Inheritance, variation + evolution

• DNA is deoxyribonucleic acid, the chemical that all of the genetic material in a cell is made of, containing coded information that determines inherited characteristics.
• Scientists analyse different types of data to work out evolutionary relationships, such as current classifications data and the fossil record.
• Genes are small sections of DNA found on chromosomes, each coding for a particular sequence of amino acids for a specific protein.
• Only 20 amino acids are used to make thousands of different proteins.
• Genes determine the order of amino acids in a protein and the type of cell it is.
• The genome is the entire set of genetic material in an organism, which scientists have worked out, allowing understanding of inherited diseases and tracing migration patterns.
• DNA strands are polymers made of repeating units called nucleotides, each nucleotide consisting of a sugar, a phosphate group and one base.
• The sugar and phosphate groups form a backbone, which alternate, with one of 4 different bases (A, T, C, G) joining to each sugar.
• The order of bases in a gene decides the order of amino acids in a protein.
• Each amino acid is coded for by a sequence on 3 bases in the gene (a codon) and the amino acids are joined to make proteins depending on base order.
• Some parts of DNA don’t code for proteins and can switch on and off to control synthesis.
• Proteins are made in the cell cytoplasm on ribosomes, which use the code in the DNA from the nucleus which can’t move.
• The correct amino acids are brought to ribosomes in the correct order by carrier molecules (tRNA).
• Proteins perform various functions, including acting as enzymes and hormones.
• Mutations are changes in DNA, which can alter the protein that a gene codes for.
• Insertions are where a new base is inserted into the DNA base sequence, changing the way the 3 bases are read, and can change the amino acids that they code for.
• Deletions are where a random base is deleted from the DNA base sequence, changing the way the base sequence is read and having knock on effects.
• Fossils show how much different organisms have evolved as life has developed, but no one fully knows how life began, there are various hypothesis though.
• Some say that life came from a swamp, or from a comet and developed.
• Cloning involves tissue culture, where plant cells are put in a growth medium and grown into a new plant.
• Cloned embryos are implanted into cows and grow into identical calves.
• Substitution mutations are where a random base is changed to a different base, not having a knock-on effect.
• Adult cell cloning involves removing the nucleus from an unfertilised egg cell and replacing it with an adult body cell nucleus, stimulating the egg cell to divide.
• The best offspring from this process are selected and bred together over several generations, strengthening the desirable characteristic.
• Embryo transplants involve taking sperm from a prize bull and eggs from a prize cow, with sperm artificially fertilising the egg and the embryo being split before differentiation.
• Cloning also involves cutting off cuttings from plants and planting them to produce genetically identical copies.
• Fossils are the remains of organisms found in rocks, providing evidence that organisms lived ages ago, and showing how much they have changed over time.
• Genetic Engineering is a controversial topic, as although it can solve problems, it could create unplanned problems which could be passed onto future generations.
• Reproduction involves the transfer of genetic material from one organism to another.
• Genetic Engineering is used to create bacteria with insulin to treat diabetes, GM crops which make them resistant to disease, insects and herbicides, sheep that can produce substances in their milk to treat human diseases and to treat inherited disease with gene therapy (inserting working genes).
• Crops with disease resistance and dogs with a good, gentle temperament are selected from the existing stock and bred with each other.
• Adult cell cloning was used to create Dolly, the famous cloned sheep.
• GM CROPS are grown in some places without any problems, but not everyone is convinced they are safe or their effects on human health.
• Genetic Engineering involves transferring a gene responsible for a desirable characteristic from one organism’s genome to another, so it also has the desired characteristic.
• Selective breeding is when humans artificially select the plants or animals that are going to breed so particular characteristics remain in the population that make them useful or attractive.
• Most have no effect on the protein or phenotype.
• The fossil record contains many species that don’t exist anymore-they are extinct.
• Environmental variation covers a wide range of differences caused by the environment, including having a tan or a plant with yellow leaves.
• Mutations are changes to the sequence of bases in DNA, which can lead to changes in the protein.
• If a rabbit ran a lot, its legs would get longer and its offspring would be born with longer legs.