Unit 2 compilation
Table of contents
v Unit compilation
- Chapter 17- Cell reproduction and differentiation
- Chapter 18- Cancer
- Chapter 19- Genetics and inheritance
- Chapter 20- DNA technology and genetic engineering
v Lab –my chromosome and DNA and RNA
Chapter 17…Cell Reproduction and Differentiation
Cells reproduce by dividing into two cells by a process called mitotic cell cycle. The cell cycle has two distinct phases, interphase and mitotic phase. Interphase has three subphases, G1, S phase, and G2. This is when the cell grows, DNA is duplicated, and getting ready for the next division. The mitotic phase consists of mitosis. Mitosis consists of prophase, metaphase, anaphase and telophase which is the cycle of cell division and when the nucleus divides. Cytokinesis is when the cytoplasm divides and two new cells are formed, called daughter cells. Mitosis is for replacing “old, worn out” cells. Meiosis produces cells for reproduction and has two stages, I and II. In meiosis I, it goes through S phase, growing and duplicating chromosomes, but in prophase, the chromosomes pair up and swap DNA, now the genes from both parents are present and instead of duplicating chromosomes, they just split apart and create two new daughter cells. Meiosis II is similar to mitosis, but chromosomes don’t duplicate, they swap a section of DNA and form sister chromatids, then separate and cytokinesis occurs and there are four haploid daughter cells. DNA is double stranded and when it replicates, it seperates and forms again into a double strand, having a parent strand and a daughter strand. If a mutation occurs from a mistake during DNA replication, it can cause diseases such as cancer and if it’s not detected, it can be passed to future cells. Differentiation is when a cell becomes different from the others and is caused by a change in the environment. Cloning is a copy of a cell, gene or molecule and can be done with an undifferentiated cell. As of now, cloning is mainly for therapeutic reasons such as curing human diseases.
Tumors can be benign or cancerous
Cancer is caused by uncontrolled cell division and differentiation. Increased cell division is hyperplaysia, which may be normal for some cells such as the uterus. When cells divide at an un-normal rapid rate they form into a tumor. Tumors that are contained and remain in one place are benign or not cancerous, also known as in situ. They may eventually need to be removed if they cause pressure or start to crowd other cells.
Cancerous cells lose control of their functions and structures
Abnormal structural change is called dysplasia, this is when cells undergo a series of changes and divide more rapidly and cells become precancerous. A tumor turns into cancer when it is no longer contained and starts spreading, this is known and metastasis. Metastisizing cancer spreads until it takes over the functions of organs. Proto-oncogenes are normal genes that promote cell growth, differentiation, etc.
How cancer develops
Mutant forms of proto-oncogenes, tumor suppressor genes, and mutator genes contribute to cancer
When these genes become mutated they are called oncogenes. Tumor suppressor genes also regulate cells, but when they become damaged they start to regularly leave cells “unchecked” and now contribute to the cancer. Mutator genes generally repair during DNA replication, when they become mutated more errors in DNA replication occur.
A variety of factors can lead to cancer
Age is the most important factor in developing cancer. Cells with repair mechanisms get worn out after a while. Some viruses and bacteria contribute to cancer such as HPV, affecting the cervix. Environmental chemicals such as asbestos or smoking causes lung cancer. Radiation from the sun, household appliances, power lines and frequent sunburns increase the risk of melanoma, especially in fair complected individuals. Diet can also affect the risk of cancer. Red meats and saturated animal fats raise the risk of colon, rectum and prostate cancer. Eating fruits and vegetables has recently been thought to reduce these risks. Antioxidants are thought to neutralize free radicals, but it is still unsure how well they affect the development of cancer. There are many different factors and roles that take part in the development of cancer. Immune system can help prevent cancer, but if it is weakened by viruses or stress, cancer may develop more easily.
Advantages in diagnosis enable early detection
Detecting cancer can be done in a few different ways. X-ray is the most common, PET scans and MRI show differences in a tumor that X-RAY cannot detect. Genetic testing to identify a mutated gene can be done, but is controversial.
Many cancers are treatable especially when detected in early stages. Conventional treatments are surgery, radiation and chemotherapy. Chemotherapy administers a cell damaging chemical, cytotoxic, to destroy cancer cells. Some chemotherapeutic drugs act everywhere in the body. It damages quickly dividing cells, like cancer cells, but also normal cell such as bone marrow or the lining in the digestive tract, causing nausea. Hair loss, anemia and low white blood cells are other side effects. The body may also become immune to the chemo and the tumors become resistant, much like how our bodies can sometimes become immune to antibiotics so they no longer work. Magnetism, photodynamic therapy and (vaccine) immunotherapy are other developing treatments to target the malignant cells more directly.
