GIVE AN ACCOUNT OF THE ROLES OF GENETIC MUTATIONS AND MEIOSIS IN GENERATING GENETIC DIVERSITY (20)
GIVE AN ACCOUNT OF THE ROLES OF GENETIC MUTATIONS AND MEIOSIS IN GENERATING GENETIC
DIVERSITY (20)
Marking Scheme
Synopsis, Clarity, English Language, sequence of events (3)
Introduction (1), Scientific content (15), Conclusion (1).
Introduction: Genetic Diversity: Every individual has a unique genotype. This is equal to the combination of alleles of all its genes.
The greater the number of genotypes in a population, the greater the genetic diversity.
Genetic mutations produce new alleles of genes that increase variation- Gene mutation are permanent changes in nucleotide sequence in codons of the gene/ produced when DNA replicates/ alters the AA sequence in the polypeptide and therefore the structureand function of the polypeptide or protein/ may be harmful e.g. cystic fibrosis or beneficial e.g. antibiotic resistance in bacteria. (3)
Roles in generating genetic diversity: Increases the number of alleles and so the range of possible genotypes and phenotypes in the population e.g. consider 1 gene with 2 alleles:- 2 phenotypes may result. But 1 gene with 3 alleles e.g. ABO blood system (including co-dominance) results in 4 phenotypes: blood groups A,B, AB, and O blood groups. Mutations occur at random. The mutated form of the gene is passed on every time the DNA replicates (4)
Chromosome Mutations e.g. Aneuploidy and Polyploidy lead to different dosage effects of particular genes in the genotypes and therefore to genetic diversity.
Meiosis: Overview of meiosis with explanation of crossing over and independent assortment. (4)
Role of meiosis in generating genetic diversity: crossing over and independent assortment mixes up existing combinations of alleles of all genes to increase range of genotypes and therefore genetic diversity). Increase in genetic diversity of gametes results. Fertilization results in random fusion of gametes; this increases genetic diversity even further in the population. (4)
Conclusion: Maintenance of genetic diversity
DIVERSITY (20)
Marking Scheme
Synopsis, Clarity, English Language, sequence of events (3)
Introduction (1), Scientific content (15), Conclusion (1).
Introduction: Genetic Diversity: Every individual has a unique genotype. This is equal to the combination of alleles of all its genes.
The greater the number of genotypes in a population, the greater the genetic diversity.
Genetic mutations produce new alleles of genes that increase variation- Gene mutation are permanent changes in nucleotide sequence in codons of the gene/ produced when DNA replicates/ alters the AA sequence in the polypeptide and therefore the structureand function of the polypeptide or protein/ may be harmful e.g. cystic fibrosis or beneficial e.g. antibiotic resistance in bacteria. (3)
Roles in generating genetic diversity: Increases the number of alleles and so the range of possible genotypes and phenotypes in the population e.g. consider 1 gene with 2 alleles:- 2 phenotypes may result. But 1 gene with 3 alleles e.g. ABO blood system (including co-dominance) results in 4 phenotypes: blood groups A,B, AB, and O blood groups. Mutations occur at random. The mutated form of the gene is passed on every time the DNA replicates (4)
Chromosome Mutations e.g. Aneuploidy and Polyploidy lead to different dosage effects of particular genes in the genotypes and therefore to genetic diversity.
Meiosis: Overview of meiosis with explanation of crossing over and independent assortment. (4)
Role of meiosis in generating genetic diversity: crossing over and independent assortment mixes up existing combinations of alleles of all genes to increase range of genotypes and therefore genetic diversity). Increase in genetic diversity of gametes results. Fertilization results in random fusion of gametes; this increases genetic diversity even further in the population. (4)
Conclusion: Maintenance of genetic diversity