Cell cycle

Question 1

Define cell cycle.

Answer 1

Cell cycle is the life of a cell from when its first formed from a parent cell until its own division into 2 cells.

Question 2

Define karyotype

Answer 2

A complete set of all chromosomes

Question 3

What is the difference between a diploid and haploid cell?

Answer 3

A diploid cell has 2 sets of chromosomes while a haploid cell has 1 set of chromosomes. A diploid cell is formed through mitosis while a haploid cell is formed through meiosis.

Question 4

What are autosomes

Answer 4

Autosomes are all the other chromosomes found in cells except sex cells.

Question 5

What is the difference between a homologous chromosome and sister chromatids

Answer 5

Sister chromatids are genetically identical to one another while homologous chromosomes are not genetically not identical. Sister chromatids are attached together at the centromere while homologous chromosomes are not joined together. Sister chromatids are separated in anaphase II while homologous chromosomes are separated in anaphase I.

Question 6

What occurs during G1 , S and G2 phase?

Answer 6

G1: Cell growth , cell increase in size and synthesis of additional organelles , proteins and mrna. Dna is in the form of chromatin fibres.
S: DNA replication, centrioles replicate , histome synthesis. DNA exists as chromatin fibres.
G2: Continues growth of cell to produce more proteins and organelles.

Question 7

Define interphase.

Answer 7

Interphase is the period of growth and synthesis in cell cycle.

Question 8

Define mitosis

Answer 8

Mitosis is the process where the cell nucleus divides to produce 2 daughter nuclei each containing identical sets of chromosomes to the parents nucleus

Question 9

What happens during telophase?

Answer 9

-Chromatids reach respective poles of spindle
-Chromosome uncoil and decondense into thread-like chromatin
-Spindle fibres disintegrate
-Nucleus envelope reforms around the chromosome of each pole and nucleoli reforms
-Nucleolus reforms.

Question 10

Difference between animal and higher plant cells mitosis?

Answer 10

-use of centrioles
-aster formation

Question 10

Significance and function of mitosis?

Answer 10

Many Gorillas Ride Alpacas.
Maintaining genetic stability mitosis produces two daughter nuclei that are genetically identical to the parent nucleus. They have the same number and type of chromosomes as the parent nuclei due to DNA replication in S phase. This results in genetic stability among populated cells.
Growth. The number of cells increase by mitosis and new cells are identical to existing cells.
Repair. Cells can sustain damage due to factors like UV radiation. Mitosis ensures that damaged cells are replaced with new cells that are identical to the original cell so that the tissue can function properly.
Asexual Reproduction. Ensures offspring are genetically identical to parent for continue survival of its species and retain advantages that allows it to adopt to its environment.

Question 11

Define cytokinesis

Answer 11

Cytokinesis is the division of the cytoplasm to form 2 separate daughter cells after nuclear division , each having equal amounts o cytoplasm and organelles.

Question 11

How is chromosome constitution preserved?

Answer 11

a) Chromosomes of parent nucleus are replicated during S-phase before mitosis
b) Arrangement of chromosomes on the spindle during Metaphase ensures that the chromosomes are equally shared between the two daughter nuclei.

Question 11

How do plants undergo cytokinesis?

Answer 11

Golgi vesicles line up along the metaphase plate
Golgi vesicles fuse to form a cell plate
Cellulose contents from Golgi vesicles form cell wall
Membrane from Golgi vesicles form the cell surface membrane
The cell plate fuse with the parent cell wall and cell membrane separating the two daughter cells.

Question 12

Define meiosis.

Answer 12

It is the nuclear division where a nucleus divides to produce 4 genetically non-identical daughter nuclei , each containing half the number of chromosomes as the parents nucleus.

Question 13

What causes genetic variation in Meiosis?

Answer 13

Crossing over between non-sister chromatids of homologous chromosomes results in sharing of genetic materials between homologous chromosomes, promoting genetic variation.

Question 14

What takes places during Prophase I?

Answer 14

-chromatin coil into visible chromosome
-homologous pair up via synapsis
-crossing over between non-sister chromatids of homologous chromosomes
-centrioles migrate to opposite ends of poles and forms spindle fibres
- nucleolus and nuclear envelope disintegrates.

Question 15

What happens during metaphase I?

Answer 15

Homologous chromosomes randomly align along the metaphase plate.
The arrangement of chromosomes of each bivalent is independent from the orientation of other bivalents .

Question 16

What happens during anaphase I?

Answer 16

Homologous chromosomes separate to opposite poles due to shortening of kinetochore microtubules.
Centromere do not divide at this stage.

Question 17

What happens during telophase I?

Answer 17

Chromosomes move to opposite poles of spindle.
Spindle fibres disintegrates.
Chromosomes uncoil and decondense into chromatin fibres.
Nucleolus and nuclear envelope reforms

Question 18

What happens during anaphase II?

Answer 18

Non-identical sister chromatid separate to opposite poles of spindle .
Centromere divides

Question 19

Significance and function of meiosis.

Answer 19

Sexual reproduction - Meiosis produces haploid gametes , due to the separation of homologous chromosomes during anaphase I.
During fertilization , nuclei of sperm and egg fuse to form a diploid zygote , restoring the diploid condition. Meiosis ensures that the number of chromosomes for each species remains the same for each generation.

Genetic variation- Meiosis allows for new combinations of alleles. Genetic variation ensures that species constantly change and adapt when environments alter. Crossing over of sister-chromatids of homologous chromosomes during anaphase I allows the exchange of DNA material , promoting genetic variation and more combinations of alleles. Independent assortment of chromosomes in metaphase I results in arrangement and separation of chromatid is independent of another chromatid during metaphase II and anaphase II , leading to variation of allele combinations. Random fertilization > random variation in zygote.

Question 20

Similarities of meiosis and mitosis?

Answer 20

Both undergo DNA replication.

Question 21

What are the aims of checkpoints.

Answer 21

G1: Ensures favourable conditions for cell growth and checks for DNA damage.
G2:Ensures accurate and complete DNA replication and checks for DNA damage before mitosis.
Metaphase: Ensures alignment of chromosomes at metaphase plate is correct and spindle attachment to prevent unequal chromosome segregation.

Question 22

What is the function of Cdk?

Answer 22

Allows cell cycle to proceed through checkpoints.

Question 23

Explain how levels of cyclin-CDK complexes fluctuates.

Answer 23

Concentration of CDK remains constant but concentration of Cyclin fluctuates due to synthesis as degradation. As concentration of cyclin increases , more cyclin will bind to CDK to form more Cyclin-CDK complexes during mitosis.

Question 24

Explain how the dysregulation of cell cycle checkpoints may lead to accumulation of mutation and cancer development.

Answer 24

When there is dysregulation in checkpoints , DNA damage cannot be repaired. Gene mutation will be passed onto daughter cells. Daughter cells will have gain of function mutation to proto-oncogenes and loss of function to tumour suppresor gene. This will cause uncontrolled cell division where rate of cell growth is higher than rate of cell death , forming a tumour.