Anatomy Chapter 4
|Mendelian Genetics||helps us realize the correlation between chromosome behavior and his laws of heredity.|
|Johann Friedrich Miescher (1844-85)|| - Swiss biochemist, studied the nuclei of white blood cells from pus extracted from bandages.|
- Coined the term nuclein, now called DNA, repository for genes.
|Sugar, phosphate groups, nitrogenous bases||By 1900, components of DNA were named|
|Deoxyribonucleic acid (DNA)|| A long, threadlike molecule with uniform diameter, but varied length.|
46 - DNA molecules in the nucleus of most human cells
--Total length of 2 meters
--Average DNA molecule 2 inches long
|Polymers and nucleotides||DNA and other nucleic acids are|
|Nucleotide|| consists of:|
-One phosphate group
-One nitrogenous base
Either pyrimidine or purine
|Pyrimidine|| Single carbon-nitrogen ring|
|Purine|| Double ring|
|Double Helix||molecular shape that resembles a spiral staircase|
|Phosphate Groups/deoxyribose||In a double helix, each sidepiece is a backbone composed of _________ alternating with the sugar _______.|
|Pairs of nitrogen bases||Steplike connections between the backbones in a double helix|
|Hydrogen Bonds|| Nitrogenous bases are united by ________.|
-A purine on one backbone with a pyrimidine on the other
- A-T two hydrogen bonds
- C-G three hydrogen bonds
|X-ray diffraction||determined geometry of DNA molecule|
|Watson, Crick, Wilkins||Won the Novel Prize awarded in 1962 (three men)|
|Rosalind Franklin||Did not win Nobel Prize, who died of cancer at 37, after discovering the X-ray data that provided the answers to the double helix.|
|Genes||Genetic instructions for synthesis of proteins|
|Gene (previous definition)|| segment of DNA that codes for a specific protein|
- Body has millions of proteins but only about 25,000 genes
- Small % of genes produce only RNA molecules
- Some segments of DNA belong to two different genes
|Genome||all the genes of one person|
|20,000 to 25,000|| Humans have an estimated ________ to _______ genes.|
- 2% of total DNA
- 98% is noncoding DNA
|Noncoding DNA|| - Plays role in chromosomes structure|
- Regulation of gene activity
- No function at all: "junk" DNA
|Chromatin||fine filamentous DNA material complexed with proteins|
- occurs as 46 long filaments called chromosomes
- 6 feet in first half of cell cycle
- Twice that amount in preparation for cell division
- In nondividing cells, chromatin is so slender it cannot be seen with light microscope
- Granular appearance under electron microscope.
|Histones|| disc-shaped cluster of eight proteins|
- DNA molecule winds around the cluster
- Repeats pattern 800,000
- Appears to be divided into segments: Nucleosomes
|Nucleosome||consists of core particle, linker DNA, and is one-third shorter than DNA alone|
|Core particle||histones with DNA around them|
|Linker DNA||short segment of DNA connecting core particles|
|Chromatin-protein complex|| thrown into complex, irregular loops and coils|
- 1,000 times shorter than original molecule
|Chromosome Territory|| each chromosome is packed into its own spheroidal region of the nucleus|
- Permeated with channels that allow regulatory chemicals to have access to the genes.
|Nondividing Cell||the chromatin is not a static structure|
|Nondividing Cell|| -Changes moment to moment according to genetic activity of cell|
-Genes get turned off and on
-Chromosomes migrate as cells develop, moving active genes on different chromosomes closer together
-Allows genes to partner to bring about developmental tasks in the cell.
|Exact copies||_____ _____ are made of all the nuclear DNA|
|Sister chromatids||each chromosome consists of two parallel filaments of identical DNA|
|Prophase|| In __________, final coiling and condensing|
- Now visible with light microscope
|Final compaction||enables the two sister chromatids to be pulled apart and carried to separate daughter cells without damage to the DNA|
|Centromere||Where sister chromatids are joined|
|Kinetochore||protein plaques on either side of the centromere|
|RNA||much smaller cousin of DNA (fewer bases)|
|Messenger RNA (mRNA)||over 10,000 bases|
|Transfer RNA (tRNA)||70 to 90 bases|
|DNA||averages 100 million base pairs|
|One nucleotide chain||not a double helix as DNA|
|Ribose||replaces deoxyribose as the sugar|
|Uracil||replaces thymine as a nitrogenous base|
|RNA|| Essential function:|
- Interprets code in DNA
- Uses those instructions for protein synthesis
- Leaves nucleus and functions in cytoplasm
|Gene (current definition)||an information-containing segment of DNA that codes for the production of a molecule of RNA that plays a role in synthesizing one or more proteins|
|Amino acid sequence||______ ______ ______ of a protein is determined by the nucleotide sequence in the DNA.|
|Genome|| all the DNA in one 23-chromosome set|
- 3.1 billion nucleotide pairs in human _______
|46 human|| ___ _______ chromosomes come in two sets of 23 chromosomes.|
- one set of 23 chromosomes from each parent
- each pair of chromosomes has same genes but different versions (alleles) exist.
