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3.1 The diagram below shows the arrangement of two pairs of homologous chromosomes in a cell undergoing meiosis - English General - NSC Life Sciences - Question 3 - 2017 - Paper 2

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3.1 The diagram below shows the arrangement of two pairs of homologous chromosomes in a cell undergoing meiosis. State TWO characteristics of homologous chromosomes... show full transcript

Worked Solution & Example Answer:3.1 The diagram below shows the arrangement of two pairs of homologous chromosomes in a cell undergoing meiosis - English General - NSC Life Sciences - Question 3 - 2017 - Paper 2

Step 1

State TWO characteristics of homologous chromosomes.

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Answer

  1. Homologous chromosomes are similar in length and shape.
  2. They carry genes for the same characteristics at corresponding loci.

Step 2

Identify structure A.

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Answer

Structure A is the spindle fiber.

Step 3

How many of EACH of the following is present in the diagram? (a) Chromatids

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Answer

(a) There are 8 chromatids present in the diagram.

Step 4

(b) Centromeres

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Answer

(b) There are 4 centromeres present in the diagram.

Step 5

Draw a labelled diagram to show ONE of the cells that would be formed at the end of telophase I.

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Answer

Telophase I Diagram

  • The diagram should include a cell with two replicated chromosomes, cell membrane, centrioles, chromosome labels, etc.

Step 6

Give the genotype of the: (a) Individual represented in the diagram

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Answer

(a) The genotype of the individual represented in the diagram is RrTt.

Step 7

(b) Possible gametes resulting from the arrangement of alleles represented in the diagram.

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Answer

(b) The possible gametes from the arrangement are RT, Rt, rT, rt.

Step 8

Determine the genotypes and phenotypes of their parents by doing a genetic cross.

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Answer

The phenotypes of the parents are Blood type A and Blood type B. Their genotypes are I^A i (for the father) and I^B i (for the mother).

Step 9

Identify the technique shown above.

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Answer

The technique shown is DNA profiling (or DNA fingerprinting).

Step 10

Which male is the biological father of the child?

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Answer

Male 3 is the biological father of the child.

Step 11

Explain your answer to QUESTION 3.3.2.

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Answer

The bands of the child's DNA are a combination of the DNA from each parent. The bands from Male 3 align perfectly with the child's bands, indicating a match.

Step 12

State TWO other uses of this technique.

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Answer

  1. This technique can be used to identify organisms from their remains.
  2. It is useful for identifying missing persons.

Step 13

What is the process called where wheat plants are altered by the insertion of genes?

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Answer

The process is called genetic engineering or recombinant DNA technology.

Step 14

State ONE other disadvantage of using insecticides.

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Answer

Insecticides can kill other beneficial organisms, harming the ecosystem.

Step 15

State TWO ways in which scientists could have improved the validity of this investigation.

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Answer

  1. Use the same field for both experiments to minimize environmental variance.
  2. Use the same number and species of wheat plants for both cases.

Step 16

What was the crop yield, in arbitrary units, of wheat plants without the insecticide gene grown in a greenhouse?

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Answer

The crop yield was 50 arbitrary units.

Step 17

Calculate the difference in yield between the wheat with the insecticide gene and the wheat without the insecticide gene grown in the field. Show ALL working.

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Answer

Difference in yield = Yield with insecticide gene - Yield without insecticide gene = 70 - 45 = 25.

Step 18

Describe the difference in results for the wheat with the insecticide gene grown in a greenhouse and the wheat in a field.

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Answer

In the greenhouse, wheat with the insecticide gene showed high yield, whereas wheat grown in the field showed lower yield due to varying environmental conditions.

Step 19

Suggest ONE possible reason for the difference described in QUESTION 3.4.6.

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Answer

The controlled conditions in the greenhouse can optimize growth factors, unlike the variability in field conditions.

Step 20

Give TWO possible reasons why farmers may be against the use of these insecticide-producing plants.

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Answer

  1. Potential health impacts on consumers due to pesticide residues.
  2. Concerns about environmental harm and interfering with natural ecosystems.

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