Genetics

DNA and Chromosomes

DNA

• Deoxyribonucleic Acid– Double Helix Shape– (Twisted Ladder)

• Genetic code – – Instruction manual

Nucleotides

• DNA is a repeating sequence of nucleotides

• Nucleotides contain

• Phosphate • Sugar• Base

DNA Structure

Base Pairs• Adenine – Thymine

• Guanine – Cytosine

DNA and Chromosomes

• DNA is wound into tight coils which form chromosomes.

• Genes - sections of chromosomes that code for a characteristic or protein.

Chromosomes

• Humans have 46 different chromosomes.

• 23 homologous pairs

Inheritance of Chromosomes

•23 homologous pairs•23 from Mum and 23 from Dad.Including•2 sex chromosomes

XX – female

XY - male

Genes and Alleles

• Genes - Sections of Chromosomes that code for a particular protein or characteristic are eg. Eye colour.

Alleles

• Alleles – Different versions of genes eg. Blue eyes, brown eyes.

• Humans have 2 alleles of each gene as we have 2 copies of each chromosome.

More to come