Topic 5 - Continuity Of Cells

Question 1

What is the cell cycle

Answer 1

The formation of new cells involves the production of additional contents before a cell can divide

Question 2

What are the 3 phases of the cell cycle, and what are they split into

Answer 2

Interphase - G1, S, G2
Mitosis - Prophase, Metaphase, Anaphase, Telophase
Cytokinesis

Question 3

What is the G1 phase, and what occurs during it

Answer 3

The first gap phase, Synthesis of macromolecules, including proteins and nucleotides, occurs and organelles are produced so that the cell increases in size

Question 4

What is the S phase, and what occurs during it

Answer 4

DNA synthesis phase, Histones are produced, the DNA and chromatids formed are identical and remain attached until separated during Mitosis

Question 5

What are Histones

Answer 5

Proteins that bind to and support the DNA with the chromatids

Question 6

What is the G2 phase, and what occurs during it

Answer 6

The second gap phase, Proteins such as tubulin are synthesised; energy storages are increased; the cell continues to grow in size

Question 7

What is the function of Tubulin

Answer 7

Tubulin forms the microtubules of the spindle fibres

Question 8

What is the first phase of Mitosis and what occurs during it

Answer 8

Prophase;
The chromatin condenses to form the chromosomes
The centrioles move towards opposite poles
The spindles begins to form
As each chromosome continues to condense, two chromatids, joined at a centromere, become apparent

Question 9

What is the second phase of Mitosis and what occurs during it

Answer 9

Metaphase;
The nuclear envelope breaks down
Spindle formation is completed as microtubules extend, forming the fibres
The microtubules of the spindle attach to the centromere of each chromosome
The chromosomes are moved by the microtubules onto the equator of the spindle

Question 10

What is the third phase of Mitosis and what occurs during it

Answer 10

Anaphase;
The centromeres divide
The spindle fibres pull the centromeres of sister chromatids apart
The sister chromatids move towards opposite poles

Question 11

What is the fourth phase of Mitosis and what occurs during it

Answer 11

Telophase;
Each chromatid is now a separate chromosome
The two groups of chromosomes reach opposite poles of the new cells
A new nuclear envelope forms around each group

Question 12

What is the Final phase of the cell cycle and what occurs during it

Answer 12

Cytokinesis - the cytoplasm is separated and the cell divides during cytokinesis to form two daughter cells

Question 13

What occurs in an Animal cell during cytokinesis

Answer 13

A cleavage furrow forms as protein microfilaments pull the cell surface membrane in along the equator; the furrow deepens and when the membranes fuse the cell is cleaved into two

Question 14

What occurs in a plant cell during cytokinesis

Answer 14

The Golgi bodies produce vesicles that collect and fuse together to form an equatorial cell plate. The vesicles secret the material of the middle lamellar on each side of which a new cellulose cell wall is laid down

Question 15

When must a cell only divide

Answer 15

• if sufficient macromolecules and organelles have been assembled so that the cell has grown to an appropriate size
• the DNA is error-free and accurately replicated
• the chromosomes have been positioned correctly during Mitosis

Question 16

Where are the 3 checkpoints in the cell cycle

Answer 16

Towards the end of G1
Towards the end of G2
During metaphase

Question 17

What is assessed during the G1 checkpoint

Answer 17

The supply of nutrients and growth factors so that the cell has reached an appropriate size
The DNA is check for damage

Question 18

What is the G0 phase

Answer 18

The resting phase where cells can remain for days, weeks or years

Question 19

What is assessed during the G2 checkpoint

Answer 19

It is checked that the DNA has replicated

Question 20

What is checked during the Metaphase checkpoint

Answer 20

This check establishes whether the chromosomes have correctly attached to the spindle fibres before Anaphase

Question 21

What is a tumour

Answer 21

A large mass of cells by which a mutation occurs in the cell, then the control mechanisms break down and the cell undergoes repeated, uncontrolled division

Question 22

What is a benign tumour

Answer 22

A tumour that does not travel to other locations of the body

Question 23

What is a Malignant tumour

Answer 23

A tumour that continues to grow unchecked and uncontrolled, that are shed and carried around the body by the circulatory system

Question 24

What are the different processes that may be targeted by anti-cancer drugs

Answer 24

DNA unzipping is inhibited, so that no DNA replication can take place
The synthesis of nucleotides is inhibited
Formation of mitotic spindle is inhibited so the chromatids can separate

Question 25

What are Genes

Answer 25

The codes for the synthesis of polypeptides and proteins

Question 26

What are two sets of chromosomes in cells called

Answer 26

Homologous pairs

Question 27

What is the term Homozygous

Answer 27

If the alleles on the homologous chromosomes are the same

Question 28

What is the term heterozygous

Answer 28

If the alleles on the homologous chromosomes are different

Question 29

What is Diploid

Answer 29

Cells contains homologous pairs of chromosomes

Question 30

Why are Chromatids genetically identical

Answer 30

Because DNA replication produces identical copies

Question 31

What is Haploid

Answer 31

A cell that contains only one of each type of chromosome

Question 32

What is a Karyotype

Answer 32

A photomicrograph taken of a cell during nuclear division

Question 33

What does a human Karyogram contain

Answer 33

23 pairs of chromosomes including a pair of sex chromosomes

Question 34

What is the difference between Meiosis 1 and Meiosis 2

Answer 34

Meiosis 1 is the separation of homologous chromosomes

Meiosis 2 is the separation of chromatids

Question 35

What occurs during Prophase 1

Answer 35

As chromosomes condense it becomes apparent that homologous chromosomes have paired and lie alongside each other; each pair is known as a bivalent
The chromatids appear: the chromatids in a bivalent are entwined at points called chiasmata
The chromatids may break at chiasmata and rejoin with a different chromatid

Question 36

What occurs during Metaphase 1

Answer 36

The bivalents move to the equator of the spindle

Each chromosome of the pair becomes attached to a spindle fibre by its centromere

Question 37

What occurs during Anaphase 1

Answer 37

Pulling by the spindle fibres causes the homologous chromosomes to move apart towards opposite poles
The homologous chromosomes are separated; each chromosome still consists of two chromatids

Question 38

What occurs during Telophase 1

Answer 38

Chromosomes reach opposite poles of the cell
A nuclear membrane forms around each separate group of chromosomes; each nuclei contains the haploid number of chromosomes

Question 39

What is the overall result of Meiosis

Answer 39

The production of 4 haploid daughter cells, each of which is genetically different from the others

Question 40

What is the significance of Mitosis

Answer 40

The daughter cells possess the same chromosome number as each other and as the parent cell. Mitosis can occur in either diploid or haploid cells
The daughter cells are genetically identical

Question 41

What is the significance of Meiosis

Answer 41

Meiosis is the type of nuclear division that transforms the diploid condition into the haploid condition
Meiosis produces daughter cells that are genetically different

Question 42

Why does Crossing-over occur in Meiosis

Answer 42

It occurs as a result of chiasmata formation between the chromatids of the homologous pairs during late Prophase I