Factors The Impact Upon Allele Frequency

Factors the impact upon allele frequency. • • The frequency data is one way that variations within a species can be compared. It is based on determining the proportions of the variations of various alleles located on one locus on a chromosome. If it is possible some alleles within a population. will have no genetic variation. This is the case when the existence of the allele in a specific form is essential to survive so that nay mutations or variations would be automatically deleted (i.e., any organisms who lack that form of an allele, would automatically die. In this case mutations are a disadvantage, because if they were to occur, the organism would die.) Factors that impact upon allele frequency • Migration For example, of a group of white moths used to live in an area where tree trunks are white (note in that area they survived as they were able to comforlarge), to an area where tree trunks are dark in colour, they are unable to survive because they cannot comforlarge. So, because of that migration, the allele frequency for white moths got reduced within that population. • Mutation Mutation are mistakes in the copying of DNA. Let’s say we have a pepped moth that had a mutation and as a result it is colour turned to be white. Let’s again that a sudden environmental changed occurred that favours white moths, that white both will survive and reproduce and thus the allele frequency for white moths will increase. • Natural selection Let’s again that a sudden environmental changed occurred that favours white moths, that white both will survive and reproduce and thus the allele frequency for white moths will increase. • Artificial selection For example, let’s say we want more white flowers, and we undergo artificial selection and insemination, and we create more white flowers. Now, if these white flowers are able to survive then they will produce more offspring of white flowers, and thus we have increased the allele frequency for white flowers. Microevolution and population genetics ✓ Natural selection over time will be called genetic drift, which leads to microevolution. ✓ Population genetics involved with the study of allele frequencies in a populations and how these change over time. ✓ Microevolution, or evolution on a small scale, is defined as a change in the frequency of gene variants, alleles, in a population over generations. The field of biology that studies allele frequencies in populations and how they change over time is called population genetics. ✓ Microevolution (small changes, such colour) is sometimes contrasted with macroevolution, evolution that involves large changes, such as formation of new groups or species, and happens over long time periods. However, most biologists view microevolution and macroevolution as the same process happening on different timescales. Microevolution adds up gradually, over long periods of time to produce macroevolutionary changes. Analysing Single Nucleotide Polymorphism (SNP) Key definitions: • • SNPs are genomic loci where alternative bases occur in at least 1% of the population. Genetic finger printing refers to the comparison of DNA to determine identity or familial relationship (e.g., in forensic matching of crime-scene biological evidence). Content • • • • • • • This method is another way to compare similarities and differences in genetic variation within and between species. SNPs are variations in one nucleotide base, such as T being substituted with C on a particular point in the DNA. The variations when compared with the general population, much occur with at least 1% frequency. SNPs may occur in coding or non-coding sections of the genome but are most common in the sections between genes. SNPs account for 90% of naturally occurring human DNA variation and occur one average once every 300 nucleotides. Genetic finger printing does not tend to use SNPs for identification because they are so frequent within a genome (genome: collection of genes). This means that dozens would have to be compared to result in identification. Advancements in technology and automation have increased the potential for SNPs. When SNPs occur within a gene or a nearby regulatory region they may impact a gene’s function and directly cause a disease. Alternative they can be used as biological markers to help scientists locate genes associated with disease. They can be used in sustainable agriculture. Applications of SNPs • • • • • Researchers have found SNPs that may help predict an individual's response to certain drugs, susceptibility to environmental factors such as toxins, and risk of developing particular diseases. SNPs can also be used to track the inheritance of disease genes within families. Gene discovery Gene mapping (locating genes) Response prediction Gene function identification Identifying trends • • • Trends are identified by comparing data over time or across different locations or population groups. Patterns are detected when there are similar trends such as an increase in allele frequency over time for several alleles. Identification or relationships occur when a trend can be linked to external factors. Changes in human skin pigmentation have been linked to adaptations for protection from skin cancer and the ability to make vitamin D from exposure to ultraviolet radiation. Limitations Collecting data on the frequency of characteristics in a population is dependent on observational data, obtaining accurate family records, and decisions about aspects of particular phenotypes. Phenotypes only provide indirect evidence of the genotype and such are an inaccurate guide to gene frequency.