The ten most common cancers
Skin cancer is classified as melanoma or non-melanoma. Basal cell carcinoma is the most common among non-melanoma, having a pink or flesh color and a smooth texture. Squamous is from epithelial cells produced by basal cells. Squamous cell cancer can metastasize rather slowly. Melanoma is the least common of the three skin cancers, but is the most deadly because it spreads very quickly. Follow the “ABCD” and now “E” rule. A=asymmetry, the two halves should match. B=border, border is irregular. C=color, color varies or is black. D=diameter, should be no larger than the size of a pencil eraser (6mm). E=evolution, if the spot changes in appearance. Breast cancer is usually detected by a physician or doing a self exam and feeling a lump or by mammogram. Risk factors are early onset of menstruation or late onset of menopause and oral contraceptives or hormone replacement therapy. Prostate cancer is most common after age 50. A yearly test is recommended for men at this age. It is detected by a digital rectal exam, or a PSA test, then confirmed with a biopsy. Treatment includes surgery, radiation and hormones. Colon cancer, lymphoma, urinary bladder cancer, kidney, uterine cancer and leukemia are others among the top ten most common cancers. Cancer can be prevented by a number of things including diet, not smoking, and staying out of the direct sunlight. If detected early on in stages, treatment options may be more effective.
Chapter 19- Genetics and Inheritance
The information needed for human development is contained in DNA. Genetics is the study of genes and their transmission from one generation to the next. Everybody inherits a set of genes from their mother and a set from the father. These sets vary slightly from person to person.
Your genotype is the genetic basis of your phenotype
Of the 23 pair of chromosomes, 22 of these are autosomes, one is a sex pair. Homologous chromosomes look alike and have a copy of the same gene in the same location. Small differences in DNA sequences exist in autosomes. The differences are in the genes anf=d they produce a different version of a gene called an allele. Alleles code for different proteins and with different structural changes in protein, structure changes protein function. If somebody has two identical alleles of a gene, the person is homozygous for that gene. Someone who has two different alleles of a gene is heterozygous. Alleles resulted from gene mutations and kept getting passed on through generations. A complete set of alleles is called genotype. Phenotype is all physical and functional traits resulting from genotype.
Genetic inheritance follows certain patterns
The way we designate two alleles to the same gene is to assign them uppercase and lowercase letters. People with the same two alleles of a gene (AA or aa) are homozygous and people with different alleles (Aa) are heterozygous. Gregor Mendel, a university- educated Austrian Monk, Did experiments with garden peas. In the 1850’s he followed traits of plants such as flower color, pea color, pea texture, and height from one generation to the next. Over a seven year period he collected large amounts of data and proposed that there were factors of heredity that united in fertilization and separated when forming sperm and egg and that pea plants inherit two units of each factor, all knowing nothing about DNA, chromosomes or genes. When Mendel did his experiments he cross-bred a green pea plant with a yellow pea plant. All the offspring produced yellow peas. It seemed that the green pea trait had disappeared until he bred two yellow pea plant offspring and 75% of the offspring produced yellow peas and the other 25% produced green peas. The green pea trait had skipped a generation. This experiment showed that each pea plant must have two alleles on the gene for pea color, that each parent donates only one allele of this gene to the offspring. This was Mendel’s first rule of inheritance. The law of segregation is whichever allele a parent contributes to a gamete is determined randomly. Dominant alleles are expressed over recessive alleles. In Mendel’s pea experiment the yellow pea was dominant (Y) and the green pea would show if there were no yellow alleles. The term dominant refers to how an allele reacts with a recessive allele that is heterozygous. Most people have homozygous recessive gene for 10 fingers and 10 toes. Some carry a dominant allele causing more fingers and toes, dominant allele traits like this is rare. Mendel formed his law of independent assortment when he performed two trait crosses. This states that alleles of different genes are distributed to egg and sperm cells independently of each other during meiosis.
Some alleles do not follow the traditional pattern. In incomplete dominance the heterozygous genotype results in phenotype that is between the two homozygous phenotypes. In codominance the products of both alleles are expressed equally.
