My topic 4

• Genetic diversity = the number of different alleles in a population
• Evolution = change in allele frequency in a population over time.
• Process of natural selection

  1 = new alleles for a gene are created by random mutations (genetic diversity)

  2 = If new allele increases chance of survival in that environment, they are more likely to survive and reproduce

  3 = Through reproduction advantageous allele is passed on to next generation

  4 = Over many generations, the new allele increases in frequency in the population
• Directional selection = one of the extremes has a selective advantage. Only occurs if there is a change in the environment. Modal trait changes
• Stabilising selection =the modal trait has the selective advantage. Occurs when there is no change in the environment. Standard deviation decreases
• What is a hierarchy?

  Smaller groups arranged within larger groups. No overlap between groups
• Why do we need classification systems?

  • understand relationships between organisms and keep track of changes
  • the system needs to be universal
• Phylogenetic classification = arranges species into groups according to their evolutionary origins and relationships
• Species diversity = the number of different species and individuals within each species in a community
• Genetic diversity = the variety of genes amongst all the individuals in a population of one species
• Ecosystem diversity = the range of different habitats
• Species richness = number of different species in a particular area at a particular time
• Biodiversity includes - species diversity + species richness + genetic diversity + ecosystem diversity
• How is index of diversity different to species richness ?

  Index of diversity = number of different species in a community + number of individuals in each species

  Species richness = number of different species in a community
• Define variation

  Differences that exist between individuals. Genetic variation is caused by differences in the genetic code. Genetic variation happens when individuals in the same species have different alleles. Alleles are different versions of the same gene.
• In what ways can variation be caused?

  It can be caused by genetic factors, such as alleles from mutations.

  It can also be caused by the environment, such as climate.

  Most variation is caused by a combination of genetic factors and environmental factors
• Why is it impossible to study a whole population?

  Because it is too large and would take too long. Instead, scientists use a sample that is representative of the species' population
• Why should the sample taken be random?

  So you can make sure that the sample isn't biased in any way.
• What could you calculate to look at variation between species?

  The mean (average)
• What is standard deviation?


  It tells you how much values in a single sample vary, by measuring the spread of values about the mean
• What does a large standard deviation mean?

  That the values in the sample vary a lot
• What does a small standard deviation mean?


  That the values in the sample varies little
• What can you use standard deviation to draw on a bar chart of mean values?


  An error bar. You would draw it one standard deviation either side of the mean value.
• How is DNA stored in eukaryotic cells?

  1) The DNA is linear and exists as chromosomes

  2)It is stored in the nucleus, and has to be wound up because it is so long

  3) It is wound around proteins called histones which help to support the DNA

  4)The DNA is coiled very tightly to make a compact chromosome
• How is DNA stored in prokaryotic cells?

  1)Prokaryotic cells carry DNA as chromosomes, but the DNA is shorter and circular

  2)It isn't wrapped around histones, so condenses into the cell by supercoiling
• What organelles in eukaryotic cells have their own DNA apart from the nucleus?


  The mitochondria and chloroplasts have their own DNA. It is similar to prokaryotic DNA as it is shorter, circular and isn't wrapped around histones.
• What is a gene?

  A gene is a sequence of DNA bases that codes for a polypeptide or functional RNA
• What forms the primary structure of proteins?

  The sequence of amino acids.
• What determines the order of amino acids in a polypeptide?

  The order of the bases
• How is each amino acid coded for?

  By a sequence of three bases in a gene called a triplet
• What is functional RNA?

  It is RNA molecules other than mRNA that perform special tasks during protein synthesis.

  
  

  tRNA and rRNA
• What is a cell's genome?


  The complete set of genes in a cell
• What is a cell's proteome?


  The full range of proteins that the cell is able to produce
• If a gene doesn't code for polypeptides, what does it code for?

  Functional RNA such as tRNA and rRNA
• What are introns?

  Sections of a gene that codes for polypeptides, that doesn't actually code for amino acids
• What are exons?

  The sections of a gene that actually code for amino acids
• When are introns removed, and why?

  They are removed during protein synthesis so it doesn't affect the amino acid order

  
• Which type of DNA does not have introns?

  Prokaryotic DNA does not have introns
• What is an allele?

  The same gene, but a different version of it
• What makes two genes alleles?

  The order of bases in each is slightly different. so they code for slightly different versions of the same polypeptide.