1
00:00:00,600 --> 00:00:01,920
[Instructor] Hello, and welcome

2
00:00:01,920 --> 00:00:04,620
to the first lecture in Module 2.

3
00:00:04,620 --> 00:00:07,380
This lecture is called,
"The Cell Perspective".

4
00:00:07,380 --> 00:00:11,760
And what I'd like to do here
is to get you to start thinking

5
00:00:11,760 --> 00:00:16,200
about biology from this
more of a cell-based

6
00:00:16,200 --> 00:00:18,180
or a microscopic perspective,

7
00:00:18,180 --> 00:00:21,030
because looking at things
from a cell's perspective,

8
00:00:21,030 --> 00:00:23,320
we can start to better understand the role

9
00:00:24,337 --> 00:00:28,783
that genetics is playing in
normal function and pathologies.

10
00:00:29,640 --> 00:00:32,753
The human body is made up of between 50

11
00:00:32,753 --> 00:00:36,600
and 100 trillion cells, and we have

12
00:00:36,600 --> 00:00:40,590
about 200 different kinds,
different types of cells,

13
00:00:40,590 --> 00:00:42,930
that have completely different functions.

14
00:00:42,930 --> 00:00:45,660
And I'm sure you're quite
familiar with some of these,

15
00:00:45,660 --> 00:00:47,940
probably some more than others.

16
00:00:47,940 --> 00:00:50,880
For example, red blood
cells have a very specific

17
00:00:50,880 --> 00:00:53,580
and different function from kidney cells,

18
00:00:53,580 --> 00:00:58,580
from neurons in the brain, from
cardiomyocytes in the heart,

19
00:00:59,220 --> 00:01:01,770
which have to beat at a particular rhythm,

20
00:01:01,770 --> 00:01:04,320
and in sync with their neighboring cells

21
00:01:04,320 --> 00:01:06,630
in order for the heart
to function properly.

22
00:01:06,630 --> 00:01:10,980
So, as you can appreciate,
they're just a huge variety

23
00:01:10,980 --> 00:01:12,570
and spectrum of different cells.

24
00:01:12,570 --> 00:01:14,760
And with those different cell types,

25
00:01:14,760 --> 00:01:18,000
you have different functions
that they're performing.

26
00:01:18,000 --> 00:01:23,000
And each is very important and
necessary for the organism,

27
00:01:23,070 --> 00:01:25,170
as a whole, to function properly.

28
00:01:25,170 --> 00:01:26,850
But it's important to keep in mind

29
00:01:26,850 --> 00:01:29,640
that despite all the variety
of different cell types

30
00:01:29,640 --> 00:01:32,100
and the trillions of cells that we have,

31
00:01:32,100 --> 00:01:34,560
each one of them, with a few exception,

32
00:01:34,560 --> 00:01:37,110
contains your full genome.

33
00:01:37,110 --> 00:01:40,500
So each of these cells, even
though they're all acting

34
00:01:40,500 --> 00:01:41,940
in very different ways,

35
00:01:41,940 --> 00:01:44,940
they each have the same genetic material.

36
00:01:44,940 --> 00:01:46,470
The one exception here that I'm noting,

37
00:01:46,470 --> 00:01:47,970
and I'll note this a couple of times,

38
00:01:47,970 --> 00:01:51,150
that I'd like to mention
is mature erythrocytes

39
00:01:51,150 --> 00:01:55,020
or red blood cells, as
they have been enucleated,

40
00:01:55,020 --> 00:01:57,300
which means they no
longer contain a nucleus,

41
00:01:57,300 --> 00:02:01,230
and they no longer contain nuclear DNA,

42
00:02:01,230 --> 00:02:05,430
or your genome is no longer
contained in those cells.

43
00:02:05,430 --> 00:02:08,490
The genome is housed
in the cell's nucleus.

44
00:02:08,490 --> 00:02:12,720
So if we're looking at a
schematic drawing of a cell

45
00:02:12,720 --> 00:02:17,720
or kinda like a generic cell
and all of its components,

46
00:02:17,760 --> 00:02:21,510
it's not really important that
you know the different names

47
00:02:21,510 --> 00:02:23,850
of the components that
are all listed here,

48
00:02:23,850 --> 00:02:26,250
I'm just showing you this
to give you a perspective

49
00:02:26,250 --> 00:02:28,950
of where in the cell you would find it.

