paper 1: All Cells Arise from Other Cells

Question 1

what is a chromosome

Answer 1

one DNA molecule folded into a condensed form, wrapped around histone proteins in eukaryotes

Question 2

after DNa replication what is a chromosome made of

Answer 2

2 genetically identical sister chromatids

Question 3

show a chromosome before and after DNA replication

Answer 3

Question 4

how are chromosome homologous pairs

Answer 4

one chromosome is inherited from the mother and one chromosome is inherited from a father

Question 5

what is the definition of a homologous chromosome

Answer 5

the same genes but potentially different alleles

Question 6

define a gene

Answer 6

a section of DNA that codes for a polypeptide or functional RNA

Question 7

define an allele

Answer 7

different forms of the same gene that code for a specific trait

Question 8

what is a chromosome number

Answer 8

the number of chromsomes possessed by an organism (n)

Question 9

define a diploid cell

Answer 9

diploid cells have a homologous pairs of chromosomes

Question 10

what is a haploid cell

Answer 10

haploid cells have one copy of each homologous chromosome

Question 11

what are the main stages of the cell cycle

Answer 11

interphase
prophase 
metaphase 
anaphase
telophase
cytokinesis

Question 12

define mitosis

Answer 12

cell division that produces 2 genetically identical daughter cells from a parent cell

Question 13

why do cells need to carry out mitosis

Answer 13

growth and repair tissues & replace cells

Question 14

what happens during interphase

Answer 14

• new proteins are synthesised
• DNA replicates
• new organelles are made

Question 15

when are chromosome visible

Answer 15

in the stages of mitosis

Question 16

what happens during prophase

Answer 16

• chromosomes condense and become visible
• nuclear membrane breaks down centrioles move to opposite poles of the cell
• spindle fibres form

Question 17

what happens during metaphase

Answer 17

• spindle fibres attach to centromere
• chromosomes are lined up at the equator of the cell

Question 18

what happens during anaphase

Answer 18

• spindle fibres contract splitting the centromere
• v-shaped sister chromatids are separated and pulled apart to opposite poles of the cell

Question 19

what happens during telophase

Answer 19

• spindle fibres break down
• a new nuclear membrane forms around each group of chromosomes
• chromosomes uncondense

Question 20

what happens during cytokinesis

Answer 20

the cytoplasm divides into 2 to create 2 separate daughter cells

Question 21

how does cancer forms

Answer 21

• if a mutation occurs in one of the control genes, then cell division continues
• uncontrolled cell division can lead to the formation of tumours and cancers
• mutation occurs at random
• mutagenic agents increase the chances if mutation

Question 22

what are some examples of mutagenic agents

Answer 22

• UV radiation, ionising radiation, carcinogens (cigarettes, asbestos)

Question 23

what are the 2 types of tumour

Answer 23

benign and melignant

Question 24

what are benign tumours

Answer 24

slow growing tumours that don’t spread to the rest of the body

Question 25

what are melignant tumours

Answer 25

fast growing tumours that cells break off of and spread to other parts of the body

Question 26

what is the difference between a tumour and a cancer

Answer 26

a tumour is a mass of cells dividing uncontrollably, if those cells break off and spread it becomes a cancer

Question 27

how do cancer treatments control the rate of cell division

Answer 27

- prevents the synthesis of enzymes needed for cell replication - damage DNA - prevent the formation of spindle fibres

Question 28

what is a negative of cancer treatments

Answer 28

the treatments cannot distinguish between healthy and cancerous cells so they destroy normal body cells that are dividing

Question 29

how do prokaryotic cells replicate

Answer 29

a process called binary fission - the circular DNA and the plasmids replicate - the copies of circular DNA move to separate poles of the cell - the cytoplasm divides to produce 2 daughter cells - each cell contains a single copy of the circular DNA but a variable number of plasmids

Question 30

how do viruses replicate

Answer 30

- they use a specific host cell to replicate - the virus attachment protein binds to a specific complimentary receptor protein on a specific host cell - the viral DNA/RNA is injected into the host cell - the host cell uses the viral genetic material and its own ribosomes and enzymes to synthesise viral proteins - the viral particles are formed and release from the host cell