Compendium 2
Chapters 18,21, 19 and 20 and power point presentation
In this review I will be covering the cell cycle, including interphase and cell division. I will also discuss mitosis and meiosis and their similarities and differences. I will touch on the inheritance of chromosomes from our parents and the effects of any changes in those chromosomes. I will also touch on the structures of DNA and RNA and how DNA replication is an integral part of mitosis. I will talk about some of the scientific findings in the studies of genetics and the technology that has been developed for the study of DNA. In this brief I will also touch on the wide topic of cancer, the formation and growth and types of cancer cells, and some of the causes of these cancer cells. And finally we will discuss the genes for specific traits, or genotype, and their physical characteristics, or Phenotypes. We will define the terms homozygous dominant, homozygous recessive and heterozygous recessive.
In the study of genetics we must study in depth the cells chromosomes and their effects on our bodies. All humans have 23 chromosomes (46 chromosomes in total). Only one of these pairs of chromosomes affects the sex of an individual. Scientists have developed a method for viewing all the chromosomes an individual has. The depiction of these chromosomes is called a karyotype. Karyotypes are achieved during the process of cell division when chromosomes are most compact and are highly visible. Cell division is the second part of what is called the cell cycle. Cell division comes after interphase. Most of the cells time is spent in interphase. The organelles carry on their typical functions and the cell readies itself to divide. About 90% of the cells time is spent in interphase. There are three phases of interphase G1 stage is when the cell doubles its organelles in preparation for division. The S stage is when DNA replication occurs, so that when the cell divides there will be like copies of DNA in both cells. G2 stage synthesizes the proteins necessary for the cell to divide. After the interphase is complete the cell division begins. The first phase of cell division is mitosis. In mitosis there are four stages.
1. Prophase of mitosis is characterized by the formation of the spindle fibers which we will discuss soon, the nucleolus has vanished and the duplicated chromosomes have become visible.
2. The metaphase of cell division can be distinguished by the spindle fibers attaching to the chromatids and the chromatids will line up at the center of the cell in preparation to be pulled apart.
3. Anaphase in cell division is when the identical chromatids are pulled apart by the shortening of the attached spindle fibers and each pole of the cell achieves the same chromosomes.
4. In the telophase the nucleoli begins to form and the cells membrane pinches together in the center and the cells are almost divided
After these steps are complete cytokinesis occurs and all the cells internal organelles are divided the cleavage furrow forms and the cells membrane pinches together and separates. Mitosis is a constant occurrence in our bodies, it is the reason we grow from a zygote to an adult and also the way in which we are able to heal after injuries and surgeries. The cell cycle control system is what stimulates the cell to divide at the appropriate times
In the process of meiosis cells divide a bit differently than mitosis. In meiosis there are two phases meiosis I and meiosis II. In meiosis I DNA replication has already occurred and the pairs of chromosomes line up at the equator in preparation for division. When this cell separates the daughter cells will take one member of each pair of chromosomes and will therefore have the haploid number of chromosomes. In meiosis II the four daughter cells are produced with the haploid number of chromosomes. The diploid (two of each type of chromosome are in the nucleus) amount of chromosomes is achieved again when fertilization occurs. Meiosis is the process for the division of cells for sexual reproduction. Some of the similarities and differences between mitosis and meiosis are that the DNA replication occurs prior to division in both scenarios but in mitosis only one cell division occurs whereas in meiosis has two. The main difference between the two is that meiosis is division of the sex cells and mitosis occurs in the rest of the body.
Normally when a zygote is formed by fertilization it then carries 22 sets of autochromosomes and 1 set of sex chromosomes. Occasionally though a person can be born with too many or too few of these chromosomes most likely due to nondisjunction (failure of the chromosomes to separate during meiosis I). This can result in Down syndrome, having three copies of chromosome 21 and turner syndrome having only one sex chromosome. Another chromosomal mutation is the seemingly inconsequential change in the structure of the chromosome. This can happen by deletion, the end of a chromosome breaks off or by duplication where a segment of a chromosome appears in the sequence more than one time. Two other forms of this type of mutation are inversion meaning that a segment of the chromosome has turned around 180 degrees, or by translocation in which a small piece of one chromosome switches places with a small piece from the other chromosome. These mutations can result in Williams syndrome and cri du chat syndrome.
DNA is seen in the cell as what is called a double helix. It looks similar to a ladder that is twisted. DNA is what stores genetic information in the cell. The supports or backbone of the DNA is comprised of phosphate sugar molecules and the rungs are formed of hydrogen bonded bases. These bases are adenine thymine base pairs and guanine cytosine base pairs. DNA replicates when an enzyme specifically for this process breaks the hydrogen bond or unzips the pairs and new strands of DNA come in to bond with the old strand to form new DNA molecules. Therefore each double helix has one new strand and one old strand. DNA replicates only in preparation for mitosis. RNA is a single stranded nucleotide that serves as a helper to DNA. There are three types of RNA, Ribosomal RNA is produced in the nucleus and joins with proteins and exits the nucleus and is used in protein synthesis. Messenger RNA is also formed in the nucleus and it carries messages necessary for protein synthesis. Transfer RNA transfers amino acids to the ribosomes thus forming a protein.
