N5315 Advanced PathophysiologyGenetics Core Knowledge Objectives with Advanced Organizers Genetics Chapter 41. Analyze the pathological processes which alter the structure and role of the DNA and RNA molecules. a. Describe the structure and function of the DNA molecule and its clinical significance. PAGE 136-137i. Four types of nitrogenous bases of DNA include adenine, cytosine, guanine, and thymine commonly represented as their first letter. Physical structure of DNA is the double- helix model which can be envisioned as a twisting ladder with chemical bonds as its rungs. Projecting from each sideof the ladder at regular intervals are the nitrogenous bases. The bases projecting from one side is bound to the base projecting from the other by a weak hydrogen bond. Adenine pairs with thymine and Guanine pairs with cytosine. Each DNA subunit consists of one deoxyribose molecule, one phosphate group, and one base called a nucleotide. ii. Function of DNA1. Genetic code, serves as a basis of genetic inheritance and provide acode for all body’s proteins. iii.b. Evaluate the process of DNA replication and describe how it is altered by mutations. PAGE 137i. DNA must be able to replicate itself accurately during cell division to serve as basic genetic material. DNA replication consists of the breaking of the weak hydrogen bonds between the bases leaving a single strand with each base unpaired. The consistent pairing of adenine with thymine and guanine with cytosine is known as the complementary base pairingand is the key to accurate replication. In base pairing the unpaired base with attract a free nucleotide only if it has the proper complementary base.EXAMPLE- ATTGCT will bond with TAACGA. When replication is complete a new double strand molecule identical to the original is formed. Several proteins are involved in replication. One protein unwinds the double helix, one holds the strands apart and many other perform distinct functions. MOST IMPORTANT is DNA Polymerase. This enzyme travels along the single DNA strand adding the correct nucleotides to the free end of the new strand. DNA Polymerase also functions as a proofreader making sure the complementary base is correct. If not correct the incorrect nucleotide is excised and replaced with the correct one. This enhances the accuracy of DNA replication. Mutation can be any inherited alteration of genetic material. Example alterations in number of chromosomes or structure. ii. Many mutagens increase the frequency of genetic mutations these include radiation produced by x-rays and nuclear fallout, and many chemicals including nitrogen mustard, vinyl chloride, alkylating agents, formaldehyde and sodium nitrate. c. Differentiate between the types of DNA mutations and describe their clinical significance. PAGE 137-138DNA Mutation Type Definition Clinical Significance Base Pair SubstitutionOne base pair is replaced by another. Sometimes called missense mutation. Substitution can be a change in amino acid sequence but because of the redundancy of the genetic code may have no consequence. MANY OF THE SERIOUS DISEASES ARE CAUSE BY THIS MUTATION!!!Sense Mutation a mutation in which a base change or substitution results in a codon that causes insertion of a different amino acid into the growing polypeptide chain, giving riseto an altered protein.Frame Shift Mutation Insertion of deletion of one ormore base pairs to the DNA molecule. Can change the entire reading frame.d. Describe the structure and function of the RNA molecule and its clinical significance. PAGE 141i. RNA transmits genetic information from DNA to proteins produced by thecell. RNA carries out the instructions encoded in DNA. RNA is similar to DNA except thymine is replaced by uracil. RNA occurs in a single strand. e. Evaluate the processes of transcription, RNA splicing, and translation and explain the significance in the maintenance of health. PAGE 141-142i. Transcription1. Process which RNA is synthesized from a DNA template. Result isthe formation of messenger RNA (mRNA). Transcription begins when an enzyme called RNA polymerase binds to a promoter site on DNA. ii. RNA Splicing1.iii. translation f. Differentiate between the processes of translation and transcription. 2. Analyze the pathological processes which alter the structure and role of chromosomes.a. Describe the structure and function of chromosomes and their clinical significance. PAGE 142-143i. Gametes (sperm and egg cells) and somatic cells make up human cells. Each somatic cell has 46 chromosomes in its nucleus. These cells are diploid cells meaning the chromosomes occur in pairs with means there is 23 pairs of chromosomes. One member of the pairs comes from mother and one comes from father. 22 of the 23 pairs are virtually identical and are homologous in males and females and are termed autosomes. The remaining pair are sex chromosomes. Two X chromosomes in Females and X and Y in males. b. Differentiate between polyploidy, aneuploidy, autosomal aneuploidy, sex chromosome aneuploidy and describe the implications for clinical practice. PAGE143-147 Chromosomal Aberrations Definition Clinical ImplicationsPolyploidyWhen a euploid cell has more than the diploid number of chromosomes. Zygote having 3 chromosomes copies is a triploidy. Tertaploidy each euploid cells have 92 chromosomes. Several body tissues including liver, bronchial, andepithelial tissues are polyploidy. Nearly all triploidand tetraploid conceptions arespontaneously aborted or stillborn. Small proportion that survive to term die shortly after birth. Aneuploidy Cells that do not contain a multiple of 23 chromosomes. An aneuploidy contains 3 copies is trisomic. Monosomyis the presence of only 1 copyMonosomy is lethal. Newborns with trisomy chromosomes 13,18, or 21 can survive. Aneuploidy of the sex chromosome isof a given chromosome. usually less serious. For the Y chromosome very little genetic material is located. Azygote bearing no X chromosome will not survive.Autosomal Aneuploidy Abnormal number of autosomes.Trisomy 16 most common amongst abortuses, not seen in live births.Trisomy 13 (Patau syndrome)Trisomy 13 is cause by an extra chromosome 13.Trisomy 18 (Edwards syndrome)Trisomy 18 is caused by an extra chromosome 18Trisomy 21 (Down syndrome)Extra chromosome 21Sex Chromosome AneuploidyPAGE 147Abnormal sex chromosomes. Less severe than aneuploidy except when X is completely absent.Most common is Trisomy X.Females have there X
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