3.2.2 all cells arise from other cells

Question 1

what is DNA coiled around

Answer 1

histones

Question 2

what do histones do

Answer 2

they support the structure

Question 3

DNA is in the form of what

Answer 3

a double helix

Question 4

what is nuclear genetic material termed as

Answer 4

chromatin

Question 5

describe the structure of a sister chromasome

Answer 5

http://www.macroevolution.net/sister-chromatids.html

Question 6

before replication chromasones are always found in matching pairs , one from the mother and one from the father . what are they called ?

Answer 6

homologous pairs

Question 7

what is the diploid number in humans

Answer 7

46 (2n)

Question 8

what is the haploid number in humans

Answer 8

23 (n)

Question 9

does every spesics have the same diploid number

Answer 9

no

peas (16)
fogs (26)
chicken (78)

Question 10

what type of cells has a haploid number

Answer 10

gamates

Question 11

when DNA is not destinguishable as individual chromosomes it is called

Answer 11

chromatin

Question 12

what is the general length of chromosomes

Answer 12

0.25 to 50 micro meters

Question 13

what does n represent in haploid and diploid number

Answer 13

it represents the amount of pairs of homologous pairs

Question 14

are all cells formed by division of existing cells ?

Answer 14

yes

Question 15

what is the definition of mitosis

Answer 15

Mitosis: division into two daughter cells that are genetically identical to each other and to the parent cell.

Question 16

what is the definition of meiosis

Answer 16

Meiosis: division into four unique daughter cells with half the chromosomes of the parent cell. Genetically different. Produces the sex cells

Question 17

what is the significance of mitosis

Answer 17

Biosynthesis- is the process by which living things use chemical reactions to create products useful for cellular metabolism

repaire tissue

asexual reproduction

The genetic stability of a multicellular organism is reliant on an accurate DNA replication system and success at various levels of DNA repair systems in the cells

Question 18

what are the advantages of a-sexual reproduction

Answer 18

All adapted to a stable environment, rapid repopulation / populate

Question 19

what are the disadvantages of a-sexual reproduction

Answer 19

Less able to adapt to environmental change, vulnerable to disease

Question 20

the cell cycle involves 3 phases what are they

Answer 20

interphase
meitosis
cytokienesis

Question 21

interphases has 3 stages what are they

Answer 21

G1 , S , G2

Question 22

what happens in G1

Answer 22

g1 phase, also called the first gap phase, the cell grows physically larger, copies organelles, and makes the molecular building blocks it will need in later steps. (growth of cytoplasm and organelles)

Question 23

what happens during S phase

Answer 23

synthasis of DNA

S phase. In S phase, the cell synthesizes a complete copy of the DNA in its nucleus. It also duplicates a microtubule-organizing structure called the centrosome. The centrosomes help separate DNA during M phase.

Question 24

what happens during g2 phase

Answer 24

g phase, the cell grows more, makes proteins and organelles, and begins to reorganize its contents in preparation for mitosis. G‍

phase ends when mitosis begins.

it requires a lot of energy due to the increase in size and activity , but also a lot more enzymes now

Question 25

what is g0 phase

Answer 25

this is the pahse in which many non dividing cells enter e.g brains cells or nerve cells)

Question 26

in which stage are proteins made for DNA synthasis

Answer 26

during interpahse

Question 27

what are the four main processes that take place during interpahse

Answer 27

1. synthasis of DNA 2. synthasis of ATP 3. synthasis of protein 4. replication of organelles

Question 28

what are the four phases of mitosis

Answer 28

prophase meteaphase anaphase telophase

Question 29

what happens in prophase

Answer 29

nuclear envelope disapears near the end of propahse chromatin condens to make chromasomes seperation of centromeres formation of miotic spindal fibers centrioles divide and migrate to opposite poles Plant cells lack centrioles but do develop spindle fibres therefore centrioles not essential for spindle fibre formation

