Rod shaped structure• Made of a single DNA molecule and

proteins called histones– Histones maintain shape of chromosomes – Aids in tight packing of DNA

• Seen during cell division• Coiled and compact

DNA and Chromosomes

double-stranded DNA molecule

centromere

homologouschromosomes

centromere

homologous chromosomes

DNA Replication

Chromosome consists of two identical halves• Each half is a chromatid

–Formed when DNA makes a copy of itself before cell division

–Each new cell will receive one chromatid from each chromosome

–Chromatids are held together by a centromere

sister chromatids

DNA replication

sister chromatids

DNA replication

23 pairs

Sex chromosomes

autosomes

Interphase- 75% of cell life cycle

G1: rapid growth S: DNA replicates; centrioles replicate.

G2: cell prepares for cell division; microtubular structures form.

Cell Division

Mitosis: cell divides its nuclear components (chromosomes).

Cytokinesis: cell divides its cytoplasmic components.

Prophase

Metaphase

Anaphase

Telophase

centrioles

chromatin

plasmamembrane

nucleolusnuclearenvelope

Chromosomes shorten and become visible (early prophase)

Chromosomes made up of 2 identical chromatin threads called chromatids

Centrioles migrate toward opposite pole pulled by kinetochore

Nuclear envelope disintegrates (late prophase).

centromere

chromosome

aster

centrioles

asterpolar fiber

chromosomal fiber

fragmenting nuclear

envelope

centrioles

nucleus

Chromosomes lined up in the middle

Mitotic spindle complete.

metaphase plate

spindle

polar fiberschromosomal fibers

sister chromatids

Chromosome at Metaphase

Sister chromatids (= identical strands of DNA) split from each other to form divided identical chromosomes.

Kinetochore fibers shorten and pull divided identical chromosomes to opposite sides of the dividing cell.

Polar microtubules slide past each other, lengthening and pushing the cell apart

daughter chromosomes

Divided chromosomes reach opposite sides of cell and begin to disperse as chromatin.

Nuclear envelopes reforms around separated collections of chromosomes to form two nuclei.

Cytokinesis- completion of cell division

Spindle apparatus disintegrates.Cytokinesis usually begins near the

end of telophase.

Separation of cytoplasmic components to yield two daughter cells

Microfilaments form a contracting ring that pinches the plasma membrane inward between the forming daughter cells

cleavage furrow

RNA

Contrasting RNA with DNA

Single-strandedRiboseBases

AdenineUracilGuanineCytosine

Double-stranded

DeoxyriboseBases

AdenineThymineGuanineCytosine

RNA DNA

• mRNA- copies DNA and directs protein synthesis

• rRNA- joins with ribosomal proteins to make ribosomes

• tRNA- transfers amino acids to ribosomes to make protein

1. Transcription-occurs in nucleus• mRNA copies DNA nucleotide

sequence

2. Translation• nucleotide sequence in mRNA is

uncoded• mRNA binds to rRNA• tRNA brings appropriate amino acid to

mRNA• Polypeptide is manufactured

DNA Sense Strand

mRNA Transcript

enzyme

mRNA

Transcription begins here

mRNA

anticodon

codon

tRNA

Ribosome

Amino Acid

tRNA

mRNA Codon Anticodon

Initiator codon

Anticodon

AA

Binding sites

Ribosome

mRNA

Stop codon

AA

1

AAAA

T A GA U C

2

AA

Complete protein

Rapid and uncontrollable development and production of cells.

1. Inheritance may increase risk2. Proto-oncogenes and tumor suppressor

genes mutate or become damaged by carcinogens

3. Known carcinogens:• Viruses and bacteria• Environmental chemicals• Tobacco• Radiation• Dietary factors

Conversion begins with a mutation (a change in DNA) by:

1. Chemical2. Physical3. Biological

Conversion

Development and Progression

• Begins when a chemical substance stimulates growth of a mutated cell

• Those chemical substances influence a 2nd stage of carcinogens called promoters.

• Promoters stimulate cell to divide uncontrollably

• Metastasis- cancer traveling to other sites; like a forest fire

ozone

• Screens out 99% of harmful UV light• Ozone produced by lightening• 1% in ozone will result in a 2% in

skin cancer

Holes in ozone:

Dupont- CFCs: hairspray, refrigerators,

air conditioning

Which country has the highest rate of

skin cancer?

1. Avoid sun between 10am to 4pm.2. Wear sunscreen w/ SPF 40+.3. Wear appropriate clothing.

• Genetic testing• Biopsy • Blood test• X-rays, PET, MRI• Visual & tactile observation

• Surgery• Radiation• Chemotherapy• Homeopathy

• Know family history• Get regular medical screenings• Learn self-exam techniques• Avoid direct sunlight• Watch your diet and weight• Don’t smoke• Drink alcohol in moderation (alcohol

decrease heart disease, but increases risk of certain cancers)

• Become educated

INQUIRY

1. What do CFC’s do?2. What is a proto-oncogene?3. Name 3 carcinogens.4. What are the ABCD’s of skin cancer?5. What is the function of ozone?6. Who is Henrietta Lacks?

INQUIRY

1. Which cells in the body are diploid and which are haploid?

2. During which stage does DNA replication occur?

3. Which stage of mitosis is seen in this picture?

4. At which stage is the cell binuclear?5. In which phase do chromosomes line up in the

center of the cell?6. Where does the kinetochore attach?