Link selection pressure and isolation to changing allele frequencies and reproductive barriers, explaining how separated populations can diverge into new species in Cambridge A Level Biology questions.
Dominant advantageous alleles and recessive advantageous alleles both naturally occur in populations.
Explain why, when a new dominant advantageous allele occurs, its frequency increases more quickly in the population than when a new recessive advantageous allele occurs.
any three from:
1 new allele initially found in heterozygotes ;
dominant advantageous allele
2 (new) dominant allele is, expressed in heterozygote / always expressed ;
3 selection can act on individuals with dominant allele straight away / AW ;
recessive advantageous allele
4 (new) recessive allele is not expressed, in heterozygote / due to dominant allele or recessive allele only expressed in homozygous recessive (genotype) ;
5 selection can only act on individuals who are homozygous recessive ;
6 it takes time for homozygous recessive (genotype) to occur / AW ;