2.1 When a thief broke into a car he cut his arm on the broken glass - NSC Life Sciences - Question 2 - 2018 - Paper 2
Question 2
2.1 When a thief broke into a car he cut his arm on the broken glass. Scientists extracted DNA from the blood found on the broken glass. They analysed this DNA sampl... show full transcript
Worked Solution & Example Answer:2.1 When a thief broke into a car he cut his arm on the broken glass - NSC Life Sciences - Question 2 - 2018 - Paper 2
Step 1
What do the diagrams above represent?
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Answer
The diagrams represent a DNA profile, which shows the unique banding pattern of DNA fragments obtained from the analysis of the blood sample.
Step 2
Which suspect is most likely the thief?
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Answer
Suspect Q is most likely the thief as the DNA bands from Q closely match the bands from the blood found on the broken glass.
Step 3
Give a reason for your answer to QUESTION 2.1.2.
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The alignment of the DNA bands suggests that suspect Q's DNA corresponds with the DNA from the blood sample, indicating a high likelihood of a match.
Step 4
State TWO possible disadvantages of using this evidence in a court of law.
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A small amount of DNA may have been used, which could lead to unreliable results.
Human error or contamination can compromise DNA analysis, potentially misleading the investigation.
Step 5
Name the process whereby insulin is produced in a normal human cell.
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Answer
The process is known as protein synthesis, specifically the transcription and translation of mRNA.
Step 6
Identify bond X.
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Bond X is a peptide bond, which links amino acids together in a protein chain.
Step 7
How many nitrogenous bases in a DNA molecule code for the amino acids in chain A?
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Three nitrogenous bases code for one amino acid; hence, chain A, which consists of 21 amino acids, requires 63 nitrogenous bases.
Step 8
Name the nitrogenous base represented by G in the mRNA codon CAG.
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The nitrogenous base represented by G in the mRNA codon CAG is Guanine.
Step 9
Read the chains from left to right and give the:
(i) First amino acid in chain B.
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(i) The first amino acid in chain B is Valine (Val).
Step 10
(ii) DNA base triplet that codes for the first amino acid in chain A.
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(ii) The DNA base triplet that codes for the first amino acid in chain A is CCT.
Step 11
Describe the process of transcription.
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Transcription is the process where the DNA double helix unwinds and unzips to expose the gene. One strand acts as a template for forming mRNA, using free RNA nucleotides that are complementary to the DNA. The mRNA then carries the coded message from the nucleus to the cytoplasm for protein synthesis.
Step 12
What term is given to the chromosomes numbered:
(a) 1 to 22
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(a) Autosomes.
Step 13
(b) 23
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(b) Gonosomes or sex chromosomes.
Step 14
State the gender of individual P.
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Individual P is male because it has an XY chromosome pair.
Step 15
Give ONE observable reason for your answer to QUESTION 2.4.2.
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The presence of one Y chromosome in individual P's karyotype indicates that it is male, as females have two X chromosomes.
Step 16
Each of the pairs shown is a homologous pair of chromosomes.
State the origin of each chromosome in a homologous pair of chromosomes.
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One chromosome in each homologous pair comes from the mother (ovum) and the other from the father (sperm).
Step 17
Use a genetic cross to show the percentage chance that this child could be a boy.
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Let P1 represent Male (XY) and Female (XX). For gametes, we get X and Y from father and X from mother. The resulting combinations for the F1 generation are 50% XY (boy) and 50% XX (girl), making the chance for a boy 50%.
Step 18
What is the term given to a genetic cross involving two characteristics?
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The term is a dihybrid cross.
Step 19
Give the phenotype of:
(a) The dominant coat colour
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(a) Black without white patches.
Step 20
(b) Dog V
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(b) Dog V has the phenotype of gray with white patches.
Step 21
(c) Dog W
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(c) Dog W is black with white patches.
Step 22
Explain why all dogs with the phenotype of dog W may not have the same genotype.
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Dogs with phenotype W can have varying genotypes, such as being heterozygous (BbWw) or homozygous recessive (bbww) for the coat colour characteristic, leading to differences despite exhibiting the same appearance.
Step 23
The two characteristics are inherited in accordance with Mendel's principle. State this principle.
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Mendel's principle of independent assortment states that alleles for different traits segregate independently during gamete formation.
