Chromosomes, Genes & Proteins (CIE IGCSE Biology: Co-ordinated Sciences (Double Award))

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Cara Head

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Cara Head

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The Structure of Genes

  • Chromosomes are located in the nucleus of cells
  • They are thread-like structures made of DNA, carrying genetic information in the form of genes
  • A gene is a short length of DNA found on a chromosome that codes for a specific protein
    • This could be a structural protein such as collagen found in skin cells, an enzyme or a hormone
  • Genes can exist in alternative forms and these are known as alleles
    • Alleles give all organisms their characteristics
    • For example we have a gene for eye colour and the different alleles might be blue, green and brown

DNA, genes and chromosomes, IGCSE & GCSE Biology revision notes Genes are short lengths of DNA that code for a protein. They are found on chromosomes

Examiner Tip

The Zoom model is always useful when trying to visualise where you are in a cell, and what molecules are doing what. Imagine a zoom lens that has the power to zoom right out to look at a whole organism, but also to zoom right into individual molecules. This helps in recognising the structures in cell nuclei visible as chromosomes, then zooming in to picture the individual genes and then, the bases that make up the DNA

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Cara Head

Author: Cara Head

Expertise: Biology

Cara graduated from the University of Exeter in 2005 with a degree in Biological Sciences. She has fifteen years of experience teaching the Sciences at KS3 to KS5, and Psychology at A-Level. Cara has taught in a range of secondary schools across the South West of England before joining the team at SME. Cara is passionate about Biology and creating resources that bring the subject alive and deepen students' understanding