cell divison by mitosis Flashcards

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1
Q

What are chromosomes made up of?

A

Chromosomes consist of DNA molecules combined with proteins, containing genes which provide the instructions for protein synthesis.

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2
Q

What is a gene?

A

A section of DNA which codes for a protein.

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3
Q

How many chromosomes are found in the nucleus of human body cells?

A

46

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4
Q

How many chromosomes are found in the nucleus of gametes?

A

23

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5
Q

How are chromosomes arranged in the nucleus of a body cell?

A

Arranged in pairs - 46 chromosomes form 23 pairs.

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6
Q

What are the three main stages of the cell cycle?

A
  1. Replication of DNA and synthesis of organelles
  2. Mitosis
  3. Division of cell
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7
Q

Why is mitosis important?

A

● Produces identical cells which all have the same genetic information.
● Produces additional cells for growth and repair.

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8
Q

Describe the first stage of the cell cycle

A

Longest stage

  • cells grow and increase in mass
  • replicate DNA
  • synthesise more organelles (eg. mitochondria, ribosomes).
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9
Q

Describe the second stage of the cell cycle

A

Each chromosome in a pair is pulled to opposite poles of the cell, then the nucleus divides.

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10
Q

Describe the third stage of the cell cycle

A

The cytoplasm and cell membrane divide - two identical daughter cells are produced.

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11
Q

What are the functions of mitosis?

A

1- essential for growth n development of multicellular organisms
2- when an organism repairs itself
3- asexual reproduction

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12
Q

What is a stem cell?

A

An unspecialised cell which is capable of differentiating into other cell types and of self-renewal.

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13
Q

What is the function of stem cells in embryos?

A
  • Embryonic stem cells can replicate themselves and differentiate into many other types of cells.
  • may be able to treat conditions such as paralysis and diabetes by dividing to replace damaged cells.
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14
Q

What is the function of stem cells in adult bone marrow?

A
  • Adult stem cells can differentiate into several cell types to replace dead or damaged tissues.
  • bone marrow stem cells can form many different types of blood cell.
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15
Q

What is the function of stem cells in plant meristems?

A

Meristem stem cells retain the ability to differentiate into any type of plant cell throughout their lifespan

  • they can differentiate into any cell which is required by the plant.
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16
Q

What is therapeutic cloning?

A
  • A cloning method where an embryo is produced with the same genetic makeup as a patient.
  • The stem cells which originate from the embryo will not be rejected by the patient’s immune system, so can be used to treat certain medical conditions.
17
Q

What are the advantages of cloning plants using meristem stem cells?

A

● Can prevent rare plants from becoming extinct.
● Can produce large numbers of plants with a favourable characteristic.
● Can produce identical plants for research.

18
Q

What are issues are associated with the use of embryonic stem cells?

A

● some people have an ethical/religious objection.
● Development of stem cell therapies is slow, expensive and difficult.
● Adult stem cells infected with viruses could transfer infections to patients.
● If donor stem cells do not have a similar genetic makeup to the patient, an immune response could be triggered.