01 History of Human Genetics and Cytogenetics — Transcript

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1. 0:27Good Morning dear students! Under the human genetic course,
2. 0:33there are four  units. Under the unit 1-
3. 0:39The first model is History of  human genetics and cytogenetics
4. 0:46The main objectives of this module are- - To know about the origin of human genetics.
5. 0:56- To know about the human cytogenetics. - To know about molecular genetics and,
6. 1:03- To know the scope of genetics.
7. 1:07Since the dawn of civilization, man influences  heredity and used for the improvement of
8. 1:16cultivation of crops and domestic animals, for example, Cross pollination of date-palms trees
9. 1:27and pedigrees of horses with  inherited characteristics.
10. 1:33However, the first recorded speculations  on heredity were seen, as a time of the
11. 1:43Ancient Greeks, and some of their ideas  are still considered relevant today.
12. 1:52The most influential early theories of  heredity were the Hippocrates and Aristotle.
13. 2:04Hippocrates (The father of Medicine) believed  in the inheritance of acquired characteristics.
14. 2:14He postulated pangenesis, that is all organs of  the body of a parent gave of invisible seeds.
15. 2:28These were like miniatures, building,  components, and were transmitted during sexual
16. 2:36intercourse resembling themselves  in the mother's womb to form a baby.
17. 2:44Later Aristotle proposed the role of blood in  heredity, where in semen and the menstrual
18. 2:58blood  of the purified blood, the  hereditary essences makes the baby.
19. 3:07Even today people still speak  of certain traits as being
20. 3:14"in the blood" and of "bloodlines"  and "blood ties" etcetera.
21. 3:23This is different from that of Mendel's idea,  where powerful hereditary factors called genes,
22. 3:33determine the distinct  differences between individuals.
23. 3:40These genes are transmitted  through sperms and eggs,
24. 3:47and guide the development of the as offspring*. Therefore, the genes are responsible for
25. 3:54reproducing the distinct features of both  parents, that are visible in their children.
26. 4:03However, most of the mechanisms  of heredity remains a mystery,
27. 4:10until the 19th century, when  genetics as systematic science begun.
28. 4:19Genetics can be defined as the study of  genes including the ways they act in the cell
29. 4:28and the ways they are transmitted  from parents to offspring.
30. 4:34In 1901, the word GENETIC was introduced  by English biologist William Bateson
31. 4:45who propagate Mendel's work and the champion  of Mendel's principles of inheritance.
32. 4:54Hence, In this episode the following  aspects are going to be emphasized-
33. 5:01A- Origin of genetics. B- The saga of human cytrogenetics.
34. 5:08C- Molecular genetics and beyond. D- The scope of genetics.
35. 5:16Let us understand each of these aspects now.
36. 5:25The origin of genetics lies during the time  of development of theories of evolution.
37. 5:34In 1858, Charles Darwin and Alfred valets developed the theory of the Origin of Species  by natural selection.
38. 5:47However,  they did not know the role of genes had to play in this phenomenon.
39. 5:57In 1865, Gregor Mendel conducted experiments  on inheritance and genetics of pea plants and
40. 6:07described the unit of heredity as a particle  without change passed on to offspring.
41. 6:17He observed that organism inherit traits by  the way of discrete the unit of inheritance.
42. 6:30This work provided the mathematical  foundation of the science of genetics, but
43. 6:37the scientific community did not recognized his work at that time,
44. 6:44because most biologists during his time had the idea that all characteristics were passed
45. 6:52to the next generation through blending inheritance, In which, traits from each parents are averaged.
46. 7:02This work is a basis of understanding  the principles of genetics even today.
47. 7:10For this contribution Gregor Mendel  is known as the father of genetics.
48. 7:19In 1866, Ernst Haeckel correctly  predicted that the hereditary material
49. 7:27was located in the nucleus.
50. 7:31Later on during 1869, Johann Friedrich Miescher
51. 7:40identified both phosphorus and nitrogen in  the nuclei of white blood cells found in pus.
