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A thermocycler follows the temperature programme shown. What is the purpose of holding the mixture at stage X? A. To expose the templates by melting hydrogen bonds B. To permit primers to anneal at the lowest temperature C. To allow the thermostable polymerase…
Living systems display diversity from molecules to communities. (a) Outline how the structures of starch and cellulose support their functions. (b) Describe adaptations through which forest plants obtain light. (c) Explain how natural selection brings about…
The same DNA region is sequenced before and after replication. Original: ACGTCCATGATC Replicated: ACGTTCATGATC Which change is present? A. One base has been replaced while sequence length stays constant B. One extra triplet has been inserted C. One nucleotide…
Common cellular features coexist with the diversity produced by evolution. (a) Describe the roles of components shared across cellular organisms. (b) Discuss how separate populations can become distinct species. (c) Outline key features of the genetic code.
The schematic shows a DNA replication fork. What does helicase do at this fork? A. Separates paired strands by disrupting hydrogen bonds between bases B. Forms peptide bonds between neighbouring nucleotides C. Adds phosphate groups to every amino acid D. Makes…
Proteins contribute to structure, recognition and defence. (a) Outline the general organization of a peptide. (b) Describe the four ABO blood groups and their molecular/genetic basis. (c) Explain the adaptive immune response to invading pathogens.
Three mRNA codons for alanine are 5′-GCU-3′, 5′-GCC-3′ and 5′-GCA-3′. Which anticodon could belong to an alanine-carrying tRNA? A. 3′-CGA-5′ B. 3′-GCU-5′ C. 3′-CGT-5′ D. 3′-AAA-5′
An unaffected couple has a child with phenylketonuria, an autosomal recessive disorder. Use P for the functional allele and p for the recessive allele. Other parts concern respiratory defence and gas exchange. (a) Describe how the disorder can be inherited in…
DNA fragments migrate from the wells through the gel. Which labelled migration distance corresponds to the longest fragments? A. A B. B C. C D. D
A membrane’s molecular organization underlies selective transport and electrical properties. (a) Outline phospholipid structure and its interactions with water. (b) Explain how proteins enable substances to cross membranes. (c) Describe the establishment of a…