17.1 Chromosomes, genes and proteins

2026 Syllabus Objectives

1. State that chromosomes are made of DNA, which contains genetic information in the form of genes
2. Define a gene as a length of DNA that codes for a protein
3. Define an allele as an alternative form of a gene
4. Describe the inheritance of sex in humans with reference to X and Y chromosomes
5. State that the sequence of bases in a gene determines the sequence of amino acids used to make a specific protein (knowledge of the details of nucleotide structure is not required)
6. Explain that different sequences of amino acids give different shapes to protein molecules
7. Explain that DNA controls cell function by controlling the production of proteins, including enzymes, membrane carriers and receptors for neurotransmitters
8. Explain how a protein is made, limited to: the gene coding for the protein remains in the nucleus; messenger RNA (mRNA) is a copy of a gene; mRNA molecules are made in the nucleus and move to the cytoplasm; the mRNA passes through ribosomes; the ribosome assembles amino acids into protein molecules; the specific sequence of amino acids is determined by the sequence of bases in the mRNA (knowledge of the details of transcription or translation is not required)
9. Explain that most body cells in an organism contain the same genes, but many genes in a particular cell are not expressed because the cell only makes the specific proteins it needs
10. Describe a haploid nucleus as a nucleus containing a single set of chromosomes
11. Describe a diploid nucleus as a nucleus containing two sets of chromosomes
12. State that in a diploid cell, there is a pair of each type of chromosome and in a human diploid cell there are 23 pairs