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Molecular Genetics PowerPoint Presentation

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Description : Check out this medical titled "Molecular Genetics”.

This medical is about molecular genetics, the study of the structure and function of genes at a molecular level. It is a branch of genetics that focuses on the molecular basis of heredity and the mechanisms by which genetic information is stored, transmitted, and expressed.

Molecular genetics involves the study of DNA, RNA, and proteins, which are the building blocks of life. It seeks to understand how genes are regulated and how mutations in genes can lead to genetic disorders. The tools and techniques used in molecular genetics include DNA sequencing, PCR (polymerase chain reaction), gene cloning, gene expression analysis, and gene editing technologies like CRISPR-Cas9.

Molecular genetics has many practical applications, such as the diagnosis and treatment of genetic disorders, the development of new drugs and therapies, and the production of genetically modified organisms. It has also revolutionized our understanding of evolutionary relationships between different species and has provided insights into the origins of life itself.

Tags : Molecular Genetics, genes, molecular basis of heredity, genetic information, DNA, RNA, proteins, Medical Genetics, Medical Genetics

Published on : Jun 01, 2023 | Views : 1171 | Downloads : 17

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Slide 1-

Molecular Genetics What are chromosomes made of?
Slide 2-

I. Introduction A. Current definition of a gene 1. a unit factor controlling the inheritance of some external trait 2. a spot on a chromosome which influences some trait 3. a poppit bead on a string of poppet beads in the laboratory 4. going to flesh out in more detail what a gene is made of and what it does in our next unit
Slide 3-

B. Two questions are going to be answered in this part of the course 1. What is a gene made of? 2. What do genes do? How do genes control the activity of a cell?
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II. Two traits are necessary to be a good candidate for the stuff genes are made of A. a genetic molecule must be able to replicate with very few mistakes B. a good genetic candidate must be able to direct the activities of the cell’s cytoplasm from the confines of the nucleus
Slide 5-

III. Protein vs. DNA A. Basic structure of the two 1. protein 2. DNA B. Which is likely candidate?
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B. Series of historical experiments that determined the chemical nature of chromosomes 1. Friedrich Miescher (1869) a. 1869-not too long ago b. exposed cells to pepsin-a proteolytic enzyme c. the proteins in the cell’s cytoplasm were liquefied but the contents of the nucleus were left relatively intact d. it was believed at this time that the genes or controlling factors of inheritance were housed in the cell’s nucleus
Slide 7-

2. Feulgen a. developed a stain specific for nucleic acids b. what region of the cell took up the stain? c. all the somatic cells of an individual stained with the same intensity-what does that tell us about developmental processes? d. the germ cells of an organism stain with half the intensity as the somatic cells
Slide 8-

3. Griffiths Work Work involved two different strains of pneumococcus Smooth-virulent strain Rough-benign strain
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d. protocol
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e. results Dead S bacteria transformed the living R bacteria into a virulent strain Later determined that the fraction of the dead S bacteria that was the transforming agent was DNA
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4. Herschey and Chase
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a. structure of a bacteriophage
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b. how do viruses work?
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c. phage infection
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d. protocol
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IV. Molecular Structure of DNA A. Monomers of nucleic acids are nucleotides which consist of three basic parts 1. pentose sugar 2. phosphate and nitrogen base 3. notice that there are two classes of nitrogen containing bases a. purines b. pyrimidines
Slide 17-

Four examples of DNA nucleotides
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B. Polymers 1. Polymers of nucleotides are produced by dehydration synthesis of nucleotides in a 5’ to 3’ direction 2. this represents a single strand of DNA 3. If another nucleotide were to join this existing strand-to where would it attach? Which end?
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C. Watson and Crick built their model of DNA on the work of others Early sixties Done in England Physically built model seen to fit data of others Pieced together information Which one is which?
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1. Chargaff’s rule a. a number of species were investigated b. the percentage of different bases found in the DNA of each species was investigated c. found that the amount of adenine was about the same as the thymine d. the amount of guanine was about the same as the amount of cytosine e. at the time, did not know what to make of the discovery f. Chargaff data h. analysis
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2. Rosalind Franklin and X-ray diffraction study
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2. Rosalind Franklin a. Watson came across knowledge of the work at a tea party b. had not been exposed to the information before c. like a light bulb going off in his head d. recurring periodicities seen -.34 nm -3.4 nm -2.0nm
Slide 24-

