ShmoopTube

00:04

And here's your shmoop du jour brought to you by

00:06

genetics otherwise known as the best excuse for problematic behavior right [Parents talking to son]

00:11

after I wasn't listening and Kafulu made me do it all right here's our question

00:16

human development is driven by genetics genes tell the cells of the body what to

00:20

do when pieced together genes make up what we know as chromosomes which of the

00:24

following chromosome pairs do we find in males and here's the potential answers...

00:31

all right let's simplify here we're only dealing with humans and the [People walking downtown]

00:35

human sex chromosomes are x and y that eliminates options D and E which all

00:40

contain Z...Z is a sex chromosome found in non-human animals like poultry not what [Eggs underneath a tree]

00:47

we're looking for...C and to help you out a little we've got some background

00:51

info that might come in handy chromosomes are thread-like structures [Structure of chromosomes]

00:55

that live within the nucleus of animal and plant cells and are made up of

00:59

protein and molecule of DNA in order for organisms to grow and work as their [Sheep on a field]

01:04

intended cells have to divide in order to produce new cells and it's essential

01:09

that DNA remain intact and evenly distributed during this process that's

01:13

what chromosomes do think of all that protein as a bunch of really tough [Security guards stood outside a protein box]

01:17

security guards ensuring that everything goes according to plan some things like

01:22

bacteria only have one or two pairs of chromosomes an insect on the other hand

01:27

might have four pairs while a plant may have something like 12 humans however

01:31

have exactly 23 pairs we inherit one copy of each chromosome from our mother [Man and woman with chromosomes]

01:36

and one copy of each from our Father this explains why you might have Dad's

01:41

nose and Moms blond hair well 22 of those pairs of chromosomes are called [Autosomes in a box]

01:46

autosomes which are effectively defined as being not sex chromosomes and contain

01:51

genes that do everything that sex chromosomes don't as in pretty much

01:55

everything about you that isn't your sex that includes all those annoying things

02:00

that make you exactly like your parents and if you think you're not like them [Son dressed like Father]

02:04

just wait 10 or 20 years you're in for a rude awakening but we're concerned with

02:08

the very last pair of chromosomes right there at the end in case

02:12

your parents haven't given you the talk yet we're about to spoil a few things [Bird drops a chromosome]

02:16

babies do not come from storks they come from an egg fertilized by a sperm that's

02:22

right there are no actual birds and bees involved or storks we know it's life [Bird carrying a will work for love sign]

02:27

changing the egg is definitely going to show up to the party with two X

02:30

chromosomes while the male sperm shows up with an X and a Y and maybe some

02:34

potato salad the Y chromosome determines the sex and once Y shows up in the

02:39

offspring it's male so let's look back at our answers XY, XX and YX so we can

02:46

eliminate choice C... XX because that would be a female offspring then we're left

02:50

with XY and YX well the first human sex chromosome in the sequence is always [Man carrying X chromosome]

02:55

X regardless of the resulting sex that's just how the world works so that

02:59

means B is our answer for at least what Cthulhu says it is...

Full Transcript