example of Evolution Extinction Variation. Genes. Inside the nucleus  chromosomes Chromosome = 1000s of coils of genes

snow
Download Presentation

Genetics and DNA

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Genetics and DNA

  2. Contents • Genes • Alleles • Clones • Tissue Culture • Animal Cloning • Evolution • Mutation • Evidence for Evolution • Layout of Fossils • Example of Evolution • Extinction • Variation

  3. Genes • Inside the nucleus  chromosomes • Chromosome = 1000s of coils of genes • Gene = comprise ‘DNA’ that decides our characteristics • DNA = deoxyribose nucleic acid (chemical) • Each gene acts as a code for a particular characteristic

  4. Genes • A human egg cell and sperm cell contains 23 chromosomes • Embryo therefore contains 23 pairs of chromosomes • Each pair contains a gene from your mother, and a gene from your father for a particular characteristic • So each pair contains two “options” for a characteristic • These options are called alleles • e.g. gene = eye colour; alleles = blue eye colour, brown eye colour

  5. Alleles • An Allele is an alternative form of a gene (one member of a pair) that is located at a specific position on a specific chromosome. • Alleles are dominant or recessive • Homozygous = two same alleles (purebred) • Heterozygous = two different alleles • Dominant + recessive  dominant • Dominant + dominant  dominant • Recessive + dominant  dominant • Recessive + recessive  recessive e.g. BB, Bb = brown eyes; bb = blue eyes Two parents are Bb + bb; offspring has 50% chance of blue eyes

  6. Eye Colour A heterozygous brown-eyed father and a blue-eyed mother: 50:50 chance of being either brown eyed or blue eyed

  7. Clones • Clone = organism that is genetically identical to its parent • Cloning in nature: • Potato tubers • Strawberry runners • Daffodils • Tissue Cultures: • Plants multiply very quickly by human intervention • A number of cells are taken from the ‘parent’ plant and are grown by mitosis in growth hormones

  8. Tissue Culture

  9. Animal Cloning • Simple organisms reproduce by mitosis (e.g. amoeba) so identical offspring are produced • Artificial Clone Example: Dolly the Sheep (1996) • Adult sheep egg removed from ovary – nucleus removed • Empty egg cell fused with DNA of udder cell of donor sheep • Fused cell developed, using donated DNA • Embryo implanted into uterus of foster-mother sheep Result: Dolly became genetically identical to donor sheep

  10. Evolution • Darwin made 4 key observations: 1) Living things tend to produce more offspring than survive 2) Population numbers in a species stay constant over time 3) Each species displays a wide variation in features 4) Some of these variations are passed on to offspring • Living things are in continuous competition with each other for food, space, mates… • ‘Survival of the Fittest’! • Natural Selection: Survival of organisms best suited to surviving and reproducing in their environment

  11. Mutation • During replication, an organism’s genetic make-up (DNA) can change or mutate. • If mutation is large… - organism will probably not survive to reproduce • If mutation is small… - change might be beneficial. Offspring will flourish, doing better than others in that species. - Many more offspring will inherit this beneficial mutation and will be better suited to that environment… • Thus continues natural selection…

  12. Evidence for Evolution • Comes from rocks and fossils… • The remains of organisms from millions of years ago are preserved as fossils in sedimentary rocks • Fossils are formed in one of two ways: 1) Organism decomposes, and minerals become implanted in the tissue so that the organism turns to rock 2) Organism’s shape leaves an impression in the ground • Fossils are formed in areas of insufficient oxygen to decay, in low temperatures (glaciers) and high soil acidity (peat bog)

  13. Example of Evolution • The horse • Fossils provide evidence for the main stages of evolution of the horse over 60 million years • Dog-sized  2m in height • Multi-toed feet for walking on forest floor  single-toed hooves for running over open country

  14. Extinction • Species or whole families of organisms die out • Any of 3 factors can contribute to extinction: - environment changes too quickly - new predator or disease kills them - beaten by another species for competition for food • The environment is slowly changing. Gradually, certain characteristics will become favourable and those species without these characteristics will die out • The environment can change quickly. This affects great numbers of species that cannot keep up with the changes required for survival

  15. Environmental Variation • Causes: climate, diet, lifestyle, culture, accidents • Environment affects how our inherited characteristics develop • Twins who grow up separately might become very different: • e.g. fashion, taste, hair colour, build, personality, aptitudes

  16. Genetic Variation • Causes: - Mixing of parent information during meiosis - Gamete forms from a unique combination of genetic information • Siblings can have both similar and very different traits • They are mixtures of their parents, each sibling can receive different characteristics of their parents • e.g. natural hair colour, eye colour, blood type

  17. Continuous vs. Discontinuous • Continuous Variation - Small differences between individuals - Greatly affected by environment - e.g. height, shoe size, length of hair - plotted on a line graph • Discontinuous Variation - Differences that are classed or categorised - Not greatly affected by environment - e.g. blood group, sex, hair colour, eye colour - plotted on a bar chart or pie chart

  18. Summary • Genes: instructions for our genetic make-up (e.g. eye colour) • Alleles: different types of the same gene (e.g. blue eyes) • Clones: genetically identical to the parent (mitosis) • Tissue Culture: Many of a specialist organism type produced • Animal Cloning: used for selective breeding • Evolution: Survival of the fittest! • Mutation: Cells mutate under certain conditions • Evidence for Evolution: Rocks and fossils • Layout of Fossils • Example of Evolution: Horse • Extinction: Occurs for 3 main reasons

More Related