C8 - Cell Replication

Question 1

What is DNA?

Answer 1

The way living things pass on traits (hair colour, eye colour, height)

Question 2

What is a chromosome?

Answer 2

A single DNA molecule containing many genes

Question 3

What are genes?

Answer 3

Sections of DNA that code for proteins

Question 4

What are homologous chromosomes?

Answer 4

2 molecules of DNA that contain the same genes (1 from each parent)

Question 5

What is the Cell Cycle?

Answer 5

The cycle of creating new cells that all cells exist in - all cells come from pre-existing cells through the completion of this cycle

Question 6

What are the different phases of the cell cycle?

Answer 6

G1, S, G2, M

Question 7

In eukaryotic cells, what are the two major stages of the cell cycle?

Answer 7

Interphase and mitotic phase

Question 8

What is interphase?

Answer 8

When the cell grows and copies its DNA

Question 9

What is the mitotic phase?

Answer 9

The cell separates it’s DNA into 2 sets and divides its cytoplasm (cytokinesis) forming two new cells

Question 10

What is cytokinesis?

Answer 10

When a cell divides its cytoplasm to form 2 new cells

Question 11

Which stages of the Cell Cycle does interphase cover?

Answer 11

G1, S and G2

Question 12

What is the G1 phase?

Answer 12

The first gap phase, the cell grows physically larger, copes organelles and makes biomolecules important for later steps

Question 13

What is the S phase?

Answer 13

Synthesis, where DNA replication occurs in the nucleus, and the centrosome (a microtubule-organising structure for seperating DNA) is duplicated

Question 14

What is the G2 phase?

Answer 14

The second gap phase, where the cell grows more, and makes proteins and organelles. This phase ends when mitosis begins

Question 15

What is the M phase?

Answer 15

Mitosis, used for growth, repair or asexual reproduction

Question 16

Does mitosis make diploid or haploid cells?

Answer 16

Diploid cells

Question 17

Is mitosis cloning?

Answer 17

Yes

Question 18

Outline the process of mitosis

Answer 18

Interphase: DNA replicates, as do organelles
Prophase: Chromosomes condense and become visible and the nucleus disappears
Metaphase: The spindle fibers have descended and attached to the centromeres and lined the chromosomes up on the cell equator (or metaphase plate)
Anaphase: The spindle fibers pull the chromosomes apart and also push the cells poles apart
Telophase: The chromosomes form chromatin again, and the contractile ring pulls the cell membrane together until the cell divides
Cytokinesis: When the cell divides into two new daughter cells

Question 19

What is meiosis?

Answer 19

The process of creating four genetically unique daughter cells with half the number of chromosomes

Question 20

When is meiosis used?

Answer 20

Sexual reproduction only

Question 21

Does meiosis create diploid or haploid cells?

Answer 21

Haploid (one chromosome)

Question 22

Outline the first stage of meiosis

Answer 22

Interphase: DNA and organelles replicates
Prophase 1: Homologous chromosomes pair up and ‘stick’ via synapsis, then segments of sister chromosomes switch in a process known as crossing over
Metaphase 1: The pairs all line up in the centre of the cell and are held in place with spindle fibers (independent assortment occurs here)
Anaphase 1: The pairs separate and two chromatids move towards each pole of the cell
Telophase 1: The two cells separate and cytokinesis occurs

Question 23

Outline the second stage of meiosis

Answer 23

Prophase 2: nucleus of intermediary daughter cells disappear and the centrosomes begin to move towards poles
Metaphase 2: Chromosomes lined up in the centre of the cell
Anaphase 2: Replicated chromosomes split
Telophase 2: Cells divide into 4 individual daughter cells (forming gametes)

Question 24

What is independent assortment?

Answer 24

Chromosomes go into each new cell randomly, so any mixed chromosome ( chromosome with changed alleles) can go into any of the four daughter cells, creating even more variation

Question 25

How do prokaryotes reproduce?

Answer 25

Via mitotic binary fission

Question 26

What is fragmentation?

Answer 26

One part splits into pieces and each develops into a new organism (flatworms)

Question 27

What is parthenogenesis?

Answer 27

When female produced eggs hatch without fertilisation (worker bees)

Question 28

What are the different types of twins?

Answer 28

Fraternal: twin eggs fertilised by 2 sperm (different genetics)
Identical: fertilised egg splits into 2 (same genetics)