52. 7:49The substance first named nuclein as  it seems to come from the cell nuclei,
53. 7:57and was later called as nucleic acid after 1874.
54. 8:04He concluded that one DNA molecule alone could not  provide
55. 8:11the level of variation observed in nature within and between species.
56. 8:20Chromosomes as units carrying genetic information  were also discovered around this time.
57. 8:28Mendel's work was rediscovered in 1900 by three Botanists- Hugo de Vries of Holland,
58. 8:39Carl Correns  of Germany, and Eric von Tschermak of Austria.
59. 8:48- Each conceived the idea of experiments  similar to Mendel's.
60. 8:55- Each independently discovered Mendel's paper.
61. 9:01- After a lengthy gestation of 35 years,  the science of Genetics was finally born.
62. 9:11In 1902, William Bateson published an  English translation of Mendel's German text,
63. 9:21Mendelism the principles of dominance,  segregation, and independent assortment.
64. 9:30Walter sutton and Theodor Boveri in 1902 led the  development of Chromosomal Theory of Inheritance
65. 9:41and established that the heredity  material resides in chromosomes.
66. 9:48In 1908, Archibald Garrod proposed  that inborn errors of metabolism
67. 9:59caused human disease alkaptonuria and  certain other hereditary diseases.
68. 10:07During 1905 to 1930 extension of Mendelian principles with linkage,
69. 10:18Hardy-Weinberg  principles of genetic equilibrium, sex linkage, genetic mapping,
70. 10:25number of linkage groups, number of chromosomes, lethal genes,
71. 10:31maternal inheritance were established.
72. 10:36This led to the understanding of the mechanism  of transmission and functions of genes.
73. 10:45After 1955 onwards, several break  throughs were seen in human genetics,
74. 10:55which had been stagnant for a long time.
75. 11:05Cytogenetics is a study of the chromosome   their inheritance and function.
76. 11:12- In 1865, Virchow published the first diagram of mammalian chromosomes from the testes of a cat.
77. 11:25- In 1879, Walter Flemming developed a new staining technique to identify chromosomes,
78. 11:36which allowed observation of the chromosomes in the cell nucleus during normal cell division.
79. 11:45- In 1882, he coined the term mitosis for cell division.
80. 11:54- In 1887, Van Beneden discovered the   number of in any body cell is constant
81. 12:06and the number characterizes a certain species.
82. 12:11He also contributed to the discovery, and the naming of meiosis.
83. 12:20In the same year Wiseman predicted  the reduction division in the meiosis.
84. 12:28In 1888, Henrich von Waldeyer who coined  the term 'Chromosome' to describe them.
85. 12:41- Mclung in 1901, named the sex chromosome
86. 12:50which was different in males and female grasshoppers.
87. 12:57In 1903, sutton and Boveri  independently hypothesizes
88. 13:05that chromosomes are the hereditary units.
89. 13:11Later in 1910, Thomas saint Morgan showed that
90. 13:17genes reside on chromosome while determining  their sex-linked traits in drosophila.
91. 13:26In 1911, Alfred Sturtevant one of the  Morgan student invented the procedure for
92. 13:37linkage mapping in Drosophila, and made the  first genetic map of a chromosome in 1930.
93. 13:49The progress of humans cytogenetics could be seen in four phases.
94. 13:551- Dark Ages- before 1952.
95. 14:01It took many years to settle the most  fundamental question in cytogenetics,
96. 14:08that is the correct diploid chromosome number.
97. 14:12- In 1912, Hans von Winiwarter reported 47  chromosomes in sperm and 48 chromosomes
98. 14:22in egg concluding an XX/XO sex determining mechanism.
99. 14:31- Painter in 1922, revised his opinion to 48 from 46
100. 14:40and correctly insisted that humans have  an XX/XY system of sex determination.
101. 14:53- Painter's study on human chromosomes
102. 14:57was by arresting cells during  division and visualize them.
103. 15:03He also used staining techniques, which allowed for limited differentiation of specific chromosomes.
104. 15:12Based on darkly versus state lightly stained areas.
