Topic 4

• The DNA in eukaryotic cells and prokaryotic cells are similar in that they are both made up of DNA nucleotides, contain deoxyribose, phosphate group, and a nitrogenous base, and are joined together by phosphodiester bonds to form a polymer chain.
• The three key differences between the DNA in eukaryotic cells and prokaryotic cells are that eukaryotic DNA is longer, eukaryotic DNA is linear, and the DNA in eukaryotes is associated with histones, while the DNA in prokaryotic cells is not associated with proteins.
• The DNA in mitochondria and chloroplasts of cells is similar to the DNA in prokaryotic cells in that it is short, circular, and neither is wrapped around histone proteins.
• Non-disjunction can occur in meiosis, resulting in changes in the whole set of chromosomes, known as polyploidy, or changes in the number of individual chromosomes, known as aneuploidy.
• Polyploidy is a change in the whole set of chromosomes, where instead of being diploid, you could have three or four copies of every chromosome.
• Aneuploidy is a change in the number of individual chromosomes, where individual homologous pairs of chromosomes fail to separate during meiosis.
• Down Syndrome is caused by non-disjunction on chromosome 21, resulting in three copies of that chromosome instead of two.
• A gene is a sequence of DNA that codes for the amino acid sequence for a particular polypeptide and also a functional RNA.
• The genetic code features three bases on DNA, known as a triplet, which code for a particular amino acid.
• The genetic code is a degenerate code, universal, and non-overlapping.
• The genetic code is degenerate, meaning there are more than one triplet of bases that codes for the same amino acid.
• The genetic code is universal, meaning the same triplet of bases codes for the same amino acid in all organisms.
• Each base in a codon is involved in one triplet, so if a point mutation occurs it will only affect one codon and therefore one amino acid.
• Introns are sequences of dna bases that do not code for polypeptides, while exons are sequences of dna bases that do code for the amino acids.
• A genome is an organism's complete set of genes in a cell, while a proteome is the full range of proteins that a cell is able to produce.
• The genome of an organism will differ between different species, for example, a bacteria contain on average six hundred thousand dna base pairs within their genome, while humans have three billion dna base pairs.
• Messenger rna is a copy of one gene, is short compared to dna, is single stranded, and is found in both the cytoplasm and the nucleus.
• Transfer rna is found in the cytoplasm, has an amino acid binding site, and its three bases at the bottom are complementary to a particular codon on mrna.
• A ribosome holds transfer rna in place to enable the joining of amino acids, has a clover leaf shape, and its lines represent hydrogen bonds.
• Courtship behavior is essential for successful mating, ensuring the survival of the species.
• Courtship behavior is a sequence of actions which is unique to every species, genetically coded for, and how animals are able to identify members of their own species to ensure reproduction with members of their own species.
• The sequence of courtship behavior could include dance moves, creation of sounds, release of pheromones, display of feathers, and fighting.
• The female observes the courtship ritual and decides if the male is worthy of mating with, based on their fitness and performance to mate.
• Courtship behavior synchronizes mating behavior, ensuring that the male and female are mating when they are sexually mature.
• Courtship behavior can help form a strong pair bond between parents, increasing the likelihood of survival of the offspring.
• Courtship behavior can help select advantageous alleles, ensuring the survival of the entire species.
• Courtship behavior can be used as a way to identify how closely related different species are, as it is genetically coded for and unique to every species.
• Phylogenetic classification arranges groups according to evolutionary origins and relationships, and humans and chimpanzees are most closely related to each other because they branch in the tree most recently.
• A hierarchy is a way of arranging smaller groups within larger groups, with no overlap between those groups.
• Robins are universally used and are closely related, but they are not the same species or genus.
• The binomial system is a universal way of identifying organisms, using two names: the genus and the species.
• Biodiversity can be measured in different ways, including looking at the range of different habitats, the variety of genes amongst all individuals of a population of one species, and the number of different species and individuals within each species in a community.
• Species diversity, a type of biodiversity, takes into account species richness, which is the number of different species in a community.
• Biodiversity can be used to describe a range of habitats, from very small local habitats like forests to the entire earth.
• Low biodiversity isn't a cause for concern in areas like the arctic or deserts, but if there is a decrease in biodiversity, it can be caused by human activity and is a cause for concern.
• The index of diversity is used to measure biodiversity, describing the relationship between the number of species in a community, which is the species richness, and the number of individuals within each species.
• The formula for the index of diversity is lowercase n times n minus one, where lowercase n is the population size of species a and n minus one is the lowest value you can get.
• The larger the value of the index of diversity, the greater the biodiversity.
• Genetic diversity within or between species can also be measured by comparing different factors, such as observable characteristics, dna base sequence, mrna-based sequence, or amino acid sequence for proteins.
• The more similar the sequences, the more closely related the species must be.