Topic 4 Abit Flashcards
What are alleles and how do they arise?
Variations of a particular gene (same locus) - different DNA base sequence
• Arise by mutation
Population
A group of organisms of the same species in a particular space at a particular time
That can (potentially) interbreed (to produce fertile offspring)
Explain the importance of genetic diversity
Enables natural selection to occur
As in certain environments, a new allele of a gene might benefit its possessor By resulting in a change in the polypeptide (protein) coded for that positively changes its properties
• Giving possessor a selective advantage
Evolution
Change in allele frequency (how common an allele is over many generations in a population
• Occurring through the process of natural selection
3 types of adaptation
Anatomical - structural / physical features that increase chance of survival
• physiological processes / chemical reactions tharine anancorso/survival
Behavioural - ways in which an organism acts that increase chance of survival
Suggest why 2 different species are unable to produce fertile offspring
Different species have different chromosome numbers → offspring may have odd chromosome number
• So homologous pairs cannot form - meiosis cannot occur to produce gametes
Describe a phylogenetic classification system
Species (attempted to be) arranged into groups, called taxa, based on their evolutionary origins (common ancestors) and relationships
• Uses a hierarchy:
Smaller groups are placed within larger groups
No overlap between groups
Suggest an advantage of binomial naming
Universal so no confusion as many organisms have more than one common name
How can genetic diversity within or between species be measured?
Comparing frequency of measurable or observable characteristics
Comparing base sequence of DNA
Comparing base sequence of mRNA
Comparing amino acid sequence of a specific protein encoded by DNA and mRNA
Explain how comparing DNA, mRNA and amino acid sequences can indicate relationships between organisms within a species and between species
More differences in sequences → more distantly related / earlier common ancestor
As mutations (change in DNA base sequences) build up over time
More mutations cause more changes in amino acid sequences
Explain the change in methods of investigating genetic diversity over time
Early estimates made by inferring DNA differences from measurable or observable characteristics
• Many coded for by more than one gene → difficult to distinguish one from another
• Many influenced by environment - differences due to environment not genes
• Gene technologies allowed this to be replaced by direct investigation of DNA sequences
Explain how data should be collected when investigating variation within a species quantitatively
Collect data from random samples → to remove bias
• Use a grid / divide area into squares
• Use a random number generator to obtain random coordinates
• Use same method of measurement each time
• Use a large sample size / measure a large number of organisms → so representative of population
• Calculate a running mean and sample until number becomes (fairly) constant
• (Where applicable ensure sampling is ethical → must not harm organism
