Bio f4 chap 6

Question 1

What will happen if the cells in the reproductive organs of humans are unable to produce haploid cells?

Answer 1

• resulting zygote will have 92 chromosomes (46 + 46)
• double that of the parent’s chromosomes
• zygote produced will degenerate by itself

Question 2

Explain the process that occurs during the S phase.

Answer 2

• DNA content will double
• DNA replication

Question 3

Predict what will happen if the spindle fibres fail to develop.

Answer 3

• For embryonic development and organism
  growth, mitosis ensures rapid cell multiplication.
• When our body is injured, mitosis will produce
  new cells to replace dead or damaged cells.
• Through mitosis, the lizard is able to grow a new tail (regeneration) if it falls off.
• Mitosis helps organisms such as hydra to
  produce new individuals through bud formation.

Question 4

Explain how meiosis I can reduce the number of chromosomes in the daughter cell.

Answer 4

• homologous chromosomes separate in anaphase I

Question 5

Why radiotherapy is used to control or stop the growth of cancer cells.

Answer 5

• uses high-powered ionising radiation to kill cancer cells
• a high dose administration is administered to the target (tumor) to heal, control or reduce symptoms of the patient
• adjacent parts may also be exposed to radiation which can lead to side effects

Question 6

The importance if cell division that happens at the tip of a plant root

Answer 6

• produce more cells
• absorb more water and mineral salts to support plant growth

Question 7

How to breed mango trees in a short time for commercial purposes?

Answer 7

• tissue culture
• explants are placed in a sterile culture medium that contains nutrients and growth hormones
• explants divide mitotically to form callus
• callus forms embryo

Question 8

Explain how this individual is born with Down syndrome.

Answer 8

• homologous chromosome 21 fail to separate due to non-disjunction that happens at anaphase I
• spindle fibres fail to form

Question 9

Explain the formation of cancer cells

Answer 9

• mutation in the DNA of a normal cell
• mitotic cell divisions to happen rapidly and without control

Question 10

Ways to avoid the development of cancer cells

Answer 10

• avoid exposure to radioactive rays
• avoid eating food that contains carcinogens

Question 11

Can RNA interference technology be used for all organisms as protection against infections?

Answer 11

• natural cell mechanism that stops gene activity
• indirectly affects protein formation
• living organisms have this mechanism as a defence mechanism against viral attacks
• produce specific RNAs to stop specific gene activity
• not limited to orchid plants
• can be used for all types of organisms