What is DNA?

What is DNA?

• DNA (Deoxyribonucleic Acid) is the hereditary material in humans and almost all other organisms.
• It is responsible for determining the structure of all proteins and for the replication of cells, individual organisms, and species.
• DNA is located in the cell nucleus.

Structure of DNA

• DNA is made up of units called Nucleotides.
• Nucleotides have three parts: Phosphate group, Sugar, and Nitrogen base.
• The structure of DNA is called a double helix.

Genes and Chromosomes

• Genes are segments of DNA that code for proteins.
• Chromosomes are long ladders of DNA twisted up tight.
• Alleles are variations of a gene.
• Capital letters represent dominant alleles, while lower case letters represent recessive alleles.

Genotype and Phenotype

• RR = homozygous dominant
• Rr = heterozygous
• rr = homozygous recessive alleles

Predicting Offspring Traits

• Punnet squares can help us make predictions about the probability of offspring with certain traits.

Mutations

• Mutations can occur when mistakes happen during the formation of eggs and sperm.
• These mistakes can be passed on to the next generation.
• Types of mutations:
  • Chromosome errors: chromalids do not separate properly, resulting in too many or too few chromosomes.
  • DNA errors: base errors can be random or due to environmental factors.
  • Types of DNA errors:
    • Insertion
    • Deletion
    • Substitution

Sex Chromosomes

• Female sex chromosomes = XX
• Male sex chromosomes = XY
• The X chromosome can also carry genes referred to as sex-linked genes, such as the gene for color blindness.