Genetics · Chapter 1: The genetic toolkit

Year 11 Science · About 15 minutes with activities · Turn your sound on

Chapter 1 · The genetic toolkit

Different hair

Different eyes

Celltrillions in your body

Nucleusthe control centre

Chromosomean organised structure of DNA

One chromosome

DNAa double helix

DNA

Genea section of DNA

Chromosome

Gene: coat colour

Allele: white fur

Allele: brown fur

Phosphate

Sugardeoxyribose

BaseA, T, C or G

Sugar–phosphate backbone

Double helix

Dr Rosalind Franklin1920–1958 · King’s College London

X-ray diffraction

Photo 51 (1952)X-shaped pattern = a helix

1953: double helix structure worked outusing Franklin’s Photo 51

Same genes at the same loci

From mum

From dad

Centromere

Sister chromatidsidentical copies

Base sequence

Polypeptide chainprimary structure of a protein

Base sequence→Amino acid order→Protein→Phenotype

Chapter 1 recap

Genetics is the study of the variation and inheritance of genes. A gene is a section of DNA that codes for a protein; an allele is an alternative version of a gene.
DNA is a double helix of nucleotides (phosphate + deoxyribose sugar + base), with A–T and C–G pairing. Rosalind Franklin’s Photo 51 helped reveal its shape.
Homologous chromosomes come in pairs, one from each parent. The base sequence is read in triplets, setting the order of amino acids in a protein.
Next: Chapter 2 · Mutations

Why don't siblings look the same?

Chapter 1 · About 15 minutes · sound on

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