Scottish Higher Higher Biology Syllabus

Higher Biology syllabus — full chapter and topic list

Expand any chapter to see its topics and sub-topics. This is the whole examinable outline for Higher Biology in Scottish Higher, not a summary of it.

1. 1

   DNA and the Genome

   5 topics

   • Structure of DNA
     • Nucleotides, base pairing and the double helix
     • DNA in prokaryotes and eukaryotes
   • Replication of DNA
     • The role of primers and enzymes
     • The polymerase chain reaction (PCR)
   • Gene Expression
     • Transcription and translation
     • RNA splicing and one gene, several proteins
   • Mutations and Evolution
     • Single-gene and chromosome mutations
     • Natural selection and speciation
   • Genomic Sequencing and Phylogenetics
2. 2

   Metabolism and Survival

   5 topics

   • Metabolic Pathways and Control
     • Anabolic and catabolic reactions
     • Enzyme action and inhibitors
   • Cellular Respiration
     • Glycolysis, citric acid cycle and electron transport chain
     • ATP synthesis
   • Metabolic Rate and Conformers vs Regulators
   • Survival in Adverse Conditions
     • Dormancy, hibernation and migration
   • Environmental Control of Metabolism in Micro-organisms
3. 3

   Sustainability and Interdependence

   6 topics

   • Food Supply and Plant Growth
     • Food security and sustainable production
     • Photosynthesis and limiting factors
   • Plant and Animal Breeding
     • Selective breeding and genetic technology
   • Crop Protection and Pest Control
   • Animal Welfare and Behaviour
   • Symbiosis and Social Behaviour
     • Parasitism and mutualism
     • Social hierarchy and cooperative hunting
   • Biodiversity and the Threats to It

Higher Biology flashcards for Scottish Higher

18 of 91 cards from the Higher Biology deck — real questions with worked answers.

1. What type of molecule is DNA, and what are the three components of each nucleotide?

   DNA is a polymer of nucleotides (a polynucleotide). Each nucleotide consists of a deoxyribose sugar, a phosphate group, and a nitrogenous base (adenine, thymine, guanine or cytosine).

2. State the complementary base-pairing rules in DNA and the type of bond holding the strands together.

   Adenine pairs with thymine ($A=T$, 2 hydrogen bonds) and guanine pairs with cytosine ($G\equiv C$, 3 hydrogen bonds). The two strands are held together by hydrogen bonds between bases.

3. Describe the antiparallel structure of the DNA double helix, including the 3' and 5' ends.

   The two strands run in opposite directions (antiparallel). The sugar-phosphate backbone has a deoxyribose carbon numbering: one strand runs $3' \to 5'$ while its complementary strand runs $5' \to 3'$. The phosphate is attached to the $5'$ carbon and the hydroxyl to the $3'$ carbon.

4. How does DNA differ between prokaryotes and eukaryotes in terms of organisation?

   Eukaryotes have linear chromosomes in the nucleus (plus circular DNA in mitochondria/chloroplasts), with DNA tightly coiled and packaged with histone proteins. Prokaryotes have a single circular chromosome in the cytoplasm and smaller circular plasmids, with no histones.

5. Name the enzyme that unwinds and unzips the DNA double helix during replication and what it breaks.

   DNA helicase (or the unwinding enzyme) breaks the hydrogen bonds between complementary bases, unzipping the double helix to form two template strands.

6. What is a primer and why is it essential for DNA replication?

   A primer is a short complementary strand of nucleotides that binds to the start of the template (the $3'$ end). It provides a $3'$ end onto which DNA polymerase can add new nucleotides, since DNA polymerase can only add to an existing $3'$ end.

7. In which direction does DNA polymerase add nucleotides, and what is the consequence for the two template strands?

   DNA polymerase adds DNA nucleotides only in the $5' \to 3'$ direction (reading the template $3' \to 5'$). This means one strand (leading) is replicated continuously while the other (lagging) is replicated in fragments.

8. Explain how the leading and lagging strands are synthesised, and the enzyme that joins fragments.

   The leading strand is synthesised continuously towards the replication fork. The lagging strand is synthesised in fragments (each needing a primer) away from the fork; DNA ligase joins these fragments together.

9. List the four requirements needed for DNA replication to occur in a cell.

   A DNA template, a supply of the four DNA nucleotides, primers, and enzymes (DNA helicase, DNA polymerase and ligase), along with ATP and $\ce{Mg^2+}$ ions.

10. What is the polymerase chain reaction (PCR) and state the three temperature stages.

    PCR is a laboratory technique to amplify (make many copies of) a target DNA sequence. The stages are: denaturation (heating to ~$92\text{-}98^{\circ}\text{C}$ to separate strands), annealing (cooling to ~$50\text{-}65^{\circ}\text{C}$ for primers to bind), and extension (~$70\text{-}75^{\circ}\text{C}$ for heat-tolerant DNA polymerase to replicate).

11. Give two practical applications of PCR.

    Amplifying DNA for forensic analysis (e.g. from crime scenes), diagnosis of disease/infection, settling paternity disputes, or studying evolutionary relationships.

12. How does the structure of mRNA differ from DNA?

    mRNA is single-stranded, contains the sugar ribose (not deoxyribose), uses the base uracil instead of thymine, and is much shorter (a copy of one gene).

13. Describe the process of transcription, naming the enzyme involved.

    In the nucleus, RNA polymerase moves along the DNA template strand, unwinding it and synthesising a complementary primary transcript of mRNA from RNA nucleotides (using uracil opposite adenine), reading $3' \to 5'$ and building $5' \to 3'$.

14. Distinguish between exons and introns and explain RNA splicing.

    Exons are the coding regions that are expressed; introns are non-coding regions. During RNA splicing the introns are removed from the primary transcript and the exons are joined together to form the mature mRNA transcript.

15. What is alternative RNA splicing and why is it biologically significant?

    The same primary transcript can be spliced in different ways, with different exons retained or removed, so a single gene can code for several different mature mRNAs and therefore different proteins.

16. During translation, what is a codon and what is an anticodon?

    A codon is a triplet of bases on mRNA that codes for a specific amino acid. An anticodon is the complementary triplet of bases on tRNA, which carries the corresponding amino acid and pairs with the codon.

17. Describe the role of tRNA and ribosomes in translation.

    tRNA carries a specific amino acid to the ribosome and matches its anticodon to the mRNA codon. The ribosome moves along the mRNA, joining amino acids with peptide bonds in sequence until a stop codon is reached, releasing the polypeptide.

18. What are start and stop codons in translation?

    The start codon (AUG) signals the beginning of translation; stop codons signal the end, causing translation to cease and the completed polypeptide to be released. Stop codons do not code for an amino acid.

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