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3.1 Errors that occur during DNA replication may sometimes lead to mutations - NSC Life Sciences - Question 3 - 2016 - Paper 2
Question 3
3.1 Errors that occur during DNA replication may sometimes lead to mutations. 3.1.1 Describe DNA replication. 3.1.2 Describe how an error in DNA replication may le... show full transcript
Worked Solution & Example Answer:3.1 Errors that occur during DNA replication may sometimes lead to mutations - NSC Life Sciences - Question 3 - 2016 - Paper 2
Step 1
Describe DNA replication.
Answer
DNA replication is the process by which a DNA molecule unwinds, allowing the hydrogen bonds between the two strands to break, resulting in the strands separating. Each strand serves as a template for synthesizing a new complementary strand. Free nucleotides in the vicinity attach to the individual strands through the pairing of complementary nitrogen bases, resulting in the formation of two identical DNA molecules under the control of enzymes.
Step 2
Describe how an error in DNA replication may lead to a gene mutation.
Answer
An error during DNA replication may occur if an incorrect nitrogen base is added to the original strand. This can happen if a nitrogen base is either added or deleted, which subsequently alters the sequence and order of the bases in the new DNA molecule, potentially leading to a change in the gene structure.
Step 3
Step 4
Step 5
Explain how the DNA named in QUESTION 3.2.2 is used to provide evidence for the hypothesis named in QUESTION 3.2.1.
Answer
Mitochondrial DNA is only inherited from the mother, allowing researchers to track any mutations along the maternal line. This provides insight into human ancestry and confirms the 'Out of Africa' hypothesis by showing a common origin.
Step 6
Step 7
Describe how a new species is formed through geographic isolation.
Answer
A population of a species can become separated by a geographical barrier, leading to the partitioning of the population into distinct groups. These groups then evolve independently as there is no gene flow between them. Each group may adapt to different environmental conditions through natural selection, resulting in genotypic and phenotypic differences over time. Eventually, even if the populations were to meet again, they may not be able to interbreed, thus forming two distinct species.
Step 8
Step 9
Explain the significance of the location of structure X in organism C.
Answer
The foramen magnum is located in a more forward position below the skull, indicating that organism C is bipedal. This positioning allows the vertebral column and spine to extend vertically from the base of the skull, helping to balance the body's weight during upright walking.
Step 12
Explain how the change in the skull from B to C could indicate a change in intelligence.
Answer
The skull from B to C shows an increase in size in the cranial region. This enlargement can accommodate a larger brain, which is indicative of greater intelligence as it provides more space for cognitive functionality.
Step 13
Step 14
Explain why both parents must be heterozygous for this characteristic.
Answer
Both parents must be heterozygous to ensure that each parent can pass on one dominant allele (N) and one recessive allele (n). This condition allows for the possibility of their children to inherit the recessive allele necessary for the expression of the disorder.
Step 16
Provide evidence from the pedigree diagram to show that this characteristic is not sex-linked.
Answer
The pedigree shows that both males and females can be affected. If the disorder was sex-linked, it would primarily be expected to affect males more than females, but the pattern illustrated in the diagram does not support this.