What is Inheritance?

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What is Inheritance?

• Standard Grade Biology

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What is Inheritance?

• By the end of this lesson you should be able to
• Know how many chromosomes are in body cells
• Understand the word phenotype
• Give examples of phenotypes
• Understand what true breeding means
• Know what the letters P, F1 and F2 represent
• Understand what dominant and recessive mean and
  be able to give examples

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What is Inheritance?

• What makes us who we are?
• Your environment The genetic information
• and your experiences you got from your
  
• parents
• YOU

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What is Inheritance?

• The characteristics that an organism has have
  mostly been inherited from the parents.
• They are determined by the genetic information
  from their mother and their father
• E.g. eye colour, blood type, flower colour

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Genes Chromosomes

• We inherit information in the form of genes.
• Each gene controls a different characteristic
• Genes can be found on CHROMOSOMES (thread like
  structures)

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Genes Chromosomes
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Chromosomes

• Chromosomes can be found in the NUCLEUS of a cell
• Every cell in an individual contains a full set
  of chromosomes in the nucleus (except sex cells)
• The number of chromosomes varies between species
• Some species can have as few as 2 chromosomes and
  others as many as 100!
• Humans have 46 chromosomes

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Chromosomes

• Each chromosome can have thousands of genes on it
• Chromosomes are passed from parents to offspring
  during fertilisation.
• This is how we acquire inherited information

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PHENOTYPE

• The PHENOTYPE is the organisms appearance which
  has resulted from the genetic information
  inherited from the parents. There can be a number
  of different forms of the phenotype e.g. wing
  type of fruit flies can be normal or vestigial.

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PHENOTYPE

• Fruit flies
• normal wings/Vestigial wings

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PHENOTYPE

• Fruit flies can have grey bodies or ebony bodies

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PHENOTYPE

• Copy the table 21.1 from P158 in Torrance

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True Breeding

• Sometimes two organisms with the opposite
  phenotype can be crossed (mate) and produce
  offspring with the different phenotypes
• 
  X

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True Breeding

• However if all the offspring show the same
  phenotype, the parents are said to be TRUE
  BREEDING

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True Breeding

• So if a true breeding black cat and a true
  breeding white cat are crossed all the offspring
  will be.
• BLACK!

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Why?????????

• This is because the gene for a black coat is
  stronger than the gene for white coat.
• The gene for a black coat is DOMINANT
• The gene for white coat is RECESSIVE

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Task

• Insert the Guinea Pig Cross- diagram 1 into
  your jotter.
• Answer the following questions in sentences
• What letter is used to represent the parents?
• What letter and number are used to represent the
  first generation?

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Task.

• Copy and complete the following paragraph
• The parents in both crosses are described as true
  breeding. This means that, when bred together,
  black guinea pigs will always produce
  offspring. True breeding white guinea pigs,
  when bred together, will always produce
  offspring.

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An example

• The gene for a long coat is dominant to the gene
  for short coat in dogs
• Imagine a cross between a true breeding short
  haired dog and another true breeding short haired
  dog.
• What will the hair of the puppies be like?

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Task

• Insert the Guinea Pig Cross- diagram 2 into
  your jotter.
• Answer the following questions in sentences
• What colour coat do the parents have?
• What colour coat are the F1 generation?
• What colour coat are the F2 generation?
• Which phenotype does not show in the F1
  generation?

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Task

• Which phenotype does show up?
• In which generation are both phenotypes present?
• In the F2 generation, which phenotype is most
  common?
• Which phenotype is dominant?
• Which phenotype is recessive?

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Task

• Copy and complete the following paragraph
• If two individuals, of different
  phenotypes are crossed, all of the offspring will
  have the of one of the parents.
• This phenotype is , the other
  phenotype is

true-breeding
phenotype
dominant
recessive
dominant
recessive
phenotype
true-breeding
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What do you know?

• Can you do the following?
• Say how many chromosomes are in body cells
• Say what the word phenotype means
• Give examples of phenotypes
• Say what true breeding means
• Say what the letters P, F1 and F2 represent
• Say what dominant and recessive mean and be able
  to give examples