The Genome & Genetics

• Genetic Key Terms:

  There are many key terms associated with the inheritance topic

  • A gene is a short length of DNA found on a chromosome that can code for a particular characteristic (expressed by the formation of different proteins)
• Genetic Key Terms:

  • Alleles are variations of the same gene
  • As we have two copies of each chromosome, we have two copies of each gene and therefore two alleles for each gene
  • One of the alleles is inherited from the mother and the other from the father
  • This means that the alleles do not have to ‘say’ the same thing
  • For example, two copies of a particular gene could contribute to eye colour but one allele could code for brown eyes and one allele could code for blue eyes
• Genetic Key Terms:

  • The observable characteristics of an organism (seen just by looking - like eye colour, or found – like blood type) is called the phenotype
  • The combination of alleles that control each characteristic is called the genotype
• Genetic Key Terms:

  • Alleles can be dominant or recessive
  • A dominant allele only needs to be inherited from one parent in order for the characteristic to show up in the phenotype
  • A recessive allele needs to be inherited from both parents in order for the characteristic to show up in the phenotype.
  • If there is only one recessive allele, it will remain hidden and the dominant characteristic will show
• Genetic Key Terms:

  • If the two alleles of a gene are the same, we describe the individual as being homozygous (homo = same)
  • Homozygous dominant means having two copies of the dominant allele
  • Homozygous recessive means having two copies of the recessive allele
  • If the two alleles of a gene are different, we describe the individual as being heterozygous (hetero = different)
• Genetic Key Terms:

  • When completing genetic diagrams, alleles are abbreviated to single letters
  • The dominant allele is given a capital letter and the recessive allele is given the same letter, but lower case
• Alleles are different forms of the same gene. You can only inherit two alleles for each gene, and they can be the same (homozygous) or different (heterozygous):

  
• • We cannot always tell the genotype of an individual for a particular characteristic just by looking at the phenotype – a phenotype associated with a dominant allele will be seen in both a dominant homozygous and a dominant heterozygous genotype
• Key Terms & Definitions Table:

  
• Key Terms & Definitions Table:

  
• The Genome:

  • The entire set of the genetic material of an organism is known as its genome
  • Within the genome, the order nucleotide base sequences in the DNA provides the instructions for making all of the proteins required by all of the cells of the organism
  • All living things have a unique genome, and the size can vary significantly between species
  • As a result of the Human Genome Project, biologists now know the entire human genome
  • They have worked out all the genes and locations of those genes in human DNA
• Genome Size Table:

  
• Genome Size Table: