Genetic variation: week 4

• Asexual reproduction is the mechanism of producing offspring that does not involve the production and fusion of gametes
• Sexual reproduction is the production of offspring through the generation and fusion of gametes
• in asexual reproduction all indivduals can bear offspring
• asexual reproduction is more efficient than sexual reproduction
• production of genetically diverse offspring leads to populations in which some individuals are better able to resit evolving pathogens and parasites
• At the evolutionary level, is it random with respect of fitness because some mutation are beneficial, neutral, bad
• Mutation creates genetic variation because there are random changes in the DNA which create new allele because the alleles are the genotype of our DNA
• Mutation occurs because of replication, when the DNA is copied which happens before mesois. It doesn't get passed on to the next generation.
• The physical cause of mutation is that any error that happens in the replication process or some damage to the DNA
• The 4 sources of genetic mutation is mutation, independent assortment, crossing over, outcrossing
• Independent crossing create genetic variation because the homologs algin at the metaphase plate and could line left to right or right to left
• Independent assortment occurs in metaphase one or metaphase two, then the sister chromatids align to left to right or right to left
• The physical cause of independent assortment is the alignment of chromosomes. the alignment is either random or independent of each other
• crossing over creates genetic variation from alleles from one chromosome going onto the other chromosomes it changes which alleles are on which chromosomes. creating variation within a single chromosome because we are sampling one allele in and out.
• crossing over happens in meiosis when the homologous pairs synapse
• homology means similarity in organisms due to common ancestry.
• the physical cause of crossing over is the synapsis or crossing over
• recombination is the result from crossing over
• outcrossing is when gametes come from two different individuals
• selfing is still sexual reproduction because we still have two separate gametes that come together
• outcrossing is selfing
• Outcrossing creates genetic variation because when you are taking genes or alleles from one individual and an allele from another individual, new combinations of new chromosomes and alleles, and because of that there might be brand new alleles from mutation, these gametes already finishing crossing over and recombination, the chromosomes have already sorted independently in the creation of these gametes.
• outcrossing occurs in fertilization when the gametes fuse together
• the physical cause of outcrossing is two haploid cells gametes that come together to create a haploid gametes that come together to create a diploid individuals
• haploid is (1n)
• Diploid is 2n
• if a plant lineage self's rather than outcrosses due to mutation, individuals may have new alleles, and due to selfing Puneet square, individuals will be homozygous for 50% of the genes where their parents are heterozygous
• if a bacteria reproduces asexually due to mutation, individual may have new alleles
• purifying selection gets rid of deleterious alleles
• How does purifying selection work?

  So if there is a deleterious allele in a population, if that population is reproducing asexually, every one of the offspring will have that deleterious allele because it is just a copy with additional mutations, right passed from generation to generation. However, if there is a deleterious allele in a population, but then sexual reproduction happens, only half of the individuals will have a deleterious allele because they are getting one allele from each parent
• A deleterious allele is a version of a gene that, on average, decreases the fitness of the organism carrying it.