In the intense study of genes, or genomics, scientists have been able to clone cells. They have also been able to produce recombinant DNA, DNA comprised from two or more donors. This has been used in genetic engineering which is the purposeful modification of organisms genes. Genetic engineering has had a profound impact on our world today; it has made the production of artificial insulin and human growth hormone possible. It also has made its impact in the farming community with the presence of plants that are resistant to insecticides and/ or herbicides. It may also be possible through genetic engineering to water crops with salt water and have them thrive. Although genetic engineering may bring conveniences to our community there is much controversy on whether or not it is safe for us. I personally do not think that it is healthy to eat genetically modified foods.
Chapters 18,21, 19 and 20 and power point presentation
In this review I will be covering the cell cycle, including interphase and cell division. I will also discuss mitosis and meiosis and their similarities and differences. I will touch on the inheritance of chromosomes from our parents and the effects of any changes in those chromosomes. I will also touch on the structures of DNA and RNA and how DNA replication is an integral part of mitosis. I will talk about some of the scientific findings in the studies of genetics and the technology that has been developed for the study of DNA. In this brief I will also touch on the wide topic of cancer, the formation and growth and types of cancer cells, and some of the causes of these cancer cells. And finally we will discuss the genes for specific traits, or genotype, and their physical characteristics, or Phenotypes. We will define the terms homozygous dominant, homozygous recessive and heterozygous recessive.
In the study of genetics we must study in depth the cells chromosomes and their effects on our bodies. All humans have 23 chromosomes (46 chromosomes in total). Only one of these pairs of chromosomes affects the sex of an individual. Scientists have developed a method for viewing all the chromosomes an individual has. The depiction of these chromosomes is called a karyotype. Karyotypes are achieved during the process of cell division when chromosomes are most compact and are highly visible. Cell division is the second part of what is called the cell cycle. Cell division comes after interphase. Most of the cells time is spent in interphase. The organelles carry on their typical functions and the cell readies itself to divide. About 90% of the cells time is spent in interphase. There are three phases of interphase G1 stage is when the cell doubles its organelles in preparation for division. The S stage is when DNA replication occurs, so that when the cell divides there will be like copies of DNA in both cells. G2 stage synthesizes the proteins necessary for the cell to divide. After the interphase is complete the cell division begins. The first phase of cell division is mitosis. In mitosis there are four stages.
1. Prophase of mitosis is characterized by the formation of the spindle fibers which we will discuss soon, the nucleolus has vanished and the duplicated chromosomes have become visible.
2. The metaphase of cell division can be distinguished by the spindle fibers attaching to the chromatids and the chromatids will line up at the center of the cell in preparation to be pulled apart.
3. Anaphase in cell division is when the identical chromatids are pulled apart by the shortening of the attached spindle fibers and each pole of the cell achieves the same chromosomes.
4. In the telophase the nucleoli begins to form and the cells membrane pinches together in the center and the cells are almost divided
After these steps are complete cytokinesis occurs and all the cells internal organelles are divided the cleavage furrow forms and the cells membrane pinches together and separates. Mitosis is a constant occurrence in our bodies, it is the reason we grow from a zygote to an adult and also the way in which we are able to heal after injuries and surgeries. The cell cycle control system is what stimulates the cell to divide at the appropriate times
In the process of meiosis cells divide a bit differently than mitosis. In meiosis there are two phases meiosis I and meiosis II. In meiosis I DNA replication has already occurred and the pairs of chromosomes line up at the equator in preparation for division. When this cell separates the daughter cells will take one member of each pair of chromosomes and will therefore have the haploid number of chromosomes. In meiosis II the four daughter cells are produced with the haploid number of chromosomes. The diploid (two of each type of chromosome are in the nucleus) amount of chromosomes is achieved again when fertilization occurs. Meiosis is the process for the division of cells for sexual reproduction. Some of the similarities and differences between mitosis and meiosis are that the DNA replication occurs prior to division in both scenarios but in mitosis only one cell division occurs whereas in meiosis has two. The main difference between the two is that meiosis is division of the sex cells and mitosis occurs in the rest of the body.
