Molecular Genetics Genetic Mutations and Biotechnology 1 2

Molecular Genetics, Genetic Mutations, and Biotechnology 1

2 The Structure of DNA Erwin Chargaff analyzed the amount of adenine, guanine, thymine, and cytosine in the DNA of various species. He found that the amount of guanine nearly equals the amount of cytosine, and the amount of adenine nearly equals the amount off thymine within a species. Adenine and guanine are purine bases Cytosine and thymine are pyrimidine bases.

3 Base-Pairings Purines only pair with pyrimidines. Three hydrogen bonds are required to bond guanine and cytosine. Two hydrogen bonds are required to bond adenine and thymine.

4 Watson, Crick, and Franklin In 1953 two scientist named Watson and Crick discovered that DNA is made of two chains of nucleotides that are joined together at the nitrogen bases by hydrogen bonds. Rosalind Franklin using special X-ray techniques, discovered DNA is made of two strands and sugarphosphate molecules make up its backbone. Watson and Crick putting the information together discovered DNA is twisted into a shape called a double helix. Complementary base pairs make up the rungs of the double helix ladder structure.

5 Chromosomes in eukaryotic cells are found in the nucleus. Chromosomes in prokaryotic cells are found floating in the cytoplasm (either as a circle plastid or looks like puddled yarn). Chromosomes contain the genetic material of organisms. A gene is a section of DNA that carries the information on how to make proteins. Somatic or body cells multiply by the process of mi. Tosis, the number of chromosomes in the new daughter cells is the same or identical to the parent cell. When gametes or sex cells are formed by MEiosis, each gamete contains half the number of chromosomes as the parent cell.

6 Chromosomes are a single strand of DNA tightly coiled around a protein called a histone. A section of DNA that carries the information to make one protein is called a gene.

7 The Structure of DNA is a very long polymer of nucleotides mainly found in the nucleus. The basic shape is a double helix. A double helix looks like a twisted ladder. The strands run in opposite directions, antiparallel, of each other. One strand runs 5’ 3’, and the other runs 3’ 5’.

8 The Structure of DNA: Nucleotides DNA is a nucleic acid chain made up of nucleotides held together by covalent bonds. Each nucleotide is composed of 3 parts: Sugar – DEOXYRIBOSE Phosphate group Nitrogen bases Adenine (A) Thymine (T) Guanine (G) Cytosine (C)

9 The Structure of DNA has four kinds of nitrogenous bases: adenine (A), guanine (G), cytosine (C), and thymine (T) Hydrogen bonds form between A and T base pairs as well as between C and G base pairs. The nitrogenous bases stick out sideways from the nucleotide chain. The nucleotides can be joined together in any order, meaning that any sequence of the bases is possible.

DNA Replication 10 Before a cell divides, it duplicates its DNA in a copying process called DNA replication during S phase of interphase. DNA replication ensures that each resulting cell has the same complete set of DNA molecules. DNA replication is semi-conservative, which means it has a template strand that will match be used to make the new strand. The template will be part of the new helix. Replication Fork Original Strand New Strands DNA Polymerase

11 DNA Replication 1. Helicase, an enzyme, breaks down the hydrogen bonds between nucleotides. 2. DNA polymerase, an enzyme, grabs free floating nucleotides and adds them to the leading or lagging strand. It forms the sugar-phosphate backbone as it passes by. 3. The leading strand is continuous, the lagging strand is not. The lagging strand is made continuous by the enzyme DNA ligase.

12 Central Dogma Crick established The Central Dogma of Molecular Biology. It states information is transferred from DNA to RNA to proteins, but once the information is in the form of a protein, the transfer cannot be reversed. DNA –Transcribed RNA – Translated Proteins https: //www. youtube. com/watch? v=yq. E SR 7 E 4 b_8

13 Comparing DNA and RNA DNA Sugar – Ribose Sugar: Deoxyribose Single-stranded Double-stranded Uracil (A, G, C, U) Thymine (A, G, C, T)

14 Three Main Types of RNA messenger RNA (m. RNA) carries copies of instructions for assembling amino acids into proteins from DNA in the nucleus; carries the genetic message from DNA to the rest of the cell ribosomal RNA (r. RNA) forms parts of ribosomes (ribbons bundled together); the cell’s protein factories; “reads” the codon from m. RNA transfer RNA (t. RNA) transfers each amino acid to the ribosome as it is specified by the coded messages in m. RNA then adds the amino acid to the protein chain being assembled

15 Protein Synthesis Proteins are made in a two step process: -Part One: Transcription in the nucleus - Part Two: Translation happens at the ribosome

16 Transcription Genes contain coded DNA instructions that tell cells how to build proteins. The first step is decoding the genetic instructions is to copy part of the base sequence from DNA to RNA. Trans. Cription: Since DNA cannot leave the nucleus; free nucleotides use a strand of DNA to make m. RNA (messenger RNA) inside the nucleus. The m. RNA strand then leaves the nucleus and travels into the cytoplasm and uses the base sequence copied from DNA to direct the production of proteins.

