- Homologous chromosomes
- Chromosomes that pair up during meiosis
- One came from each parent
- Contain the same genes
- Each is one long DNA molecule
- A gene is a short region of the molecule
Homologous chromosomes, genes & alleles
Autosomes: 22 pairs of homologous chromosomes
Sex chromosomes:
- Females have 2 X chromosomes (XX)
- Males have X and Y (XY)
- X is bigger than the very small Y
Most mutations are neutral or harmful. Mutations that are beneficial are pretty rare.
Different alleles arose from a mutation.
Alleles in an individual
- Homozygote - same two alleles (AA or aa)
- Heterozygote - two different alleles (Aa)
- Genotype - the genetic makeup of the individual
- Phenotype - observable characteristics
- Alternative versions of genes (alleles) cause variation in inherited traits
- Offspring inherit one allele from each parent
- An allele is dominant if it has exclusive control over the phenotype of an organism when paired with a different allele
- Two copies of a gene separate in meiosis and end up in different gametes
- Gametes fuse without regard to which alleles they carry
1:1 ratio of blue to brown