2.6 cell division

Question 1

What happens in G1?

Answer 1

The cell grows and new organelles and proteins are made. at the G1 check point, the cell checks that the chemicals needed for replication are present and for any damage to the DNA before entering S.

Question 2

What happens in S?

Answer 2

Cell replicated it’s DNA, ready to divide for mitosis.

Question 3

What happens during G2?

Answer 3

The cell keeps growing and proteins needed for division are made. There is another check point where the cell checks whether all the DNA has been replicated without any damage. If it had, the cell will enter mitosis.

Question 4

What happens during prophase?

Answer 4

The chromosomes condense, getting shorter and fatter. Centrioles start moving to opposite ends of the cell, forming a network of protein fibres called the spindle. The nuclear envelope breaks down and the chromosomes lie free in the cytoplasm.

Question 5

What happens in metaphase?

Answer 5

The chromosomes line up along the middle of the cell and become attached to the spindle at their centromere. At the metaphase checkpoint, the cell checks that all the chromosomes are attached to the spindle before mitosis can continue.

Question 6

What happens during anaphase?

Answer 6

The centromeres divide, separating each pair of sister chromatids. The spindles contract, pulling chromatids to opposite ends of the cell, centromere first.

Question 7

What happens during telophase?

Answer 7

The chromatids reach the opposite poles on the spindle. They uncoil and become long and thin again. They are now called chromosomes again. A nuclear envelope forms around each group of chromosomes so there are 2 new nuclei

Question 8

What happens during cytokinesis?

Answer 8

The cytoplasm divides. In animal cells, a cleavage furrow forms to divide the cell membrane. There are now two genetically identical daughter cells.

Question 9

Describe the structure of chromosomes.

Answer 9

DNA is one long molecule. It wraps itself around a histone. This is called chromatin which super condenses to form chromosomes, which then replicate themselves. The replicated chromosomes are called sister chromatids and are held together by a centromere.

Question 10

What happens in meiosis: prophase 1?

Answer 10

Chromosomes condenses, and the nuclear envelope disintegrates. Spindles fibres begins to form. Homologous chromosomes pair up forming bivalents, and crossing over occurs.

Question 11

What happens in meiosis: metaphase 1?

Answer 11

Chromosomes alone in the cell equator, the spindle fibres attach to centromeres. Then independent assortment occurs. This is when the position of each bivalent is independent of the other Chromosomes. The maternal and paternal chromosomes can be either side of the equator.

Question 12

What happens in meiosis: anaphase 1?

Answer 12

the spindle fibres contract, separating the homologous pairs - one chromosome goes to each end of the cell.

Question 13

What happens in meiosis: telophase 1 and cytokinesis?

Answer 13

A nuclear envelope forms around each group of chromosomes. Then the cytoplasm splits and two haploid daughter cells are produced.

Question 14

What happens in meiosis 2?

Answer 14

The two daughter cells undergo the stages again, similar to mitosis, making 4 genetically different haploid daughter cells.

Question 15

What is potency?

Answer 15

A measure of how many types of cells a stem cell can make. Eg Multipotent or pluripotent.

Question 16

What are stem cells?

Answer 16

unspecialized cells from which differentiated cells develop

Question 17

Where are stem cells found?

Answer 17

In early human embryos or the bone marrow of adults

Question 18

What is bone marrow?

Answer 18

Bones are in living organisms containing nerves and blood vessels. The main bones contain marrow in the centres. Here, adult stem cells divide and differentiate to replace worn out blood cells - erythrocytes and neutrophils

Question 19

What are meristems?

Answer 19

In plants, stem cells are found in meristems. In the root and stem, stem cells of the vascular cambium divide and differentiate to become xylem vessels or phloem sieve tubes.

Question 20

How can stem cells cure Parkinson’s?

Answer 20

Patients suffer from tremors, as there is a loss of a particular type of nerve cell found in the brain, which produce the hormone dopamine (helps movement). Stem cells could help regenerate the dopamine-producing cells.

Question 21

What specialized cells do animals have?

Answer 21

Neutrophils, erythrocytes, epithelial cells and sperm cells.

Question 22

How are neutrophils specialized?

Answer 22

(White blood cell) their flexible shape allows them to engulf foreign particles or pathogens. The many lysosomes in their cytoplasm contain digestive enzymes to digest the engulfed particles.

Question 23

How are erythrocytes specialized?

Answer 23

(Red blood cells) their biconcave shape provides a large surface area for gas exchange. They have no nucleus so there’s more room for haemoglobin.

Question 24

How are epithelial cells specialised?

Answer 24

Ciliated epithelial cells have cilia that beat harmful particles away from places like the lungs to places like the stomach where they can be dissolved by HCl. Squamous epithelium are very thin to allow for efficient diffusion of gases.

Question 25

How is a sperm cell specialised?

Answer 25

They have a flagellum so they can swim to the egg. They also have lots of mitochondria to provide the energy to swim. They acrosome contains digestive enzymes to enable the sperm to penetrate the surface of the egg.

Question 26

What specialised cells do plants have?

Answer 26

Palisade mesophyll cells, root hair cells and guard cells.

Question 27

How is a palisade mesophyll cell specialised?

Answer 27

Contains many chloroplasts, so they can absorb lots of sunlight. The walls are thin so CO2 can easily diffuse.

Question 28

How are root hair cells specialised?

Answer 28

They have a large surface area for absorption and a thin permeable walls, for entry of water and ions. They cytoplasm contains extra mitochondria to provide the energy needed for active transport.

Question 29

How are guard cells specialised?

Answer 29

In the light, they take up water and become turgid. Their thin outer walls and thickened inner walls force them to bend outwards, opening the stomata. This allows the Leaf to exchange gasses for photosynthesis