Other factors influence inheritance patterns and phenotype
Polygenic inheritance: Phenotype is influenced by many genes
Inheritance of phenotypic traits that depend on many genes is called polygenic inheritance. Eye color is controlled by at least three genes and determined by the amount of melanin in the iris, along with the color of the skin and the amount of melanin in the skin. Some health conditions are also influenced by polygenic inheritance such as high blood pressure, cancer and stroke.
Both genotype and the environment affect phenotype
An example of environmental influence is the effect that diet has on height and body size. Some populations have a trend toward increased height and weight, within a one generation time frame, which is too short of a time frame for genetics to be in charge of. The environment also has to do with our phenotype and developing diseases. For example, if you know your family has a history of skin cancer, your sun exposure should be limited.
Sex linked inheritance: X and Y chromosomes carry different genes
Of the 23 pairs of chromosomes, 22 are matched pairs. The last pair does not match because they are the sex chromosomes, X and Y are considered a pair because you get one from each parent. The sperm determines the gender of the offspring because the male gene is XY and female gene is XX. If the male donates the X chromosome the offspring will be female, if a Y is donated then the offspring will be male. Males are more susceptible to recessive diseases than females because they only have one X chromosome.
Chromosomes may be altered in number or structure
Failure of homologous chromosomes or sister chromatids to separate properly is called nondisjunction. Sometimes sister chromatids go to one of the two cells or fail to separate which changes the number of egg or sperm cells. Down syndrome is caused by having a third copy of chromosome 21. Other sex chromosome combinations can occur such as having and extra X or Y chromosome causing genetic mutations. Deletion is when part of a chromosome breaks off and is lost. Translocation is when it breaks off and reattaches somewhere else.
Inherited genetic disorders involve recessive alleles
Disease can be inherited I f two defective recessive alleles are inherited. Phenylketonuria is a homozygous recessive disease where people can’t produce the enzyme needed for metabolizing phenylalanine. If this accumulates it turns toxic and can cause mental retardation. Huntington disease is caused by a dominant alleles and is fatal.
Genes make instructions for making proteins which may cause certain behavior that is inherited, such as schizophrenia.
Chapter 20 DNA technology and genetic engineering
Biotechnology is the technical application of biological knowledge for human purposes. Recombinant DNA technology is taking apart DNA, analyzing it and recombining it in new ways producing never before existing molecules of DNA. Genetic engineering is the manipulation of genetic makeup of cells or organisms, including humans.
There is a series of sequencing for DNA to b synthesized. The goal of DNA recombinant technology is to transfer DNA from one organism to another. The genes are used to insert certain genes into bacteria for production of useful proteins. Restriction enzymes break bonds in DNA strands to prevent bacteria from viral invasions. DNA ligases are the enzymes that bond the fragments back together. Plasmids are circular self DNA replicating molecules found in bacteria that help bacterial replication. The steps for (human) recombinant DNA are: first to isolate DNA plasmids and the human DNA of interest. Second, cut the DNA. Third, combine the DNA with the plasmid. Fourth, add the ligases so the two combine. Fifth, introduce the new plasmid into bacteria. Sixth, choose the bacteria containing the gene of interest and reproduce. DNA fingerprinting is for finding the source of a fragment of DNA and is used mainly for Criminal investigations.
Genetic engineering creates transgenic organisms
Transgenic organisms are organisms that have been genetically engineered so that they can carry one or more foreign genes to another organism. Transgenic bacteria are used to make certain essential proteins such as insulin. Insulin at one time was produced from the pancreas of slaughtered pigs. Now it is produced by transgenic bacteria. Genes that code for certain proteins are inserted into harmless bacteria. This is how vaccines are produced. Transgenic plants are also being reproduced, some of which are tomato plants that last longer, golden rice, which is high in beta carotene, a nutrient that is converted by the body into vitamin A. Gene pharming is the process of producing proteins in farm animals for medical uses. Genes are inserted into animals and the needed/wanted protein comes out through their milk. Producing transgenic animals is harder because animal cells don’t take to the plasmids as well.
Gene therapy: the hope for the future
Gene therapy is the insertion of human genes into human cells to treat or correct diseases. The hopes for gene therapy, is that mutations causing disorders can be fixed. Though transgenic animals are difficult to create, correcting human disease is harder. A gene that codes for a certain protein would have to be inserted into every cell in the body to correct mutations. No procedures for doing this exist yet. Some ideas and experimental techniques are transporters, or vectors which take cells from the body and are exposed to retroviruses, which are then injected back into the patient, in hopes that the retroviruses would then incorporate themselves back into the cells and correct themselves. Although gene therapy is still being studied and not often does it work, there have been cases where it has worked with vectors.
