Cell cycle and Reproduction

BIO…LIFE….

THINK ABOUT THIS:

What do we do in our lifetime?

What are the major stages of our life?

What are the Major stages of physical development in our lives? What would it look like

if we put this into a pie

chart?

Cell cycle: repeating sequence of cellular growth and division during the life of an

organism; check points trigger the next stage of the cycle

The life of a cell Cells have a life cycle just like we do- born, grow, reproduce,

and die. They only spend part of

their life cycle reproducing (M)- mitosis

Imagine you are a bacteria:What are the major stages in your life?

TRY ME: What is A? B? C? What is D/E/F/G collectively

called? What is D? What is E? What is F? What is G?

https://www.youtube.com/watch?v=65SODTL_QsA

Figure 9-8 The eukaryotic cell cycle

G1: cell growth and differentiation

telop

hase an

dc

yto

kin

es

is

anap

hase

metaphase

prophase

S: synthesis of DNA; duplication of chromosomes

G2: cell growth and preparation for cell division

Cell Cycle

1. Interphase (G1, S, G2) – cell grows, prepares to divide (G phases) and DNA replicates (S phase)

2. Mitosis: nucleus divides; each nuclei winds up with the same # and kind of chromosomes as the parent (P-M-A-T)

3. Cytokinesis: division of cytoplasm

WHY DO CELLS DIVIDE?WHY DO THEY DO MITOSIS???

UNICELLULAR vs. MULTICELLULAR?

Why do cells divide?

UNICELLULAR

To reproduce (asexual reproduction)- budding/binary fission Ex. Bacteria hydra

vs. MULTICELLULAR? Grow Repair/replace cells that have been lost or damaged

Let’s think a second:THINK: Why do we have cycles and cells split? Why doesn’t the cell just get bigger and bigger?

Which turtle has bigger cells?

Neither!!!

Their cells are the same size… this one just has MORE!

Why don’t cells continue to grow?

There are two main reason why cells divide instead of continue to grow:

1. The larger the cell becomes, the more demands the cell places on its DNA

2. The cell has more trouble moving enough nutrients and wastes across the cell membrane.

DNA “Overload” Information that controls a cell’s function is stored in a

molecule knows as DNA In eukaryotic cells, DNA is found in the nucleus

DNA “Overload” When a cell is small, the information stored in the DNA is

able to meet all of the cell’s needs If a cell was too large an “information crisis” would occur and

the cell would not function properly

Example: Small library in a large city

Exchanging Materials

Food, water and nutrients enter the cell through its cell membrane

Waste products leave in the same way

Exchanging Materials

Example: Small streets in a big town

Exchanging Materials The relationship between a cell’s volume and its surface

area is the key to understanding why cells must divide as they grow!

Ratio of Surface Area to Volume

Ratio of Surface Area to Volume

The volume increases much faster than the surface area, causing the ratio of surface area to volume to decrease.

This decrease creates serious problems for the cell.

Formula for calculating ratio:

Ratio = Surface Area/Volume

SPLIT GROUPS: FIND SA , Volume and ratios for

3x3, 5x5, 8x8, 10x10

Lab surface/volume ratio

CAN WE FIND THIS EXPERIMENTALLY???

FIND SA , Volume and ratios for

For: 3x3, 5x5, 8x8, 10x10

Problem: What happens to the surface/volume ratio when a cube gets really big?

Hypothesis:

Methods:

Result table in excel:

Conclusion:

So what happens when cells get TOO LARGE????

THEY SPLIT- MITOSIS.

DNA replicates in interphase?Which part of cell cycle???

What happens in each:PROPHASEMETAPHASE ANAPHASETELOPHASEhttp://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter11/animations.html#

no cell wall cell wall

Mitosis

46chromosomes

92chromosomes

46chromosom

es

46chromosom

es

parent cell

daughter cells

AMEOBA SISTERS: https://www.youtube.com/watch?v=gwcwSZIfKlM&list=PLwL0Myd7Dk1F1pp-DaLx3ygO_7xA-yyd4&index=3

BUT WHY CELLS DON’T JUST SPLIT ALL THE TIME????

Or in other words….

What happens if things go wrong with checkpoints?

THINK ABOUT THIS!!!!

Loss of Control of the Cell Cycle

If checkpoints are not working properly, the cell cycle can cause the cell to grow

uncontrollably

leads to cancer .

THINKING QUESTION:What biomolecule controls checkpoints?

AMEOBA SISTERS: https://www.youtube.com/watch?v=lpAa4TWjHQ4&list=PLwL0Myd7Dk1F1pp-DaLx3ygO_7xA-yyd4&index=2.