105. 15:18The number of human chromosomes remained  48 for over 30 years in science books.
106. 15:272- Hypotonic Period 1952 to 59.
107. 15:34During the spirit, so use a solution with a low salt concentration,
108. 15:43and the cells absorb water through the membrane and swell, but not burst.
109. 15:52However, Chromosome readily separated   and make them easier to count.
110. 15:59The correct number and morphology of the human chromosome could not be identified
111. 16:07for 60 years after first study by Fleming's.
112. 16:14In 1956, theZO and Levon had  analyzed 265 preparations
113. 16:25from 22 different cell cultures  made from the embryonic lung tissues
114. 16:33of four different legally aborted embryos.
115. 16:38They reported that the karyotype of females was 46 xx and males 46 xy.
116. 16:503- Trisomy period 1959 to 69.
117. 16:57The development of method to determine  the human karyotype enhanced discoveries
118. 17:04of a variety of aberration in the  number and morphology of chromosomes.
119. 17:13The first Trisomy 21 was discovered  in 1959 by Lejeune and his colleagues.
120. 17:24Their paper is still recognized as  one of the classic in human genetics.
121. 17:32Later, calcetto syndrome by  Jacobs and Strong in 1959.
122. 17:40Turner syndrome by Ford and his colleagues in 1959
123. 17:46and POTS* syndrome by POTS and his  colleagues in 1963 were discovered.
124. 17:58The metaphase chromosomes were  then classified into seven groups,
125. 18:04based on the Denver classification in 1960,
126. 18:09with revisions at the London conference in  1963, and at the Chicago conference in 1966.
127. 18:214- Banding Era- 1969 to 79.
128. 18:28Two techniques revolutionized the study of human chromosomes.
129. 18:34The first was a report of Caspersson and his associate in 1970 that certain fluorescent
130. 18:45derivatives of quinacrine bind differently to different parts of the chromosomes.
131. 18:55This is called as Q-banding. This technique was less than
132. 19:01optimal for routine studies as the  fluorescent staining quickly quenched.
133. 19:10Hence, several other banding techniques were  developed for example- G-R-C and NOR banding.
134. 19:21Each having its specific  properties and applications.
135. 19:26Later, G banding became the most  prominent and frequently used
136. 19:33method as it gave better resolution  than the Q banding and also allowed
137. 19:40permanent preparations, and did not  necessitate the use of fluorescence microscopy.
138. 19:50Pardue and Gall in 1970 first reported  C- bands, when they discovered that
139. 19:59centromeric region of mouse chromosome  or rich in repetitive DNA sequences.
140. 20:08Nucleolar organizing region and war* banding  techniques stains the an hour of the chromosome.
141. 20:18Goodpasture's and Discolleagues in 1975 developed  this simple cellar staining technique,
142. 20:28which is  useful in clinical practice to study specific  chromosome polymorphism, such as double satellite.
143. 20:41The second technical development was  the high-resolution banding technique,
144. 20:48This technique help in identifying the  small chromosomal aberration more elegantly.
145. 20:565- Molecular era- 1980 onwards.
146. 21:01In 1980's,  Pardue and Gall developed a method to visualize chromosomes using
147. 21:11fluorescent-labelled probes called Fluoroscent  in-situ Hybridization(FISH) in tissue samples.
148. 21:20This allowed the detection of chromosomal  abnormality that involve small segments of DNA.
149. 21:32Based on these principles advanced  techniques were later made
150. 21:39such as Spectral Karyotyping and multiplex fish.
151. 21:44SKY technique was developed by   stroke and his colleague in 1996.
152. 21:52Which allowed the investigator to unambiguously display and identify all the human chromosomes
153. 22:01at one time without any prayer*   knowledge of any abnormalities involved.
154. 22:10Today, there are many ways to attach molecular labels to particular genes and chromosomes
155. 22:20the specific RNAs and proteins.
156. 22:23These molecules are significantly  facilitating cytogenetic research.
157. 22:37Molecular genetics began only after 1941, when George Wells Beadle and Edward Lawrie Tatum
158. 22:46showed that the genes are coding for  catalytic protein called enzymes.
