Unformatted text preview:

Chapter 12: The Cell Cycle- Multicellular organisms depend on cell division for:o Development from a zygoteo Growtho Repair- Cell division is an integral part of the cell cycle, the life of a cell from formation to its own division- Most cell division (mitosis, non sex) results in daughter cells with identical DNA (identical to daughter and parent)- Meiosis produces non-identical daughter cells (gametes: sperm and egg cells)- All the DNA in a cell constitutes the cell’s genome- DNA molecules in a cell are packaged into chromosomes- Every eukaryotic species has a characteristic number of chromosomes in each cell nucleus- Somatic cells (non-reproductive cells) have two sets of chromosomes (1 from each parent)- Gametes (reproductive cells:sperm and eggs) have half asmany chromosomes as somaticcells- Eukaryotic chromosomes consistof chromatin, a complex of DNAand protein that condenses duringcell division- In preparation for cell division,DNA is replicated and thechromosomes condense- Each replicated chromosome hastwo sister chromatids, whichseparate during cell division- The centromere of the replicatedchromosome is where the twochromatids are most closely attached- Figure 12.4 Chromosome duplication and distribution during cell division- Eukaryotic cell division consists of:o Mitosis , the division of the nucleus o Cytokinesis , the division of the cytoplasm (cell)- The cell cycle consists of:o Mitotic (M) phase: the dividing phase (mitosis and cytokinesis)o Interphase: the non-dividing phase (cell growth and copying of chromosomes in preparation for cell division, preparing to divide)- Interphase (about 90% of the cell cycle) can be divided into subphases:o G1 phase (“first gap”)o S phase (“synthesis”)o G2 phase (“second gap”)- The cell grows during all three phases, butchromosomes are replicated only during the Sphase - Figure 12.5 The cell cycleMitosis- Mitosis is conventionally divided into fivephases:o Prophaseo Prometaphaseo Metaphaseo Anaphaseo Telophase- Cytokinesis is well underway bylate telophase- Figure 12.6 The mitotic divisionof an animal cell- Homologous chromosomes arenot identical to each other, onecame from mom, one camefrom dad***- Sister chromatids are identical(S phase)- The mitotic spindle (string, DNAsynthesis) is an apparatus ofmicrotubules that controlschromosome movement duringmitosis- During prophase, assembly ofspindle microtubules begins inthe centrosome, themicrotubule organizing center- The centrosome replicates, forming two centrosomes that migrate to opposite ends of the cell, as spindle microtubules grow out from them- During prometaphase, some spindle microtubules attach to the kinetochores of chromosomes and begin to move the chromosomes - At metaphase, the chromosomes are all linedup at the metaphase plate, the midway pointbetween the spindle’s two poles- Figure 12.7 The mitotic spindle at metaphase- In anaphase, sister chromatids separate andmove along the kinetochore microtubulestoward opposite ends of the cell- Non-kinetochore microtubules from oppositepoles overlap and push against each other,elongating the cell- In telophase, genetically identical daughternuclei form at opposite ends of the cell- In animal cells, cytokinesis occurs by a process known as cleavage, forming a cleavage furrow- In plant cells, a cell plate forms during cytokinesis, which will form the cell walls of the daughter cells.Binary Fission- Prokaryotes (bacteria and archaea) reproduce by a type of cell division called binary fission- In binary fission, the chromosome replicates, and the two daughter chromosomes actively moveapartThe Cell Cycle Control System- The sequential events of the cell cycle aredirected by a distinct cell cycle controlsystem, which is similar to a clock- The clock has specific checkpoints where thecell cycle stops until a go-ahead signal isreceived- Figure 12.14 Mechanical analogy for the cellcycle control system- For many cells, the G1 checkpoint seems tobe the most important one- If a cell receives a go-ahead signal at the G1checkpoint, it will usually complete the S,G2, and M phases and divide- If the cell does not receive the go-ahead signal, it will exit the cycle, switching into a nondividing state called the G0 phase- Two types of regulatory proteins are involved in cell cycle control: cyclins and cyclin-dependent kinases (Cdks)- The activity of cyclins and Cdks fluctuates during the cell cycleLoss of Cell Cycle Controls in Cancer Cells- Cancer cells do not respond normally to the body’s control mechanisms- Cancer cells may not need growth factors to grow and divide:o They may make their own growth factoro They may convey a growth factor’s signal without the presence of the growth factoro They may have an abnormal cell cycle control


View Full Document

LSU BIOL 1201 - Chapter 12: The Cell Cycle

Documents in this Course
Notes

Notes

12 pages

Notes

Notes

2 pages

Notes

Notes

4 pages

Unit 2

Unit 2

14 pages

MITOSIS

MITOSIS

3 pages

Notes

Notes

10 pages

Science

Science

141 pages

Cells

Cells

13 pages

Ocean

Ocean

36 pages

Unit 1

Unit 1

14 pages

Exam 1

Exam 1

3 pages

Notes

Notes

1 pages

The Ocean

The Ocean

24 pages

Meiosis

Meiosis

22 pages

Exam 4

Exam 4

4 pages

The Ocean

The Ocean

55 pages

Exam 1

Exam 1

8 pages

Test #1

Test #1

42 pages

Load more
Download Chapter 12: The Cell Cycle
Our administrator received your request to download this document. We will send you the file to your email shortly.
Loading Unlocking...
Login

Join to view Chapter 12: The Cell Cycle and access 3M+ class-specific study document.

or
We will never post anything without your permission.
Don't have an account?
Sign Up

Join to view Chapter 12: The Cell Cycle 2 2 and access 3M+ class-specific study document.

or

By creating an account you agree to our Privacy Policy and Terms Of Use

Already a member?