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4. a - VCE - SSCE Biology - Question 4 - 2012 - Paper 1
Question 4
4. a. Draw a labelled diagram to outline the process of DNA replication. b. Briefly describe how the process of binary fission varies from that of mitosis. c. Defi... show full transcript
Worked Solution & Example Answer:4. a - VCE - SSCE Biology - Question 4 - 2012 - Paper 1
Step 1
a. Draw a labelled diagram to outline the process of DNA replication.
Answer
To illustrate the process of DNA replication, draw the following components:
- DNA polymerase: Label it to show its role in synthesizing new DNA strands.
- DNA unwinding: Illustrate the helicase enzyme separating the double helix.
- Replication fork: Show the point at which the strands separate into two.
- Leading and lagging strands: Indicate the continuous synthesis of the leading strand and the formation of Okazaki fragments on the lagging strand, noting the role of DNA ligase in joining these fragments.
- Semi-conservative nature: Label each of the two new DNA molecules that consist of one original strand and one newly synthesized strand.
Step 2
b. Briefly describe how the process of binary fission varies from that of mitosis.
Answer
Binary fission differs from mitosis in several key aspects:
- In binary fission, the chromosome does not line up on the equator as in mitosis.
- During binary fission, the chromosome does not separate at the centromere. Instead, the single circular chromosome is replicated and then divided.
- There are no spindle fibers involved in binary fission; it is a simpler process, usually occurring in prokaryotic organisms.
Step 3
c. Define apoptosis and outline the role it plays with respect to the prevention of syndactyly.
Answer
Apoptosis is a programmed cell death process essential for removing unwanted cells during development. In relation to syndactyly, apoptosis plays a crucial role in the proper separation of digits by ensuring that the tissues between fingers and toes are eliminated during fetal development. When apoptosis occurs appropriately, it prevents webbing, ensuring normal digit formation.
Step 4
d. What is the chance that a child of Ruby and Jonah will have syndactyly? Assign symbols to represent the alleles of syndactyly. Show all working.
Answer
To determine the chance of their child having syndactyly:
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Assign alleles: Let 'S' denote the dominant allele for syndactyly and 's' for the recessive normal condition.
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Ruby has syndactyly; her genotype may be either 'SS' or 'Ss'. Let’s assume she is heterozygous (Ss). Jonah has normal fingers; thus, his genotype is 'ss'.
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Perform a Punnett square for the cross:
S s S SS s Ss -
The offspring genotypes are:
- 25% SS (affected)
- 50% Ss (affected)
- 25% ss (not affected)
- Therefore, there is a 75% chance that a child of Ruby and Jonah will have syndactyly.