Chromosomes, Genes & Proteins (Cambridge (CIE) IGCSE Biology): Revision Note
Exam code: 0610 & 0970
The structure of genes
Inheritance of chromosomes, genes and DNA
Inheritance is the transmission of genetic information from generation to generation
Chromosomes are located in the nucleus of cells
They are thread-like structures 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 control our characteristics as they code for proteins (opens in a new tab) that play important roles in what our cells do
Alleles are variations of the same gene
Humans have two copies of each chromosome (one from each parent), so they have two copies of each gene - and therefore two alleles for each gene
One of the alleles for each gene is inherited from the mother and the other from the father
The two alleles code for the same characteristic, but may code for different versions of it
For example, an individual has two copies of a gene for eye colour, but one allele could code for brown eyes and one allele could code for blue eyes
Examiner Tips and Tricks
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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