Genetics

• Genotype


  The genetic make-up of an organism
• Phenotype


  The outward expression or physical appearance of the organism
• Allele

  Alternative/different forms of a gene
• Dominant


  An allele that can express its trait even in the presence of a recessive allele
• Recessive


  An allele that only expresses its trait when two copies are present
• Homozygous

  Having two copies of the same allele
• Heterozygous


  Having one of each type of allele
• Carrier


  A person who is heterozygous for a certain allele and carries the recessive allele without expressing it
• The passing on of characteristics from one generation to the next is called inheritance
• The study of inheritance involves a branch of science called genetics
• Types of inheritance


  • Complete dominance
  • Co-dominance
  • Incomplete dominance
  • Sex-linked
• Complete dominance


  • Two alleles influence one trait; dominant allele overrides recessive allele
• Co-dominance


  • Two alleles influence one trait; both alleles are expressed at the same time
• Incomplete dominance


  • Two alleles influence one trait; both alleles are blended together
• Sex-linked


  • The gene is present in the X chromosome only
• A pedigree is a pictorial family tree that traces a particular characteristic or trait from one generation to the next
• Careful analysis of a pedigree can determine whether a characteristic is dominant or recessive
• Homozygous dominant and heterozygous are both affected in autosomal dominant disorders
• Homozygous recessive is affected in autosomal recessive disorders
• Heterozygous is a carrier in autosomal recessive disorders
• Autosomal recessive disorders can skip a generation
• Punnett squares


  1. Predict outcome of a cross

  2. Determine probability of offspring genotype

  3. Summarise combinations of alleles
• Human blood types are a great example of codominant inheritance
• Haemophilia is an X-linked recessive disorder
• Pedigree symbols are used to represent traits in a family tree
• What is a karyotype?


  The complete set of a person's chromosomes
• How can karyotypes be used in medicine?

  Karyotypes can help identify diseases
• What is the structure of DNA?

  A double helix
• How does the structure of DNA relate to its function?

  The double helix allows it to split into two strands, aiding replication
• What is the relationship between DNA, genes, and proteins?

  Genes contained within DNA help the body construct proteins
• What is the process and importance of DNA replication?

  • DNA replication allows the body to constantly renew
  • Ensures every cell has the same DNA
• What is a mutation?

  A permanent change to your DNA that alters something about you
• What is a mutagen?

  A mutagen is something that causes mutations, like radiation
• How can mutations reduce an organism's chance of survival?

  Negative mutations can impact a person's body and life, reducing reproductive success
• Give an example of a beneficial mutation.


  Webbed fingers and feet can help an organism swim faster
• What is another example of a beneficial mutation in camels?

  A camel's urine is very concentrated to conserve water in the desert
• Name three different types of mutation.

  Deletion, substitution, insertion
• What is a genome?

  All the genetic code and material of an organism
• What is the difference between haploid and diploid?

  A haploid has 23 separate chromosomes, while a diploid has a full set of 46 chromosomes
• Compare the processes of mitosis and meiosis.


  • Mitosis: Cell splits into 2 separate daughter cells
  • Meiosis: Chromosomes make 4 diverse daughter cells to create gametes (eggs and sperm)