- Chromosomes and the Cell Cycle
- Mitosis
- Meiosis
- Comparison of Meiosis and Mitosis
- Chromosome Inheritance
Cancer
- Cancer Cell
- Causes and Prevention of Cancer
- Diagnosis of Cancer
- Treatment of Cancer
Patterns of Genetic Inheritance
- Genotype and Phenotype
- One and Two Trait Inheritance
- Beyond Simple Inheritance Patterns
- Sex-Linked Inheritance
DNA Biology and Technology
- DNA and RNA Structure and Function
- Gene Expression
- Genomics
- DNA Technology
- Interphase- time when organelles carry on usual functions. The cell grows larger, the organelles double, chromatin doubles, and DNA synthesis occurs. Lasts approximately 20hrs. Interphase is divided into three stages G1 (before synthesis), S (includes synthesis), G2 (after synthesis)
- Cell Division- follows interphase, has 2 stages. Mitosis (the sister chromatids separate becoming chromosomes and are distributed to the two daughter nuclei). Cytokinesis (division of the cytoplasm).
The cell cycle happens continuously in certain tissues such as red blood cells, skin cells, and the cells that line the respiratory and digestive tracts. Apoptosis(programmed cell death) does away with any cells that are dividing when they shoudn't be
Mitosis
Is duplication division. The nuclei of the two new cells (daughter cells) have the same number and kind of chromosomes as the cell that divides (parent cell).
The centrosome (microtubule organizing center) is also duplicated. After they are duplicated, they separate and form the poles of the miotic spindle. Here they assemble microtubules to make spindle fibers. The chromosomes are attatched to the spindle fibers at their centromeres.
The centrioles (short cylinders of microtubules present in centrosomes) lie at right angles.
There are four phases of Mitosis 
- Prophase- centrosomes have duplicated, spindle fibers appear, nuclear envelope fragments, nucleolus disappears
- Metaphase- nuclear envelope is fragmented, spindle occupies former nucleus region, chromosomes are at the equator.
- Anaphase- separation of the
sister chromatids, the 2n number of chromosomes move towards each pole. - Telophase- begins when chromosomes arrive at poles. They become chromatin again, spindle disappears, and nuclear envelope components reassemble in each cell
- Cytokinesis- the division of cytoplasm and organelles started by cleavage furrow.
Meiosis
Is reduction division involving two divisions creating 4 daughter cells. Each daughter cell has one of each kind chromosome (half as many as the parent) This is called haploid, and these daughter cells become gametes. Meiosis ensures chromosome numbers stay constant throughout 
generations. Also the genetic recombination ensures offspring will be genetically different from each other and from the parents.
At the start, the chromosomes occur in pairs and are called homologous chromosomes. These come together and line up side by side (synapsis). When they separate, the daughter nucleus receives on member of each pair. Interkinesis is this period of time between miosis 1 and 2
In meiosis 2 the centromeres divide and sister chromatids separate. In the end, each of four daughter cells has haploid chromosomes and each chromosome has one chromatid. These daughter cells mature into gametes that will fuse during fertilization. Fertilization will restore the diploid number of chromosomes in the zygote (first cell of the new individual)
There are four stages of Meiosis(they are repeated in meiosis 1 and meiosis 2) These are the same as in Mitosis, with key differences in the first 2 phases
- Prophase 1- synapis occurs, spindle appears, nuclear envelope fragments and nucleolus disappears, the exchange of genetic material occurs between the nonsister chromatids and the homologous pair (crossing over)
- Metaphase 1- homologous pairs align at the equator and the maternal or paternal pair can be oriented at either pole making a possibility of 8 combinations in the resulting gametes.
Comparison of Meiosis and Mitosis
Meiosis occurs only in the reproductive organs to produce the gametes. Mitosis occurs in all tissues during growth and repair.
- DNA replication take place only once prior to both. Meiosis needs 2 nuclear divisions instead of one
- Meiosis produces 4 daughter nuclei, and after cytokinesis there are 4 daughter cells, while in mitosis there are only 2
- The 4 daughter cells in meiosis are only haploid while the 2 in mitosis are diploid
- Daughter cells from meiosis are not genetically identical to each other or parent cells, while in mitosis the daughter cell are genetically identical to each other and parents.
Chromosome Inheritance
An individual carries 22 pairs of autosomes and two sex chromosomes. Each pair of autosomes carries alleles for particular traits. When a person ends up with too many or few autosomes or sex chromosomes this is called nondisjunction. Nondisjunction happens during meiosis 1 when both members of a homologous pair go into the same daughter cell, or it can also happen in meiosis 2 when the sister chromatids fail to separate and both daughter chomosomes end up in the same gamete.
- Trisomy- An egg with 24 chromosomes is fertilized by a normal sperm. Only trisomy 21 (Down Syndrome) has a chance of survival after birth. Trisomy in the sex chromosomes has a greater chance of survival. Cells of females function with only one X chromosome( the other is a mass of chromatin called a Barr body). Poly X females and XXY(Klinefelter syndrome) males are seen frequently XYY (Jacobs syndrome) is due to nondisjunction during meiosis2 of spermatogenisis.