Question 30

what happens during metaphase

Answer 30

The nuclear membrane has disappeared. the chromosomes align upon a theoretical line known as the metaphase plate. The centrosomes arer on opposite ends of the cell. At this stage, the cell will check that all the chromosomes are aligned along the metaphase plate, with their kinetochores correctly attached. This helps to ensure sister chromatids are split evenly between the two daughter cells. An error in chromosomal alignment or spindle attachment will result in the cell halting further progress until the problem is fixed. Spindle fibres attach to centromeres holding the pairs of sister chromatids together https://teachmephysiology.com/biochemistry/cell-growth-death/mitosis/

Question 31

what happens during anaphase

Answer 31

The centromeres divide separating the sister chromatids The spindle fibres contract pulling the sister chromatids apart to opposite poles. Centromere moves first making the chromatids appear v-shaped Spindle fibres not attached to chromatids will elongate the cell to prepare it for division.

Question 32

what happens during telophase

Answer 32

The chromatids have arrived at the poles and are now called chromosomes. They become long and thin once more A nuclear envelope reforms around each set. In this phase, the cell has elongated and is nearly finished dividing. Cell-like features begin to reappear such as the reformation of two nuclei (one for each cell). The chromosomes then de-condense and the mitotic spindle fibres are broken down.

Question 33

what happens during cytokeinsis

Answer 33

The third phase in the cell cycle It is the physical process of cell division Parental cell cytoplasm divides Production of two daughter cells microfiliments pull in cell surface membrane drawing it inwards ( givinf a pinching effect)

Question 34

how do plant cells under go cyokeinesis

Answer 34

Golgi vesicles carrying materials to make a Cell wall accumulate in the centre region of the cell. The Golgi vesicles fuse and form a CELL PLATE. Inside the vesicles a middle lamella forms with cellulose either side of it. Two new separate cells are formed

Question 35

state two diffrences in plant and animal mitosis

Answer 35

animal cells : centrioles act as a focous for spindal fibers which form arcs cytokiensis is by microfilliments (pinch) plant cells : no centrioles , no spindal fibers , fibers are parrallel than curved cytokeinesis is by cell plates formation , as golgi vesicles secreate new cell wall

Question 36

cancer is causes by what ?

Answer 36

1. mutagens 2. enviroment e.g sun 3. error in copying DNA

Question 37

how would you measure if a tissue is cancerous or not ?

Answer 37

mitotic index number of cells with visibal chromasomes/total number of cells

Question 38

infocard (read and recite)

Answer 38

An interphase cell in the g0 phase is not preparing for division, but is instead performing all of the other functions appropriate for that particular cell type. some mature cells such as skeletal muscle cells and most neurones remain in g0 indefinitely and never divide. in contrast , stem cells which divide repeatedly with very brief interphase periods, never enter g0

Question 39

infocard (read and recite)

Answer 39

G1 (8 or more hours) ac ell that is ready to divide first enters the G1 phase in this phase the cell makes enoughmitochondria, cytoskeletal elements , endoplasmic reticula , ribosomes , golgi membranes , and cytosol for two functional cells , centriole replication begins in G1 and commonly continues until G2 . in cells dividing at top speed , G1 may last just 8-12 hrs such cells pour all their energy into mitosis and all other activies cease if G1 lasts for days weeks or months preparation for mitosis occurs as the cells perform their normal functions

Question 40

infocard (read and recite)

Answer 40

S phase (lasts between 6 to 8 hrs) when the activities of the G1 phase have been compleasted the cell enters the S phase over the next 6-8 hours the cell deuplicates its chromosomes . this involves DNA replication and the synthesis of histones and other proteins in the nucleus

Question 41

infocard (read and recite)

Answer 41

G2 (last for around 2 to 5 hrs) once DNA replication has ended there is a brief (2-5 hr) G2 phase devoted to last-min protein synthesis and to the completion of centrioles replication.

