cell division

Cell Division2.5 Cell Division

3.3 DNA Structure

3.4 DNA Replication

3.3 DNA StructureSyllabus Statements:Outline DNA nucleotide structure of sugar

(deoxyribose), nitrogenous base and phosphate group.State the names of the four bases in DNA (Adenine,

Guanine, Cytosine, and Thymine).Outline how DNA nucleotides are linked together by

covalent bonds into a single strand.Explain how a DNA Double Helix is formed using

complimentary base pairing and hydrogen bonds.Draw and label a simple diagram of the molecular

structure of DNA.

3.5 RNASyllabus Statements:

3.5.1 Compare the structure of RNA and

DNA.

DNA/

RNA

Revie

w Vi

deo

The Nucleic Acids• Store and transmit hereditary,

or genetic, information.

• Contain hydrogen, carbon, nitrogen, oxygen, and phosphorus.

• The monomers of nucleic acids are nucleotides, which contain three parts: a 5-carbon sugar, a phosphate group, and a nitrogen base.

• Examples: Deoxyribonucleic Acid and Ribonucleic Acid

Comparing DNA & RNADNA RNA

NAME: Deoxyribonucleic Acid Ribonucleic Acid

STRAND: Double Stranded (Helical)

Single-Stranded (Helical)

NITROGENOUSBASES:

Adenine (A), Guanine (G), Cytosine (C) &

Thymine (T)

Adenine (A), Guanine (G), Cytosine (C), & Uracil (U)

SUGAR: Deoxyribose Ribose

PHOSPHATE GROUP:

YES YES

OTHER: In Eukaryotes, DNA associated with Protein

Messenger RNA (mRNA), Transfer RNA (tRNA),

Ribosomal RNA (rRNA)

17 Things You Should Know About DNA

DNA & RNA Structure Game(s)

3.4 DNA ReplicationSyllabus Statements:

Explain DNA replication in terms of unwinding the double helix and separation of the strands by helicase, followed by formation of the new complimentary strands by DNA polymerase.

Explain the significance of complimentary base pairing in the conservation of the base sequence of DNA.

State that DNA replication is semiconservative.

DNA Replication Animation

DNA Replication Involves “Unzipping”

• DNA Replication is the process by which DNA copies itself. We would say that DNA is ‘self-replicating.’ DNA copies DNA.

• The process of DNA Replication involves a number of important enzymes . . . We will focus on DNA Helicase and a group of enzymes called DNA Polymerases.

• DNA Replication is considered ‘Semi-Conservative.’

DNA Replication is Semi-Conservative

Formation of Two Complimentary Strands• DNA replication will occur during cell division

(interphase) within the nucleoplasm of the nucleus.

• Replication requires free nucleotides or nucleoside triphosphates (A, T, C and G) that form the new DNA strands.

With the help of the enzyme DNA Helicase, the original double-stranded DNA molecule with “unzip”.

Helicase will break the hydrogen bonds holding complimentary base pairs together.

(A2T, G3C).The unpaired nucleotides now act as ‘template’

strands.

Formation of Complimentary Strands (continued)

• As soon as the DNA becomes ‘unzipped’, free-floating nucleotides will be covalently bonded to nucleotides on the template strands.

• Another enzyme, DNA polymerase, will catalyze this reaction (dehydration synthesis reaction). DNA polymerase will operate on both strands but in opposite directions.

• This process can occur at multiple points (origin of replication or replication bubble) along the DNA strand.

Significance of Complimentary Base Pairing

• This pattern of DNA replication ensures that two identical copies of DNA are produced.

Again . . . DNA replication is described as a semi-conservative process because half of a pre-existing DNA molecule is always saved

(conserved).

DNA & DNA REPLICATION TUTORIALS

Extra (and a bit more detailed) DNA Replication Animation(s)

2.5 Cell DivisionSyllabus Statements: 2.5.1 Outline the stages in the cell cycle, including interphase

(G1,S,G2), mitosis and cytokinesis. 2.5.2 State that tumors (cancers) are the result of uncontrolled

cell division and these can occur in any organ or tissue. 2.5.3 State that interphase is an active (growth) period in the

life of a cell, when many metabolic reactions occur, including protein synthesis, DNA replication and in increase in the number of mitochondria and/or chloroplasts.