|Human Genome Project (1990-2003)||identified the nitrogenous base sequences of 99% of the human genome.|
|Genomics||the comprehensive study of the whole genome and how its genes and noncoding DNA interact to affect the structure.|
|Homo sapiens|| (Findings of Human Genome Project)|
______________ has fewer genes than the 100,000 previously believed
|Genes|| (Findings of Human Genome Project)|
________ generate millions of different proteins
- not the old one gene, one protein theory
- single gene can code for many different proteins
|3,000|| (Findings of Human Genome Project)|
Genes average about _______ bases long
- Range up to 2.4 million bases
|99.9% / single-nucleotide polymorphisms|| (Findings of Human Genome Project)|
All humans are at least ______% genetically identical
- 0.01% variations that we can differ from one another in more than 3 million base pairs.
- Various combinations of these _______ _______ ________ account for all human variation.
|Gene-rich/gene-poor|| (Findings of Human Genome Project)|
Some chromosomes are ____ ____ and some are ____ ____.
|1,400/genomic medicine|| (Findings of Human Genome Project)|
We now know the locations of more than _____ disease-producing mutations.
- opens the door for a new branch of medical diagnosis and treatment called ____ _____.
- Before HGP, we knew locations of fewer than 100 disease producing mutations.
|20 amino acids/ four nucleotides||Body can make millions of different proteins, all from the same ____ _______ ______, and encoded by genes made of just ____ _______ (A, T, C, G)|
|Genetic code||a system that enables these four nucleotides to code for the amino acid sequence of all proteins|
|three nucleotides||Minimum code to symbolize 20 amino acids is _______ ______ per amino acid.|
|Base triplet||a sequence of three DNA nucleotides that stands for one amino acid|
|Codon||the 3-base sequence in mRNA|
|64 possible codons|| available to represent the 20 amino acids|
- 61 code for amino acids
|Stop codons--UAG, UGA, and UAA||signal "end of message," like period at the end of the sentence.|
|Start codon--AUG||codes for methionine, and begins the amino acid sequence for the protein|
|Genomic Medicine|| -application of our knowledge of the genome to the prediction, diagnosis, and treatment of disease. |
- Relevant to disorders (e.g., cancer, Alzheimer disease, schizophrenia, obesity, AIDS, tuberculosis)
-Allows for early detection of diseases, more effective clinical intervention.
-Expands potential for gene-substitution therapy
|Protein Synthesis|| - All body cells, expect sex cells and some immune cells, contain identical genes.|
- Different genes are activated in different cells
- Any given cell uses one-third to two-thirds of its genes
- Rest remain dominate and may be functional in other types of cells.
|Activated gene||Messenger RNA (mRNA), Ribosomes, Transfer RNA (tRNA)|
|Messenger RNA (mRNA)|| a mirror image of the gene is made|
- migrates from the nucleus to cytoplasm
- its code is read by the ribosomes
Ribosomes assemble amino acids in the order directed by the codons of mRNA
|Ribosomes||cytoplasmic granules composed of ribosomal RNA (rRNA) and enzymes|
|transfer RNA (tRNA)||delivers amino acids to the ribosomes|
|DNA ---> mRNA ------> protein||process of protein synthesis|
|Transcription|| step from DNA to mRNA|
- Occurs in the nucleus where DNA is located
|Translation|| step from mRNA to protein|
- most occurs in cytoplasm
- 10% to 15% of proteins are synthesized in the nucleus
|Transcription|| DNA to large to leave nucleus and participate directly in cytoplasmic protein synthesis|
- Necessary to make a small mRNA copy that can migrate through a nuclear pore into the cytoplasm
* copying genetic instructions from DNA to RNA
|RNA polymerase||enzyme the binds to the DNA and assembles the mRNA|
- Base sequences TATATA or TATAAA inform the polymerase where to begin.
