Chapter 8 The Cell Cycle Honors Biology Why is the Cell Cycle Important? Growth ◦ So an...
74
Chapter 8 The Cell Cycle Honors Biology
Chapter 8 The Cell Cycle Honors Biology Why is the Cell Cycle Important? Growth ◦ So an organism’s surface area can keep up with its growing volume Repair
Why is the Cell Cycle Important? Growth So an organisms surface
area can keep up with its growing volume Repair Replaces cells that
wear out or become damaged To form a new layer of skin at the site
of an injury
Slide 4
Phases of the Cell Cycle 1. INTERPHASE Period between cell
divisions when the cell is very active, duplicates chromosomes
& prepares for division. 2. MITOSIS (cell division) -
Chromosomes are separated and pulled into two identical daughter
cells
Slide 5
INTERPHASE made up of 3 phases G1- Cell grows, organelles are
replicated, nucleotides & proteins are made G 0 can occur here-
these are non-dividing cells, metabolically active, and sustaining
life. S- DNA Synthesis DNA Replication occurs- exact copies of
chromosomes are made G2- Pre-Mitosis Final checks & preparation
for mitosis
Slide 6
Slide 7
G 1 vs. G 2 G 1 chromosomes have not replicated yet G 2
chromosomes have already replicated (in the S phase right before)
The nucleus of a G 2 cell would have more chromosomal material than
a G 1 cell.
Slide 8
Cell cycle series of events that occur in a cell that leads to
division and duplication https://highered.mcgraw-
hill.com/sites/0072495855/student_view0/chapter2/animation__mitosis_and_cytokinesis.html
Slide 9
8 Chromosomes and DNA Our traits are determined by our genes.
Genes make up DNA DNA is what makes up our chromosomes
Slide 10
Slide 11
10 DNA by the Numbers Each cell has about 2 m of DNA. The
average human has 75 trillion cells. The average human has enough
DNA to go from the earth to the sun more than 400 times. DNA has a
diameter of only 0.000000002 m. The earth is 150 billion m or 93
million miles from the sun.
Slide 12
11 DNA Deoxyribonucleic Acid DNA contains the instructions for
making proteins within the cell. http://www.thehpp.org/
http://www.thehpp.org/ http://www.thehpp.org/
Slide 13
12 Watson & Cricks Model
Slide 14
The Race to Discover DNAs Structure James Watson Francis Crick
1953 Compiled data from previous scientists to build a double-
helical model of DNA
Slide 15
The Race to Discover DNAs Structure
Slide 16
Linus Pauling 1940s Discovered the alpha- helical structure of
proteins.
Slide 17
The Race to Discover DNAs Structure 1950 Chargaffs Rule: Equal
amounts of Adenine and Thymine, and equal amounts of Guanine and
Cytosine Erwin Chargaff Why do you think the bases match up this
way? Purine + Purine = Too wide Pyrimidine + Pyrimidine = Too
Narrow Purine + Pyrimidine = Perfect Fit from X-ray data
Slide 18
The Race to Discover DNAs Structure Maurice Wilkins Rosalind
Franklin X-Ray diffraction image of DNA taken by Franklin in
1951
Slide 19
The Race to Discover DNAs Structure was Over DNA is made up of:
Four nucleotides: Adenine, Thymine, Guanine and Cytosine These
follow the rules of base-pairing: Adenine bonds with Thymine
Guanine bonds with Cytosine A sugar-phosphate backbone DNA is
arranged in an double-helix
Slide 20
19 One Strand of DNA The backbone of the molecule is
alternating phosphates and deoxyribose sugar The steps are
nitrogenous bases. phosphate deoxyribose bases
Slide 21
20 Why do we study DNA ? Why do we study DNA? We study DNA for
many reasons, e.g., drug design-cure and treat disease
Understanding gene function/protein function better food crops feed
the hungry, immunizations in food
Slide 22
Nitrogenous Bases Double ring PURINES Double ring PURINES
Adenine (A) Guanine (G) Single ring PYRIMIDINES Single ring
PYRIMIDINES Thymine (T) Cytosine (C) 21 T or C A or G
Slide 23
Base-Pairings Purines only pair with Pyrimidines Three hydrogen
bonds required to bond Guanine & Cytosine 22 CG 3 H-bonds
Slide 24
Two hydrogen bonds are required to bond Adenine &
ThymineTwo hydrogen bonds are required to bond Adenine &
Thymine 23 T A
Slide 25
24 Two Stranded DNA Remember, DNA has two strands that fit
together like a zipper. The teeth are the nitrogenous bases but why
do they stick together?