- Monosomy-An egg with 22 chromosomes is fertilized by a normal sperm. A zygote with one X chromosome is called Turner syndrome
Changes in chromosome structure is another type of chromosomal mutation
- Deletion- an end of a chromosome breaks off, or two simultaneous breaks lead to the loss of an internal segment
- Duplication-presence of a chromosomal segment more than once in same chromosome
- Inversion- segment of chromosome is turned 180
- translocation- movement of a chromosome segment to another nonhomologous chromosome
Chapter 19 Cancer
Cancer Cells
Cancer is really over 100 different diseases, but cancer cells have common characteristics
- Cells lack differentiation- they are non specialized and don't contribute to the functioning of a body part
- Cells have abnormal nuclei- enlarged and may contain an abnormal number of chromosomes. These cells fail to undergo apoptosis
- Cells have unlimited replicative potential- immortal and keep dividing unlimitedly. Telomeres protect the ends of chromosomes and get shorter each time, in cancer telomerase rebuilds telomere sequences, keeping the telomeres at a constant length so the cell can keep dividing.
- Cells form tumors- they do not stop dividing when they come into contact with neighbors
- Cells have no need for growth factors- cancer cells continually divide even when stimulatory growth factors are absent and inspite of inhibitory growth factors.
- Cells gradually become abnormal- the cell has a mutation that causes it to start dividing (initiation). A tumor developes, cells continue to divide and undergo mutations (Promotion). One cell has a selective advantage over the others and is eventually able to invade surrounding tissue ( Progression).
- Cells undergo angiogenesis and metastisis- formation of new blood vessles and the spread of cancer throughout the body from the place of origin
The cell cycle is able occur repeatedly due to mutations in two types of genes, Photo-oncogens (prevent apoptosis and accelerate the cell cycle), and Tumor-suppressor genes (inhibit the cell cycle and promote apoptosis)
The photo-oncogens become oncogens (this is a gain of function mutation and over expression is the result). Also the tumor-suppressor genes become inactive (this is a loss of function mutation)
Types of Cancer
- Carcinomas- epitheal tissues
- Sarcomas- muscle and connective tissue
- Leukemias- blood
- Lymphomas- lymphatic tissue
Causes and Prevention of Cancer
Cancer can be caused by different facters including
- hereditary,
- environmental carcinogens (such as ultraviolet light from sunlight and tanning lamps, radon gas, and nuclear emissions). Also under the environmental category is organic chemicals such as tobacco products which are responsible for 80% of all cancers. Pollutants and viruses (hepatitis B and C, Epstein-Barr and HPV)
- Dietary choices- high fat diets
Diagnosis of Cancer
Tests for cancer include: pap test, mammogram, tumor marker test, tests for gentic mutations, biopsy and imaging.
C hange in bowel of bladder habits
A sore that does not heal
U nusual bleeding or discharge
T hickening or lump in breast or elsewhere
I ndigestion or difficulty in swallowing
O bvious change in wart or mole
N agging cough or hoarsness
Treatment of Cancer
Standard therapies are surgery (effective for CIS), radiation (localized, causes chromosomal breakage and cell cycle disruption), and chemotherapy ( treats the entire body, and whenever possible, chemotherapy is specifically designed for a particular cancer)
Newer therapies are immunotherapy (immune cells are genetically engineered to bear the tumors antigens), p53 therapy(this gene triggers cell death in only cancer cells)
Chapter 2o Patterns of Genetic Inheritance
Genotype and Phenotype
Genotype refers to the genes of the individual. Alleles are alternative forms of a gene having the same position on a pair of chromosomes and affecting the same trait. These are designated by a letter, a capital for dominant allele and lowercase for recessive. Alleles occur in pairs, normally 2 for each trait. (homozygous dominant AA, homozygous recesive(aa), heterozygous (Aa) )
Phenotype is the physical appearance of the individual, for example freckles. The phenotype is not necesarily easily observable, for example color blindness.
One and Two Trait Inheritance
When the chromosomes are reduced in gametogenesis, so are the alleles meaning that the gametes carry only one allele for each trait-no 2 letters in a gamete can be the same letter of the alphabet.
One trait crosses are easily shown through punnett squares. These allow you to figure the chances or probability of an offspring having a certain genotype/phenotype.
In two trait crosses a gamete will receive one short and one long chromosome of either trait. All possible combinations of chromosomes and alleles are in the gametes. The alleles for two genes are on these homologues. A gamete will never have two of the same letter. A dihybrid genotype occurs when an individual is heterozygous in two regards (WsSs)
With genetic diseases there are two types: Autosomal Dominant (alleles AA or Aa) and Autosomal Recessive (aa). Some examples of dominant diseases are: marfan syndrome and huntington disease. Examples of recessive diseases are: tay-sachs disease, cystic fibrosis, phenylketonuria, and sickle cell.
Beyond Simple Inheritance Patterns
Polygenic traits (skin color and height) are governed by more than one set of alleles. Each dominant allele codes for a product , consequently these dominant alleles have a quantitative effect on the phenotype and the effects are additive. This results in continuous variation of phenotypes, with distribution resembling a bellshaped curve.
