Topic 3 - Exam Questions

Question 1

Explain why the nucleus cannot be observed at the end of prophase in a eukaryotic cell (2 Marks)

Answer 1

~ Nuclear membrane is broken down.

~ DNA condenses, into chromosomes.

Question 2

Give two reasons why a sieve tube element does not require rough endoplasmic reticulum or ribosomes (2 Marks)

Answer 2

~ No transcription or translation.

~ No proteins would be synthesised.

Question 3

Explain why DNA is replicated before mitosis begins (2 Marks)

Answer 3

~ To ensure that one copy of each chromosome, is in each daughter cell.

~ To ensure daughter cells are genetically different.

Question 4

Explain how large number of cells with the same phenotype can be produced in a tissue (2 Marks)

Answer 4

~ Phenotype is determined by the genotype and the effect of the external environment.

~ Mitosis produces cells with the same genotype.

Question 5

State and justify which arrangement is most likely to produce the results shown in the table (3 Marks)

Answer 5

~ Arrangement 2.

~ Genes are closer together.

~ Are most likely to be inherited together.

Question 6

Compare and contrast the results of mitosis and meiosis in the production of sperm cells from stem cells (4 Marks)

Answer 6

~ Both increase the number of cells.

~ Mitosis produces diploid, meiosis produces haploid cells.

~ Mitosis produces genetically identical cells, meiosis produces genetically different cells.

~ Mitosis results in 2 daughter cells, meiosis results in 4 daughter cells.

Question 7

Explain why an electron microscope was used to obtain this image instead of a light microscope (2 Marks)

Answer 7

~ Higher resolution.

~ Higher magnification.

Question 8

(3 Marks)

Answer 8

~ 45 x 1000 = 45,000µm. 45,000µm / 10 = 4,500. Magnification = x4500.

~ 95 x 1000 = 95,000µm. 95,000µm / 4500 = 21.111.

~ Actual Diameter = 21.1µm.

Question 9

Explain the importance of specialised cells in a multicellular organism (2 Marks)

Answer 9

~ Cell differentiate to perform a specific function.

~ These cells then form the basis of tissues, organs and organ systems.

Question 10

Mitochondrial diseases such as Leigh syndrome are passed on by the mother during fertilisation.

Explain why a fertilised egg cell will contain only maternal mitochondria (2 Marks)

Answer 10

~ Only the nucleus of the sperm enters the egg.

~ Therefore all the mitochondria come from the egg cell.