b rod shaped structure made of a single dna molecule and proteins called histones –histones...
Post on 21-Dec-2015
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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
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
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.
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).
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
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
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
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
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
• 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
• 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?
• 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?