Module 3 - Genetics & Information Transfer.pptx

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1. Dr. Pravin D. Patil Module 3 Genetics & Information Transfer

2. What is genetics Mendel’s law Gene interactions Single Gene Disorders Genetic Material and Genetic Code DNA Replication Protein Synthesis, Central Dogma of Life: Transcription and Translation 2 Objectives:

3. 3 Genetics:

4. Genetics is a field of biology that studies how traits are passed from parents to their offspring. The passing of traits from parents to offspring is known as heredity ; therefore, genetics is the study of heredity. Genetics is built around molecules called DNA. DNA molecules hold all the genetic information for an organism. It provides cells with the information they need to perform tasks that allow an organism to grow, survive and reproduce. 4 Genetics: The passing of traits from parents to offspring is known as heredity

5. Humans have 23 pairs of chromosomes--22 pairs of numbered chromosomes, called autosomes , and one pair of sex chromosomes , X and Y. Each parent contributes one chromosome to each pair so that offspring get half of their chromosomes from their mother and half from their father. 5 Genetics:

6. A gene is one particular section of a DNA molecule that tells a cell to perform one specific task. Heredity is what makes children look like their parents. During reproduction, DNA is replicated and passed from a parent to their offspring. This inheritance of genetic material by offspring influences the appearance and behavior of the offspring. The environment that an organism lives in can also influence how genes are expressed. 6 Genetics:

7. 7 Genetics: The passing of traits from parents to offspring is known as heredity

8. 8 Genetics: Meiosis and Formation of zygote

9. 9 Genetics:

10. 10 Mendel’s Experiment What does the word "inherit" mean? You may have inherited something of value from a grandparent or another family member. To inherit is to receive something from someone who came before you. You can inherit objects, but you can also inherit traits. For example, you can inherit a parent's eye color, hair color, or even the shape of your nose and ears! Gregor Johann Mendel conducted hybridization experiments on garden pea ( Pisum sativum ) for seven years (1856-1863) and proposed the laws of inheritance in living organisms. He is also known as Father of Genetics.

11. 11 Mendel’s Experiment: He selected garden pea plant as a sample for following reasons: ( i ) Pea is available in many varieties on a large scale to observe alternate traits. (ii) Peas are self-pollinated and can be cross-pollinated also to prevent self-pollination. (iii) These are annual plants with a short life cycle. So, several generations can be studied within a short period. (iv) Pea plants could easily be raised, maintained and handled. (v) Many varieties are available with distinct characteristics, which provide many easily detectable contrasting characters.

12. 12 Mendel’s Experiment: Pollination is the transfer of pollen from a male part of a plant to a female part of a plant, later enabling fertilization and the production of seeds, most often by an animal or by wind.

13. 13 Mendel’s Experiment: Mendel conducted artificial pollination/cross-pollination experiments using several true-breeding pea line. A true-breeding line refers to one that have undergone continuous self-pollination and showed stable trait inheritance and expression for several generations. Mendel selected 14 true-breeding pea plant varieties, as pair, which were similar except for one character with contrasting traits.

14. 14 Terminology: Gene A gene is the basic physical and functional unit of heredity. Genes are made up of DNA. Some genes act as instructions to make molecules called proteins. However, many genes do not code for proteins. In humans, genes vary in size from a few hundred DNA bases to more than 2 million bases. Every person has two copies of each gene, one inherited from each parent. Most genes are the same in all people, but a small number of genes (less than 1 percent of the total) are slightly different between people. Allele Since human cells carry two copies of each chromosome, they have two versions of each gene. These different versions of a gene are called alleles. Alleles can be either dominant or recessive.

15. 15 Terminology: Homozygous – An individual with two identical alleles. Heterozygous – An individual with two different alleles.

16. 16 Terminology: F1 generation : The hybrid offspring of the parental generation. F2 generation : The self-fertilized progenies of F1 generation plants Monohybrid cross : A cross between parents differing in only one trait or characters. Dihybrid cross : A cross between parents differing in two traits or characters.

17. 17 Character : Morphological, Anatomical or behavioural feature of an organism - Genotype - Phenotype

18. 18 Concepts of recessiveness and dominance : Different versions of a gene are called alleles. Alleles are described as either dominant or recessive, depending on their associated traits. Since human cells carry two copies of each chromosome, they have two versions of each gene. These different versions of a gene are called alleles. Alleles can be either dominant or recessive. Dominant alleles show their effect even if the individual only has one copy of the allele (also known as being heterozygous).