17 Transcription

18 Codon These bases form a “language, ” or genetic code, with just four letters: A, C, G, and U. Each three-letter “word” in m. RNA is known as a codon. A codon consists of three consecutive bases that specify a single amino acid to be added to the protein chain.

19 Anticodons are three unpaired bases of t. RNA. These bases are complementary to m. RNA codons.

20 Translation Trans. Lation occurs at the ribosome. A three letter codon on m. RNA code for specific amino acids at the top of t. RNA. There are 64 different combinations or codons, but only 20 amino acids. When the amino acids link together in a peptide bond, they produce proteins. Genes directly control the synthesis of proteins. https: //www. youtube. com/watch? v=41_Ne 5 m. S 2 ls

21 Reading Codons Suppose you wanted to determine which amino acid is encoded by the CAU codon. Find the first base “C” in the left column. Find the second base “A” in the top row, Find the box where these two letters intersect. Find the third base “U” in the right column. Find where all three intersect. CAU codes for His (histidine) Stop codons indicate the protein is complete so the chain stops and the protein goes to where it is needed.

Codon Wheel: Read 3 letters at a 22 time, inside to outside.

23 Mutations are changes in the genetic material. Mutations that produce changes in a single gene are known as gene mutations. Gene mutations involving a change in one or a few nucleotides are known as point mutations because they occur at a single point in the DNA sequence. Point mutations include substitutions, insertions, and deletions. http: //learn. genetics. utah. edu/content/basics/mutation/

24 Substitutions usually affect no more than a single amino acid.

25 Frameshift Mutations The effects of insertions or deletions are more dramatic. The addition or deletion of a nucleotide causes a shift in the grouping of codons. Changes like these are called frameshift mutations. In an insertion, an extra base is inserted into a base sequence. In a deletion, the loss of a single base is deleted and the reading frame is shifted.

26 Chromosomal Mutations Nondisjunction is when a chromosome doesn’t separate correctly during meiosis; may result in a chromosomal mutation in offspring. Chromosomal mutations involve changes in the number or structure produce changes in the whole chromosomes. Chromosomal mutations include deletions, duplications, inversions, and translocations.

27 Examples Deletions involve the loss of all or part of a chromosome. Duplications produce extra copies of parts of a chromosome.

28 Examples Inversions reverse the direction of parts of chromosomes. Translocations occurs when part of one chromosome breaks off and attaches to another.

29 Significance of Mutations Many mutations have little or no effect on gene expression. Some mutations are the cause of genetic disorders. Polyploidy is the condition in which an organism has extra sets of chromosomes.

30 Disruption of the Cell Cycle: Cancer If an abnormal cell or a cell with mutations grows and divides uncontrollably, a tumor is formed. Benign tumors are noncancerous; they form a mass but do not invade and destroy healthy tissue. Benign tumors are called cysts. Malignant tumors are cancerous; they invade and destroy healthy tissue. Cancer results from cells growing and dividing abnormally and invading healthy tissues.

31 Disruption of the Cell Cycle: Cancer Carcinogens are environmental factors that damage DNA in cells and transforms the cells into cancer cells. Common examples of carcinogens are asbestos, UV radiation, xrays, some viruses (like HPV), and cigarette smoke. Carcinogens can cause a mutation and change the DNA sequence. If the gene that controls the cell cycle becomes mutated, it can become an oncogene, a gene that has potential to cause cancer. Cancer may result from uncontrolled cell division. Cells divide in an uncontrolled way by skipping the normal signals that shut down cell division. Metastasis is the spread of cancer to other areas of the body through either the blood or lymph vessels.

32 How Normal Cells Change After Cancer

33 Cancer Treatment One way of treating cancer is chemotherapy drugs that work by disrupting the cell cycle in cancer cells. The drawback is chemotherapy can also disrupt the cell cycle in normal cells. Radiation therapy is a type of cancer treatment that uses beams of intense energy to kill cancer cells. Radiation therapy most often uses X-rays, but protons or other types of energy also can be used. https: //www. youtube. com/watch? v=QVCjd. Nx. J re. E

34 Biotechnology DNA technology is often called gene technology. Genetic engineering involves manipulating and making changes in an organism's DNA that may include cloning, stem cell research, transgenic organism production, and DNA fingerprinting just to name a few.

