Genetic Inheritance

• Gamete


  A haploid sex cell formed from meiosis, that is capable of fusing with another gamete of the opposite sex, to form a diploid zygote.
• Fertilization


  The fusion of the male gamete (sperm) and the female gamete (egg) to form a diploid zygote. 
• Allele


  Alleles are different forms of the same gene.
• Genotype


  Alleles are different forms of the same gene.
• Phenotype


  The physical appearance of an organism. 
• Dominant allele


  A dominant allele is an allele that gets expressed. It prevents the working of a recessive allele. 
• Recessive Allele


  A recessive allele is an allele that is not expressed and is prevented from working due to the presence of the dominant allele.  
• Homozygous


  Homozygous is the term used for two alleles that are the same
• Heterozygous


  Heterozygous is the term used for two alleles that are different
• Progeny


  Progeny means the offspring of a cross.
• Monohybrid cross


  The study of only one characteristic
• Dihybrid cross


  Dihybrid crosses involve two characteristics being studied
• Autosome


  These are the 22 pairs of non-sex chromosomes that humans have. 
• Sex chromosomes


  XX female, XY male
• Incomplete Dominance


  Neither allele is dominant or recessive with respect to the other.
• Examples of incomplete dominance in plants and animals


  Plants - red and white snapdragon make pink offspring, animals - red and white cattle breed roan
• Describe Mendel's first law, the law of segregation


  Inherited characteristics are controlled by pairs of factors (alleles). These factors separate from each other at gamete formation, with only one member of each pair found in each gamete.
• Describe Mendel's second law, the law of independent assortment 


  When gametes are formed, each member of a pair of alleles may combine randomly with either of another pair of alleles.
• Ratio of a dihybrid cross between parents that are heterozygous for both traits

  9:3:3:1
• Which parent determines the sex of a baby?

  Father, sperm can have either X or Y chromosome
• Dihybrid crosses


  The study of two contrasting characteristics, e.g. seed colour and seed shape
• Linked genes are the exception to Mendel's second law. What are they?

  Genes for two different characteristics that are on the same chromosome and are passed on together in the gametes, to the next generation.
• Sex linked genes


  Genes found on the X chromosomes without a corresponding gene on the Y chromosome.