Inheritance

Worked examples (12)extended set

• 1Completing a genetic diagram for the inheritance of sex
• 2Reading a family tree for albinism
• 3Is the condition dominant or recessive? (multiple choice)
• 4Which guinea pigs must be heterozygous?
• 5Probability of an affected child from a family tree
• 6Finding carriers of colour blindness in a family (multiple choice)
• 7Birth records and the 1 : 1 sex ratio
• 8How the allele for albinism causes pale skin
• 9Why a son cannot inherit colour blindness from his father
• 10Cystic fibrosis: probability and the faulty membrane protein
• 11Showing that a condition is not sex-linked
• 12Why seedlings without chlorophyll die

Model answers (6)

• ✓Model answer — Paper 4 short-answer style
• ✓Model answer — Paper 4 short-answer style
• ✓Model answer — Paper 4 structured style
• ✓Model answer — Paper 4 (Extended) structured style
• ✓Model answer — Paper 4 (Extended) structured style
• ✓Model answer — Paper 4 (Extended) extended-response style

Worked examples (12)extended set

• 1From nucleus to gene: identifying the structures
• 2Gene, allele or chromosome? (multiple choice)
• 3Counting chromosome pairs: haploid and diploid
• 4Why two enzymes have different shapes
• 5Identifying the stages of protein synthesis on a diagram
• 6Putting protein synthesis in order and correcting errors
• 7Why only salivary gland cells make amylase (multiple choice)
• 8A different allele for a neurotransmitter receptor
• 9Extracting DNA from strawberries
• 10Which proteins does each cell make?
• 11One amino acid changed: why the enzyme no longer works
• 12A mushroom toxin that stops mRNA being made

Model answers (6)

• ✓Model answer — Paper 4 short-answer style
• ✓Model answer — Paper 4 short-answer style
• ✓Model answer — Paper 4 structured style
• ✓Model answer — Paper 4 (Extended) structured style
• ✓Model answer — Paper 4 (Extended) structured style
• ✓Model answer — Paper 4 (Extended) extended-response style

Worked examples (12)extended set

• 1Which is not a role of mitosis? (multiple choice)
• 2Completing a description of stem cells
• 3Describing mitosis in the healing of a cut
• 4Choosing the daughter nucleus after mitosis (multiple choice)
• 5Reading a graph of DNA mass during the cell cycle
• 6How long to produce 32 cells?
• 7Chromosomes before and after mitosis
• 8Regrowing a lizard's tail
• 9Root tip practical: where are cells dividing?
• 10Stem cells in bone marrow
• 11Why identical twins are genetically identical
• 12Correcting a student's notes on mitosis

Model answers (6)

• ✓Model answer — Paper 4 short-answer style
• ✓Model answer — Paper 4 short-answer style
• ✓Model answer — Paper 4 structured style
• ✓Model answer — Paper 4 (Extended) structured style
• ✓Model answer — Paper 4 (Extended) structured style
• ✓Model answer — Paper 4 (Extended) extended-response style

Worked examples (12)extended set

• 1Statements about meiosis (multiple choice)
• 2Finding the haploid number from a diagram
• 3Why meiosis matters in the anthers of a flower
• 4Which nucleus could be an egg? (multiple choice)
• 5Chromosome numbers in the human life cycle
• 6DNA mass in body cells and sperm cells
• 7Why brothers are genetically different
• 8Chromosome numbers and sex chromosomes in human cells
• 9Mitosis, meiosis or both?
• 10How many different gametes can one cell make?
• 11Why mules cannot produce gametes
• 12Counting chromosomes in root tip and anther cells

Model answers (6)

• ✓Model answer — Paper 4 short-answer style
• ✓Model answer — Paper 4 short-answer style
• ✓Model answer — Paper 4 (Extended) structured style
• ✓Model answer — Paper 4 (Extended) structured style
• ✓Model answer — Paper 4 (Extended) structured style
• ✓Model answer — Paper 4 (Extended) extended-response style

Worked examples (12)extended set

• 1Genetic terms and pure-breeding
• 2Completing a genetic diagram for a 1 : 1 cross
• 3Two carriers of a recessive condition: the chance of an affected child
• 4Using a test cross to find an unknown genotype
• 5Counting kernels on maize cobs: testing a 3 : 1 ratio
• 6Which parents could have children of all four blood groups? (multiple choice)
• 7Codominance in snapdragon flowers
• 8ABO blood groups: an AB parent and an O parent
• 9Red-green colour blindness: a sex-linked cross
• 10Why is colour blindness more common in men? Survey data
• 11Tortoiseshell cats: codominance and sex linkage together
• 12Deducing dominance and genotypes from three crosses

Model answers (6)

• ✓Model answer — Paper 4 short-answer style
• ✓Model answer — Paper 4 short-answer style
• ✓Model answer — Paper 4 (Extended) structured style
• ✓Model answer — Paper 4 (Extended) structured style
• ✓Model answer — Paper 4 (Extended) structured style
• ✓Model answer — Paper 4 (Extended) extended-response style