50
00:02:28,950 --> 00:02:32,340
The nucleus, I mean, it
depends upon the cell,

51
00:02:32,340 --> 00:02:35,910
but very often found sort
of in the middle of the cell

52
00:02:35,910 --> 00:02:39,480
and it has its own membrane to protect it.

53
00:02:39,480 --> 00:02:44,480
Contained within the nucleus
is all of the genetic material.

54
00:02:46,590 --> 00:02:49,200
One exception to this, and
this will be a recurring theme

55
00:02:49,200 --> 00:02:51,540
where I keep saying the
one exception to this

56
00:02:51,540 --> 00:02:53,610
because one thing that I'm sure

57
00:02:53,610 --> 00:02:55,170
you're probably familiar with

58
00:02:55,170 --> 00:02:58,320
but is absolutely the case in
really any study of biology is

59
00:02:58,320 --> 00:03:01,740
that for every rule there is an exception

60
00:03:01,740 --> 00:03:05,040
and that is going to keep coming up.

61
00:03:05,040 --> 00:03:06,630
So I apologize for that.

62
00:03:06,630 --> 00:03:09,000
I'd like to be able to
make blanket statements

63
00:03:09,000 --> 00:03:10,290
'cause I know that makes it easier.

64
00:03:10,290 --> 00:03:12,750
And I'll try to do that when possible,

65
00:03:12,750 --> 00:03:15,570
but I will pretty much always have

66
00:03:15,570 --> 00:03:17,940
to make some kind of disclaimer of,

67
00:03:17,940 --> 00:03:20,160
well, there may be a few exceptions.

68
00:03:20,160 --> 00:03:22,290
And in this case, so the genome is housed

69
00:03:22,290 --> 00:03:26,310
in the cell nucleus,
yes, a very small amount

70
00:03:26,310 --> 00:03:30,402
of specific genetic material
related to metabolism

71
00:03:30,402 --> 00:03:34,980
and specifically oxidative
phosphorylation is housed

72
00:03:34,980 --> 00:03:37,260
in the mitochondria of cells.

73
00:03:37,260 --> 00:03:41,790
And you can kinda see this little,

74
00:03:41,790 --> 00:03:42,700
these little guys here,

75
00:03:42,700 --> 00:03:45,810
these little yellow jelly bean things

76
00:03:45,810 --> 00:03:50,810
with the folds in there
and their membranes here

77
00:03:51,450 --> 00:03:56,450
are depicting mitochondria,
they contain a handful of genes

78
00:03:57,510 --> 00:04:00,840
which are specifically related
to mitochondria function.

79
00:04:00,840 --> 00:04:03,870
You can say, as a general rule though,

80
00:04:03,870 --> 00:04:08,870
that 99.999% of your genetic
material is actually contained

81
00:04:10,410 --> 00:04:12,813
within the cell's nucleus.

82
00:04:14,970 --> 00:04:18,780
So let's take a a zoomed
in view here, again.

83
00:04:18,780 --> 00:04:21,300
This what looks like a big hairball

84
00:04:21,300 --> 00:04:26,300
that you might find in your shower is DNA.

85
00:04:27,630 --> 00:04:29,410
So these are strands of DNA

86
00:04:30,690 --> 00:04:33,030
and we'll talk about in a lot more detail

87
00:04:33,030 --> 00:04:34,590
what that means shortly.

88
00:04:34,590 --> 00:04:36,600
Just know that this is where it's located.

89
00:04:36,600 --> 00:04:38,100
It's protected from the rest of the cell

90
00:04:38,100 --> 00:04:39,840
through a nuclear membrane.

91
00:04:39,840 --> 00:04:42,180
So this is keeping it, your DNA,

92
00:04:42,180 --> 00:04:44,610
your genetic material is very precious

93
00:04:44,610 --> 00:04:46,650
and needs to be protected.

94
00:04:46,650 --> 00:04:51,180
So the cell protects it by
keeping it in the nucleus.

95
00:04:51,180 --> 00:04:56,180
All information from your
DNA basically will be copied

96
00:04:57,600 --> 00:05:00,210
and sent out through the nucleus

97
00:05:00,210 --> 00:05:04,470
into what's called the
cytoplasm of the cell,

98
00:05:04,470 --> 00:05:09,470
which is basically all of the
space outside of the nucleus

99
00:05:09,600 --> 00:05:13,500
that's not within one of
these other structures.

