Biology: Chromosomes and Inheritance

Sex Chromosomes and Genes

• Female sex chromosomes are XX
• Male sex chromosomes are XY
• The X chromosome can carry sex-linked genes, such as the gene for color blindness, which is recessive

Chromosome Errors and Mutations

• Mistakes can occur during egg and sperm cell division, leading to errors in the next generation
• Chromosome errors can result in too many or too few chromosomes
• DNA errors can occur due to random mistakes or environmental factors, including:
  • Insertions
  • Deletions
  • Substitutions

Alleles and Genotype

• Alleles are variations of a gene
• Capital letters represent dominant alleles, while lowercase letters represent recessive alleles
• Examples of genotype:
  • RR: homozygous dominant
  • Rr: heterozygous
  • rr: homozygous recessive

Predicting Traits with Punnett Squares

• Punnett squares can be used to predict the probability of offspring with certain traits

DNA Structure and Function

• DNA (Deoxyribonucleic Acid) is the hereditary material in humans and most organisms
• DNA is located in the cell nucleus and determines the structure of proteins and replicates cells, individuals, and species
• DNA is composed of nucleotides, each consisting of:
  • Phosphate group
  • Sugar
  • Nitrogen base
• The structure of DNA is a double helix
• Genes are sections of DNA that code for proteins
• Chromosomes are long, tightly coiled DNA molecules