YouTube transcript (GhABWQC3YDs) — Transcript

Full transcript

1. 0:04today we're going to be talking about
2. 0:06the only two types of nucleic acids that
3. 0:08exist
4. 0:10dna
5. 0:11and rna
6. 0:14dna stands for
7. 0:16deoxyribonucleic acid
8. 0:18and rna stands for ribonucleic acid
9. 0:23as nucleic acids both dna and rna are
10. 0:27long organic macro molecules which means
11. 0:31they are very large molecules that
12. 0:34contain the element carbon
13. 0:38both dna and rna are composed of nucleic
14. 0:42acid monomers called nucleotides
15. 0:46nucleotide monomers always contain
16. 0:49a phosphate group
17. 0:51a five carbon sugar sometimes referred
18. 0:54to as a pentose
19. 0:56and a nitrogenous base
20. 0:59but
21. 1:00dna nucleotides have the five carbon
22. 1:03sugar
23. 1:04deoxyribose while rna has a different
24. 1:07five carbon sugar called ribose
25. 1:11the pentose sugar in dna has one less
26. 1:14oxygen than ribose in rna which leads to
27. 1:17its name deoxyribose
28. 1:21let's focus on the nitrogenous bases in
29. 1:24dna for a moment
30. 1:26each dna nucleotide contains only one of
31. 1:30four possible nitrogenous bases
32. 1:33adenine
33. 1:34guanine
34. 1:35thymine and cytosine
35. 1:39these four bases are usually abbreviated
36. 1:41a
37. 1:42g
38. 1:43t
39. 1:44and c
40. 1:46when nucleotide bases connect through
41. 1:48hydrogen bonds it's important to know
42. 1:51that the bases always pair up with the
43. 1:54same partners
44. 1:56adenine only pairs with thymine
45. 1:59and guanine only pairs with cytosine
46. 2:04this is called the base pair rule
47. 2:09scientists classify nitrogenous bases
48. 2:12according to the shape of their
49. 2:13molecules
50. 2:15adenine and guanine both have a double
51. 2:18ring structure containing a six membered
52. 2:20and a five-membered nitrogen-containing
53. 2:23ring fused together
54. 2:26these types of ring structures are
55. 2:28chemically classified as purines
56. 2:33but thymine and cytosine both only have
57. 2:36a single six-membered
58. 2:37nitrogen-containing ring shape so they
59. 2:40are chemically classified as pyrimidines
60. 2:44here's a little hint to help you
61. 2:45remember this
62. 2:46pyrimidine has a y in its name and so do
63. 2:50the bases classified as pyrimidines
64. 2:53thymine and cytosine
65. 2:57like dna an rna nucleotide may have the
66. 3:00nitrogenous bases adenine guanine or
67. 3:04cytosine
68. 3:05but unlike dna which has the nitrogenous
69. 3:08base thymine
70. 3:10rna has the nitrogenous base uracil
71. 3:14instead
72. 3:16this means that any nucleic acid that
73. 3:19contains thymine must be a strand of dna
74. 3:24and that any nucleic acid that contains
75. 3:26uracil must be a piece of rna
76. 3:31like thymine uracil has a single
77. 3:34nitrogen-containing ring so it would
78. 3:37also be classified as a pyrimidine
79. 3:43so what do the nitrogenous bases have to
80. 3:45do with building a dna molecule
81. 3:48well
82. 3:50each strand of dna begins to assemble
83. 3:52when the phosphate group in one
84. 3:54nucleotide bonds with the five carbon
85. 3:57sugar in another nucleotide
86. 4:02the two strands that make up a dna
87. 4:04molecule are linked through hydrogen
88. 4:06bonds between their nitrogenous bases
89. 4:10when the spiral dna molecule is
90. 4:13untwisted
91. 4:14these base pairs look like rungs on a
92. 4:17ladder
93. 4:18the spiral dna molecule is described as
94. 4:21having a double helix shape
95. 4:27james watson and francis crick first
96. 4:29described dna's double-stranded helical
97. 4:31structure in 1953
