Genes and Health

What Genes and Health covers

Covers gas exchange and how substances cross membranes, the structure of DNA and how it is read into protein, enzymes, replication and mutation, and the inheritance, effects and screening of cystic fibrosis.

The 19 subtopics

Each one has its own page. Edexcel AS Biology A students sit this topic in the first year.

• Gas exchange surfaces and Fick's LawRecall questions on what makes a good exchange surface, Fick's Law and its terms, and how the alveoli are adapted for gas exchange.Open →
• The fluid mosaic model of the cell membraneRecall questions on the phospholipid bilayer, cholesterol, proteins, glycoproteins and glycolipids, and on how temperature and alcohol affect permeability.Open →
• Osmosis, diffusion and active transportRecall questions on osmosis, diffusion, facilitated diffusion, active transport, endocytosis and exocytosis, and the proteins each uses.Open →
• Surface area and volume calculationsRecall questions on the formulae for the area and volume of common shapes, and on why the ratio between them matters biologically.Open →
• The structure of DNA and RNARecall questions on mononucleotides, purines and pyrimidines, base pairing and hydrogen bonding, and the double helix.Open →
• TranscriptionRecall questions on RNA polymerase, the template strand, and how messenger RNA is built.Open →
• Translation and the genetic codeRecall questions on ribosomes, transfer RNA, codons and anticodons, start and stop codons, and why the code is described as triplet, non-overlapping and degenerate.Open →
• Amino acids and the levels of protein structureRecall questions on the structure of an amino acid, the peptide bond, and the primary, secondary, tertiary and quaternary levels.Open →
• Globular and fibrous proteins: haemoglobin and collagenRecall questions on what distinguishes globular from fibrous proteins, and on the structures of haemoglobin and collagen.Open →
• Alternative splicing and tissue-specific proteinsRecall questions on how one gene can produce several proteins, and on post-transcriptional modification.Open →
• Enzyme specificity, the active site and activation energyRecall questions on the lock and key and induced fit models, activation energy, and intracellular against extracellular enzymes.Open →
• Rates of reaction, Vmax and Core Practical 4Recall questions on measuring initial rate, the effect of enzyme and substrate concentration, Vmax, and the controls in Core Practical 4.Open →
• Semi-conservative replication and Meselson-StahlRecall questions on the role of DNA polymerase, and on how Meselson and Stahl showed replication to be semi-conservative.Open →
• Types of mutation and the CFTR geneRecall questions on substitution, deletion, insertion and frameshift mutations, and on the mutation that causes cystic fibrosis.Open →
• Alleles, genotype and monohybrid inheritanceRecall questions on genes, alleles, genotype and phenotype, dominance, and the ratios expected from a monohybrid cross.Open →
• Pedigree diagrams and the inheritance of cystic fibrosisRecall questions on reading a pedigree, identifying carriers, and the inheritance pattern of cystic fibrosis.Open →
• The effects of cystic fibrosis, and the chi-squared testRecall questions on the CFTR protein and the effects on the lungs, digestion and fertility, and on using the chi-squared test.Open →
• Prenatal genetic testing: PGD, amniocentesis and CVSRecall questions on what each test involves, when it can be carried out, and the risks attached.Open →
• The ethics of genetic screeningRecall questions on false positives and negatives, confidentiality, and the ethical arguments for and against screening.Open →

What you need to know

Answer each one before you reveal it.

Take Genes and Health further

The same content, four other ways.

Commonly confused

Pairs that lose marks when they are blurred together.

• Gene vs Allele

  Gene: base sequence coding for a polypeptide or functional RNA. Allele: alternative version found at a particular locus.

• Transcription vs Translation

  Transcription: production of messenger RNA from a DNA template. Translation: assembly of a polypeptide using a messenger RNA template.

• Carrier vs Affected individual

  Carrier: heterozygous individual possessing a recessive disease version. Affected individual: person expressing the disease phenotype.

Questions from this topic

Each one with the model answer underneath.

1. 1

   Why do gas exchange surfaces have a large surface area to volume ratio?

   Model answer

   To maximise the area available for diffusion.

2. 2

   How does the thickness of a gas exchange surface affect its efficiency?

   Model answer

   Gas exchange surfaces are thin to minimise the diffusion distance, which increases the rate of diffusion.

3. 3

   Why must gas exchange surfaces maintain a steep concentration gradient?

   Model answer

   To maximise the rate of diffusion across the surface.

4. 4

   How does surface area affect the rate of diffusion?

   Model answer

   The rate of diffusion is directly proportional to the surface area.

5. 5

   What is the relationship between the thickness of an exchange surface and the rate of diffusion?

   Model answer

   The rate of diffusion is inversely proportional to the thickness of the exchange surface.

6. 6

   How does concentration difference affect the rate of diffusion?

   Model answer

   The rate of diffusion is directly proportional to the concentration difference.

What is inside Levo

Six ways to work the same material.

Genes and Health revision questions

Is Genes and Health examined at AS in Edexcel Biology A?

Yes. It sits in Papers 1, 2 and 3, which you take in the first year, so it is on the AS paper as well as counting towards the full A level.

What does Genes and Health cover in Edexcel AS-Level Biology A?

19 subtopics: gas exchange surfaces and fick's law, the fluid mosaic model of the cell membrane, osmosis, diffusion and active transport, surface area and volume calculations, the structure of dna and rna, transcription, translation and the genetic code, amino acids and the levels of protein structure, globular and fibrous proteins: haemoglobin and collagen, alternative splicing and tissue-specific proteins, enzyme specificity, the active site and activation energy, rates of reaction, vmax and core practical 4, semi-conservative replication and meselson-stahl, types of mutation and the cftr gene, alleles, genotype and monohybrid inheritance, pedigree diagrams and the inheritance of cystic fibrosis, the effects of cystic fibrosis, and the chi-squared test, prenatal genetic testing: pgd, amniocentesis and cvs and the ethics of genetic screening. Each one has its own page with questions and model answers.

How is Genes and Health organised?

By the Edexcel 9BN0 specification, subtopic by subtopic, so it matches the order you are taught it in.