Incomplete dominance is when the heterozygote is intermediate between two homozygotes (wavy hair). Codominance is when alleles are equally expressed in a heterozygote (blood type AB)
Sex linked Inheritance
An allele on the x chromosome is x-linked and one on the y chromosome is y-linked. Most sex linked alleles are only on the x chromosome. Usually a sex linked disorder is recessive so females must receive a recessive allele from each parent. With x-linked traits, a male only needs to receive the trait from one allele from the mother. Examples are: color blindness, muscular dystrophy, and hemophilia.
DNA Biology and Technology
DNA and RNA Structure and Function
Genetic material must be able to replicate, store information, and undergo mutations to provide genetic variability. DNA is composed of two strands that spiral about each other. Each of these strands is a polynucleotide. These strands run in opposite directions and are attatched by the four bases. DNA replication lets each strand serve as a template for a new strand, thus cutting down on the errors.
RNA is made up of nucleotides containing the sugar ribose (adenine, uracil, cytosine,,and guanine). RNA is single stranded and helps DNA with protein synthesis. 
- Ribosomal RNA (rRNA)is produced in the nucleolus and joins with proteins in the cytoplasm to form subunits of ribosomes.
- Messenger RNA (mRNA) is produced in the nucleus can carries genetic information from DNA to the ribosomes
- Transfer RNA (tRNA) is produced in the nucleus and transfers amino acids in proteins.
Gene Expression
The first step is transcription. A strand of mRNA forms complementary to a portion of DNA. The second step is translation. A sequence of nucleotides is translated into amino acids. The genetic code
is a triplet code in order to be able to code for at least 20 amino acids.
- Transcription- begins with RNA polymerase which opens the DNA helix in front. RNA polymerase joins the RNA nucleotide to make a mRNA molecule.
- Translation- tRNA brings amino acids to the ribosomes where polypeptide synthesis occurs. Each ribosome has a binding site for mRNA and two sites for 2 tRNA molecules. At the other end of the tRNA is a specific anticoden (group of 3 bases that are complementary to the mRNA codon). Poly peptide synthesis starts with initiation where mRNA binds to smaller ribosomal unit after which the larger unit associates with the smaller.
Elongation means the polypeptide lengthens and incoming tRNA complex arrives at the A site and receives the peptide from outgoing tRNA. Termination occurs at a codon, that does not code for an amino acid, and teh ribosome dissociates into the two sub units and falls off the mRNA molecule.
There are a variety of factors that mechanisms regulate gene expression. These are sectioned in 4 levels of control. Two for the nucleus and two for the cytoplasm
- Transcriptional Control- in the nucleus, regulates what genes and how fast transcription occus
- Posttranscriptional Control- in the nucleus, affects how the mRNA is processed before exiting the nucleus and how fast the mature mRNA leaves
- Translational control- in the cytoplasm, before there is a protein product, this controls the life expectancy of mRNA
- Postranslational control- in the cytoplasm, after protein synthesis, the polypeptide product may have to undergo more changes before it become biologically functional.
Genomics
This is the study of genomes. Due to the Human Genome Project they were able to find the order of A, T, C, and G in our genome. Genome size is not proportionate to the number of genes and does not correlate to the complexity of the organism.
Functional genomics works to find out how the 25000 genes function in cells, and how they work to create a human being. Proteomics is the study of the structure, function, and interaction of cellular proteins. Bioinformatics is the application of computer technologies to the study of genome.
Gene therepy can be used to modify a person's genome by inserting genetic material into human cells to treat a disorder. This is done either by Ex vivo gene therapy is outside the body and in vivo gene therapy is inside the body. Gene therapy is growing more popular as a part of cancer therapy to make healthy cells more tolerant and tumor more vulnerable.
DNA technology
Genes can be isolate and cloned using recombiant DNA. To create this the technician needs a vector (a way the gene of interest is introduced to a host cell). A restriction enzyme cleaves, human DNA and plasmid DNA. Then the enzyme DNA ligase is used to seal foreign DNA into the opening created in the plasmid. Bacterial cells take up the plasmid alowing gene cloning to occur as the plasmid replicates. The bacterium is transformed and can now make a product (such as insulin) that it was unable to make before.
Specific DNA sequences can be cloned. The polymerase chain reaction can create copies of a segment of DNA. PCR requires the use of DNA polymerase and a supply of nucleotides for the new DNA stands. Advances in DNA technology is rapidly moving towards coming up with solutions for curing diseases and new ways of fighting cancer.
Works Cited
Mader, Sylvia Human Biology 10th edition
Frolich Power Points
Links for Pictures
1. http://www.accessexcellence.org/RC/VL/GG/images/protein_synthesis.gif
2. http://www.allthingsbeautiful.com/all_things_beautiful/images/metastasizing_cancer.jpg
3. http://www.tobacco-facts.info/images/chest_x-ray_lung-cancer.jpg
4. http://upload.wikimedia.org/wikipedia/commons/archive/5/56/20061004031648!%20Macs_killing_cancer_cell.jpg
5. http://www.allthingsbeautiful.com/all_things_beautiful/images/metastasizing_cancer.jpg
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