Question 42

what causes cancer

Answer 42

a mutation in a gene which controls the cell cycle causing damage to the gene leading to the develpment of a tumour. cancer is most common in lungs , prostate gland , breasts , ovaries , stomach , oesophgus and pancreas

Question 43

read this artical

Answer 43

https://teachmephysiology.com/biochemistry/cell-growth-death/mitosis/

Question 44

what is a benign tumour

Answer 44

Benign Tumours – tumours that do not spread from their point of origin but they may still be painful because they compress surrounding tissues and displace them. Benign tumours are usually encased in a fibrous capsule and do not invade the tissue in which they originate. Do not cause cancer and do not metastasise

Question 45

what is a malignant tumours

Answer 45

Malignant Tumours – divide in a more uncontrolled way than benign tumours and can be carried by the blood stream or lymphatic system to invade other tissues, causing secondary cancers. This process is called metastasis.

Question 46

what is a tumour

Answer 46

Tumour – A mass of abnormal cells that have developed by uncontrolled cell division

Question 47

how do malignant tumours cause secondary tumours

Answer 47

1. mechanisms controlling cell division breaks down 2 . primary tumour formed by repeated division of affected cell 3. cancerous cells escapes to blood or lymph 4. cancerous cell carried to diffrent tissue 5. secondary tumour (metastasis ) formed anywhere in the body metastasis - the development of secondary malignant growths at a distance from a primary site of cancer.

Question 48

what are the two families that controll the cell cycle

Answer 48

tumer-supressor gene proto-oncogene

Question 49

how does a proto oncogene work and become oncognee

Answer 49

A proto-oncogene is a gene that encodes a protein that is involved in regulation of cell growth or proliferation Can be mutated into a cancer promoting oncogene where the gene is stuck in a state of constant activity Uncontrolled growth leading to tumour development it is responsible for the 'gas' for the cell cycle

Question 50

how does a tumour suppressor gene work and how does a mutation cause cancer

Answer 50

Tumour suppressor genes encode proteins that inhibit cell proliferation. Loss of these genes can contribute to the development of cancer

Question 51

what is prolification

Answer 51

reproduction involving a cell growing directly from an older one.

Question 52

what are the three ways to treat cancer

Answer 52

Surgery-removal of the tumour Radiotherapy-radiation damages the DNA and causes cells to kill them selves Chemotherapy- drugs are used to kill cancerous cells preventing them from dividing or damaging them so they kill themselves.

Question 53

what are the two types of chemotherapy

Answer 53

1. Prevent the DNA from replicating Some drugs target G1 region in interphase Prevent the synthesis of enzymes needed for DNA replication and therefore cell is unable to enter S phase Some drugs target the S phase Includes radiation as DNA becomes so damaged cell will kill itself (checkpoints) 2.Inhibit the metaphase stage of mitosis by interfering with spindle formation

Question 54

describe the process of cell divition in prokaryotes

Answer 54

By Binary Fission A sexual reproduction in unicellular organisms in which a single cell divides to form two identical daughter cells Very similar to mitosis genetic material is replicated before the prokaryote splits Into two. Replicated large loop of DNA attaches to cytoplasmic membrane. As cell grows the DNA is separated The main DNA loop is only replicated once, but plasmids can be replicated numerous times Daughter cells can contain variable numbers of plasmids

Question 55

how do viral virasis replicate

Answer 55

Attachment: The virus attaches to a host cell. In the case of the bacteriophage it will attach to a bacterium. Entry: The virus forms a hole in the membrane or cell wall of the host. The nucleic acid of the virus enters the host cell. Synthesis: The virus’ nucleic acid is used to make new viral nucleic acid and proteins for the new viruses being produced. (The host cells’ DNA becomes deactivated) Assembly: New viruses are made inside the host cell. Release: The host cell bursts to release the new viruses. The bursting is called lysis.  

Question 56

what is meristems

Answer 56

Meristems are regions of plant cells that are actively dividing by mitosis. They are small unspecialised cells forming a tissue called Meristematic tissue. Meristematic tissue is found in growing regions of root tips, stem tips and in the cambium which is involved in thickening growth (between xylem and phloem tissue).