And what controls the making of proteins? DNASO WHAT’S THE DIFFERENCE BETWEEN PROKARYOTIC AND EUKARYOTIC DNA

How Is the DNA in Eukaryotic Chromosomes Organized?

Eukaryotic chromosomes differ from prokaryotic chromosomes in important ways Eukaryotic chromosomes are separated from the

cytoplasm by a membrane-bound nucleus Eukaryotic cells always have multiple chromosomes Eukaryotic chromosomes are longer and have more

DNA than prokaryotic chromosomes (human chromosomes are 10 to 80 times longer and have 10 to 50 times more DNA)

These differences account for the complexity of eukaryotic cell division

How Is the DNA in Eukaryotic Chromosomes Organized?

The eukaryotic chromosome consists of a linear DNA double helix bound to proteins

Each human chromosome contains a single DNA double helix, about 50 million to 250 million nucleotides long

Most of the time, the DNA in each chromosome is wound around proteins called histones These DNA-histone spools are further folded into coils Another layer of folding occurs as the coiled strand folds into loops, which are then

attached to protein scaffolding, so that the chromosome is 1,000 times shorter than the extended DNA molecule

During cell division, more proteins fold up the DNA and histones, until it is 10 times shorter than during its resting state

Figure 9-4 Chromosome structure

DNA double helix

histone proteins

DNA woundaround histoneproteins

Loops attachedto a protein scaffold;this stage of partialcondensation typicallyoccurs in a nondividingcell

Coiled DNA/histone beads

protein scaffold

Foldedchromosome,fully condensedin a dividing cell

WHAT DO THE FOLLOWING TERMS MEAN? HOW ARE THEY RELATED?

DRAW THEM. DNA- GENES- SISTER CHROMATIDS- CENTROMERE CHROMOSOMES- HISTONES- LOCI- TELOMERE-

GENES, CHROMOSOMES, and DNA

The DNA in a chromosome consists of two long strands of nucleotides wound around each other, as a ladder would look if it was twisted into a corkscrew shape

This structure is called a double helix

The units of inheritance, called genes, are segments of DNA

The specific sequence of nucleotides in genes spells out the instructions for making the proteins of a cell

When a cell divides, it replicates its DNA to make two identical copies, and gives each daughter cell one of the two copies

9.3 How Is the DNA in Eukaryotic Chromosomes Organized?

Genes are segments of the DNA of a chromosome

Genes are sequences of DNA from hundreds to thousands of nucleotides long

Each gene occupies a specific place, or locus (plural, loci) on the chromosome

9.3 How Is the DNA in Eukaryotic Chromosomes Organized?

In addition to genes, every chromosome has specialized regions that are crucial to its structure and function Two telomeres One centromere The two ends of a chromosome consist of repeated nucleotide sequences called

telomeres, which are essential for chromosome stability

9.3 How Is the DNA in Eukaryotic Chromosomes Organized?

Genes are segments of the DNA of a chromosome (continued)

The second specialized region of the chromosome is the centromere, which has two principal functions

1. It temporarily holds two daughter DNA double helices together after DNA replication

2. It is the attachment site for microtubules that move the chromosomes during cell division

Eukaryotes Chromosomes carry the DNA…but you need

two IDENTICAL COPIES of DNA to go to the 2 cells

chromosome # varies between species

humans-46 chromosomes (23 pairs)

REMEMBER: The life of a cell

Before cells

can divide,

DNA needs to be replicated

So the code can be

passed on.

Which phase does this happen in????

DNA Replication

Process of copying a double stranded DNA to form 2 double stranded molecules

Basis of biological inheritance used by all living things

Occurs before a cell divides (mitosis)

DNA Replication

1. Enzymes break the hydrogen bonds between the bases so the chains of DNA can separate or unwind

2. Other enzymes add new nucleotides, which form new hydrogen bonds with their complimentary nucleotide.

Red = original strandBlue = new strand

DNA Replication

DNA Replication

Results in 2 semi-conservative double stranded molecules

WHAT IS THE ROLE OF:

Helicase-

SSB-

Replication fork-

DNA Polymerase-

ANIMATIONS OF DNA REPLICATION

http://www.bioteach.ubc.ca/TeachingResources/MolecularBiology/DNAReplication.swf

http://www.mcb.harvard.edu/Losick/images/TromboneFINALd.swf

http://highered.mcgraw-hill.com/sites/0072556781/student_view0/chapter11/animation_quiz_2.html

http://www.sinauer.com/cooper/4e/animations0601.html

AMEOBA SISTERS:https://www.youtube.com/watch?v=5qSrmeiWsuc&index=1&list=PLwL0Myd7Dk1F1pp-DaLx3ygO_7xA-yyd4