100
00:05:13,500 --> 00:05:16,560
So the cytoplasm, that's literally just

101
00:05:16,560 --> 00:05:18,750
like, the goo within a cell

102
00:05:18,750 --> 00:05:21,000
that is not what are called organelles

103
00:05:21,000 --> 00:05:22,920
or these little structures

104
00:05:22,920 --> 00:05:25,083
that have other specific functions.

105
00:05:27,030 --> 00:05:31,235
So again, you do not need
to know what is a golgi

106
00:05:31,235 --> 00:05:35,340
or a lysosome or endoplasmic
reticulum necessarily.

107
00:05:35,340 --> 00:05:36,870
If you're interested, I'm more than happy

108
00:05:36,870 --> 00:05:38,850
to talk with you about it.

109
00:05:38,850 --> 00:05:42,810
But as it stands, really
all it's important here is

110
00:05:42,810 --> 00:05:44,850
to know that there's a nucleus,

111
00:05:44,850 --> 00:05:46,290
it's contained within a cell,

112
00:05:46,290 --> 00:05:50,463
and within the nucleus is
housed your genetic information.

113
00:05:51,420 --> 00:05:54,060
All cells came from one fertilized egg.

114
00:05:54,060 --> 00:05:58,080
Here, this is showing a
scanning electron micrograph

115
00:05:58,080 --> 00:06:00,990
of an egg being fertilized by lots

116
00:06:00,990 --> 00:06:05,610
of very excited go-getter sperm.

117
00:06:05,610 --> 00:06:08,610
One of those lucky guys
will make it into the egg

118
00:06:08,610 --> 00:06:09,750
and will fertilize the egg

119
00:06:09,750 --> 00:06:13,113
and will deposit its genetic information.

120
00:06:13,950 --> 00:06:16,980
And from that, it'll form a zygote.

121
00:06:16,980 --> 00:06:21,210
So a fertilized egg will
have the full compliment

122
00:06:21,210 --> 00:06:25,770
of DNA that that
individual will ever have.

123
00:06:25,770 --> 00:06:28,860
So you start out from day one, really

124
00:06:28,860 --> 00:06:31,590
at the moment of conception is the point

125
00:06:31,590 --> 00:06:34,230
at which all genetic information

126
00:06:34,230 --> 00:06:37,620
that you will really ever
have is contained within you.

127
00:06:37,620 --> 00:06:39,690
Now, that's not to say
your genetic information

128
00:06:39,690 --> 00:06:41,520
can't change slightly over time,

129
00:06:41,520 --> 00:06:45,330
and it certainly does,
a very small percentage

130
00:06:45,330 --> 00:06:48,423
of it will mutate or change over time,

131
00:06:49,380 --> 00:06:52,260
but the vast, vast majority
of it is going to be identical

132
00:06:52,260 --> 00:06:56,310
to what was present at
the time of conception.

133
00:06:56,310 --> 00:06:58,860
So of course this is a single cell.

134
00:06:58,860 --> 00:07:02,820
It then goes on to divide, and
I'm sure you're very familiar

135
00:07:02,820 --> 00:07:04,590
with this process, it divides

136
00:07:04,590 --> 00:07:08,460
into multiple cells after that.

137
00:07:08,460 --> 00:07:12,330
And the process of cell
division is called mitosis.

138
00:07:12,330 --> 00:07:14,730
And we'll talk about that in more detail

139
00:07:14,730 --> 00:07:16,863
in a subsequent module.

140
00:07:18,360 --> 00:07:21,810
But for now it's just suffice
it to say the cell divides

141
00:07:21,810 --> 00:07:26,643
and as it divides, it also
duplicates its DNA exactly,

142
00:07:27,660 --> 00:07:31,950
again, within 99.999%, exactly the same

143
00:07:31,950 --> 00:07:34,050
as what it originally started with.

144
00:07:34,050 --> 00:07:37,440
So one cell becomes two, two
become four, four become eight,

145
00:07:37,440 --> 00:07:38,700
and so on and so on.

146
00:07:38,700 --> 00:07:42,993
And this is during very
early stages of development.

147
00:07:44,700 --> 00:07:46,440
So each cell in the human body contains

148
00:07:46,440 --> 00:07:47,820
the same DNA originally found

149
00:07:47,820 --> 00:07:49,620
in the fertilized egg at conception.

