GCSE Biology OCR A J247

explain the following terms: gamete, chromosome, gene, allele/variant, dominant, recessive, homozygous, heterozygous, genotype and phenotype

describe the genome as the entire genetic material of an organism

describe that the genome, and its interaction with the environment, influence the development of the phenotype of an organism

use of examples of discontinuous and continuous variation e.g. eye colour, eight and height

Recall that all variants arise from mutations, and that most have no effect on the phenotype, some influence phenotype and a very few determine phenotype

**describe how genetic variants may influence phenotype:

• in coding DNA by altering the activity of a protein
• in non-coding DNA by altering how genes are expressed

*- in coding: DNA related to mutations affecting protein structure, including active sites of enzymes

• in non-coding: DNA related to stopping transcription of mRNA (use of terms promoter, transcription factor not required)***

explain some of the advantages and disadvantages of asexual and sexual reproduction in a range of organisms

the number of live offspring per birth, how quickly the organisms can reproduce verses the need for the introduction of variation in a population caused by environmental pressures

explain the terms haploid and diploid

explain the role of meiotic cell division in halving the chromosome number to form gametes

that this maintains diploid cells when gametes combine and is a source of genetic variation

explain single gene inheritance

the context of homozygous and heterozygous crosses involving dominant and recessive genes

predict the results of single gene crosses

describe sex determination in humans using a genetic cross

recall that most phenotypic features are the result of multiple genes rather than single gene inheritance

describe the development of our understanding of genetics

the work of Mendel