CELL DIVISION

WHY DO CELLS UNDERGO CELL DIVISION?

1. The Cell Becomes Too Large• DNA/Information Overload• Exchange with the environment (traffic/diffusion

problems).2. Repair and Growth 3. Reproduction

• Asexual Reproduction

GENETIC MATERIALNucleic Acids: DNA & RNA

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)

DNA & RNA STRUCTURE GAME(S)

17 Things You Should Know About DNA

EUKARYOTIC VS PROKARYOTIC DNA

EUKARYOTES PROKARYOTESDNA is found within a nucleus

DNA is confined to the nucleoid region

DNA is associated with proteins called histones.

“Naked” DNA

DNA REPLICATION

https://www.youtube.com/watch?v=uxeLRvsNytg

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 A SEMI-CONSERVATIVE PROCESS

• DNA Replication results in two identical copies of DNA.

• Half of a pre-existing DNA molecule is always saved (conserved).

FORMATION OF TWO COMPLIMENTARY STRANDS

• DNA replication will occur during cell division (interphase) within the nucleus.

• Replication requires free nucleotides that form the new DNA strands.

With the help of the enzyme DNA Helicase, the original double-stranded DNA molecule will “unzip”. Helicase will break the hydrogen bonds holding complimentary base pairs

together.(A2T, G3C).

. . . .FORMATION OF COMPLIMENTARY STRANDS

• 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). 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.

DNA & DNA REPLICATION TUTORIALS

CELL DIVISION

LIFE SPAN OF HUMAN CELLS

Cell Type Life Span Cell DivisionEsophageal 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: AN OVERVIEW

INTERPHASE

PROPHASE, METAPHASE, ANAPHASE, TELOPHASE

CYTOKINESIS IN ANIMALS AND PLANTS

MITOSIS ANIMATION(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

REGULATING THE CELL CYCLE

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.

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

Cancer cells are your own body cells that divide 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.

WHAT IS CANCER?

WHAT ARE TUMORS?A tumor (neoplasm) is an abnormal growth of tissue that can

be:

Malignant: An unusually 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 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 or Secondary Cancer)

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 . . . )