150
00:07:50,520 --> 00:07:53,850
So here are a few exceptions
that, again, I have to note.

151
00:07:53,850 --> 00:07:55,530
One is mature erythrocytes,

152
00:07:55,530 --> 00:08:00,300
which again, do not contain
any nuclear genetic material

153
00:08:00,300 --> 00:08:03,450
because they do not contain a nucleus,

154
00:08:03,450 --> 00:08:06,810
and egg and sperm, which only contain half

155
00:08:06,810 --> 00:08:10,590
of the DNA that you started with

156
00:08:10,590 --> 00:08:12,600
at the time of conception.

157
00:08:12,600 --> 00:08:16,230
Because when an egg and
sperm fuse, you don't want

158
00:08:16,230 --> 00:08:21,230
to have twice as much DNA as
you would want in the end.

159
00:08:21,810 --> 00:08:25,500
We'll talk about this again in
another module in the future

160
00:08:25,500 --> 00:08:28,410
when we talk about the process of meiosis.

161
00:08:28,410 --> 00:08:31,980
So each cell in your body
has the same DNA, roughly,

162
00:08:31,980 --> 00:08:34,920
but each cell has very different function.

163
00:08:34,920 --> 00:08:36,153
So how does this happen?

164
00:08:37,710 --> 00:08:39,390
We're not going to spend
a lot of time on this,

165
00:08:39,390 --> 00:08:42,630
but cell differentiation is the process

166
00:08:42,630 --> 00:08:47,630
in which cells take on unique
characteristics and functions.

167
00:08:48,000 --> 00:08:51,960
All starting though from
that original same cell,

168
00:08:51,960 --> 00:08:55,680
divide, divide, divide,
become a blastocyst stage.

169
00:08:55,680 --> 00:08:58,650
And then you have gastrulation,
and I imagine you've come

170
00:08:58,650 --> 00:09:02,253
across this in other
coursework that you've had.

171
00:09:03,780 --> 00:09:07,050
In the gastrula stage of development

172
00:09:07,050 --> 00:09:10,593
it's still very early on,
very early zygote stage,

173
00:09:11,640 --> 00:09:13,440
there are different layers.

174
00:09:13,440 --> 00:09:17,220
And each of these layers
will become different types

175
00:09:17,220 --> 00:09:20,370
of, can become different
types of cells depending

176
00:09:20,370 --> 00:09:22,950
upon signaling events around them.

177
00:09:22,950 --> 00:09:26,070
Now again, they still
contain the same DNA,

178
00:09:26,070 --> 00:09:28,770
but the way that the cell goes

179
00:09:28,770 --> 00:09:32,670
about basically becoming
different from another cell

180
00:09:32,670 --> 00:09:35,880
with both of them having the same DNA, is

181
00:09:35,880 --> 00:09:40,770
that one cell will start to express,

182
00:09:40,770 --> 00:09:44,310
which means turning on or turning off,

183
00:09:44,310 --> 00:09:46,530
or it can also mean slightly turning up

184
00:09:46,530 --> 00:09:49,380
or turning down the the level

185
00:09:49,380 --> 00:09:52,710
to which the gene is expressed.

186
00:09:52,710 --> 00:09:55,320
So while all cells possess the same genes,

187
00:09:55,320 --> 00:09:58,110
some turn off or turn on subsets of genes

188
00:09:58,110 --> 00:10:00,120
and this is called gene expression,

189
00:10:00,120 --> 00:10:02,730
which enables only the
necessary functions.

190
00:10:02,730 --> 00:10:06,240
So in the case of, let's
take for example a neuron

191
00:10:06,240 --> 00:10:09,210
in the brain, you do not want a neuron

192
00:10:09,210 --> 00:10:12,120
in the brain secreting insulin.

193
00:10:12,120 --> 00:10:13,530
There's no reason for it.

194
00:10:13,530 --> 00:10:15,210
It would be detrimental potentially

195
00:10:15,210 --> 00:10:17,670
to the surrounding tissue

196
00:10:17,670 --> 00:10:20,043
and it would be confusing to the body.

