Genetic Crosses

• Some genetic disorders are inherited from parents, while others are caused by spontaneous mutations.
• A Punnett square is a diagram used to predict the possible genotypes and phenotypes of offspring in a genetic cross.
• The Law of Dominance states that in a heterozygous individual, one allele will be expressed over the other.
• An allele is an alternative form of the same gene
• A gamete transports genetic information from one generation into the next.
• A locus is a position of a gene on a chromosome
• In incomplete dominance, neither allele is completely dominant or recessive, resulting in a new phenotype.
• Homozygous means both alleles for a characteristic are the same.
• Heterozygous means two alleles for a characteristic are different.
• A dominant allele is always expressed when present.
• Recessive alleles are hidden in the presence of dominant alleles.
• The genotype is the genetic makeup of an organism.
• The phenotype is the physical expression of the genotype
• A mono-hybrid cross studies the inheritance of a single characteristic.
• A pedigree is a diagram showing the genetic history of a group of related individuals.
• Autosomes are non-sex chromosomes.
• Di-hybrid crosses involve studying the inheritance of two characteristics at the same time.
• Mendel's Law of Independent Assortment states that when gametes are being formed, either pair of alleles is equally likely to combine with another pair of alleles.
• F – First two from each trait – AB ​

  O – Outer two from each trait A b​

  I – Inner two from each trait aB​

  L – Last two from each trait ab
• Linkage means that genes are located on the same chromosome.
• Sex linkage is genes which are located on the X chromosome only
• Men are more prone to sex-linked traits as they only require one recessive allele to suffer the diseases.