How many chromosomes in a human body cell?
Reveal answer
46 (23 pairs).
Key words: 46
4(b) INHERITANCE · RECALL
4.15 Chromosomes and genes
15 recall questions. Answer from memory, reveal the answer, then rate yourself. Ratings stay on this device.
Ratings are saved in this browser on this device, under a KS4 key kept separate from International A Level recall. Written answers are temporary and cleared when you leave the page. Use Reset to clear the ratings on this device.
What is a chromosome made of?
Reveal answer
A long coiled DNA molecule (with proteins).
Key words: DNA
Why are chromosomes in pairs?
Reveal answer
One set from each parent → egg and sperm.
Key words: parent
What are different versions of a gene called?
Reveal answer
Alleles.
Key words: alleles
What is a picture of all the chromosomes arranged in pairs?
Reveal answer
A karyotype.
Key words: karyotype
What is meant by the term locus?
Reveal answer
Specific position of a gene on a chromosome.
Key words: locus
What is meant by the term homologous chromosomes?
Reveal answer
Chromosome pair carrying the same genes at corresponding loci.
Key words: homologous chromosomes
What is meant by the term sister chromatids?
Reveal answer
Replicated chromosome copies joined before separation.
Key words: sister chromatids
Chromosome relationships: for Unreplicated chromosome, give the relationship and the key feature.
Reveal answer
Relationship: One DNA molecule. Key feature: Carries many genes.
Key words: Unreplicated chromosome
Chromosome relationships: for Sister chromatids, give the relationship and the key feature.
Reveal answer
Relationship: Replicated copies joined together. Key feature: Initially nearly identical.
Key words: Sister chromatids
Chromosome relationships: for Homologous chromosomes, give the relationship and the key feature.
Reveal answer
Relationship: Maternal and paternal pair. Key feature: Same loci, potentially different alleles.
Key words: Homologous chromosomes
Chromosome relationships: for Gene locus, give the relationship and the key feature.
Reveal answer
Relationship: Position on a chromosome. Key feature: Corresponds between homologues.
Key words: Gene locus
True or false, and why? “Every chromosome contains the same genes.”
Reveal answer
False. Different chromosome types carry different gene sets.
True or false, and why? “Homologous chromosomes are identical copies.”
Reveal answer
False. They have corresponding genes but may carry different alleles.
True or false, and why? “A replicated chromosome counts as two chromosomes immediately.”
Reveal answer
False. Joined sister chromatids are generally counted as one replicated chromosome until separation.