197
00:10:21,060 --> 00:10:25,860
So instead in, for example,
the pancreatic cells

198
00:10:25,860 --> 00:10:29,160
where you would have
expression of insulin,

199
00:10:29,160 --> 00:10:30,720
you would not have expression

200
00:10:30,720 --> 00:10:33,093
of say, a neurotransmitter receptor,

201
00:10:34,110 --> 00:10:36,330
but in the neuron you
would have expression

202
00:10:36,330 --> 00:10:39,450
of a neurotransmitter receptor gene,

203
00:10:39,450 --> 00:10:44,450
but you would not have
expression of the insulin gene.

204
00:10:46,350 --> 00:10:49,050
So you can imagine this
multiplied by thousands

205
00:10:49,050 --> 00:10:50,757
and thousands when we're
talking about different genes

206
00:10:50,757 --> 00:10:53,070
and different combinations of genes.

207
00:10:53,070 --> 00:10:56,520
This allows for all of
the unique characteristics

208
00:10:56,520 --> 00:10:58,743
that we see in different types of cells.

209
00:11:01,410 --> 00:11:03,690
So here, I'm just giving you a few images

210
00:11:03,690 --> 00:11:05,880
of different types of cells,

211
00:11:05,880 --> 00:11:08,640
and I'm sure you've seen many of these,

212
00:11:08,640 --> 00:11:10,200
if you've done any kind of mic,

213
00:11:10,200 --> 00:11:13,233
if you've done some microscopy
work or pathology work.

214
00:11:15,030 --> 00:11:18,690
So here, just to give you kind of a gamut

215
00:11:18,690 --> 00:11:22,080
of different types of
cells and morphologies,

216
00:11:22,080 --> 00:11:24,330
dermal fibroblasts so found in the skin

217
00:11:24,330 --> 00:11:27,690
which provide elasticity
and strength to the skin.

218
00:11:27,690 --> 00:11:29,280
So they form these sheets.

219
00:11:29,280 --> 00:11:31,380
And as you can see the cell or maybe you,

220
00:11:31,380 --> 00:11:35,733
hopefully you can see the cells
are kind of outlined here.

221
00:11:36,840 --> 00:11:39,420
These are individual cells
that I'm sort of drawing

222
00:11:39,420 --> 00:11:40,530
around with the arrow.

223
00:11:40,530 --> 00:11:43,950
This would be one cell,
this would be another cell.

224
00:11:43,950 --> 00:11:46,050
And they form these sheets

225
00:11:46,050 --> 00:11:47,760
so they're actually
connected to one another.

226
00:11:47,760 --> 00:11:50,430
And they need to do that so
that the skin can provide

227
00:11:50,430 --> 00:11:52,743
the barrier that's necessary.

228
00:11:53,610 --> 00:11:57,960
Compare that with a neuron
where you have, you know,

229
00:11:57,960 --> 00:12:00,030
very different morphology.

230
00:12:00,030 --> 00:12:01,710
This is the center of the cell

231
00:12:01,710 --> 00:12:04,290
and it sends out all of these processes

232
00:12:04,290 --> 00:12:07,200
and connects with cells in
its surrounding environment,

233
00:12:07,200 --> 00:12:08,520
but in a very different way.

234
00:12:08,520 --> 00:12:11,220
And as you can see, it
looks quite different.

235
00:12:11,220 --> 00:12:13,770
T cells on the other hand,
which are, of course,

236
00:12:13,770 --> 00:12:16,080
immune cells and they
float around in the body,

237
00:12:16,080 --> 00:12:19,740
they're not adhered to
any particular substrate

238
00:12:19,740 --> 00:12:22,170
like a dermal fibroblast would be,

239
00:12:22,170 --> 00:12:25,050
which basically stay put in the skin.

240
00:12:25,050 --> 00:12:27,930
T cells are floating around in the body

241
00:12:27,930 --> 00:12:30,540
and clearly have very
different morphology, as well.

242
00:12:30,540 --> 00:12:32,850
And it's necessary for their function.

243
00:12:32,850 --> 00:12:36,350
Compare that with erythrocytes,
mature erythrocytes

244
00:12:36,350 --> 00:12:40,860
in which I wanted to
show here just an image

245
00:12:40,860 --> 00:12:42,270
of some erythrocytes.

246
00:12:42,270 --> 00:12:45,480
You can see they have, as
I'm sure you're familiar,

247
00:12:45,480 --> 00:12:46,410
they have that characteristic

248
00:12:46,410 --> 00:12:48,780
round dented shape in the center.

