Summary: Biology Hl

Read the summary and the most important questions on Biology HL

• 1 Molecules

• 1.8.1 DNA replication as production of exact copies of DNA with identical base sequences.

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• Why is DNA replication required for reproduction?

  The base sequences of parents need to be passed down to their offspring to ensure genetic information is passed faithfully from one generation to the next
  --> parents must replicate their DNA before reproducing

• What is the role of DNA replication in growth and tissue replacement in multicellular organisms?

  Each cell in a multicellular organism needs a full set of the organism’s base sequences. Before a cell divides into two daughter cells, it must replicate all of its DNA for growth and tissue replacement, where cells have been lost.

• 1.8.2 Semi-conservative nature of DNA replication and role of complementary base pairing.

• What is the meaning of "semi-conservative" in relation to DNA replication?

  DNA replication is described as semi-conservative because each new DNA molecule consists of one original parental strand and one newly synthesized strand. This ensures accurate genetic continuity due to the parental DNA template being very reliable

• How does complementary base pairing allow genetic information to be replicated accurately?

  CBP allows for high accuracy in DNA replication, as adenosine only pairs with thymine and guanine only pairs with cytosine --> specificity of nucleotide pairing reduces risk of errors in replication --> increased accuracy

• What is the basis of complementarity in DNA?

  Complementarity in DNA is based on hydrogen bonding. Adenine (A) pairs with Thymine (T) by forming 2 hydrogen bonds and Guanine (G) pairs with Cytosine (C) by forming 3 hydrogen bonds, in the basis that purines (adenosine and guanine) can only be paired with pyramidines (cytosine and thymine), preventing any other irregular pairings. This ensures accurate DNA replication.

• What should the newly synthesized strand on each template strand have?

  The newly synthesized strand on each of the two template strands should have exactly the same base sequence as the other template strand.

• What happens to the parent molecule during DNA replication?

  In DNA replication, the parent molecule unwinds, and two new daughter strands are built based on base-pairing rules. This process ensures the accurate duplication of DNA.

• Briefly describe the conservative model of DNA replication.

  In the conservative model, a new double helix is made containing no part of the parent double helix, which is conserved separately. This model is not how DNA actually replicates, but was a competing model of DNA replication

• What is the dispersive model of DNA replication?

  The dispersive model suggests parental DNA segments are distributed throughout both the daughter DNA molecules. This model does not accurately describe DNA replication, but was a competing model of DNA replication

• 1.8.3 Role of helicase and DNA polymerase in DNA replication.

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• Why must the double helix structure of the DNA molecule be unwound for DNA replication?

  To expose the parental template strands such that other enzymes can work on the template strands seperately.