- RNA polymerase opens up the DNA helix about 17 base pairs at a time
- Reads base from one strand of DNA
- Makes corresponding mRNA
- Where it finds C on the DNA, it adds G to the mRNA
- Where it finds A on the DNA, it adds U to the mRNA
|RNA polymerase|| ______ ________ rewinds the DNA helix behind it.|
- Gene can be transcribed by several polymerase molecules at once.
|Terminator||base sequence at the end of a gene which signals polymerase to stop|
|Pre-mRNA||immature RNA produced by transcription|
|Exons|| "sense" portions of the immature RNA |
- will be translated to protein
|Introns|| "nonsense" portions of the immature RNA|
- must be removed before translation
|Alternative splicing|| removing the introns by enzymes and splicing the exons together into a functional RNA molecule|
- One gene can code for more than one protein
- Exons can be spliced together into a variety of different mRNAs
|Translation||the process that converts the language of nucleotides into the language of amino acids|
|Ribosomes|| translate sequence of nucleotides into the sequence of amino acids|
- Occur mainly in cytosol, on surface of rough ER, and nuclear envelope.
- consists of two granular subunits, large and small
- each made of several rRNA and enzyme molecules.
|leader sequence / codon (AUG) / methionine||mRNA molecule begins with _______ ________|
- Acts as binding site for small ribosomal subunit
- Large subunit attaches to small subunit
- Ribosome pulls mRNA molecule through it like a ribbon, reading the bases as it goes.
- When start ______ _______ is reached, protein synthesis begins.
- All proteins begin with _________ when first synthesized.
|transfer RNA / anticodon||translation requires the participation of _________ _____.|
- small RNA molecule
- Coils on itself to form an angular L shape
- One end of the L includes three nucleotides called an __________.
- Other end has binding site specific for one amino acid
- Each tRNA picks up specific amino acids from pool of free amino acids in cytosol.
- One ATP molecule is used to bind amino acid to site.
- Provides energy for peptide bond formation.
|codon-anticodon / peptide bond||Translation: |
- Some imprecision in _______ - _______ pairing
- Takes only 48 different tRNAs to pair with 61 different codons.
- Ribosome binds and holds tRNA and its specific amino acid.
- Large ribosomal subunit contains an enzyme that forms ______ _______ that links amino acids together.
- First tRNA released from ribosome
- Second tRNA temporarily anchors growing peptide chain- Ribosome shifts and third tRNA brings its amino acid to the site.
|Polyribosome|| one mRNA holding multiple ribosomes|
- One ribosome can assemble protein of 400 amino acids in 20 seconds
- 300,000 identical mRNA molecules may be undergoing simultaneous translation.
Cell can produce 150,000 protein molecules per second.
|Primary Structure / Primary and Tertiary structure|| - Protein synthesis is not finished when the amino acid sequence (_______ _______) has been assembled.|
- To be functional it must coil or fold into precise __________ and _________ _________.
|Chaperone Proteins/ stress proteins or heat-shock proteins||- Older proteins that pick up new proteins and guide the new proteins in folding into the proper shapes.|
- Helps to prevent improper association between different proteins.
- Also called _____ _____ or ______-_______ ______.
- Chaperones produced in response to heat or stress.
- Help damaged proteins fold back into correct functional shapes.
|Protein Processing and Secretion||- Proteins to be used in the cytosol are likely to be made on free ribosomes in the cytosol.|
- Proteins destined for packaging into lysosomes or secretion from the cell are assembled on rough ER an dsent to Golgi complex for packaging
- Entire polyribosome migrated to the rough ER and docks on its surface.
- Assembled amino acid chain completed on rough ER
- Sent to Golgi for final modification.
|ER surface/ ER/||Proteins assembled on ____ _____, threads itself through a pore in the _____ membrane into cisterna.|
|posttranslational modification|| ER modifies protein by __________ _________.|
- removing some amino acid segments; folding the protein; stabilizing protein with disulfide bridges; adding carbohydrates.
|Transport vesicle / clathrin|| When rough ER is finished with protein|
- Pinches off bubblelike _______ _______ coated with _______.
- Clathrin helps select the proteins to be transported in vesicles and helps mold forming vesicle.
- Vesicles detach from ER and carry protein to the nearest cisterna of Golgi complex.
|Golgi cisterna||- Vesicles fuse and unload proteins into ______ ______.|
|exocytosis||Golgi complex further modifies the protein|
- Passes from cisterna closest to ER to cisterna farthest from ER.
