4. Genetics, variation and interdependence

• a cell's genome is the complete set of genes in the cell
• a cell's proteome is the full range of proteins that the cell is able to produce
• introns are non-coding regions of DNA
• A gene is a base sequence of DNA that codes for the amino acid sequence of a polypeptide or a functional RNA molecule.
• alleles are different versions of the same gene
• alleles coding for the same gene will be found on the same locus
• mRNA is made during transcription
• mRNA is a single polynucleotide strand
• tRNA is involved in translation
• tRNA is a single polynucleotide strand, that is clover shaped and has an anticodon
• what are the three key features of the genetic code?

  non-overlapping, degenerate and universal
• what does it mean that the genetic code is degenerate?

  there are more possible combinations of triplets than there are amino acids, so the same amino acid can be coded for by more than one triplet
• what does in mean that the genetic code is non-overlapping?

  Each nucleotide in the genetic code is only read once and is not shared by multiple codons.
• what does in mean that the genetic code is universal?

  the same specific base triplets code for the same amino acids in all living things
• DNA from one generation is passed to the next by gametes
• how does meiosis produce genetically different cells?

  crossing over of chromatids and independent segregation of chromosomes
• chromosome mutations are caused by errors in cell division
• what is a non-disjunction mutation?

  chromosome mutations where chromosomes fail to separate properly
• a substitution mutations is when one base is substituted with another
• a deletion mutation is when one base gets deleted
• what are 4 examples of mutagenic agents?

  UV radiation, ionising radiation, some chemicals and viruses
• lots of different alleles means a high genetic diversity
• what increases genetic diversity within a population?

  mutations and gene flow
• gene flow is the introducing of new alleles into a population from outside
• genetic diversity is what allows for natural selection
• a population is a group of organisms of one species living in a particular habitat
• genetic diversity is the number of different alleles of genes in a species or populaiton
• a genetic bottleneck is an event that causes a big reduction in a population
• the founder effect is what happens when a few organisms from a population start a new colony and there are only a small number of different alleles in the initial gene pool
• a gene pool is the total number of alleles in a population
• natural selection increases advantageous alleles in a population
• what are the 3 possible types of adaptations?

  behavioural, physiological and anatomical
• directional selection is when individuals with alleles of an extreme type are more likely to survive and reproduce
• stabilising selection is where individuals with alleles for characteristics towards the middle of the range are more likely to survive and reproduce
• phylogeney tells us about the evolutionary history of organisms
• taxonomy is the science of classification
• what are the 8 taxas in order?

  Domain, kingdom, phylum, class, order, family, genus, species
• a species is a group of organisms that are able to interbreed to produce fertile offspring
• what are the names used in the binomial naming system of species?

  genus name, species name
• what are three methods used to look at evolutionary relationships of organisms?

  genome sequencing, amino acid sequencing, immunological comparisons