2.5.4 Describe the events that occur in the four phases of mitosis (PMAT).

2.5.5 Explain how mitosis produces 2 genetically identical nuclei.

2.5.6 State that growth, embryonic development, tissue repair and asexual reproduction involve mitosis.

Why Do Cells Undergo Cell Division?

1. The cell becomes too large:

• DNA/Information Overload

• Exchange with the environment (traffic problems).2. Repair and Growth (including embryonic dev.)3. Reproduction:

• Asexual Reproduction

ASEXUAL REPRODUCTION(RELIES ON MITOSIS/CELL DIVISION)

Daughter cells are identical to parent cells

Life Span of Human CellsCell Type Life Span Cell Division

Esophageal 2-3 days Can divideIntestinal (small) 1-2 days Can divideIntestinal (large) 6 days Can divideRed Blood Cells <120 days Can’t DivideWhite Blood Cells 10 hrs-decades Many don’t

div.Smooth Muscle Long-lived Can divideHeart Cells Long-lived Can’t DivideSkeletal Muscle Long-lived Can’t DivideNeurons Long-lived Most don’t

div.

CELL DIVISION(A Super Simple Overview)

Inte

rpha

se

Sister Chromatids

Prop

hase

Metaphase

Anaphase

Telo

phas

e

Cytokinesis

Mito

sis

Anim

atio

n(s)

http://outreach.mcb.harvard.edu/animations/cellcycle.swf

http://www.youtube.com/watch?v=7hQ5xXJSmK4&feature=related

http://www.youtube.com/watch?v=VGV3fv-uZYI

REGU

LATI

NG T

HE

CELL

CYC

LE

The cell cycle is controlled by dozens of regulatory proteins inside and outside the cell:

1.Internal regulators: proteins that respond to signals inside the cell. (ex. Cyclins)

2.External regulators: proteins that respond to signals outside the cell. Growth factors are important in wound healing and embryonic development.

Regu

latin

g th

e Ce

ll Cy

cle(a

nim

atio

n)http://outreach.mcb.harvar

d.edu/animations/checkpoints.swf

ApoptosisProgrammed cell death. Once apoptosis is

triggered, the cell will begin a “self destruct” sequence.

Programmed cell death is important during embryonic development.

Wha

t is C

ance

r?(U

ncon

trolle

d ce

ll gro

wth)

Cancer cells don’t respond to signals regulating the cell cycle.

Cancer risk is increased through: genetics, tobacco use, radiation exposure, ultraviolet radiation, poor diet, viral infections, chemicals, pollution, etc.

http://outreach.mcb.harvard.edu/animations/checkpoints.swf

What are Tumors?A tumor (neoplasm) is an abnormal growth of tissue that can be:

Malignant: A usually fast-growing, sometimes fatal tumor that invades surrounding tissue and sheds cells that spread throughout the body, creating new tumors. Cancerous.

Benign: A well-defined, slow-growing mass with smooth boundaries that simply grows in diameter. Not seriously harmful unless it’s size compresses surrounding tissues. Benign tumors are non-cancerous.

Cells may break away from malignant tumors and spread throughout the body (Metastasis)

How Do We Treat Cancer?• Biopsy: Surgical removal of cells/a mass for

identification.• Surgery (Removal of a malignant tumor)• Radiation Therapy (kills cells)• Chemotherapy with anti-mitotic drugs)• But . . . Sometimes there is no treatment.

What are some of the Side Effects of Cancer Treatment?

(Sterility, Hair Loss, Pain Destruction of non-cancerous cells, Nausea, Vomiting, Depression .

. . )

Cancer Cells(Videos)

Examples of Cancers and/or Benign/Malignant Tumors.

My Shocking Story