cell cycle and division

Question 1

cell cycle definition

Answer 1

a regulated process in a sequence of events which cells divide into daughter cells in complete cell division. this consists of three main stages: interphase, mitosis and cytokinesis

Question 2

interphase part of cell cycle

Answer 2

G1, S, G2
phase between divisions
DNA is unwound as chromatin so genes are accessible for transcription
cells are metabolically active
cell growth and DNA replication occurs

Question 3

S

Answer 3

signal received causing cell division
DNA replicates and is synthesised
amount of DNA doubles

Question 4

G1 phase

Answer 4

cells make RNA, enzymes and other proteins for growth
organelles are replicated

Question 5

G2 phase

Answer 5

cell continues to grow
new DNA is syhthesised and checked

Question 6

mitosis products

Answer 6

2 genetically identical diploid daughter cells

Question 7

mitosis function

Answer 7

growth. (increasing cell number), repair of damaged tissues and asexual reproduction

Question 8

staged of mitosis in order

Answer 8

Prophase, Metaphase, Anaphase, Telophase

Question 9

prophase

Answer 9

chromosomes condense (now visible if stained)
two centrioles move towards opposite poles
nuclear envelope break down (now visible on light microscope)
Nucleolus disappears
Spindle fibres form

Question 10

metaphase

Answer 10

centrosomes reach opposite poles
spindle fibres extend from centrosome
chromosomes line up at the equator
spindle fibres reach chromosomes and attach to centromere
each sister chromatid is attached to a spindle fibre originating from opposite poles

Question 11

anaphase

Answer 11

sister chromatids separate at the centromere
spindle fibres begin to shorten
separated sister chromatids (chromosomes) are pulled to opposite poles by spindle fibres

Question 12

telophase

Answer 12

chromosomes arrive at opposite poles and begin to decondense
nuclear envelope reforms
spindle fibres break down

Question 13

Formation of specialised cells from stem cells

Answer 13

Chemical stimulus (e.g. growth substance)
Genes activated
Active genes transcribed
mRNA translated to make proteins
Proteins modify cell structure and function permanently

Question 14

Things which are only observed in meiosis

Answer 14

Chiasmata
Pairing of homologous chromosomes
Synapsis
Formation of bivalents

Question 15

How generic variation occurs in meiosis

Answer 15

Crossing over and independent assortment
CO: crossing over sections of chromatid
IA: random selection of maternal and paternal chromosomes by spindle fibres in metaphase 1
Causing new allele combinations