AQA A Level Biology

Revision Notes

1.5.7 Semi-Conservative Replication

The Purpose of Semi-Conservative Replication

  • Before a (parent) cell divides, it needs to copy the DNA contained within it
    • This is so that the two new (daughter) cells produced will both receive the full copies of the parental DNA
  • The DNA is copied via a process known as semi-conservative replication (semi = half)
    • The process is called so because in each new DNA molecule produced, one of the polynucleotide DNA strands (half of the new DNA molecule) is from the original DNA molecule being copied
    • The other polynucleotide DNA strand (the other half of the new DNA molecule) has to be newly created by the cell
    • Therefore, the new DNA molecule has conserved half of the original DNA and then used this to create a new strand

The importance of retaining one original DNA strand

  • It ensures there is genetic continuity between generations of cells
  • In other words, it ensures that the new cells produced during cell division inherit all their genes from their parent cells
  • This is important because cells in our body are replaced regularly and therefore we need the new cells to be able to do the same role as the old ones
    • Replication of DNA and cell division also occurs during growth

Exam Tip

Make sure you don’t confuse ‘parent cell’ with ‘parent organism’. A parent cell is any cell in the body that divides into two cells and the terminology is used to refer to the ‘original’ cell that the DNA came from before it was split and replicated semi-conservatively.

Author: Amelia

While studying Biochemistry at Oxford University, Amelia started her own tutoring service, helping to connect Science tutors with students in her local area. Amelia has experience teaching the sciences and Maths at all levels to UK and international students and, as well as being our Biology Lead, designs revision resources for Chemistry.

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