Unit 6 DNA & The Cell Cycle

Test date 11-9

GENETIC MATERIAL

In the middle of the 1900’s scientists were asking questions about genes.

What is a gene made of?How do genes work?How do genes determine characteristics of organisms?

DO PROTEINS CARRY THE GENETIC CODE?

At the time most scientists believed that _________ had to be the molecules that made up genes.

There were so many different kinds proteins and DNA seemed to be too monotonous . . . repeating the same ___ subunits. 4

proteins

SEE GRIFFITH’s EXPERIMENT1928 – Frederick Griffith looked atpneumonia bacteria trying tofigure out what made people die

Images from: http://microvet.arizona.edu/Courses/vsc610/mic205/griffith.jpg

S (SMOOTH) strain- killed mice

R (Rough) strain-mice lived

If he heated the LETHAL strain first

_______________

Images from: http://microvet.arizona.edu/Courses/vsc610/mic205/griffith.jpg

The heat killed bacteria were no longerLETHAL.

Heat killed + live rough = dead mouse

. . . mice lived.

Griffith called this process __________________ because one strain of bacteria had been changed permanently into another.

But what was the factor that caused thetransformation?

A protein ? A lipid ? A carbohydrate ?A nucleic acid ?

TRANSFORMATION

Griffith 1928 (British)

Studied: Better way to fight pneumonia

Experiments:

Smooth bacteria=dead mouse.

Rough bacteria = alive mouse.

Heat killed smooth= live mouse

Heat killed smooth + rough=Dead mouse

Conclusions: Some molecules or group of molecules changed the harmless rough bacteria into deadly smooth bacteria. Called transformation

1944-Oswald Avery’s team of scientistsrepeat Griffith’s experimentslooking for the transforming molecule.

After heat killing the LETHAL Pneumonia bacteria, he treated them with digestive enzymes that destroy specific kinds of molecules.

If proteins, polysaccharides, lipids, or RNA’s were destroyed .. .______________________________

http://cystitis-cystitis.com/Images/testtube.jpg

http://en.wikipedia.org/wiki/Oswald_Avery

http://faculty.uca.edu/~johnc/mbi1440.htm

Transformation still occurred!

But when they treated the heat-killedLETHAL bacteria with enzymes todestroy _____ there was NOtransformation! . . . the mice lived!

DNA was the moleculethat caused the genetic change.

DNA

http://web.jjay.cuny.edu/~acarpi/NSC/12-dna.htm

GRIFFITH EXPERIMENT (PNEUMONIA-RAT)

Showed ____________ could bepassed between bacteria & cause achange.

AVERY EXPERIMENT (Digestive enzymes)

showed that the genetic material was _____DNA

genetic material

Avery 1944

Studying: Process of transformation as a key to finding heredity

Experiments: Repeated above experiment: Treated heat-killed smooth with enzymes that destroyed either proteins, lipids, carbohydrates, RNA. None affected transformation. When DNA was destroyed transformation was blocked.

Conclusions: Genes are made of DNA

Scientists are skeptical… it takes more than one experiment to convince them.

1952-Alfred Hershey and Martha Chaseexperimented with viruses that infect bacteria = _________________

Knew bacteriophages were made of ________ and _______

bacteriophages

http://www.mun.ca/biology/scarr/Chase_&_Hershey_1953.jpg

Hear about their

cool experiment

proteins DNA

http://www.mun.ca/biology/scarr/hersheychase-experiment.jpg

HERSHEY-CHASE BLENDER EXPERIMENT

Showed_______________ entered cell during infection.

Conclusion:______________in virus was_____ not protein

only DNA not protein

Genetic material DNA

BACTERIAL VIRUSES

http://faculty.uca.edu/~johnc/mbi1440.htm

Hershey & Chase 1950

Studying: Skeptical of Avery’s conclusion. Wanted more support

Experiments: Bacteriophage- virus infects bacteria. Knew viruses made of protein & DNA. Used radioactive isotopes to mark them Protein-sulfur-35, DNA-phosphorus-32 Found phosphorus-32 in bacteria

Conclusions: Genetic material is DNA, not protein

Chargaff 1950

Studying: Studied nucleotide composition in DNA

Experiments: Showed that there was the same amount of adenine & thymine, and cytosine & guanine

Conclusions: Chargaff’s rule: Always!! A-TC-G

(Ash Tray / Garbage Can)

DNA is a DOUBLE HELIXhttp://en.wikipedia.org/wiki/Rosalind_Franklin

http://www.time.com/time/time100/scientist/profile/watsoncrick.html

X-ray experiments by Rosalind Franklin led James Watson and Francis Crick to thediscovery of the structure of DNA in 1953

Franklin 1951

Studying: Studied DNA using

x-ray diffraction

Experiments: Powerful x-ray beams is aimed at a sample, ten the scattering pattern of the x-ray is recorded on the film

Conclusions: By itself does not reveal the structure of DNA SHE WAS CHEATED OUT OF THE PRIZE!!!