35 Reproductive Cloning is the process of creating genetically identical copies of genes, cells, tissues, or entire organisms. DNA Reproductive cloning – process of creating an organism that is genetically identical to a donor cell How does it work? https: //www. youtube. com/watch? v=Yo. EWYJHf 0 k. U Just because we can, should we? https: //www. youtube. com/watch? v=6 -MNsjxq. Wr. M

36 Stem Cells Stem cells are undifferentiated cells that can be differentiate into other types of specialized cells https: //learn. genetics. utah. edu/content/stemcells/scintro/ Therapeutic cloning is a process of creating a cloned embryo specifically for harvesting its stem cells. Ethics https: //www. youtube. com/watch? v=d. Iy-z. Ca. Fa. Ww

37 Recombinant DNA Most DNA molecules are too large to be analyzed, so biologists cut them into smaller fragments using restriction enzymes. Recombinant DNA is used in producing insulin and producing growth hormones from different sources. examples: chickens that grow faster and make human insulin (Bacteria (Transformation)joined with human insulin) https: //www. youtube. com/watch? v=cg. Jmao. F 5 M 6 U https: //www. youtube. com/watch? v=glt 8 i. Aq. K 8 NQ Ethics: https: //www. youtube. com/watch? v=y. Ao. Oe 5 x 84 bc

38 Genetically Modified Transformation- the process used to place recombinant DNA back into a living organism Transgenic- term used to describe an organism that contains the DNA from a different organism using recombinant example: disease resistant plants Selective breeding allows only those organisms with desired characteristics to produce the next generation. Humans use selective breeding to pass desired traits on to the next generation of organisms. Nearly all domestic animals and most crop plants have been produced by selective breeding. https: //www. youtube. com/watch? v=p. Im. FFh. U 0 cl. I https: //www. youtube. com/watch? v=JMPE 5 wl. B 3 Zk

39 Selective Breeding Selective breeding involves choosing parents with particular characteristics to breed together and produce offspring with more desirable characteristics. Humans have selectively bred plants and animals for thousands of years including: crop plants with better yields ornamental plants with particular flower shapes and colors farm animals that produce more, better quality meat or wool dogs with particular physiques and temperaments, suited to do jobs like herd sheep or collect pheasants. Selective breeding aims to adapt an organism’s characteristics in a way that is desirable to the humans that breed them. https: //www. youtube. com/watch? v=a. QHBm. Y 6 Lbi. A

40 Gel Electrophoresis & DNA Fingerprinting Small DNA samples can be obtained from blood, hair, skin, or semen Technology that separates DNA fragments so they can be analyzed into a DNA fingerprint by using restriction enzymes It is used to find the similarities and differences in genomes of different organisms, identify parents, catch criminals, because no two people, except identical twins, have the exact same DNA https: //learn. genetics. utah. edu/content/labs/gel/

Who is guilty? 41

Who is guilty? 42

43 Who are the parents?

44 PCR: Polymerase Chain Reaction The polymerase chain reaction (PCR) is a biomedical technology in molecular biology used to amplify a single copy or a few copies of a piece of DNA across several orders of magnitude, generating thousands to millions of copies of a particular DNA sequence. https: //learn. genetics. utah. edu/content/labs/pcr/ https: //www. youtube. com/watch? v=0 HCWm. D 7 Mv 8 U

45 Human Genome Project The Human Genome Project was an international scientific research project with the goal of determining the sequence of nucleotide base pairs that make up human DNA, and of identifying and mapping all of the genes of the human genome from both a physical and a functional standpoint. The HGP has revealed that there are probably about 20, 500 human genes. The completed human sequence can now identify their locations. https: //www. youtube. com/watch? v=j. EJp 7 B 6 u_d. Y

53 How to read a Pedigree A diagram used by geneticists to chart a trait from one generation to the next Circle = Female Square = Male Fully Shaded = affected person Half-Shaded = Carrier (not affected, but carry the gene) Mating = connected by horizontal line Offspring = connected to parents by vertical line Generations = Roman numerals Death = line through it

54 A marriage with five children, two daughters and three sons. The eldest son is affected by the condition. Eldest child Youngest child

55 Sex-linked? Autosomal? Dominant? Recessive? Autosomal recessive traits and disorders show up in either male or female offspring from unaffected parents. Although it is not indicated, the parents must be carriers (heterozygous). If it is around a 50/50 ratio between men and women, the disorder is autosomal. If the disorder is dominant, one of the parents must have the disorder. Autosomal dominant traits will often show up in every generation. Both male and female offspring are affected equally. If one parent is heterozygous, about half the offspring will have the trait. If one parent is homozygous, every offspring will have the trait. Sex-linked traits are usually carried on the X chromosome. (Males XY; Females XX). Sex-linked will be similar to autosomal recessive except they will mainly show up in male offspring. Female carriers will have affected sons. . ALL daughters of affected male parent will be carriers. Rarely, sex-linked traits will be carried on the Y chromosome. Every male offspring of an affected male will have the trait every generation (Y comes from dad). Females are unaffected because they do not have a Y chromosome.

56 Autosomal Recessive disorders/traits Tay-Sachs disease Cystic fibrosis Sickle Cell Anemia Earlobe attachment (attached earlobes is a recessive trait) Being unable to roll your toungue Having a smooth chin Being left handed Straight hair

57 Dominant traits and diseases Marfan Syndrome Achondroplasia Widow’s peak Bent pinkies The way you cross your thumbs (left over right is dominant)

58 X-linked traits Red-green color blindness Hemophilia A (blood cannot clot)

59 Y-linked traits Male-ness

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61 Is this a sex-linked trait? No, it’s autosomal How do you know? About 50 of those affected are females.

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