19. 19 Concepts of recessiveness and dominance : If both alleles are dominant, it is called co-dominance . The resulting characteristic is due to both alleles being expressed equally. An example of this is the blood group AB which is the result of co-dominance of the A and B dominant alleles. Recessive alleles only show their effect if the individual has two copies of the allele (also known as being homozygous). For example, the allele for blue eyes is recessive, therefore to have blue eyes you need to have two copies of the 'blue eye' allele.

20. 20 Punnett square :

21. 21 Punnett square : The Punnett square is a square diagram used to predict the genotypes of a cross or breeding experiment. It is named after Reginald C. Punnett, the biologist who devised the approach. Biologists use the Punnett square to determine the probability of an offspring having a particular genotype. The Punnett square is a tabular summary that shows possible combinations of maternal and paternal alleles, allowing examination of genotypical outcome probabilities for single or multiple trait crosses.

22. 22 Laws of Genetics : Mendel's Laws of Heredity are usually stated as: 1) The Law of Segregation: During the formation of gametes, the paired alleles separate (segregate) randomly so that each gamete receives one allele or the other. The two alleles of a gene present in the F1 (Filial-child) do not contaminate each other; they separate and pass into different gametes in their original form producing two different types of gametes in equal proportion. 2) The Law of Independent Assortment: Genes for different traits are sorted separately from one another so that the inheritance of one trait is not dependent on the inheritance of another. 3) Law of Dominance: Incomplete and co-dominance

23. 23 Laws of Genetics :

24. 24 Laws of Genetics :

25. 25 Gene interaction : Incomplete Dominance or Blending Inheritance (1:2:1): A dominant allele may not completely suppress other allele, Here F1 hybrids are not related to either of the parents but exhibit blending of characters of two parents. In Mirabilis jalapa , the cross between pure bred red-flowered and white-flowered plants yields pink-flowered F1 hybrid plants (deviation from parental phenotypes), i.e., intermediate of the two parents. When F1 plants are self-fertilized, the F2 progeny shows three classes of plants in the ratio 1 red: 2 pink: 1 white, instead of 3:1

26. 26 Gene interaction : Co-dominance: Here both the alleles of a gene express themselves equally in F1 hybrids. Phenotypes of both the parents appear in F1 hybrid rather than the intermediate phenotype. In human, MN blood group in man is an example of co-dominance. The persons with MN blood type produce both antigen M and N and not some intermediate indicating both the genes are functional.

27. 27 Father (Black eyes) (B 1 Br) Mother (Blue eyes) (B 2 Br)

28. 28 Gene mapping: Gene mapping describes the methods used to identify the locus of a gene and the distances between genes . Assigning/locating of a specific gene to particular region of a chromosome and determining the location of and relative distances between genes on the chromosome is called gene mapping. A locus in genetics is a fixed position on a chromosome, like the position of a gene or a marker. Each chromosome carries many genes. Human's estimated protein coding genes are 19,000–20,000, on the 23 different chromosomes. A variant of the similar DNA sequence located at a given locus is called an allele. The ordered list of loci known for a particular genome is called a gene map. Gene mapping is the process of determining the locus for a particular biological trait.

29. 29 Gene mapping: Researchers begin a genetic map by collecting samples of blood or tissue from family members that carry a prominent disease or trait and family members that don't. Scientists then isolate DNA from the samples and closely examine it, looking for unique patterns in the DNA of the family members who do carry the disease and DNA of those who don't carry the disease. These unique molecular patterns in the DNA are referred to as polymorphisms, or markers. In gene mapping, any sequence feature that can be faithfully distinguished from the two parents can be used as a genetic marker. Genes, in this regard, are represented by "traits" that can be faithfully distinguished between two parents.

30. 30 Gene mapping:

31. 31 Gene mapping: Disease Diagnosis: Identifies genes causing disorders for better diagnostics. Personalized Medicine: Enables tailored treatments based on genetic profiles. Evolution Insights: Shows genetic links across species. Agriculture: Enhances crop/livestock traits via targeted breeding. Forensics: Supports DNA-based identification. Research: Drives discoveries in gene function and regulation.