249
00:12:48,780 --> 00:12:50,640
And part of the reason why it's dented is

250
00:12:50,640 --> 00:12:52,020
because the nucleus is gone.

251
00:12:52,020 --> 00:12:54,480
The nucleus is normally
sitting kind of in the middle

252
00:12:54,480 --> 00:12:58,080
and would sort of press
the cell membrane out.

253
00:12:58,080 --> 00:13:00,240
And it also allows for
greater surface area

254
00:13:00,240 --> 00:13:01,860
for oxygen to bind.

255
00:13:01,860 --> 00:13:04,680
So, you know, each of
these has its own function,

256
00:13:04,680 --> 00:13:06,270
has its own characteristics,

257
00:13:06,270 --> 00:13:09,210
yet they all have the
same genetic material.

258
00:13:09,210 --> 00:13:11,430
So let's summarize what
we've talked about here.

259
00:13:11,430 --> 00:13:15,180
The human body is made up
of 50 to 100 trillion cells.

260
00:13:15,180 --> 00:13:18,540
The cells contain their
genome in the nucleus,

261
00:13:18,540 --> 00:13:20,700
so that's where it's housed.

262
00:13:20,700 --> 00:13:23,520
A fertilized egg contains
the complete genome,

263
00:13:23,520 --> 00:13:25,950
which is replicated each
time the cell divides

264
00:13:25,950 --> 00:13:29,160
and cell division is called mitosis.

265
00:13:29,160 --> 00:13:31,290
All cells in a person's body originated

266
00:13:31,290 --> 00:13:35,460
from the same fertilized egg,
thus have the same genome

267
00:13:35,460 --> 00:13:39,210
because with each cell
division, the cell replicates

268
00:13:39,210 --> 00:13:43,143
its genome and passes that
on to all subsequent cells.

269
00:13:44,280 --> 00:13:46,620
Even though all cells
in a person's body have

270
00:13:46,620 --> 00:13:48,420
the same genetic sequence,

271
00:13:48,420 --> 00:13:50,490
cells take on very
different characteristics

272
00:13:50,490 --> 00:13:52,860
by expressing genes in different ways.

273
00:13:52,860 --> 00:13:55,680
So turning some genes off or on,

274
00:13:55,680 --> 00:13:57,870
or even just up or down slightly

275
00:13:57,870 --> 00:13:59,820
can make a big difference in terms

276
00:13:59,820 --> 00:14:03,360
of the functionality of the cell.

277
00:14:03,360 --> 00:14:06,060
We'll talk more about gene expression,

278
00:14:06,060 --> 00:14:07,290
what that means and some

279
00:14:07,290 --> 00:14:10,950
of the details of that in module three.

280
00:14:10,950 --> 00:14:13,170
So what's next in this module?

281
00:14:13,170 --> 00:14:17,040
The next lecture video I'd
like you to watch is entitled

282
00:14:17,040 --> 00:14:18,750
The Structure of DNA.

283
00:14:18,750 --> 00:14:22,650
And then in that one, we're going to start

284
00:14:22,650 --> 00:14:26,160
to talk a little bit about
the actual physical structure

285
00:14:26,160 --> 00:14:31,160
of DNA, how it's housed in the nucleus.

286
00:14:31,320 --> 00:14:35,253
The final lecture for this
module is The Central Dogma,

287
00:14:36,330 --> 00:14:39,300
which almost sounds more
philosophical than scientific,

288
00:14:39,300 --> 00:14:44,300
but this was such an enormous advancement

289
00:14:45,150 --> 00:14:48,240
in the understanding of not just genetics

290
00:14:48,240 --> 00:14:50,550
but molecular biology as a whole

291
00:14:50,550 --> 00:14:53,760
that it is, I think, rightly still called

292
00:14:53,760 --> 00:14:56,940
The Central Dogma, which is we'll use

293
00:14:56,940 --> 00:15:01,940
to understand what exactly does DNA do.

294
00:15:02,280 --> 00:15:04,020
So we'll talk about that

295
00:15:04,020 --> 00:15:07,680
in the third lecture in this module.

296
00:15:07,680 --> 00:15:11,580
So until then, I look forward to speaking

297
00:15:11,580 --> 00:15:13,860
with you on the Structure of DNA.

298
00:15:13,860 --> 00:15:14,823
Thanks very much.