Please enable JavaScript.
Coggle requires JavaScript to display documents.
Genetic diversity and Mutation (Meiosis (Replication of sex cells (Haploid…
Genetic diversity and Mutation
Meiosis
Replication of sex cells (Haploid cells)
Starts with a diploid cell (gamete) which double their chromosomes to 92
Meiosis 1 same stages as mitosis homologous chromosomes line up in equator of cell genetic recombination occur (crossing over of parts of chromosome)
Genetic recombination is an area of variation in addition to independent segregation of homologous chromosomes
Meiosis two chromatids move apart to create another cell so four are made in total
Locus is the position of a gene on a chromosome
(2N)2 will give number of chromosome combinations following meiosis
Mutation
Change in quantity of base sequence or DNA is referred to as a mutation
most are not helpful and few are harmful
Base Substitution
Replacement of base in DNA causing different amino acid being coded for so may cause deficiency's
relatively harmless due to genetic code bein degenerate so same amino acid could still be coded for
Base Deletion
Removal of base from Gene sequence causing frame shift completely different proteins and amino acids will be coded for may cause various conditions base addition is same principle frame shift works other way
Chromosomal mutation
changes in structure or number of chromosomes is referred to as a chromosomal mutation
Change in number of chromosomes occurs during meiosis and a non disjunction can occur where extra or less chromosomes are present in a cell
Genetic diversity
Species is a group of genetically similar individuals which can interbreed
Genetic diversity is reduced when a population has a small range of alleles
Described as the total number of different alleles in a population
greater genetic diversity of a population the more likely they are to survive an environmental change
within any population of a species there is a gene pool
random mutations in gene pool can lead to a new allele
certain environment new allele may provide advantage
if they reproduce successfully alleles will be passed onto the next generation
more likely to survive and continue to breed
better adapted and better at competing for resources
frequency of advantageous allele increases
types of selection
Stabilising selection
Phenotypes closest to mean favoured provides best chance of survival
extreme phenotypes are not favoured as they provide no advantage as environment does not change
Environmental conditions remain stable
Directional selection
Antibiotic resistance
Constant environmental changes
Extreme ends of population will be favoured through selection pressures
Mean population or other extreme face selection pressure as they cant compete