Slide 26
25 C C C C N N O N C C C C N N O N N N C Hydrogen Bonds The
bases attract each other because of hydrogen bonds. Hydrogen bonds
are weak but there are millions and millions of them in a single
molecule of DNA.
Slide 27
DNA 26 P P P O O O 1 2 3 4 5 5 3 3 5 P P P O O O 1 2 3 4 5 5 3
5 3 G C TA
Slide 28
Antiparallel Strands One strand of DNA goes from 5 to 3
(sugars) The other strand is opposite in direction going 3 to 5
(sugars) 27
Slide 29
DNA Replication When DNA is copied (S phase of interphase) When
DNA is copied (S phase of interphase) Complimentary strands are
split apart forming a replication fork (Y-shaped region).
Complimentary strands are split apart forming a replication fork
(Y-shaped region). copyright cmassengale28 ReplicationFork Parental
DNA Molecule 3 5 3 5
Slide 30
DNA Replication http://www.youtube.com/watch?v=EYGrElVyHnU
http://www.youtube.com/watch?v=EYGrElVyHnU First the enzyme
Helicase separates the 2 DNA strands by breaking the weak hydrogen
bonds. At the same time another enzyme Topoisomerase helps to
unwind the 2 DNA strands so it doesnt knot up as the DNA is
separated. First the enzyme Helicase separates the 2 DNA strands by
breaking the weak hydrogen bonds. At the same time another enzyme
Topoisomerase helps to unwind the 2 DNA strands so it doesnt knot
up as the DNA is separated. Second, Single-Strand Binding Proteins
(SSBPs) Second, Single-Strand Binding Proteins (SSBPs) attach and
keep the 2 DNA strands separated and untwisted so it can be
replicated. 29
Slide 31
DNA Replication Third, RNA primers (RNA or DNA Primase) assume
position along the strands being copied to Third, RNA primers (RNA
or DNA Primase) assume position along the strands being copied to
start the addition of new nucleotides. Fourth, DNA polymerase adds
new complimentary DNA nucleotides DNA polymerase I removes the RNA
primer DNA polymerase III adds comp. DNA nucleotides at a rate of
1000 nucleotides per second 30
Slide 32
Order of replicationSynthesis of the New DNA Strands The
Leading Strand single strand The Leading Strand is synthesized as a
single strand from the point of origin toward the opening
replication fork DNA is read 3-5 and made in 5-3 direction 31
RNAPrimer DNA Polymerase Nucleotides 35
Slide 33
Synthesis of the New DNA Strands The Lagging Strand is
discontinuously The Lagging Strand is synthesized discontinuously
against overall direction of replication This strand is made in
MANY short segments It is replicated from the replication fork
toward the origin 32 RNA Primer Leading Strand DNA Polymerase 5 3
Lagging Strand 5 3
Slide 34
Lagging Strand Segments Okazaki Fragments - lagging strand
Okazaki Fragments - series of short segments on the lagging strand
Must be joined together by an enzymecalled Ligase Must be joined
together by an enzymecalled Ligase 33 Lagging Strand
RNAPrimerDNAPolymerase 3 5 Okazaki Fragment
Slide 35
Joining of Okazaki Fragments Ligase joins the Okazaki fragments
together to make one strand Ligase joins the Okazaki fragments
together to make one strand 34 Lagging Strand Okazaki Fragment 2
DNA ligase DNA ligase Okazaki Fragment 1 5 3
Slide 36
Replication of Strands 35 Replication Fork Point of Origin
Slide 37
Slide 38
Proofreading New DNA DNA polymerase initially makes about 1 in
10,000 base pairing errors DNA polymerase initially makes about 1
in 10,000 base pairing errors DNA Polymerase will proofread and
correct these mistakes DNA Polymerase will proofread and correct
these mistakes 37
Slide 39
Semiconservative Model of Replication After replication, half
the original DNA molecule is saved, or conserved in the daughter
molecules. Thus the process is called semi-conservative. New DNA