Normally when a zygote is formed by fertilization it then carries 22 sets of autochromosomes and 1 set of sex chromosomes. Occasionally though a person can be born with too many or too few of these chromosomes most likely due to nondisjunction (failure of the chromosomes to separate during meiosis I). This can result in Down syndrome, having three copies of chromosome 21 and turner syndrome having only one sex chromosome. Another chromosomal mutation is the seemingly inconsequential change in the structure of the chromosome. This can happen by deletion, the end of a chromosome breaks off or by duplication where a segment of a chromosome appears in the sequence more than one time. Two other forms of this type of mutation are inversion meaning that a segment of the chromosome has turned around 180 degrees, or by translocation in which a small piece of one chromosome switches places with a small piece from the other chromosome. These mutations can result in Williams syndrome and cri du chat syndrome.
DNA is seen in the cell as what is called a double helix. It looks similar to a ladder that is twisted. DNA is what stores genetic information in the cell. The supports or backbone of the DNA is comprised of phosphate sugar molecules and the rungs are formed of hydrogen bonded bases. These bases are adenine thymine base pairs and guanine cytosine base pairs. DNA replicates when an enzyme specifically for this process breaks the hydrogen bond or unzips the pairs and new strands of DNA come in to bond with the old strand to form new DNA molecules. Therefore each double helix has one new strand and one old strand. DNA replicates only in preparation for mitosis. RNA is a single stranded nucleotide that serves as a helper to DNA. There are three types of RNA, Ribosomal RNA is produced in the nucleus and joins with proteins and exits the nucleus and is used in protein synthesis. Messenger RNA is also formed in the nucleus and it carries messages necessary for protein synthesis. Transfer RNA transfers amino acids to the ribosomes thus forming a protein.
In the intense study of genes, or genomics, scientists have been able to clone cells. They have also been able to produce recombinant DNA, DNA comprised from two or more donors. This has been used in genetic engineering which is the purposeful modification of organisms genes. Genetic engineering has had a profound impact on our world today; it has made the production of artificial insulin and human growth hormone possible. It also has made its impact in the farming community with the presence of plants that are resistant to insecticides and/ or herbicides. It may also be possible through genetic engineering to water crops with salt water and have them thrive. Although genetic engineering may bring conveniences to our community there is much controversy on whether or not it is safe for us. I personally do not think that it is healthy to eat genetically modified foods.
In the study of cancer or oncology doctors and scientists have been able to discover how cancer is formed, causes of cancer, the different types of cancer as well as different treatments for it. In the formation of cancer one cell mutates giving it an abnormally large nucleus and the ability to divide an unlimited amount of times among other traits. Cancer cells divide multiple times forming a tumor, tumors can be benign meaning that they are enclosed in a capsule or they can be malignant in which the possibilities are virtually endless. Malignant tumors invade the underlying tissues and even have the possibility to sprout new formations in distant tissues. There are four different types of cancers
1. Carcinomas are cancers of the epithelial tissues such as skin, breast, lung and prostate to name a few
2. Sarcomas are cancers of the muscle or connective tissue like bone
3. Leukemias are cancers of the blood
4. Lymphomas are cancers of the lymphatic tissue such as the lymph nodes and the tonsils.
Cancers can be caused by hereditary inheritances and also by the environment. Environmental carcinogens include radiation, as seen in the effects of nuclear activity, organic chemicals such as tobacco, pesticides and asbestos, and also can be caused by viruses. We can greatly increase our chances of not getting cancer by staying away from cigarette smoke and other chemicals and making wise dietary choices such as organically grown fruits and vegetables and staying away from processed foods. It is a good idea to get checked for the common types of cancer regularly but also be aware of our bodies and follow up with physicians about any abnormal changes we have.
In chapter 20 the patterns of genetic inheritance are discussed in detail. Alleles are pairs of genes that occupy a specific position on a specific chromosome. Alleles are classified into dominant alleles, which are assigned uppercase letters, while lowercase letters are assigned to recessive alleles. Alleles occur in pairs because one half is contributed by the mother and the other half by the father. When two dominant alleles appear in a chromosome, it is given the name homozygous dominant. When one dominant and one recessive allele appear in a chromosome it is known as homozygous recessive. When two recessive alleles appear it is called heterozygous. The physical appearance of these genotypes is a person’s phenotype. One of the methods used to discover all possibilities in a cross where both parents are heterozygous is known as a Punnett square. We did some practice with this in our fly lab. Crosses get a little trickier when they are two trait crosses. The punnett square can also be very useful in discovering the possibility of a child inheriting a genetic disorder. Some of the more common genetic disorders we learned about were Tay-Sachs disease which is an autosomal recessive disorder meaning that both parents are carriers of the gene, but do not show any symptoms.
These four chapters and the power point presentation had a huge amount of information; I now have a solid base understanding of cell division, both mitosis and meiosis, the structure and functions of both DNA and RNA. I have gained more knowledge of genetic engineering; I was unaware that insulin was a genetically engineered product! The chapter I found the most interesting was chapter 19, the chapter on cancer. As I stated before I am in this class to become an RN and I hope to specialize in pediatric oncology, so this chapter held a wealth of information for me.
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