Question

Discussion Board 2.1: Cellular Metabolism and Reproduction: Mitosis and Meiosis

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Description:

In this discussion, you will examine genetic mutations and genetic disorders.

Objectives:

• Define the stages of the cell cycle.
• Know the basic structure of the DNA molecule, including what the nitrogen base pairs are and how they pair up in the DNA molecule.

Instructions:

Respond to the following:

Cellular reproduction and genetic mutations are closely related. As cells reproduce, they usually produce exact copies of themselves. Sometimes, however, cellular mutations occur. Genetic mutations are alterations to the sequences of DNA that comprise genes.

• Identify two genetic mutations or genetic disorders. What do you find significant or intriguing about these mutations or disorders?
• Does genetic testing exist for either disorder? Explain.
• Do you think that babies ought to be tested for either of these mutations or disorders before or at birth? Why or why not?

*Be sure to cite any outside sources in APA format.

Answer 1

STAGES OF CELL CYCLE The cell cycle is divided in to 2 basic phases INTERPHASE and M-PHASE. It again divided in to 4-stage process consisting of Gap 1 (G1), Synthesis, Gap 2 (G2) and mitosis. An active eukaryotic cell will undergo these steps as it grows and divides. After completing the cycle, the cell either starts the process again from G1 or exits the cycle through G0.The M phase represent the phase when the actual cell division or mitosis occurs and the interphase represants the the phase between two successive M phases though it is the resting phase it is the time during which the cell preparing for division by undergoing both cell growth and DNA replication in an orderly manner.The interphase is further divided in to 3 phases G1 , Synthesis and G2 phases. It is significant to note that in the 24hr average duration of cell cycle of a human cell, cell division proper last for only about an hour. The interphase last more than 95% of duration of the cell cycle. M-PHASE:It starts with the nuclear division ,correspond to the separation of daughter chromosomes(karyokinesis) and usually ends with division of cytoplasm(cytokinesis) G1 PHASE: It correspond to the interval between mitosis and initiation of DNA replication.In this phase the cell is metabolically active and continously grow but doesnot replicates its DNA. S or SYNTHESIS PHASE: Period during which DNA synthesis or replication take place.During this time the amount of DNA per cell doubles. G2 PHASE:Proteins are synthesised in preparation for mitosis while cell growth continous. G0 PHASE:Some cells in the adult animals donot appear to exhibit division(eg; heart cells) and many other cells divide occasionally, as needed to replace cells that have been lost because of injury or cell death. These cells that donot divide further exit G1 phase to enter an inactive stage called quiscent stage (G0). M PHASE:It is divided into 4 stages of nuclear division PROPHASE,METAPHASE, ANAPHASE,TELOPHASE STRUCTURE OF DNA MOLECULE DNA is made up of molecules called nucleotides. Each nucleotide contains a phosphate group, a sugar group and a nitrogen base. The four types of nitrogen bases are adenine (A), thymine (T), guanine (G) and cytosine (C).It is a chain of chemical building blocks called nucleotides that are a combination of a nitrogen base, a sugar called deoxyribose and a phosphate group. The DNA molecule is shaped like a ladder that is twisted into a coiled configuration called a double helix.There are four nitrogenous bases in DNA, two purines (adenine and guanine) and two pyrimidines (cytosine and thymine). Adenine always bonds with thymine, and cytosine always bonds with guanine. GENETIC DISORDERS Down syndrome , Hemophilia , Sickle cell anemia , Cystic fibrosis etc are common genetic disorders DOWN SYNDROME: It is usually caused by an error in cell division called “nondisjunction.” Nondisjunction results in an embryo with three copies of chromosome 21 instead of the usual two. Prior to or at conception, a pair of 21st chromosomes in either the sperm or the egg fails to separate.It varies in severity among individuals, causing lifelong intellectual disability and developmental delays. It's the most common genetic chromosomal disorder and cause of learning disabilities in children. It also commonly causes other medical abnormalities, including heart and gastrointestinal disorders. HEMOPHILIA:Hemophilia is a rare, inherited bleeding disorder in which blood cannot clot normally at the site of a wound or injury. The disorder occurs because certain blood clotting factors are missing or do not work properly. Because a clot does not form, extensive bleeding can be caused from a cut or wound. This is called external bleeding.Hemophilia affects males almost exclusively, but there are rare circumstances when a female can be affected with the disorder.

There are two main types of inherited hemophilia:

• Type A, the most common type, is caused by a deficiency of factor VIII, one of the proteins that helps blood to form clots. This type is known as classic hemophilia.
• Type B hemophilia is caused by a deficiency of factor IX. This type is also called Christmas disease.

Although hemophilia is usually diagnosed at birth, the disorder can also be acquired later in life if the body begins to produce antibodies that attack and destroy clotting factors. However, this acquired type of hemophilia is very rare. Acquired hemophilia is also called autoimmune hemophilia, or acquired hemophilia A (AHA). Both disorders can be detected before birth .Diagnostic tests that can identify Down syndrome include: Chorionic villus sampling (CVS). In CVS, cells are taken from the placenta and used to analyze the fetal chromosomes. This test is typically performed in the first trimester, between 10 and 13 weeks of pregnancy.Hemophilia diagnosis includes screening tests and clotting factor tests. Screening tests are blood tests that show if the blood is clotting properly. Clotting factor tests, also called factor assays, are required to diagnose a bleeding disorder. This blood test shows the type of hemophilia and the severity.Types of screening tests are complete blood count (CBC), activated partial thromboplastin time (APTT) test, prothrombin time (PT) test, and fibrinogen test. Yes babies are to be tested for genetic disorders before birth , if it identified before first trimester then MTP can be done , it is to decrease the number of genetically defective population