The diagram shows the inheritance of sex in humans. What is the chance of the couple's next child being male?

17.5.1 Define genotype as the genetic make-up of an organism in terms of the alleles present

17.5.10 Use genetic diagrams to predict the results of monohybrid crosses and calculate phenotypic ratios, limited to 1:1 and 3:1 ratios

17.5.11 Use Punnett squares in crosses which result in more than one genotype to work out and show the possible different genotypes

17.5.12 Use Punnett squares in crosses which result in more than one genotype to work out and show the possible different genotypes

17.5.13 Use Punnett squares in crosses which result in more than one genotype to work out and show the possible different genotypes

17.5.14 Use Punnett squares in crosses which result in more than one genotype to work out and show the possible different genotypes

17.5.15 Explain how to use a test cross to identify an unknown genotype

17.5.16 Explain co-dominance by reference to the inheritance of ABO blood groups

17.5.17 Define a sex-linked characteristic as a characteristic in which the gene responsible is located on a sex chromosome and that this makes it more common in one sex than in the other

17.5.18 Describe colour blindness as an example of sex linkage

17.5.19 Use genetic diagrams to predict the results of monohybrid crosses involving co-dominance or sex linkage and calculate phenotypic ratios

17.5.2 Define phenotype as the observable features of an organism

17.5.3 Define homozygous as having two identical alleles of a particular gene

17.5.4 State that two identical homozygous individuals that breed together will be pure-breeding

17.5.5 Define heterozygous as having two different alleles of a particular gene

17.5.6 State that a heterozygous individual will not be pure-breeding

17.5.7 Define dominant as an allele that is expressed if it is present

17.5.8 Define recessive as an allele that is only expressed when there is no dominant allele of the gene present

17.5.9 Interpret pedigree diagrams for the inheritance of a given characteristic