- Buds off new coated Golgi vesicles containing finished protein.
- Some Golgi vesicles become lysosomes
- Others become secretory vesicles and migrate to plasma membrane, fuse to it, and release their cell product by ________.
|Gene Regulation|| - Genes are turned on and off from day to day, hour to hour.|
- Their products may or may not be needed.
- Many genes are permanently turned off in any given cell.
- Examples: genes for hemoglobin or digestive enzymes.
|prolactin / casein|| (Gene Regulation)|
Several ways to turn genes on or off
- Mother giving birth to first baby
- Hormone _______ stimulates cells of the mammary glands to begin synthesizing components of breast milk, including protein _______.
|receptors / transcription activator / casein gene / RNA polymerase / mRNA||(Gene Regulation)|
1. Prolactin binds to _________.
- Pair of proteins in plasma membrane of mammary cell.
2. Receptors trigger the activation of a regulatory protein (_________ ________) in cytoplasm.
3. Regulatory protein moves into the nucleus and binds to the DNA near the ______ ______.
4. The binding enables _______ ________ to bind to the gene and transcribe it, producing the ______ for casein.
5. The casein mRNA moves to the cytoplasm and is translated by ribosomes an the rough endoplasmic reticulum
6. The Golgi complex packages casein into secretory vesicles.
7. The secretory vesicles release the casein by exocytosis, and it becomes part of the milk.
|Glycogen, fat, steroids, phospholipids, pigments, and other compounds|| (Synthesizing Compounds Other Than Proteins)|
Cells synthesize _____, _____, _____, _____, _____, and ______.
- No genes for these.
- Synthesis under indirect genetic control
- Produced by enzymatic reactions
- Enzymes are proteins encoded by genes
|Testosterone production|| (Synthesizing Compounds Other Than Proteins)|
Example: ______ ______
- A steroid
- A cell of the testes takes in cholesterol
- Enzymatically converts it to testosterone
- Only occurs when genes for enzyme are activate
|Behavior, aggression, and sex drive|| (Synthesizing Compounds Other Than Proteins)|
Genes may greatly affect such complex outcomes as _____, _____, and _____.
|duplicate its DNA||Before a cell divides, it must _____ _____ so it can give a complete copy of all its genes to each daughter cell.|
|cellular function||Since DNA controls all _____ _____, this replication process must be very exact.|
|Law of Complementary Base Pairing|| we can predict the base sequence of one DNA strand if we know the sequence of the other.|
- Enables a cell to reproduce one strand based on the information in another.
|histones|| (DNA Replication)|
1. Double helix unwinds from ______.
|DNA helicase / Replication fork|| (DNA Replication)|
2. Enzyme ___ _____ opens one short segment of helix at a time exposing its nitrogenous bases.
- _______ _____-- the point where the DNA is opened up (like two separated halves of a zipper)
|DNA polymerase||(DNA Replication)|
3. ____ ____ molecules move along each strand
- Read the exposed bases
- Match complementary free nucleotides
- The two separated strands of DNA are copied by separate polymerase molecules proceeding in opposite directions.
- The polymerase molecule moving toward the replication fork makes a long, continuous, new strand of DNA.
|DNA ligase / parental DNA , daughter / Semiconservative replication||(DNA Replication)|
DNA polymerase cont:
- The polymerase molecule moving away from the replication fork makes short segments of DNA at a time -- ____ ____ joins them together.
- From the old _____ _____ molecule, two new _____ DNA molecules are made.
- _____ _____ -- each daughter DNA consists of one new helix synthesized from free nucleotides and one old helix conserved from the parental DNA.
4. New histones are synthesized in _____.
- Millions of histones are transported into the nucleus within a few minues after DNA replication.
- Each new DNA helix wraps around them to make a new nucleosome.
- Each DNA polymerase works at a rate of 100 base pairs per second.
- Would take weeks for one polymerase to replicate one chromosome.
- Thousands of polymerase molecules work simultaneously on each DNA molecule.
- All 46 chromosomes are replicated in 6 to 8 hours.
|DNA polymerase|| _____ _____ does make mistakes|
- Multiple modes for correction of replication errors.
- Double checks the new base pair and tends to replace incorrect, biochemically unstable pairs with more stable correct pairs.