Watson & Crick 1953

Studying: What is the structure of DNA? What held the two strands together?

Experiments: Analyzed other scientists’ work. Few weeks after Franklin’s x-ray experiments- they solved the puzzle of the structure of DNA. Made sketches & built models

Conclusions: Two strands twisted around one another Double Helix

Hydrogen bonds between the bases

DNA REPLICATION

Prior to _________, the DNA must ______. DNA can replicate itself exactly due to ___________Replication occurs in the ________of the cell and requires the participation of several _________.

cell division

replicate

Chargaff’s rules

nucleus

enzymes

Summary of DNA Replication

1. Enzyme _______“unzips” DNA by breaking the _________ bonds between the______________.

Where unzipping begins is called the__________________; the continuation of unzipping is the ______________, Occurs in several places in each _____________; like a ______________

2. __________________________ hold the separated DNA strands apart.

helicase

hydrogen

nitrogen bases

origin of replicationreplication fork

chromosome

broken zipper

Single-strand binding proteins

Summary of DNA Replication

3. ______________ adds nucleotides to both sides of the DNA molecule according to base pairing rules.

DNA polymerase has two restrictions:

a. it can only add nucleotides in a ______ direction

b. it can only add nucleotides to an existing strand.

DNA polymerase

5’ – 3’

Summary of DNA Replication4. Two sides of DNA are replicated differently because nucleotides can only be added in a _____________

_____________- side replicated in the ____________ as the replication fork. __________ are moved in by DNA polymerase in a 5’ – 3’ direction as the DNA is unzipped.

5’ – 3’ direction

Leading strand

same direction

Nucleotides

Summary of DNA Replication

____________- nucleotides are __________ from the replication fork. ______________ of nucleotides are synthesized, as the DNA is unzipped. These short segments are known as _______________. Eventually, the ____________ “glues” together the ________________to

create a continuous

strand of nucleotides

Lagging strand

added away

Short segments

Okazaki fragments

enzyme ligase

Okazaki fragments

Summary of DNA Replication

5. Another type of DNA polymerase _________ the replicated DNA to ________ the change of ________.

6. Results in ___________ DNA molecules, each consisting of one _______ strand and one ____ strand.

proofreads

minimize mutation

two identical

originalnew

Summary of DNA Replication

These two identical DNA molecules are the ______________ that proceed through _______

Once replication has

been completed, the

cell moves into ___

and then,

_________________.

sister chromatids

mitosis

G2

prophase of mitosis

Cellular Growth

The third statement of the Cell Theory states that all cells come from ______________. The continuity of life is based on the reproduction of cells or ___________ . In most organisms, cells increase to a certain size and then divide into two cells. This cycle of growth and cell division is known as the __________.

pre-existing cell

cell division

cell cycle

Cellular Growth

The cell cycle is defined as the period of time from the beginning of ___________ to the _____________________. This type of cell division is ________ reproduction. In asexual reproduction, the genome or _____ of the cell is exactly replicated resulting in ________________.

cell division

beginning of the nextasexual

DNA2 identical cells

I. IMPORTANCE OF ASEXUAL REPRODUCTION

A. Single-celled Organisms

Single-celled organisms like _______________ use asexual reproduction to ______________________________

bacteria & yeast

make new organisms-reproduce

I. IMPORTANCE OF ASEXUAL REPRODUCTION

B. Multicellular Organisms

1. Growth & Development – Organisms grow through ___________, rather than unlimited growth of a cell because if a cell gets too large, it cannot meet its own needs and maintain ____________. A cell grows to a certain size, and then it divides.

cell division

homeostasis

2. Renewal & Repair – Cell division is used to replace cells that die from normal wear & tear; for example, __________. Other types of cells maintain the ability to divide, but keep it in reserve unless severely damaged; for example, __________. Other cells do not appear to divide at all in a mature human; for example, ____________________________, although recent experimental findings appear to dispute this long-standing _______.

