Topic 1 - The cell cycle

Question 1

what is mitosis

Answer 1

the process by which a cell divides to produce 2 genetically identical daughter cells

Question 2

what is meiosis

Answer 2

a form of cell division in which the chromosome number of the original cell is halved, leading to the formation of the gametes

Question 3

what is asexual reproduction

Answer 3

the production of genetically identical offspring from a single parent ot organism

Question 4

what is sexual reproduction

Answer 4

the production of offspring that are genetically different from the parent organisms by the fusing of 2 gametes

Question 5

what are histones

Answer 5

positively charged proteins involved in the coiling of DNA to form dense chromosomes in cell division

Question 6

what are nucleosomes

Answer 6

dense clusters of DNA wound around histones

Question 7

what is a karyotype

Answer 7

a way of displaying an image of the chromosomes of a cell to show the pairs of autosomes and sex hormones

Question 8

what is the cell cycle

Answer 8

a regulated process of 3 stages (interphase, mitosis, cytokinesis) in which cells divide into 2 genetically identical daughter cells

Question 9

what is interphase

Answer 9

the period between active cell division when cells increase in size and mass, replicate their DNA and carry out normal metabolic activities

Question 10

what is a chromatid

Answer 10

one strand of the replicated chromosome pair that is joined to the other chromatid at the centromere

Question 11

what are cyclins

Answer 11

small proteins that build up during interphase and are involved in the control of the cell cycle by their attachment to cycle-dependent kinases

Question 12

what are Cyclin-dependent kinases (CDKs)

Answer 12

enzymes involved in the control of the cell cycle by phosphorylating other proteins, activated by attachment to cyclins

Question 13

what is DNA made up of

Answer 13

a mass of coiled threads of DNA and proteins

Question 14

when the cell is not actively dividing, what colour are the chromosomes

Answer 14

translucent

Question 15

when the cell is actively dividing, why do the chromosomes take up the stain

Answer 15

the chromosomes condense by becoming shorter and denser

Question 16

how is a chromosome coiled up efficiently

Answer 16

the DNA winds around the histones to form a nucleosome. These then interact to produce more coiling and supercoiling to form dense chromosome structures

Question 17

how many chromosomes do humans have

Answer 17

46

Question 18

how many pairs of chromosomes do humans have

Answer 18

23

Question 19

when does G1 (gap 1) happen in the cell cycle

Answer 19

the time between, the end of the previous round of mitotic cell division and the start of chromosome duplication

Question 20

what happens in G1 (gap 1)

Answer 20

• the cell increases in size as it produces necessary components for mitotic cell division
• All of the organelles duplicate
• The cell carries out normal metabolic cell division
• the cell checks for sufficient nutrition & energy reserves, proper growth and absence of DNA damage

Question 21

what happens in S

Answer 21

• Each chromosome is copied to form two identical sister chromatids held together by a centromere
• Histones are synthesized and incorporated into newly formed DNA
• The centrosome is also duplicated

Question 22

what happens in G2 (gap 2)

Answer 22

• tubulin is produced for the synthesis of spindle fibres
• any errors in the replicated DNA are corrected to prevent mutations
• The cell checks that the DNA has been replicated, it is undamaged, and if the cell is large enough

Question 23

what happens during M (mitosis) in the cell cycle

Answer 23

the cells are actively dividing

Question 24

what happens during C (cytokinesis) in the cell cycle

Answer 24

the new cells seperate

Question 25

when does the cell cycle slow down or stop in multicellular organisms

Answer 25

when the organism is mature

Question 26

what is the cell cycle controlled by

Answer 26

a number of chemical signals made in response to different genes

Question 27

how are the chemicals that control the cell cycle controlled

Answer 27

proteins called cyclins build up and attach to enzymes called CDKs. The cyclin/CDK complex formed phosphorylates other proteins, changing their shape and bringing about the nexts stage in the cell cycle