Genetics and inheritance

• What is a gene?


  segment of DNA
• Where are genes located?


  chromosomes in each cell
• What do genes carry?


  The instructions that create are physical and non-physical characteristics
• What is an allele and where do we get them from?


  A pair of the same gene one from mum and one from dad

  e.g. gene for hair colour
• What is meant by genotype?


  a persons actual genetic make up
• What is a genotype a collection of?


  Collection of your inherited genes from your mum and dad
• Why doesn't your genotype solely determined your characteristics ?


  Genes interact with the environment
• What is a phenotype ?


  How the genes are physically expressed
• What is the phenotype a result of ?


  Environment + Genotype = Phenotype
• How are identical twins an example of environment + genotype = phenotype ?

  Identical twins have different phenotypes even though they have the same genotype as they may be exposed to different environments
• What are monozygotic twins?


  Identical twins - one egg and one sperm

  share 100% same DNA
• What are dizygotic twins?

  Non - identical twins - 2 eggs 2 sperm

  Share 50% same DNA
• Do twins have same phenotype and genotype?

  Not same phenotype but same genotype - nature VS nurture (inherited VS environment)
• What is the SRY gene?

  Sex determining gene
• What does the SRY gene do ?

  Switches on other genes

  XY embryo develops testis - produces male sex hormones during development making it genetically male
• Strengths of genetics and inheritance

  • understand the difference between geno and phenotype - depression is caused by predisposition (genotype) but its triggered by the environment - removing the environment can reduce depression
  • Understand SRY gene functions - cannot be copied - causes mutation - males develop some female parts
• Weaknesses of genetics and inheritance 


  • inaccurate views on how genes work - "gene" for depression - genes can increase the risk but do not cause depression