Cell cycles and divisions

Question 1

cell cycle

Answer 1

phases a cell passes through to produce daughter cells by cell division

Question 2

prokaryotes

Answer 2

cell division is called binary fission, replication of the entire single-celled organism

Question 3

(prokaryotes) cell division signals

Answer 3

usually external factors such as nutrient concentration and environmental conditions

Question 4

prokaryotes- replication

Answer 4

most prokaryotes have one, circular chromosome
two important regions:
- ori = where replication starts (origin)
- ter = where replication ends (terminus)

Question 5

prokaryotes - DNA segregation

Answer 5

when replication is complete, ori regions move to opposite ends of the cell, segregating the daughter chromosomes

Question 6

prokaryotes - cytokinesis

Answer 6

cell membrane pinches in, protein fibers form a ring.
new cell wall materials are synthesized, resulting in separation of the two cells

Question 7

Eukaryotes

Answer 7

cell division is through mitosis or in some tissues meiosis
cell division is regulated based on the needs of the entire organism

Question 8

why is DNA replication more complicated in eukaryotes?

Answer 8

• they have ore than one chromosome
• replication starts at may origins on each
• replication is limited to one part of the cell cycle

Question 9

eukaryotes- interphase

Answer 9

• nucleus is visible
  cell functions occur
  three subphases:
• growth 1 G1
• synthesis S
• growth 2 G2

Question 10

G1 PHASE

Answer 10

• chromosomes are single (unreplicated)
• duration is variable, from minutes to years
• ends at the G1-to-S TRANSITION, when commitment is made to DNA replication and cell division

Question 11

S PHASE

Answer 11

• DNA replicates
• sister chromatids remain together until mitosis

Question 12

G2 PHASE

Answer 12

-cell prepares for miosis, e.g., by synthesizing the structures that move the chromatids

Question 13

M PHASE

Answer 13

includes mitosis and cytokinesis

Question 14

mitosis

Answer 14

leads to the production of two nuclei that are genetically identical to each other and to the nucleus of the cell that entered the cell cycle in G1

Question 15

5 stages of mitosis

Answer 15

• prophase
• prometaphase
• metaphase
• anaphase
• telophase

Question 16

asexual reproduction

Answer 16

• based on mitosis
• a single-celled organism reproduces itself with each cell cycle
• some multicellular organisms also reproduce asexually

Question 17

meiosis

Answer 17

sexual reproduction requires meiosis
- offspring are not identical to the parents
- gametes are created by meiosis
- gametes and offspring differ genetically from each other and from the parents

Question 18

how many nuclear divisions are there in meiosis?

Answer 18

2, but DNA is only replicated once.

• it reduces the chromosome number from diploid to haploid
• ensures each haploid product has a complete set of chromosomes

Question 19

how does meiosis generate genetic diversity

Answer 19

-recombination
-independent assortment of alleles
-crossing over: exchange of genetic material between non-sister chromatids

Question 20

independent assortment of alleles

Answer 20

it is a mater of chance how the homologous chromosomes line up in anaphase I and which ones go to which daughter cell

Question 21

sexual life cycles

Answer 21

evolution has generated many different versions of the sexual life cycle
- al involve meiosis to produce haploid cells
- fertilization and meiosis alternate
- haploid cells or organisms alternate with diploid cells or organisms