- Result is only one error per 1 billion bases replicated.
|Mutations|| _______--changes in DNA structure due to replication errors or environmental factors (radiation, viruses, chemicals)|
- Some of them cause no ill effects, others kill the cell, turn it cancerous, or cause genetic defects in future generations.
|Cell cycle||the cell's life cycle that extends from one division to the next.|
|G1 Phase|| The first gap phase|
- interval between cell division and DNA replication
- Accumulates materials needed to replicate DNA
|S phase|| synthesis phase|
- Duplicates centrioles
- DNA replication occurs
|G2 Phase|| second gap phase|
- Interval between DNA replication and cell division
- Finishes centriole duplication
- Synthesizes enzymes that control cell division
- Repairs DNA replication errors
|M Phase|| mitotic phase|
- Cell replicates its nucleus
- Pinches in two to form new daughter cells
|Interphase||collection of G1, S, and G2 phases.|
|G0 (G Zero) phase|| cells that have left the cycle for a "rest"|
- Muscle and nerve cells
|Varies||Cell cycle duration _______ between cell types.|
|Mitosis||Cell division in all body cells except the eggs and sperm|
|Mitosis|| Functions of ______.|
- Development of the individual from one fertilized egg to some 40 trillion cells.
- Growth of all tissues and organs after birth
- Replacement of cells that die
- Repair of damaged tissues.
|Prophase, Metaphase, Anaphase, Telophase||Four phases of mitosis|
|Prophase / Spindle Fibers||-Chromosomes shorten and thicken, coiling into compact rods|
-Easier to distribute to daughter cells than chromatin
-Two chromatids per chromosome
-One molecule of DNA in each chromatid
•Nuclear envelope disintegrates and releases chromosomes into the cytosol
•Centrioles sprout elongated microtubules, called _______ ______.
-Push centrioles apart as they grow
-Pair of centrioles lies at each pole of the cell
|Metaphase / Cell equator / Mitotic spindle|| -Chromosomes are aligned on _____ ______.|
-Oscillating slightly and awaiting signal that stimulates each of them to split
•____ _____—lemon-shaped array of spindle fibers
-Long spindle fibers (microtubules) attach to chromosomes
-Shorter microtubules (aster) anchor centrioles to plasma membrane at each end of cell.
|Anaphase||-Activation of an enzyme that cleaves two sister chromatids apart at centromere|
-Daughter chromosomes migrate toward each pole of the cell with centromere leading the way
-Motor proteins in kinetochore crawling along the spindle fiber as the fiber itself is ―chewed up‖ and disassembled at the chromosomal end
-Daughter cells of mitosis are genetically identical
|Telophase|| -Chromatids cluster on each side of the cell|
-Rough ER produces new nuclear envelope around each cluster
-Chromatids begin to uncoil and form chromatin
-Mitotic spindle breaks up and vanishes
-Each nucleus forms nucleoli
•Indicating it has already
|Cytokinesis||•______—the division of cytoplasm into two cells|
-Telophase is the end of nuclear division but overlaps cytokinesis
-Early traces of cytokinesis visible in anaphase
•Achieved by motor protein myosin pulling on microfilaments of actin in the terminal web of cytoskeleton
•Creates cleavage furrow around the equator of cell
•Cell eventually pinches in two
|divide||Cells _____ when:|
•They have enough cytoplasm for two daughter cells
•They have replicated their DNA
•They have adequate supply of nutrients
•They are stimulated by growth factor
-Chemical signals secreted by blood platelets, kidney cells, and other sources
•Neighboring cells die, opening up space in a tissue to be occupied by new cells
|stop dividing / contact inhibition|| Cells ____ ____ when:|
•They snugly contact neighboring cells
•Nutrients or growth factors are withdrawn
•They undergo _____ _____—the cessation of cell division in response to contact with other cells
|Heredity||_______—transmission of genetic characteristics from parent to offspring|
|Karyotype||_______—chart of 46 chromosomes laid out in order by size and other physical features|
|Homologous chromosomes / autosomes / sex chromosomes / female / male|| -1 chromosome from each pair inherited from each parent|
•22 pairs called _____.
