All cells arise from other cells

Question 1

What type of cell does binary fission occur

Answer 1

Prokaryotic cells

Question 2

Where is the genetic information stored in prokaryotic cells

Answer 2

Circular DNA and plasmids

Question 3

Describe the process of binary fission

Answer 3

1) Bacteria replicates by binary fission
2) Replication of circular DNA
3) Division of cytoplasm to produce 2 daughter cells
4) Each with single copy of circular DNA

Question 4

Define mitosis

Answer 4

Production of two genetically identical daughter cells that have the same number of chromosomes as the parent cell and each other

Question 5

Where does mitosis occur

Answer 5

In body cells / somatic cells

Question 6

Define homologous chromosomes

Answer 6

Two chromosomes that carry the same gene

Question 7

Define interphase ( mitosis)

Answer 7

• Chromosomes have disappeared
• Each chromosomes replicated
• Chromosomes made up off 2 sister chromatids joined at centromere

Question 8

Define prophase ( mitosis)

Answer 8

• Chromosomes shorten and thicken to become visible
• Nuclear envelope breaks down
• Centrioles move to the poles of the cell and start forming spindle fibers
• Chromosomes appear as chromatids joined at the centromere

Question 9

Define metaphase ( mitosis)

Answer 9

• Chromosomes line up at the equator
• Chromosomes attach to spindle fibers by their centromere

Question 10

Define anaphase ( mitosis)

Answer 10

• Spindle fibers contract
• The centromere splits
• Sister chromatids are pulled to opposite poles

Question 11

Define telophase ( mitosis)

Answer 11

• Spindle fibers break down
• Nuclear envelope reforms
• Chromosomes disappear
• Chromosomes uncoil and become thinner
• Cytokinesis begins

Question 12

Define meiosis

Answer 12

Production of four genetically different daughter cells that have half the number of chromosomes as the parent cells

Question 13

Where does meiosis occur

Answer 13

Production to make sex cells ( gametes)

Question 14

Define interphase 1 ( meiosis)

Answer 14

• Chromosomes are dispersed ( uncoil)
• Each chromosomes replicated

Question 15

Define prophase 1 ( meiosis)

Answer 15

• Chromosomes shorten and thicken to become visible
• Chromosomes appear as two sister chromatids joined at centromere
• Homologous pairs of chromosomes from bivalents
• Chiasm from where the chromosomes cross over each other
• This produces a new combination of alleles

Question 16

Define metaphase 1 ( meiosis)

Answer 16

• Homologous chromosomes ( in bivalents) line up on the equator
• Chromosomes attached to spindle fibers by their centromere
• Independent segregation of the homologous chromosomes will result in a different combination of alleles within the daughter cells

Question 17

Define anaphase 1 ( meiosis)

Answer 17

• Homologous chromosomes are pulled apart to opposite poles

Question 18

Define telophase 1 ( meiosis)

Answer 18

• Chromosomes uncoil and become thinner
• Cytokinesis begins

Question 19

Define prophase 2 ( meiosis)

Answer 19

• Chromosomes shorten and thicken to become visible
• Chromosomes appear as a pair of sister chromatids joined at the centromere

Question 20

Define metaphase 2 ( meiosis)

Answer 20

• Chromosomes line up on the equator
• Chromosomes attached to spindle fibers by their centromere

Question 21

Define anaphase 2 ( meiosis)

Answer 21

• Chromatids are pulled to opposite poles
• By contraction of spindle fibers

Question 22

Define telophase 2 ( meiosis)

Answer 22

• Chromosomes uncoil and become thinner

Question 23

Define cytokinesis ( meiosis)

Answer 23

• Cytoplasm divides
• Membranes form around new cells
• 4 haploid cells produced

Question 24

What is the difference between meiosis 1 and meiosis 2

Answer 24

Meiosis 1 - Homologous pairs of chromosomes are separated ( reductive division)
Meiosis 2 - Pairs of chromosomes are separated ( non- reductive division)

Question 25

What is the difference between meiosis and mitosis

Answer 25

Meiosis- 1) Reduces the chromosome number 2) Crossing over and independent segregation 3) Two divisions 4) Genetically different Mitosis- 1) Maintains the same chromosome number as in the parent nucleus 2) No crossing over nor independent segregation 3) One division 4) Genetically identical

Question 26

What is crossing over

Answer 26

Homologous pairs of chromosomes form a bivalent. Chiasmata form alleles are exchanged. Producing new combinations of alleles

Question 27

What is independent assortment

Answer 27

How different combination of homologous chromosomes can be separated during anaphase 1 leading to genetically unique gametes

Question 28

How does meiosis result in variation

Answer 28

- Homologous chromosomes pair up - Independent segregation - Maternal and paternal chromosomes are re-shuffled in any combination - Crossing over leads to exchange of parts of (non-sister) chromatids/ alleles between homologous chromosomes - Both creating new combination of alleles

Question 29

Why is meiosis is important in sexual reproduction

Answer 29

Produces haploid cells so fertilisation maintains the chromosomes number in next generation

Question 30

What is the cell cycle

Answer 30

The cell cycle is an ordered set of events, leading to cell growth and division

Question 31

Describe the cell cycle

Answer 31

1) Interphase occupies most of the cell cycle - G1 phase : synthesis of proteins - S phase : DNA is replicated - G2 phase : Organelles grow and divide, ATP stores increased 2) Nuclear division - Mitosis 3) Cell division - Cytokinesis

Question 32

Where are the 3 main checkpoints in the cell cycle

Answer 32

1) G1/S - can DNA synthesis begin? 2) G2/M - has DNA synthesis been done correctly? 3) Spindle - all chromosomes attached to spindles ( can sister chromatids separate correctly) ?

Question 33

What is cancer

Answer 33

Is essentially the incorrect replication of DNA. It is the result of damage to the genes that control cell mitosis and the cell cycle

Question 34

How is cancer often treated

Answer 34

By blocking some part of the cell cycle. Prevent DNA replication. Inhibiting the metaphase by interfering with spindle formation

Question 35

What is the problem by using drugs that inhibit the cell cycle for treating cancer

Answer 35

Mostly effective against rapid cell division but they also disrupt the cell cycle of healthy cells. Hair producing cells divide rapidly, explaining hair loss

Question 36

Why are tumours damaging to the body

Answer 36

May damage organ concerned, cause blockage and they may exert pressure on other organs