The Cell Cycle and DNA Test Study Material

What does DNA stand for?

Deoxyribonucleic Acid (DNA)

In eukaryotes, where is DNA found?

the nucleus

Functions of DNA

controls all cellular functions, has the same basic structure in all organisms, codes for the physical expression of traits

Griffith discovered..

one form of bacteria was transformed into another form, perhaps by a gene

Avery discovered..

used enzymes to destroy various organic compounds, and after destroying DNA, transformation did not occur; therefore, DNA must transmit genetic info.

Hershey & Chase discovered..

used radioactively labeled bacteriophages

-labeled DNA with Phosphorus (P) and protein with Sulfur

-bacteria found to have radioactive Phosphorus after bacteriophage attached to bacterial cells, therefore genetic material is DNA.

Erwin Chargaff

discovered base pairing rules

Rosalind Franklin

saw X-shaped pattern with X-ray diffraction

James Watson and Francis Crick

after seeing Franklin’s X-ray photograph, immediately began to figure out structure—they are credited with the discovery of the shape of DNA known as the Double Helix (1953) and won the Nobel Prize in 1963.

structure of DNA

nucleic acid made of monomers called nucleotides

3 parts of a nucleotide

1. Deoxyribose sugar (5-carbon, pentagon shaped)

2. Phosphate group

3. Nitrogen base

Nitrogen bases

purines - Adenine and Guanine

pyrimidines - Thymine and Cytosine

DNA is _____ stranded.

DNA is double stranded.

Bases attach in center by weak ______ bonds.

weak hydrogen bonds

base pairing rules

adenine always goes with thymine, guanine always goes with cytosine.

Base pairing rules create two strands that are _________ to one another

Base pairing rules create two strands that are complementary to one another

DNA forms a singular ______ strand of DNA in prokaryotes

single circular strand

DNA replication occurs..

in nucleus before cell division so each new . Each half of the double helix serves as a template to make a new strand cell has the correct amount of DNA.

DNA Replication Process

Simplified process

1. Enzymes (DNA helicases) unwind then unzip

DNA by breaking hydrogen bonds in middle of double helix

2. Free nucleotides are attached to the template by DNA polymerases

3. DNA recoils so that there are now 2 copies of the DNA.

Prokaryotes replicate their DNA in the _________

cytoplasm

for eukaryotes, replication occurs during the ______ phase of Interphase.

the S phase

replication is ...

“semi-conservative” meaning each double stranded DNA molecule is composed of one new strand & one old strand following replication

define gene

segment of DNA that codes for a protein and thus determines a given hereditary trait

define chromosomes

structure that carries genes from parent cell to new daughter cells in eukaryotes.

define sister chromatids

DNA replicates before cell divison to create two identical copies of DNA strands.

cells divide and grow forever because…

DNA cannot control extra cell functions as cells grow, and transport of materials across the cell membrane becomes difficult as cells get larger.

define the cell cycle

the sequence of growth & division of a cell.

two major phases a cell goes through

interphase and M phase

interphase

G1: Cell growth, new proteins and organelles are made

S: DNA is copied/replicated--so new cells will have the same genetic information as parent cells. After this phase, there are two exact copies of the DNA

3. G2: Preparation for nuclear division

-organelles and molecules necessary for cell division are produced

Prophase

DNA coils into visible replicated chromosomes, centrioles separate and move to opposite poles of the cell, spindle-forms between the centrioles and replicated chromosomes become attached to spindle fibers. nuclear envelope breaks down and nucleolus disappears.

metaphase

replicated chromosomes move to the equator/center of cell and line up.

-attached to spindle fibers.

anaphase

replicated chromosomes break apart. Now, sister chromatids are called “individual daughter chromosomes” and will move to opposite poles of the cell (spindle fibers breaking down cause this).

-”New” individual daughter chromosomes are now identical to the original DNA of parent cell.

telophase

Begins once daughter chromosomes reach opposite poles of the cell.

-Chromosomes unwind, spindle breaks down, and nucleolus reappears, new nuclear envelope appears

-Mitosis is now complete

cytokinesis

usually occurs at the same time as telophase. Cytoplasm is cleaved/cut in half.

cytokinesis - In animals, the plasma membrane pinches in to create a _______.

cleavage furrow

cytokinesis - in plants, a _______ forms in the middle of the cell. A new cell wall forms on either side of the cell plate creating two new cells.

cell plate

define zygote

single cell formed when egg and sperm fuse.

define diploid

a cell with two copies of each type of DNA

Homologous DNA strands

-paired DNA strands (one comes from EACH parent)

-same shape and size 

-have genes for the same traits arranged in the same order

-NOT identical to each other since there are different possible forms for each gene

Regulation of Cell Cycle

• cell growth and division are carefully controlled

• cells closest to an injury begin to divide to begin the healing process.

• as healing finishes, cell division slows down

• proteins (enzymes called cyclins) control the cell cycle in eukaryotes.

define cancer

uncontrolled cell growth & division

     -produce masses of tissue called tumors that deprive non-cancerous cells of nutrients

     -results from problems with enzymes that control/regulate cell division so cells can’t respond correctly. 

Traits of a Normal Cell

large cytoplasm, single nucleus, single nucleolus, fine chromatin

Traits of a Cancerous Cell

small cytoplasm, multiple nuclei, multiple and large nucleoli, coarse chromatin