3. Work of Linus Pauling a. worked on helical nature of proteins b. saw parallel in nucleic acid structure c. denied travel visa to attend a DNA conference that was being held in England d. linked to the communist movement in USA because he had opposed nuclear bomb used against Japan
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Diary of Pauling Diary shows complementary base pairing before proposed by Watson and Crick
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I believe that Linus Pauling won the Nobel Peace prize later in life
Slide 27-

V. DNA double helix A. Complementary base pairing as suggested by work of Chargaff and Franklin
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B. Double helix
Slide 29-

C. Properties 1. antiparallel 2. complimentary base pairing 3. periodicities seen 4. covalent vs. hydrogen bonding Importance of accessibility of information Where is information stored in the molecule
Slide 30-

5. The information in the DNA molecule is carried in the base pair sequence of the molecule 6. Notice also that because of complimentary base pairing, the two sides of the molecule are mirror images of each other 7. each strand contains the information needed to produce the second strand 8. Watson and Crick proposed an early model of replication in their first paper describing the structure of DNA
Slide 31-

VI. Replication A. Size of the problem 1. approximately 40,000 human genes in a nucleus 2. the length of the DNA in one human cell is approximately 2 meters 3. (length of 1 bp)(number of bp per cell)(number of cells in the body) = (0.34 x 10-9 m)(6 x 109)(1013) = 2 x 1013 meters 4. That is the equivalent distance from the earth to the sun and back.
Slide 32-

B. Semi-conservative model as proposed
Slide 33-

C. There were three possible modes of replication conservative mode-the parent molecule would remain intact while the newly synthesized molecule is totally brand new semi-conservative model-each new molecule of DNA is half new and the other half comes as a template from the parent 3. dispersive model-the two strands of the old molecule would break up and be scattered in the composition of the two new molecules
Slide 34-

D. Work of Meselsohn and Stahl Verified the semiconservative nature of DNA replication Used heavy nitrogen technology introduced by Kornberg along with in vitro DNA replication
Slide 35-

3. Protocol
Slide 36-

E. Replication-the real story 1. Mentioned above the sheer size of the DNA molecules in the nucleus a. the amount of information held in the nucleus is enough to fill 600 volumes of 500 pages each b. the enzymes copying DNA add 100 nucleotides together per second in mammals c. 1000 nucleotides together per second in bacterial cells d. huge amount of information to be processed
Slide 37-

2. Very accurate process-not a duplication event a. one in every billion base pairs there is a mistake b. in the typing of the 600 volumes above, that would translate to about 4 mistakes
Slide 38-

3. Replication origins replilcation can start at the beginning of the molecule as well as internally at special recognition sites
Slide 39-

4. Helicases unwind double helix a. double helix must be unwound in order for the templates to be accessed by free nucleotides b. single stranded binding proteins also keep the separated strands separated
Slide 40-

5. DNA polynucleotide strands cannot start from nothing a. the first nucleotide must connect to something else b. RNA primer piece must be laid down first c. notice that with many replication forks, this piece of primer must be laid down every time a new section of DNA is manu.
Slide 41-

6. Nucleotides add to a growing chain in the 5’ to 3’ direction a. new bases cannot add onto the 5’ end of the polynucleotide chain b. DNA is an antiparallel molecule c. at the replication fork this causes confusion d. DNA polymerase can only operate in one direction
Slide 42-

6. cont. e. terms to know: leading strand, lagging strand, Okazaki fragments, ligase f. the Okazaki fragments are 1000-2000 fragments long in bacteria g. the Okazaki fragments are 100-300 fragments long in mammals h. the Okazaki fragments are joined by an enzyme called ligase
Slide 43-

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7. Summary Slide
Slide 45-

8. The final problem a. Chromosomes shorten with repeated divisions b. The position where the primer RNA was found on the leading strand leaves a gap at the end with each replication c. The daughter molecules get shorter and shorter d. Important information can be eroded
Slide 46-

e. telomeres are basically like buffers f. able to be eroded away without getting into the coding sequence of the chromosomes g. repeating nucleotide base sequence TTAGGG h. there may be over 100 to 1000 of these repeats
Slide 47-

8. The final problem cont. i. telomerase not present in all cells j. lack of enzyme and shortening of chromosomes may be a built in clock for life of cell k. telomerase is present in germ lines l. also present in tumors which exhibit uncontrolled mitotic divisions
Slide 48-

VII. VII. What is a chromosome anyways?2 A. Recall that each nucleus possesses about 2 meters of DNA B. It appears as chromatin in a nondividing cell C. In a mitotic cell the chromatin must be organized to accomplish an efficient division process
Slide 49-

D. Terms to remember 1. Histone proteins 2. Nucleosomes 3. Scaffolding proteins
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