-Look alike and carry the same genes
•1 pair of ____ _____ (X and Y)
-Normal _____ has homologous pair of X chromosomes
-Normal _____ has one X and one much smaller Y chromosome
|Diploid||any cell with 23 pairs of chromosomes (somatic cells)|
|Haploid / germ cells||contain half as many chromosomes as somatic cells: sperm and egg cells ( ____ ____ )|
|Fertilization||restores diploid number to the fertilized egg and the somatic cells arise from it.|
|Locus||the location of a particular gene on a chromosome.|
|Alleles||different forms of gene at same locus on two homologous chromosomes.|
|Dominate Allele|| (represented by capital letter)|
- Corresponding trait is usually detectable in the individual
- Masks the effect of any recessive allele that may be present
- Produces protein responsible for visible trait
|Recessive allele|| (represented by lower case letter)|
- Expressed only when present on both of the homologous chromosomes
- No dominant alleles at that locus
|Genotype / Homozygous / Heterozygous|| _______--- the alleles that an individual possesses for a particular trait|
-______ alleles—two identical alleles for a trait
-______ alleles—different alleles for that gene
|Phenotype|| an observable trait|
-An allele is expressed if it shows in the _______ of an individual
|Genetic counselors||perform genetic testing or refer clients for tests, advise couples on the probability of transmitting genetic diseases, and assist people on coping with genetic disease|
|Punnett square|| shows how two heterozygous parents with cleft chins can have child with uncleft chin|
-Heterozygous carriers of hereditary diseases such as cystic fibrosis - Both parents healthy
|Gene pool||collective genetic makeup of population as a whole|
|Multiple alleles|| •Multiple alleles—more than two allelic forms for a trait|
-100 alleles are responsible for cystic fibrosis
-3 alleles for ABO blood types
•IA, IB, i alleles for ABO blood types
|Codominant|| both alleles equally dominant|
-IAIB = type AB blood
-Both are phenotypically expressed
|Incomplete dominance||Phenotype intermediate between traits each allele would have produced alone.|
|single phenotypic trait||Genes at two or more loci, or even different chromosomes, contribute to a ____ _____ ____ (skin and eye color, alcoholism, mental illness, cancer, and heart disease)|
|Alkaptonuria|| •One gene produces multiple phenotypic effects|
-______: mutation on chromosome 3 that blocks the breakdown of tyrosine
-Sickle-cell disease is another example of pleiotropy
|Sex-linked traits|| ______ ______carried on the X and Y chromosomes, and therefore tend to be inherited by one sex more than the other|
•Recessive color blindness allele on X, no gene locus for trait on Y, so red-green color blindness more common in men (mother is carrier)
|Penetrance||________—the percentage of a population with a given genotype that actually exhibits the predicted phenotype|
|polydactyly|| •A dominant allele causes ______|
-Presence of extra
|Role of environment|| •_____ of _______|
-No gene can produce a phenotypic effect without nutritional and other environmental input
-Need both the genetic recipe and the ingredients
-Brown eye color requires phenylalanine from diet to produce melanin pigment
|dominant / recessive / recessive / dominant|| •Common misconception that ______alleles must be more common in the gene pool than ______ alleles|
•Some ______ alleles, blood type O, are the most common
•Some ______ alleles, polydactyly and blood type AB, are rare in the population
|Benign tumor||Slow growth; contained in fibrous capsule; will not metastasize; usually easy to treat|
|Malignant tumor / metastasize|| called cancer|
-______ : give off cells that seed the growth of multiple tumors elsewhere
|Oncology||medical specialty that deals with both benign and malignant tumors|
|Tumor angiogenesis||in growth of blood vessels stimulated by energy-hungry tumors.|
|Carcinomas||cancer in epithelial tissue|
|Lymphomas||cancer in lymph nodes|
|Melanomas||cancer in pigment cells of epidermis (melanocytes)|
|Leukemias||cancer in blood-forming tissues|
|Sarcomas||cancer in bone, other connective tissue, or muscle|
|Carcinogen|| environmental cancer-causing agent|
- only 5% - 10% of cancers are hereditary
- trigger gene mutations
|Radiation||ultraviolet rays, X-rays|
|Chemical||cigarette tar, food preservatives, industrial chemicals|
|Viruses||human papilomavirus, hepatitis C, and type 2 herpes simplex|
|Oncogenes|| -Cause cell division to accelerate out of control|
•Excessive production of growth factors that stimulate mitosis
•The production for excessive growth-factor receptors
|Tumor-suppressor genes|| -Inhibit development of cancer|
•Oppose action of oncogenes
•Codes for DNA-repair enzymes
|Wilms tumor||-Malignant tumor of the kidney occurring especially in children|
|Lethal Effects of Cancer|| •Replace functional tissue in vital organs|
•Steal nutrients from the rest of the body
-Cachexia: severe wasting away of depleted tissues
•Weaken one's immunity
•Open the door for opportunistic infections
•Often invade blood vessels, lung tissue, or brain tissue