consists of 1 PARENTAL (original) and 1 NEW strand of DNA 38
Parental DNA DNA Template New DNA
Slide 40
Slide 41
Mutations Any change in the sequence of a cells DNA May not be
harmful Many human diseases including cancer are caused by
mutations Mutagens chemicals/radiation that cause mutations to
occur
Slide 42
After DNA Replication Chromosomes look different A duplicated
chromosome contains 2 sister chromatids joined at the
centromere
Slide 43
Slide 44
Chromatid: One single chromosome
Slide 45
Sister chromatids Identical chromatids joined at the
centromere(only seen in a duplicated chromosome)
Slide 46
Notes for 8.6-8.9 Mitosis and Cell Division Cell Cycle
Regulation
Slide 47
Chromosomes Chromosomes with 2 sister chromatids (what a
duplicated chromosome looks like) Chromosome Segregation:
Separation of sister chromatids so that each new cell receives one
copy of each chromosome.
Slide 48
Do all of our body cells need the same number and type of
chromosomes? YES! All of our cells must be genetically
identical
Slide 49
How does that happen? Before a cell divides, all of the
chromosomes must be duplicatedthis way the daughter cells can have
the exact same genetic information as the parent cell. Aneuploid
cells: daughter cells that have an abnormal number of
chromosomes
Slide 50
M Phase - Mitosis Occurs after Interphase Occurs in 4 phases 1.
Prophase 2. Metaphase 3. Anaphase 4. Telophase - Cytokinesis occurs
at the end of telophase
http://micro.magnet.fsu.edu/micro/gallery/mitosis/m
itosis.html
Slide 51
Prophase: Nuclear membrane disappears Chromosomes condense are
now totally visible Centrioles produce spindle fibers and move to
opposite poles of the cell
Slide 52
Metaphase: Spindle fibers organize the chromosomes into the
MIDDLE of the cell
Slide 53
Slide 54
Anaphase: Spindle fibers shorten to separate the two sister
chromatids, pulling them to opposite poles of the cell.
Slide 55
Telophase: Chromatids are now at opposite poles Nuclear
membrane reappears producing two new nuclei. Cleavage furrow forms
and cytokinesis begins.
Slide 56
CYTOKINESIS Division of the cytoplasm into 2 new daughter
cells. In Plant cells, there is no cleavage furrow a cell plate
made of cellulose forms between the two cells.
Slide 57
Cytokinesis: Animal vs. Plant Plant cells form a CELL PLATE
instead of cleavage furrow
What is the end result of mitosis? TWO genetically IDENTICAL
and smaller daughter cells These two daughter cells now enter the G
1 phase of the cell cycle or they can enter G o
Slide 67
How do cells know when to divide, duplicate their chromosomes,
or enter another phase of the cell cycle? With CYCLINS
Slide 68
Cyclins - proteins that regulate the cell cycle
Slide 69
Checkpoints
Slide 70
What is the result when cells lose the ability to control cell
growth? CANCER = abnormal or uncontrolled cell division. Cells will
not respond to the cyclins needed to control cell division.
Slide 71
Cancer Terms Proto-oncogenes- are normal genes that promote
cell division When mutated, they are converted into oncogenes that
stimulate cells to leave G0 and divide, signal or not Oncogenes
mutated proto-oncogenes
Slide 72
Cancer Terms Tumor Suppressor genes- normal genes that inhibit
cell division by activating checkpoint proteins When mutated,tumor
suppressor genes are inactivated and the cell cycle continues with
or without a signal.
Slide 73
Tumor A dense collection of cells created when cell division is
out of control. Benign tumor: Harmless, not cancerous. Slower
growing cells that clump together. Malignant tumor: Cancerous
tumor. Can spread to other parts of the body.
Slide 74
Metastasis When part of a malignant tumor breaks off and
travels to another part of the body.
