B2.7 intro

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B2.7 intro

  1. 1. B2.7 Cell division and inheritance
  2. 2. B2.7 Cell division and inheritance Characteristics are passed on from one generation to the next in both plants and animals. Simple genetic diagrams can be used to show this. There are ethical considerations in treating genetic disorders.
  3. 3. Key words Cell Nucleus Chromosomes DNA Characteristics Generation Gene Genetic diagrams Inherited Dominant Recessive Alleles You are the result of two things... and
  4. 4. Inside each cell is a nucleus. Inside the nucleus are 46 chromosomes. Each chromosome contains thousands of genes. Chromosomes are made of a chemical called DNA. largest smallest
  5. 5. You have 46 chromosomes. There are 23 pairs of chromosomes. 23 of your chromosomes come from your mother. 23 of your chromosomes come from your father.
  6. 6. You have 46 chromosomes. There are 23 pairs of chromosomes. The 23rd pair = the sex chromosomes. 23 of your chromosomes come from your mother. 23 of your chromosomes come from your father. XX = female XY = male
  7. 7. You have 46 chromosomes. There are 23 pairs of chromosomes. The 23rd pair = the sex chromosomes. 23 of your chromosomes come from your mother. 23 of your chromosomes come from your father. XX = female XY = male A gene found on the Y chromosome causes embryos to develop as male
  8. 8. So - chromosomes come in pairs, and you have 23 pairs of chromosomes. Your genes also come in pairs.
  9. 9. Different versions of genes are known as alleles. The gene for ear lobe attachment is shown here. E = unattached e = attached. Which allele is dominant? Will this person have attached or unattached ear lobes?
  10. 10. genetic cross Mother = Ee unattached Earlobes Father = Ee unattached Earlobes
  11. 11. genetic cross Mother = Ee unattached Earlobes Father = Ee unattached Earlobes
  12. 12. genetic cross Mother = Ee unattached Earlobes What percentage of their offspring are likely to have attached earlobes? Father = Ee unattached Earlobes EE Ee Ee ee
  13. 13. genetic cross Mother = Ee unattached Earlobes What percentage of their offspring are likely to have attached earlobes? As e is recessive and E dominant then only 1 out of 4 will have unattached earlobes: 25% Father = Ee unattached Earlobes EE Ee Ee ee

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