Inheritance – What you need to know The numbers refer to pages in ‘Leckie & Leckie Success Guide’ Variation (p74-75, 82) G State that a species is a group of organisms which can interbreed and produce fertile offspring G State that variation can occur within a species G Give examples of continuous and discontinuous variation C Explain what is meant by continuous and discontinuous variation What is inheritance? (p76-81) G State that some characteristics of an organism are determined by genetic information received from the parents G State the meaning of the term phenotype and identify examples of phenotypes of the same characteristic G Identify examples of true-breeding, dominant and recessive characteristics G Identify generations as P, F1 and F2 in examples of crosses C State that the parents in experimental monohybrid crosses are usually true-breeding and show different phenotypes of the same characteristic C Predict the proportions of the phenotypes of the F2 offspring in a mono-hybrid cross G State that the phenotypes of the F1 generation in a true-breeding cross are all the same G State that each body cell has two matching sets of chromosomes G State that sex cells are called gametes G State that the number of chromosomes is halved during gamete formation to a single set G State that each sex cell carries one set of chromosomes G Describe how a complete double set of chromosomes is achieved at fertilisation G State that genes are parts of chromosomes G State that a characteristic is controlled by two forms of a gene C State that different forms of a gene are called alleles G State that each parent contributes one of the two forms G State that each gamete carries one of the two forms of the gene G State that the word genotype means the type of genes which an organism possesses C Explain the effects of chance in causing differences between predicted and observed ratios in monohybrid crosses G State that the sex of a child is caused by chromosomes called X and Y G State that in humans, each male gamete (sperm) may have an X or a Y chromosome while each female gamete (egg) has an X chromosome G Explain how the sex of a child is determined with reference to X and Y chromosomes Genetics and society (p82-83) G Give two examples of an improved characteristic resulting from selective breeding e.g. increased yield, increased disease resistance or increased growth C Give one plant and one animal example of the improvement of a characteristic through selective breeding G Describe one example of a human condition caused by a chromosome mutation e.g. Down’s syndrome C Give an example of an advantageous chromosome mutation (of economic importance to man) in a plant or animal G State that amniocentesis can be used to detect chromosome abnormalities before birth C Give an example of a factor which can influence the rate of mutation in an organism