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 homologous chromosomes

DNA Replication

 10 Replication 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) S phase during interphase of the cell cycle Nucleus of eukaryotes Mitosis -prophase -metaphase -anaphase -telophase G1G1 G2G2 S phase interphase DNA replication takes place in the S phase.

12 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  Begins at Origins of Replication  Two strands open forming Replication Forks (Y-shaped region)  New strands grow at the forks 3’ 5’ 3’ 5’

DNA 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 RNA Primer DNA Polymerase Nucleotide 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 RNA Primer DNA Polymerase Nucleotides 3’5’

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’ 5’ 3’ Lagging Strand 5’ 3’

22 Lagging Strand Segments  Okazaki Fragments - series of short segments on the lagging strand  Must be joined together by an enzyme Lagging Strand RNAPrimerDNAPolymerase 3’ 5’ Okazaki 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’ 3’

Replication 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-3 ’

29 Answer: DNA 5’-CGTATG-3’ DNA 3’-GCATAC-5’ DNA REPLICATION hill.com/sites/ /student_view0/chapter3/animation__dna_replication__quiz_1_.html

b 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

23 pairs Sex chromosomes autosomes

Interphase- 75% of cell life cycle G 1 : rapid growth S: DNA replicates; centrioles replicate. G 2 : 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

Prophase late

Centrioles During Prophase centrioles nucleus

Metaphase

polar fibers chromosomal fibers sister chromatids Metaphase

Chromosome at Metaphase

Anaphase

Telophase

Cytokinesis cleavage furrow

Cytokinesis

RNA

Contrasting RNA with DNA lSingle-stranded lRibose lBases Adenine Uracil Guanine Cytosine lDouble- stranded lDeoxyribose lBases Adenine Thymine Guanine Cytosine 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 U A G A U C 2 AA Complete protein hill.com/sites/ /student_view0/chapter3/animation__how_translation_ works.html

Rapid and uncontrollable development and production of cells.

1.Inheritance may increase risk 2.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.Chemical 2.Physical 3.Biological Conversion

Development and Progression

Begins when a chemical substance stimulates growth of a mutated cell Those chemical substances influence a 2 nd 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 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

Cervical Cancer Vaccine Controversy Michelle Bachmann Bashes HPV vaccine 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?