Reproduction, DNA and inheritance

The idea

Sexual reproduction joins male and female gametes (sperm and egg; pollen and egg cell), mixing genes and causing variation. Asexual reproduction involves one parent and mitosis, giving clones. Meiosis halves the chromosome number and makes four genetically different gametes. DNA is a polymer of two strands forming a double helix. A gene codes for a protein. Alleles are versions of a gene; dominant alleles are always expressed, recessive ones only when two copies are present.

1. Use the key words: allele, dominant, recessive, homozygous, heterozygous, genotype, phenotype.
2. Draw a Punnett square for a single gene.
3. Give the probability as a fraction, ratio or percentage.

Watch out Genotype is the alleles (Bb); phenotype is the characteristic seen (brown eyes).