IGCSE Biology Paper-4: Specimen Questions with Answers 88 - 91 of 279

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Question 88

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Describe in Detail

Essay▾

What is antisense RNA Technology? What are the main applications of this technology?

Explanation

This technology is used for inhibition of gene expression. The concept behind it is that an antisense nucleic acid sequence base pairs with its complementary sense RNA strand and prevents it from being translated into a protein.

Image Shows Transcription of Antisense Strand of DNA

Applications of Antisense RNA Technology

  • Such techniques are used in fundamental research
  • It is used for the treatment of genetic disorder or infections
  • Antisense drugs are being researched to treat cancer, HIV, CMV etc.

Passage

Diagram shows a chart

The Production of Two Different Cells by a Pollen Mother Cell

Question 89 (1 of 2 Based on Passage)

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Write in Short

Short Answer▾

Complete the given chart

Explanation

Production of Two Different Cells by a Pollen Mother Cell

Question 90 (2 of 2 Based on Passage)

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Write in Short

Short Answer▾

What is the difference between part A and B.

Explanation

Cell A is bigger in size and it has abundant food reserve. It has a larger irregularly shaped nucleus. Cell B is small and it floats in cytoplasm of vegetative cell.

Question 91

Describe in Detail

Essay▾

Diagram shows a process done by plant leaves. Which process is it? What factors affect such process?

Image Shows a Process Occur in Plants

Explanation

Diagram shows transpiration process in which moisture is carried by plants from roots to small pores on the underside of leaves, where it changes to vapor and is released to the atmosphere. Transpiration is essentially evaporation of water from plant leaves.

Factors affecting transpiration- There are a number of factors that affect transpiration rates:

1- Temperature- Transpiration rates increase as the temperature goes up, especially during the growing season, when the air is warmer due to stronger sunlight and warmer air masses

2- Relative humidity- As the relative humidity of the air surrounding the plant enhance the transpiration rate decrease.

3- Wind and air movement- Increased circulation of the air near plant will result in increased level of transpiration rate

4- Soil-moisture availability- When moisture is lacking, plants can begin to premature ageing, which can result in leaf loss and transpire less water

5- Type of plant-Plants transpire water at different rates. Some plants which grow in dry areas, such as cactus, save water by transpiring less water than other plants.

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