All language subtitles for 27031x_PR_Mendelian_Genetics_02_Phenotype_Observati-en

PETER REDDIEN: What we're going to do

is work with something that has some characteristic that

looks--

instead of being some kind of continuous characteristic,

something that's a state, like a discrete state, where

individuals either have the state or they

don't have this state, all right?

So that's one choice we're going to make

to try to understand some of these core genetic principles.

So what we're going to look at is the phenotype

of an organism, which I'm going to begin some

of our definitions today that we'll

be using throughout the class.

So phenotype refers to the characteristics

of an organism, essentially all the characteristics

of an organism.

Its common usage will be referring

to some characteristic under observation.

So we'll start with some example that we'll use today.

So let's say we want to figure this out

and we decide to work with fruit flies.

So we go outside, let's say, and we look for some trait.

We need something that's variant between different individuals

in a population.

If everything looks the same, then we're

never going to be able to figure anything out.

So we look for some discrete state

that looks different in some of the flies, all right?

So now let's say we find a fly that is not moving very well.

So we'll have a fruit fly that is paralyzed.

We see it moving a little bit so we know it's still alive,

but it's not moving very well.

So now we're going to try to-- the idea is now

we have something different in this group of flies.

And we want to use that to try to figure out

how we explain this trait.

So what-- first, let's start with this.

So why could the fly be paralyzed?

Any hypotheses?

Yeah.

It could be injured.

Any other ideas?

Yeah, in the back.

STUDENT: [INAUDIBLE].

PETER REDDIEN: Say again.

STUDENT: Mutations in actin.

PETER REDDIEN: So it could be-- you've

got a very specific hypothesis.

It could be a mutation in actin filament protein.

But we could generalize that and say

it could have some mutation in something that's

important for movement.

So, yeah, it could have a mutation or multiple mutations.

Anything else?

Yeah.

STUDENT: Side effect of some virus.

PETER REDDIEN: Infection.

It could be some kind of infection.

So maybe this fly was infected by some virus or something

else.

Could be old.

So anyway there's a number of things that could

have happened to this fly.

And we could group a number of these categories

as environmental influences, like infection, accident,

things like that.

And then we could have a set of hypotheses

around genetic, heritable-based mechanisms

to explain this difference.

And one of the complexities in real world genetics

is that environmental exposures to things, experiences

can influence some phenotypes.

Nonetheless, most phe-- attributes of an organism

have a very strong heritable component.

We'll get into this later in the course.