98. 4:35after looking at x-ray images of a dna
99. 4:38molecule taken by rosalind franklin
100. 4:43now let's look at the structure of rna
101. 4:46and see how it compares to the structure
102. 4:48of dna
103. 4:50while dna is a double-stranded molecule
104. 4:54rna is always single stranded
105. 4:59in eukaryotic cells dna is found only in
106. 5:03the nucleus
107. 5:05but rna can be found in the cytoplasm as
108. 5:08well as in the nucleus
109. 5:13dna controls heredity by containing the
110. 5:16code or set of instructions for building
111. 5:19the functional and structural proteins
112. 5:21that make up your body
113. 5:27and rna uses these varied instructions
114. 5:30to build all the proteins a living
115. 5:32organism needs
116. 5:35there are three types of rna
117. 5:38messenger rna referred to as mrna
118. 5:42ribosomal rna referred to as rrna
119. 5:46and transfer rna referred to as trna
120. 5:53messenger rna starts off in a cell's
121. 5:56nucleus
122. 5:57here it transcribes or copies the
123. 6:00instructions for assembling a protein
124. 6:03from a portion of the cell's dna
125. 6:07next the messenger rna takes these
126. 6:09instructions or protein recipe to a
127. 6:12ribosome in the cytoplasm
128. 6:16the ribosome which is made out of
129. 6:18ribosomal rna and proteins is the site
130. 6:22where this recipe is read and translated
131. 6:25into a protein
132. 6:29finally transfer rna in the cytoplasm
133. 6:33brings specific amino acids to the
134. 6:35ribosome so that the particular protein
135. 6:38encoded by the recipe can be made
136. 6:42we'll cover more detail about the way
137. 6:44dna and rna make proteins in another
138. 6:47video
139. 6:48to sum up
140. 6:50dna and rna are the only two nucleic
141. 6:53acids that exist
142. 6:56both dna and rna are built from nucleic
143. 6:59acid monomers called nucleotides
144. 7:03nucleotides always contain a phosphate
145. 7:06group of five carbon sugar and a
146. 7:08nitrogenous base
147. 7:11deoxyribose
148. 7:12is the sugar in dna
149. 7:14and ribose is the sugar in rna
150. 7:18the nitrogenous bases in dna are adenine
151. 7:22thymine cytosine and guanine
152. 7:25the nitrogenous bases in rna are adenine
153. 7:29uracil
154. 7:30cytosine and guanine
155. 7:33in dna
156. 7:34adenine always pairs together with
157. 7:37thymine
158. 7:38and cytosine always pairs together with
159. 7:41guanine
160. 7:42adenine and guanine are purines
161. 7:46cytosine thymine and uracil are
162. 7:48pyrimidines
163. 7:50dna is composed of two strands linked
164. 7:53through hydrogen bonds between their
165. 7:55nitrogenous bases
166. 7:57the two dna strands are twisted into a
167. 8:00double helix shape first identified by
168. 8:02watson and crick
169. 8:04rna is a single stranded molecule
170. 8:08in cells
171. 8:09dna is found only in the nucleus while
172. 8:12rna is found in the cytoplasm as well as
173. 8:15the nucleus
174. 8:17dna controls heredity by containing the
175. 8:20instructions for building the proteins
176. 8:23that make up an organism and allow it to
177. 8:25function
178. 8:27rna uses these instructions to build
179. 8:30proteins
180. 8:31there are three types of rna
181. 8:34messenger rna ribosomal rna and transfer
182. 8:38rna messenger rna copies the
183. 8:41instructions for building a protein and
184. 8:44takes them to a ribosome
185. 8:46ribosomal rna is the site where the
186. 8:48instructions are translated into a
187. 8:50protein
188. 8:52transfer rna brings specific amino acids
189. 8:55to the ribosome so the correct proteins
190. 8:58can be made
191. 9:02[Music]
192. 9:07[Music]
193. 9:18you