32. 32 Single gene disorders in humans: Single gene disorders are caused by DNA changes in one particular gene, and often have predictable inheritance patterns. Over 10,000 human disorders are caused by a change, known as a mutation , in a single gene . These are known as single gene disorders . The mutated version of the gene responsible for the disorder is known as a mutant , or disease, allele . Individually, single gene disorders are very rare, but as a whole, they affect about one per cent of the population . Since only a single gene is involved, these disorders can be easily tracked through families and the risk of them occurring in later generations can be predicted. Single gene disorders can be divided into different categories: dominant, recessive and X-linked.

33. 33 Single gene disorders in humans:

34. 34 Dominant diseases: Dominant diseases are single gene disorders that occur in the heterozygous state – when an individual has one mutant copy of the relevant gene and one healthy copy. The effects of the mutant version of the gene (allele) override the effects of the healthy version of the gene. So, the mutant allele causes disease symptoms even though a healthy allele is present. Father Mother

35. 35 Dominant diseases: Dominant disorders tend to crop up in every generation of an affected family because everyone carrying a dominant mutant allele shows the symptoms of the disease. Dominant disorders spread vertically down family trees, from parent to child. In rare cases when an individual has two copies of the mutant gene (also known as being homozygous) the disorder symptoms are generally more severe. An example of a dominant single gene disorder is Huntington’s disease , which is a disease of the nervous system. Father Mother

36. 36 Recessive diseases: Recessive diseases are single gene disorders that only occur in the homozygous state - when an individual carries two mutant versions (alleles) of the relevant gene. The effects of the healthy allele can compensate for the effects of the mutant allele. The mutant allele does not cause disease symptoms when a healthy allele is also present. However, if a parent inherits two mutant alleles, there are no healthy alleles, so the mutant allele can exert its effect. Examples: Cystic Fibrosis, Sickle Cell Anemia

37. 37 Recessive diseases: Recessive diseases are more difficult to trace through family trees because carriers of a mutant allele do not show symptoms of the disease. It therefore appears that the disease has skipped a generation when it is seen in groups of children within a family. Dominant (Healthy gene) Recessive (Abnormal gene) Father Mother

38. 38 Recessive diseases: The risk of an individual having a recessive disorder increases when two people who are closely related have a child together (consanguinity). This is because there is a much greater chance that the same mutant allele will be present in related parents. Dominant (Healthy gene) Recessive (Abnormal gene) Father Mother

39. 39 X-linked disorders: X-linked disorders are single gene disorders that result from the presence of a mutated gene on the X chromosome. Because females (XX) have two copies of the X chromosome but males (XY) only have one copy, X-linked disorders are more common in males. If a male’s single copy on the X chromosome is mutated, he has no healthy copy to restore healthy function. The inheritance patterns of X-linked diseases are simplified by the fact that males always pass their X chromosome to their daughters but never to their sons. Like other single gene disorders, X-linked disorders can be either recessive or dominant. Male Sex Chromosomes Female Sex Chromosomes Father Mother X X X Y X X X Y X X X Y X Y X X

40. 40 X-linked dominant diseases: Male Sex Chromosomes Female Sex Chromosomes Father Mother X X X Y X X X Y X X X Y X Y X X Ex. Rett syndrome (a brain disorder)

41. 41 X-linked recessive diseases: Male Sex Chromosomes Female Sex Chromosomes Father Mother X X X Y X X X Y X X X Y X Y X X Ex. Male pattern baldness, red-green color blindness, and hemophilia A

42. Dr. Pravin Patil Information Transfer

43. 43 Introduction : Genetic Composition

44. Nucleic acid structure (DNA Diagram): The following diagram explains the DNA structure representing the different parts of the DNA. DNA comprises a sugar-phosphate backbone, and the nucleotide bases (guanine, cytosine, adenine and thymine). 44 Genetic Composition :

45. The DNA structure can be thought of like a twisted ladder. This structure is described as a double-helix, as illustrated in the figure above. It is a nucleic acid, and all nucleic acids are made up of nucleotides. The DNA molecule is composed of units called nucleotides, and each nucleotide is composed of three different components, such as sugar, phosphate groups, and nitrogen bases. 45 Genetic Composition : DNA Structure

46. The basic building blocks of DNA are nucleotides, which are composed of a sugar group, a phosphate group, and a nitrogen base. The sugar and phosphate groups link the nucleotides together to form each strand of DNA. Adenine (A), Thymine (T), Guanine (G) and Cytosine (C) are four types of nitrogen bases. 46 Genetic Composition : DNA Structure

47. These 4 Nitrogenous bases pair together in the following way: A with T, and C with G. These base pairs are essential for the DNA’s double helix structure, which resembles a twisted ladder. 47 Genetic Composition : DNA Structure

