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PROFESSOR: Hello and welcome
to the help session on

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complementation.

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Today, we will briefly be
reviewing the concept of

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complementation.

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And then, we will discuss
complementation with a

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non-biological example.

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So to begin, complementation is
generally used to determine

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if two mutations fall in the
same gene or if they fall in

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different genes.

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So here, we have two mutants--
mutant one and mutant two.

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Both of these have
mutations in the

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lysine biogenesis pathway.

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So on their own, they cannot
produce lysine.

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To determine if these mutations
fall in the same

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gene or in different genes, we
need to cross the two mutants

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together and examine
their progeny.

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If the progeny can grow, this
means that the two mutations

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were in different genes,
and thus, they

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complement each other.

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However, if the progeny cannot
grow, this means that the two

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mutations were in the same
gene, and they do not

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complement each other.

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So now, let me explain

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complementation yet another way.

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So over here, we have the
knitting pathway.

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It's very simple and
straightforward.

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In order to knit, you
need two things.

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You need both the knitting
needles and you need yarn.

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When you have both of these
things together, you can knit

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a nice scarf.

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So to explain how this is
related to complementation, I

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have brought along my friend
Robert to give us a hand.

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All right.

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So in the first scenario, we're
going to have me with

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yarn and Robert with needles.

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When I have yarn, I can't knit
by myself, because I am

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lacking needles.

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This is equivalent to having a
mutation in what we'll call

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the gene for needles.

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Robert, on the other hand, has
needles, but by himself, he

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has no yarn.

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So he can't knit.

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So alone, neither of us
are able to knit.

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However, if we team up and we
work together and we share our

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resources, now we have both yarn
and needles, so we can

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knit a nice scarf.

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All right.

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So how about the case of
non-complementation?

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If I have needles now, and
Robert also has needles, me by

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myself, I cannot knit, because
I have a mutation in that I

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have to no yarn.

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Robert also has needles and he
also does not have yarn.

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So by himself, he can't
knit either.

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This time, when we team up and
we try to work together, even

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if we share our needles, we
still can't knit, because we

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have no yarn.

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So this is the case of
non-complementation.

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Thanks, Robert.

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This concludes the help session
on complementation.

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Thanks for joining us.