159. 22:55Subsequent studies in other organisms showed  that genes generally code for proteins.
160. 23:05Further Oswald Avery, Colin M. MacLeod  and Maclyn McCarty showed that that
161. 23:16Bacteria genes are made up of DNA. This was later extended to all organisms.
162. 23:25A ground breaking discovery was attained  in 1953, when James D Watson Francis Crick
163. 23:36and Racing Wilson created a double  helical model for DNA structure.
164. 23:45They demonstrated that DNA is capable of self replications by
165. 23:51separating  its complementary strands.
166. 23:55These strands act as templates for  the synthesis of new DNA molecules.
167. 24:03Each strand of DNA was made up of four nucleotide.
168. 24:09They also proposed that a specific nucleotide sequence of DNA could contain a code for
169. 24:16an amino acid sequence, and hence protein structure.
170. 24:23In 1955, Symovenger demonstrated  that the mutant sites within a gene.
171. 24:33Which can be mapped to each other,
172. 24:37the linear map indicated that the gene itself is a linear structure.
173. 24:45- In 1958, The semi conservative method of DNA replication was demonstrated experimentally
174. 24:54for the first time by  Matthew Meselson and Franklin's taught.
175. 25:01- In 1961, Francis Crick and Sydney Brenner   showed that the genetic code is a triplet code.
176. 25:10The all 64 possible triplet code once and   the specific ammonia Archie's
177. 25:16the code for was deduced by Marshall   Nirenberg and Her Govind Khorana.
178. 25:25Later studies in many organisms showed that the double helical structure of DNA,
179. 25:32its replications, and genetic code  are the same in virtually all organisms.
180. 25:41- In this spirit various advanced technologies including molecular biology,
181. 25:48recombinant technology, biotechnology methods were made much progress
182. 25:55in understanding the concept  of modern biology and genome biology.
183. 26:07Genetics is the most rigorous and  conceptionally complete field of biology.
184. 26:15The field of human genetics has enormous scope  in education, clinical research and healthcare.
185. 26:24The field of human genetics also allows  learning innovation keeping the extremes of
186. 26:32genetic knowledge, alive and pause on the  knowledge gained to the next generation.
187. 26:39Human genetics emphasizes on understanding and treating genetic diseases
188. 26:46and genetically influenced ill health.
189. 26:50Human genetic laboratory research dealing  with the mechanism of human gene function,
190. 26:58malfunctions and treatments.
191. 27:01Because of a high degree of evolutionary conservation between organism,
192. 27:08research and model organism, which are easier to study often provides
193. 27:14valuable insights into human gene function.
194. 27:20In 1963, WHO declared that the genetic considerations, and a new dimension to public health work,
195. 27:30a concern not only for the health and well-being of persons, now living but also for generation had come.
196. 27:40Later, In 1980 WHO expanded its  focus on the genetic approaches to
197. 27:51prevention and control of major hereditary  single-gene diseases and significant
198. 28:00non communicable diseases in particular - Cancer. - Diabetes.
199. 28:06- Cardiovascular diseases and. - Asthma.
200. 28:09as well as a concern for the ethical  aspects of genetic service delivery.
201. 28:17Further to facilitate global networks of expert  to address multiple issues on human genetics.
202. 28:28WHO has made provision for on-site support  for the delivery of genetic services to expand
203. 28:38partnerships and collaboration especially  with low to middle-income countries.
204. 28:47The human genetic programs is also addressing  various genetic issues of ethics, legal, social
205. 28:56implications, and global arena of public health.
206. 29:02Now, the internet revolution has changed the face of communications in our world,
207. 29:10and is making global communications   and networks faster and more far-reaching.
208. 29:16This will help to understand the genetics
209. 29:19and expand the possibilities for participation,  public engagement, and information exchange.
210. 29:27To conclude- Knowledge of human genetics helps to contribute
211. 29:35to translation and research in the healthcare  industry for a new effective diagnosis
212. 29:44and treatment option for human diseases.
213. 29:47Thank you!