48. The order of the nitrogenous bases determines the genetic code or the DNA’s instructions. Among the three components of DNA structure, sugar is the one which forms the backbone of the DNA molecule. It is also called deoxyribose. The nitrogenous bases of the opposite strands form hydrogen bonds, forming a ladder-like structure. (DNA Structure Backbone) 48 Genetic Composition : DNA Structure

49. 49 Concept of genetic code:

50. 50 Concept of genetic code:

51. 51 DNA to DNA DNA to mRNA Concept of genetic code:

52. Main functions of Nucleic Acid: 1. Replication process: Transferring the genetic information from one cell to its daughters and from one generation to the next and equal distribution of DNA during the cell division 2. Mutations: The changes which occur in the DNA sequences 3. Transcription 4. Cellular Metabolism 5. DNA Fingerprinting 6. Gene Therapy 52 Function of Nucleic Acid:

53. 53 DNA Replication vs Central Dogma of Life:

54. DNA replication, also known as semi-conservative replication, is the process by which DNA is essentially doubled. It is an important process that takes place within the dividing cell. In this article, we shall look briefly at the structure of DNA, at the precise steps involved in replicating DNA (initiation, elongation and termination), and the clinical consequences that can occur when this goes wrong. 54 DNA Replication:

55. 55 DNA Replication

56. DNA replication is a complex process that ensures the accurate duplication of genetic material. It involves the coordination of various enzymes to unwind the DNA double helix, synthesize new strands, and proofread for errors. Here is a step-by-step explanation of DNA replication, along with the six enzymes involved: Step 1: Helicase Helicase is an enzyme that unwinds the DNA double helix by breaking the hydrogen bonds between the complementary base pairs. It separates the two DNA strands, forming a replication fork. 56 DNA Replication: Steps

57. Step 2: Primase: Primase is an enzyme that synthesizes RNA primers. It adds short RNA sequences called primers to the DNA template strands. These primers provide a starting point for DNA polymerase to initiate DNA synthesis. Step 3: DNA Polymerase III: DNA Polymerase III is the main enzyme responsible for DNA synthesis during replication. It adds nucleotides to the growing DNA strand, using the parental DNA strands as templates. DNA Polymerase III can only add nucleotides in the 5' to 3' direction, so it synthesizes the new DNA strand in a continuous manner on the leading strand. 57 DNA Replication: Steps

58. Step 4: Exonuclease: Exonucleases are enzymes that remove RNA primers from the DNA template. After the RNA primers are synthesized by primase, exonucleases degrade them, creating gaps in the DNA strands. Step 5: DNA Polymerase I: DNA Polymerase I is an enzyme that fills in the gaps left by the removal of RNA primers. It replaces the RNA nucleotides with DNA nucleotides, ensuring that the DNA strands are fully continuous. DNA Polymerase I also possesses exonuclease activity, allowing it to proofread and correct any errors that may have occurred during replication. 58 DNA Replication: Steps

59. Step 6: Ligase: Ligase is the final enzyme involved in DNA replication. It seals the nicks or gaps in the DNA backbone by catalyzing the formation of phosphodiester bonds between adjacent nucleotides. Ligase ensures the integrity and continuity of the newly synthesized DNA strands. Overall, the coordinated action of helicase, primase, DNA Polymerase III, exonuclease, DNA Polymerase I, and ligase allows for the faithful replication of DNA, preserving the genetic information during cell division and ensuring the inheritance of genetic traits. 59 DNA Replication: Steps

60. 60 DNA Replication:

61. 61 Central dogma of life :

62. 62 Central dogma of life :

63. 63 Central dogma of life :

64. To summarize what we know to this point, the cellular process of transcription generates messenger RNA (mRNA), a mobile molecular copy of one or more genes with an alphabet of A, C, G, and uracil (U). Translation of the mRNA template converts nucleotide-based genetic information into a protein product. This flow of genetic information in cells from DNA to mRNA to protein is described by the Central Dogma, which states that genes specify the sequence of mRNAs, which in turn specify the sequence of proteins. 64 Central Dogma of Life: Concept of genetic code:

65. The decoding of one molecule to another is performed by specific proteins and RNAs. Because the information stored in DNA is so central to cellular function, it makes intuitive sense that the cell would make mRNA copies of this information for protein synthesis, while keeping the DNA itself intact and protected. 65 Concept of genetic code:

66. 66 Central dogma of life :

67. 67 Thank you…