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

DNA Replication

10

Replication FactsReplication Facts

DNA has to be copied before a cell divides

Its copied during the S phase New cells will need identical

DNA strands

Synthesis Phase (S phase)Synthesis Phase (S phase)• S phase during interphase of the

cell cycle

• Nucleus of eukaryotes

Mitosis-prophase-metaphase-anaphase-telophase

G1 G2

Sphase

interphase

DNA replication takesDNA replication takesplace in the S phase.place in the S phase.

1212

DNA ReplicationDNA Replication Before new DNA strands can form,

there must be RNA primers present to start the addition of new nucleotides

Primase is the enzyme that synthesizes the RNA Primer

DNA polymerase can then add the new nucleotides

DNA ReplicationDNA Replication Begins atBegins at Origins of ReplicationOrigins of Replication Two strands open forming Two strands open forming

Replication Forks (Y-shaped Replication Forks (Y-shaped region)region)

New strands grow at the forksNew strands grow at the forks3’

5’

3’

5’

DNA ReplicationDNA Replication

DNA ReplicationDNA Replication• As the 2 DNA strands open at the

origin, Replication Bubbles form• Prokaryotes (bacteria) have a

single bubble• Eukaryotic chromosomes have

MANY bubbles

16

DNA Replication

• Enzyme Helicase unwinds and separates the 2 DNA strands by breaking the weak hydrogen bonds

• Single-Strand Binding Proteins attach and keep the 2 DNA strands separated and untwisted

copyright cmassengale

DNA Replication• Enzyme Topoisomerase attaches

to the 2 forks of the bubble to relieve stress on the DNA molecule as it separates

DNA Replication Before new DNA strands can

form, there must be RNA primers present to start the addition of new nucleotides

Primase is the enzyme that synthesizes the RNA Primer

DNA polymerase can then add the new nucleotides

DNA Replication DNA polymerase can only add

nucleotides to the 3’ end of the DNA This causes the NEW strand to be

built in a 5’ to 3’ direction

RNAPrimerDNA Polymerase

Nucleotide

5’

5’ 3’

Direction of Replication

Synthesis of the New DNA Strands

The Leading Strand is synthesized as a single strand from the point of origin toward the opening replication fork

RNAPrimerDNA PolymeraseNucleotides

3’5’

5’

Synthesis of the New DNA Strands

The Lagging Strand is synthesized discontinuously against overall direction of replication

This strand is made in MANY short segments It is replicated from the replication fork toward the origin

RNA Primer

Leading Strand

DNA Polymerase

5’

5’

3’

3’

Lagging Strand

5’

5’

3’

3’

22

Lagging Strand SegmentsLagging Strand Segments

Okazaki Fragments - series of short segments on the lagging strand

Must be joined together by an enzyme

Lagging Strand

RNARNAPrimerPrimer

DNADNAPolymerasePolymerase

3’

3’

5’

5’

Okazaki FragmentOkazaki Fragment

copyright cmassengale

Joining of Okazaki Fragments

• The enzyme Ligase joins the Okazaki fragments together to make one strand

Lagging Strand

Okazaki Fragment 2

DNA ligase

Okazaki Fragment 1

5’

5’

3’

3’

Replication of StrandsReplication of Strands

Replication Fork

Point of Origin

Proofreading New DNA

DNA polymerase initially makes about 1 in 10,000 base pairing errors

Enzymes proofread and correct these mistakes

The new error rate for DNA that has been proofread is 1 in 1 billion base pairing errors

Semiconservative Model of Replication

Idea presented by Watson & Crick The two strands of the parental molecule

separate, and each acts as a template for a new complementary strand

New DNA consists of 1 PARENTAL (original) and 1 NEW strand of DNA

Parental DNA

DNA Template

New DNA

DNA Damage & Repair Chemicals & ultraviolet radiation damage

the DNA in our body cells Cells must continuously repair DAMAGED

DNA Excision repair occurs when any of over

50 repair enzymes remove damaged parts of DNA

DNA polymerase and DNA ligase replace and bond the new nucleotides together

Question:

• What would be the complementary DNA strand for the following DNA sequence?

DNA 5’-CGTATG-3DNA 5’-CGTATG-3’’

29

Answer:Answer:

DNA 5’-CGTATG-3’DNA 5’-CGTATG-3’

DNA 3’-GCATAC-5’DNA 3’-GCATAC-5’

DNA REPLICATIONhttp://www.youtube.com/watch?v=4jtmOZaIvS0https://highered.mcgraw-hill.com/sites/0072507470/student_view0/chapter3/animation__dna_replication__quiz_1_.html

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

Interphase

Prophase

centrioles

Early

Prophaselate

Centrioles During

Prophase

centrioles

nucleus

Metaphase

polar fiberschromosomal fibers

sister chromatids

Metaphase

Chromosome at Metaphase

Anaphase

Telophase

Cytokinesis

cleavage furrow

Cytokinesis

http://www.loci.wisc.edu/outreach/bioclips/CDBio.html

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

Ribosome

tRNA

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

Transcription

DNA Sense Strand

mRNA Transcript

mRNA

anticodon

codon

tRNA

Ribosome

Amino Acid

tRNA

mRNA Codon Anticodon

Initiator codon

Anticodon

AA

Binding sites

Ribosome

mRNA

u

u

Stop codon

AA

1

AAAA

U A GA U C

2

AA

Complete protein

https://highered.mcgraw-hill.com/sites/0072507470/student_view0/chapter3/animation__how_translation_works.html http://www.youtube.com/watch?v=41_Ne5mS2ls

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

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?

CFC’s and Ozone Depletion

Sept 2011

Antarctica

Both UVA and UVB are responsible for photoaging and sunburn.

Tanning beds produce both UVA and UVB rays

Strong melanoma candidate

Melanoma facts

From 1996 to 2000, the national average rate for melanoma was 17.5 for every 100,000 people,

while the state of Hawaii average was 15.1 cases per 100,000.

• Fair skin or freckles.• Being male.• Family or personal history of

melanoma.• Chronic UV light exposure. • Severe sunburns. • Unusual moles or a large number

of moles.• Weak immune system.

Factors that may also influence the chance of getting melanoma include

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

Lung Cancer

Cells provided:• Polio vaccine• research into cancer• AIDS• effects of radiation• Effects of toxic substances• gene mapping

Cervical Cancer

Chromosomes: 82• four copies of chromosome

12 • three copies of chromosomes

6, 8, and 17

http://www.cbsnews.com/8301-205_162-57597182/lacks-family-nih-reach-agreement-on-hela-cell-genome-data/

Cervical Cancer Vaccine Controversy

Michelle BachmannBashes HPV vaccine

http://www.npr.org/blogs/health/2011/09/13/140445104/pediatricians-fact-check-bachmanns-bashing-of-hpv-vaccine

Gardasil Vaccine

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?