skin cells

liver cells

nerve cells, cardiac muscle cells

theory

II. Cell Size Limitations

Ratio of surface are to volume- As the cell grows, its volume (__________) increases much more rapidly than the surface area (______________). The cell will have difficulty supplying ___________________ enough waste products. By remaining small, cells have a _______ ratio of surface area to volume and can sustain themselves more easily.

cytoplasm

cell membrane

nutrients & expelling

higher

Surface Area (length

x width x 6)

Volume

(length x width x height)

Ratio of Surface Area to

Volume

Transport of substances- movement of substances within the cell managed more easily in a small cell vs. a large.

1. _________- diffusion over long distances is slow & inefficient because it relies on random movement

2. ______________- ____________ transportation network becomes

less efficient for a cell if the

distance to travel becomes

too large.

Diffusion

Motor Proteins cytoskeleton

Cellular Communications- Cell size affects the ability of the cell to communicate ____________ for cellular functions; if too large it becomes __________ for cellular communications. Ex. The signals that trigger protein synthesis might not reach the _____________ enough for protein synthesis to occur.

instructions

impossible

ribosome fast

CELL CYCLE IN PROKARYOTES (p. 252 & 520)

All ________ undergo a type of cell division known as _____________. Binary fission is a less complex, faster process than eukaryotic cell division because bacteria lack a ______________________________ and have only __ chromosome.

bacteria

binary fission

nucleus, membrane bound organelles

1

The Cell Cycle

The Cell Cycle

G1 Phase- (Gap 1) Cell is growing, carrying out normal cell functions & preparing to replicate DNAS phase- synthesis- the period when a cell copies its DNA in preparation for cell divisionG2 phase- (Gap 2) Cell is preparing for cell division

*Producing microtubules*Taking inventory

M phase- Mitosis

Interphase

Cell grows & carries out normal cell processDNA replicates

Prophase❑ Nuclear

membrane disintegrates

❑ Nucleolus disappears

❑ Chromosomes condense

❑ Spindle apparatus begins to form between the poles

Metaphase

Chromosomes attach to spindle apparatus & align along the equator of cell

Anaphase

Microtubules shorten, moving chromosomes to opposite poles

Telophase

➢ Chromosomes reach poles of cells

➢ Nuclear envelope reforms

➢ Nucleolus reappears

➢ Chromosomes decondense

Cytokinesis

Plant cell: Cell plate forms dividing daughtersAnimal cells: Cleavage furrow forms at equator of cell & pinches inward until cell divides in two

Normal Cell Cycle

The timing & rate of cell division are important to the health of an organism. The _________ of cell division varies depending on the type of cell

A. Cyclins (__________) & cyclin-dependent kinases (____________) (CDKs)- bind to each other to start various activities of the cell cycle. Ex. Signal start of cell cycle, ________________, protein synthesis, nuclear division & end of the ____________( different _____________for each)

rate

proteins

enzymes

DNA replication

Cell cycle

combination

Normal Cell Cycle

B. _____________- cell cycle built in checkpoints that __________ the cycle & can stop it if something goes wrong.

a. Checkpoint near end of G1 monitors for _____________& can stop the cycle before entering the S stage,

b. ________________checkpoints during S phase & after

c. _____________________if problem with spindle can stop before ____________

checkpoints

monitors

DNA damage

Quality control

Spindle checkpoints

cytokinesis

Abnormal Cell Cycle: Cancer (page 11 of booklet)

______________ is the uncontrolled growth & division of cells- a failure in the regulation of the cell cycle.

cancer

Causes of Cancer

Cellular- ________ occurs is not repaired by cell. cancer can result.Carcinogens-___________ & agents that are know to cause cancer. Include: tobacco, UV rays GeneticsBiological agents-__________________

mutations

substances

Bacteria & viruses

Apoptosis- (page 11 of booklet)

_____________ cell death.Cell going through will shrink & shrivel in a controlled process. Ex. During development of human _________________________Plants- localized death of cells results in leaves falling in autumnCells damaged beyond repair

Programmed

Hand and foot webbing

Stem Cells/Pluripotent-Page 11 of booklet

Stem cells or pluripotent cells-are __________ cells that can develop into _____________ cells with the proper ________ 2 types___________stem cells___________stem cells

unspecialized

specialized

signals

embryonic

adult