Make a Karyotype


what we are going to do today is we're

going to learn how to make our own

karyotype and a karyotype is an

individual's chromosome composition and

we start looking at the karyotypes and

this is what is already done for you you

can tell that there is a sort of our

relationship with all these chromosomes

and lined up from 1 through 22 is that

it goes from the longest as you can see

the longest to the shortest and we do

the sex chromosomes less so let's get

started and I want to show you that

these first 22 pairs these are called


and the last pair are the sex


sex chromosomes and the first one we do

our own karyotype are when you start

making your own karyotype just line up

the chromosomes from longest to shortest

first and don't worry about the sex

chromosomes so worry about those last

okay so what we look for in creating our

own chromosomes are matching the

homologous pair is we look for the

location of the centromere and the

centromere is this little bit of a pinch

in the center of the chromosome and

that's where the senate sent the

centromere is located we also look at

the banding patterns and so the banding

patterns here you can see the dark

banding patterns and you can sell the

dark banding patterns in the bottom half

of the chromosome and along with the

darker banding patterns for darker

banding patterns following it and so we

look at the location of the centromere

here we look at the banding patterns

these are the banding patterns and we

also look at the length of the

chromosome and so when we start out the

first one is usually the easier one so

we look we look for something that's we

look for the homologous pair that is the

longest and so there are two it looks

like we have this one and this one so

let's start with this one since it seems

to be one of the longest ones and

sometimes don't be fooled by because

it's of the length of it so we put this

right next to it some quote unquote

homologous pair and we can see that it's

slightly off the banding pattern of this

one there is near the centromere it's

dark at these areas whereas you got this

light portion here near the centromere

area and the centromere here is actually

in the center of the chromosome so

that's good called a metacentric

location and here it's slightly above


located here it's slightly above the

chromosome so that's a sub metacentric

location so it's not exactly the same

and the banding patterns are also very

different the other thing we were

looking at is this one so if you put it

close to right next to its homologous

pair you can see the very the

similarities so here we have the light

thinning pattern around the centromere

the top portion of the chromosome and we

also have following it or the darker

banding patterns there are two and we

have a light bending pattern here the

top portion here the bottom portion

bottom half of the chromosome we have

the dark banding pattern it's not as

long as this first one but you've got

the dark one there the dark banding

pattern and you'll have one two three

four banding patterns following it and

that the tips you get this dark portion

so that is the homologous pair

chromosome let's look the matchup

chromosome number two here as you can

see that we have a couple of longer ones

so we have this you can also work with

this you can almost we can work with a

couple of things so we said that one of

the longer chromosomes was this one and

this one so let's take a look at this

chromosome and that's line it up with

that and as you can see it's slightly

different we have it seems like it

depends on the dye and how well the dye

shows up but the banding patterns are

you know they do match they're very

similar we got these dark banding

patterns here this portion and we got

this sort of light it looks like it's

shown light here but it's done it's got

the tips of it are very similar but the

bottom portion of it look take a look at

that how very similar they are although

you can't see in the top portion the

bottom portion you can see it's very

clear that it's got the banding patterns

aren't the dark patterns here and as

well as the dark portions at the bottom

tip and the centromere location is very


so slightly above the center this is the

center does that's the metacentric and

then the slightly above the center is

the subnet eccentric location of the

centromere and so we're going to go

ahead and complete all these the

matching areas the matching homologous

pairs from 1 through 22 and we're going

to do the sex chromosomes last so let's

start again we'll go back and do this

one and I'm going to do this fairly

quick and so this obviously is yeah

might be you can see that it's slightly

off so it's not going to match because

of the length of the chromosome so let's

go with this one this is the third

longest very very similar here and it's

very apparent so that's going to match

let's do this one and match it up and

see very similar again as you can see

homologous pairs so we're going to it's

going to stick to that and we'll do

we'll just keep going until until we get

all of it

so what I've done is I've completed this

karyotype and as you can see you can

find you can tell the homologous pairs

of each one some are slightly off but

that's okay it's through due to the dye

that they use to make this this

karyotype but but there are very similar

and banding patterns are similar and so

are the so are the centromeres and the

lengths are also very similar but then

when you get to the last portion which

is the sex chromosome and you have here

it's longer chromosome and the X

chromosome is usually longer and this

mystery chromosome is short the male's

actually have our homologous at the tips

of the chromosome so they're actually

shorter the Y chromosome is shorter than

the X chromosome if you get female which

is xx what you'll find is that the

chromosome is very it's not very much I

call to the x-chromosome because their

two exes because this is a lie its

homologous at the homologous at the tip

of the chromosome so it's usually it's

usually shorter and what we find here is

you have completed the karyotype just as

excited geneticist would and you have to

determine the sex of this person

it's either male or female when you can

select male and there you have it you

have determined that this is a male a

normal male human karyotype usually what

we'll find is if a person has a genetic

disorder of some sort you will either

find extra chromosomes inserted in

either one of these autosomes or in

extra chromosomes inserted in the sex

chromosomes there are it can happen that

the person can have X X Y or X Y Y or X

with a deletion of a sex chromosome so

with that that does happen and it can

happen that a person could have an extra

chromosome in chromosome 13 that is

called Down syndrome so the total

chromosome of that person is not 46 but

47 and that's it for our lesson on how

to make a karyotype