Human genome on chromosome 22
My chromosome (part 1)
Introduction: Human chromosomes hold genes that may or may not affect certain individuals by dominant or recessive alleles. When all the genes work in conjunction, they make up our genome.
Results: Of the 23 chromosomes, here are eight deciphered genes of chromosome 22.
CHEK2 This gene makes the protein checkpoint kinase 2, which acts as a tumor suppressor by regulating cell division. This protein is activated when a DNA strand breaks naturally or is damaged by radiation, chemical or UV rays. This protein then interacts with other proteins, including tumor protein 53(fromTP53 gene). These proteins together regulate cell division and determine whether or not a cell will repair its damage.
MYH9 This protein is one part of the myosin IIA protein. It plays a role in cell movement, maintaining the cells shape and cytokinesis.
NAGA This make the enzyme alpha-N-acetylgalactosaminidase, which works within the lysosomes (compartments of the cell that recycle and digest materials) to help remove a molecule called alpha-N-acetylgalactosamine, which can build up in a cell and cause it to die.
NEFH This gene produces a protein component of neurofilaments which are essential for nerve-cell structure. Neurofilaments are mainly in nerve cells of the brain and spinal cord for muscle movement control.
NF2 This gene produces Merlin, which is made in the nervous system, specializing in cells that wrap around and insulate nerves. Merlin is involved in controlling cell shape, movement and cell communication. Also acts as a tumor suppressor.
PLA2G6 This makes an enzyme called an A2 phospholipase, which is involved in metabolizing phospholipids which helps to maintain the integrity of the cell membrane. A2 phopholipase regulates phosphatidylcholine, present in the cell membrane.
PRODH This gene produces proline oxidase, found mainly in the liver, brain and kidneys. This enzyme produces energy within the cells of these organs.
SHANK3 This gene is involved in the functioning of synapses (connections between neurons for cell to cell communication). It makes sure signals are received. It is also involved in forming and maturing of dendritic spines, which are growths from dendrites that send a stronger nerve impulse.ll
My favorite gene is CHEK2 because it is a tumor suppressor. Cancer is the most awful thing on this planet, it has taken many loved ones from me. If a gene can slow down or regulate the process of cell division or differentiation to prevent cancer, I wish more people had these genes. And hopefully a cure will be found soon.
Conclusion: I have never before realized actually how complex the individuality of DNA is for each individual. I knew about dominant and recessive, but I didn’t know that it was on something called an allele, I also thought that if a trait was dominant, that gene would be passed on, instead there is a whole complexity for homozygous and heterozygous genes that make up our genome.
Replication, Transcription and Translation
DNA and RNA (part two)
Introduction: DNA is the human genome. It replicates itself, transcribing into RNA, which in turn, translates into proteins that the human body needs.
Procedure: A DNA code was taken and modeled with blue ribbon. It was then transcribed into RNA. Cytosine transcribes into Guanine, Guanine into cytosine, Adenine into Uracil, and Thymine into Adenine, using pink ribbon to create a model. RNA is then translated into codons, which are a triplet code that produce protein, this is modeled with beads strung on a ribbon.
TTT AAA TTT ACC CTG GCT TTT AAA GGA ATA GGG TAC ACT GTT TTT TCT TTA CCA CTT CTA TCT CTT TCT C
AAA UUU AAA UGG GAC CGA AAA UUU CCU UAU CCC AUG UGA CAA AAA AGA AAU GGU GAA GAU AGA GAA AGA G
Translated into polypeptides
Amino acid 1-Lysine (Lys)
Amino acid 2-Phenylalanine (Phe)
Amino acid 3-Lysine (Lys)
Amino acid 4-Tryptophan (Trp)
Amino acid 5-Aspartic acid (Asp)
Amino acid 6-Arginine (Arg)
Amino acid 7-Lysine (Lys)
Amino ascid 8-Phenylalanine (Phe)
Amino acid 9-Proline (Pro)
Amino acid 10-Tyrosine (Tyr)
Sources: http://www.dnai.org/c/index.html,on February 20, 2012
Conclusion: The model of DNA is a visual for a better understanding of how replication, transcription and translation works. This helped me learn in it a more effective way and shows how the human body converts things for its benefit.
DNA transcribed into RNA
RNA translated into proteins