© Weston, 2010
A little mo’ about Joe…
Circa 1993…
A little mo’ about Joe…
Joe’s all grown up now, but his aunt
Hey Boy!
Wanna go to the
park???
Let’s see more about what we’re talking
about.
still tells him how much he looks like his
Mom every time she sees him. And
that shouldn’t be surprising, since Joe is
half his Mom!
#1
Heredity
If we take a look at Joe’s family picture again:
We see that Joe inherited (had passed down
from parents) certain physical traits.
Some traits seem to come from one parent:
•Joe got his smile from his Mom. That’s why
his Aunt says “You look just like my sister!”
every time she sees him. Joe hates this.
•Joe got his toes from his dad. You can’t really tell, though.
•Joe laughs like his mom—lots of “ha ha ha” instead of “hee hee hee” like his Dad.
Yeah, his aunt has noticed this, too.
Some of Joe’s traits seem to be a combination or blending of his Mom and Dad:
•He is skinny, like both parents.
•The shape of his eyes seem to be “in the middle” of the shape of his parents’.
Still, other traits seem to have come out of nowhere:
•Why is he red? Neither parent is, and red isn’t a blending of green and purple.
•Why doesn’t he have hair like Mom and Dad do?
#2 All of these traits…
…not just the ones that he clearly inherited from one parent…
…not just the ones that are a combination or blending from both parents…
…but even the ones that seem to exist in Joe for no good reason…
This is the basis for everything we know about the study of heredity, or the study of
how offspring share similar traits to their parent organisms. We see it everywhere in
the world:
This young oak
tree is very much
like the oak trees
that combined to
make the acorn
it sprouted from.
Baby seal here got half of its
inherited code from its mama.
(Father, the other half, not
pictured)
#3 And the same is true for all of
us.
Here’s Yao Ming and his parents:
It’s pretty clear that he
inherited his trait of
extreme height from his
parents. Dad is 6’10”
and his mom is 6’3”.
Here’s actor Martin Sheen, and his sons Charlie and Emilio. What traits did the sons
inherit from their dad?
#4 Write!
Write Your Name
Notes – Heredity & Reproduction
I. Heredity – how offspring share similar traits to
the prior generation (parents)
This is why lion cubs look like mini, not-yet-grown
versions of the parent lions.
Sometimes, weird situations do arise after reproduction:
It’s all based on…
#5 The Stuff Inside Your Cells!
Well, technically, not all the stuff
inside your cells.
Heredity isn’t based on lysosomes,
vacuoles, or endoplasmic reticulum.
Instead, it’s the nucleus, or what’s
contained within the nucleus that counts.
DNA (deoxyribonucleic acid) is the key to how you ended up being you. Let’s look at
DNA a little bit and how it’s packed into each cell’s nucleus.
#6 You’ve probably seen diagrams
like this:
This is what DNA looks like. Looking at DNA up
close, it’s fairly impossible to tell if this is the DNA
from a catfish, a rose bush, or a human.
Up close like this, DNA looks like a twisted ladder,
or “double helix” design.
When you zoom out a little bit, though, you can see that your
DNA looks like very long strings, just twisted around &
around.
#7 And if you zoom farther out…
Here’s a whole cell.
The easiest organelle to see in most cells is the
nucleus. A lot of that has to do with all the
twisted strands of DNA crammed inside the
nucleus of the cell.
Why does this DNA matter? Two reasons:
1. It tells the cell and other organelles within
how to function properly.
2. It is the code for what made YOU.
#8HairDNA
=
your
codes
Susceptibility
to diabetes
straightness
Thumb flexibility
Eye
color
The chemicals that make
up DNA are arranged in a
way that your body can
“read” them like a book,
using that information as
instructions. These make
your traits.
2nd toe length
For example, just making stuff up here…let’s say this portion of your DNA coded for
the length of your 2nd toe.
If you continue to travel down the ladder-like DNA, you’ll keep reaching codes for
more and more traits.
And how many of these traits do you have? Somewhere around 25 to 30 THOUSAND.
The instructions for these traits are called genes and they’re located on the DNA you
have in each and every cell.
#9 Write it out.
Notes – Heredity & Reproduction
I. Heredity – how offspring share similar traits to
the prior generation (parents)
A. Genes – codes/instructions for traits
•Found on DNA strands
•DNA found in nucleus of each cell
So, genes are the codes for you…your physical traits, and other things
that aren’t so easy to see—your emotional make-up and natural
intelligence. Even ancestral memories carried as instincts wind up in
your DNA to be passed on from one generation to the next. Cool stuff.
#10 Genes in the DNA cause:
…this guy to have little
dark eyebrows that look
like caterpillars.
…cheetah cubs to inherit blazing
speed from mom and dad.
…the whale calf to know how to swim immediately after
birth, without having to be taught or observe its mother
swimming.
Traits are coded for by genes, found in the DNA in the
nucleus of every cell an organism has.
#11 So, why aren’t we an exact blend
of
mom
and
dad’s
traits?
Here’s where the science of genetics comes into play.
A lot of big companies hire a lot of smart scientists who studied a lot about heredity and
learned the rules that nature seems to play by. This type of science is genetics.
By the way, these are similar to many of the skills and procedures performed by forensic
scientists, who might need strong knowledge of genetics to do their job.
#12
More
on
Genetics
You’ll eventually learn about this guy:
Gregor Mendel
…and his pea plants…
…down the road in science. We’ll simplify his stuff here.
Mendel, and countless others before him, often wondered about the question posed last slide—
why does heredity seem to be so random? Bob looks just like his dad, but Marcy looks nothing
like either of her sisters, and little Sally looks nothing like either of her parents?
Mendel discovered a few important things about genetics—the science of HOW heredity works.
#13 Both Parents are Equals
The most obvious thing to us is something that not everybody believed in ancient times—that
both parents are equally important in crafting a child, whether it’s a boy or girl.
Your genes come half from your mom, and half from your dad!
Mendel also noticed that some forms of a trait seemed to “win out” over other forms. Here’s
an example:
Two parent mice have lots of
baby mice.
What conclusion would you
draw about the fur color in
mice?
#14 Mendel Called These “powerful”
Genes…
DOMINANT.
Dominant genes were ones that were most likely to show up.
On the other hand, RECESSIVE genes were ones that were most likely to be masked by the
presence of the dominant gene.
Dominant genes in humans include things like:
being able to tongue roll
Having your left thumb on top when you fold
your hands together.
#15 Write
Notes – Heredity & Reproduction
I. Heredity – how offspring share similar traits to
the prior generation (parents)
A. Genes – codes/instructions for traits
•Found on DNA strands
•DNA found in nucleus of each cell
II. Genetics – Science of results of half your genes
coming from mom, half from dad.
•Dominant gene – “wins out” and is likely to be
shown
•Recessive gene – “loses out” in a conflict with
a dominant gene
#16 So how do you get oddball kids?
How is it possible (because it is!) for two parents who can roll their tongues to have a daughter
who can’t?
It goes back to this sentence: Half your genes come from mom, half from dad.
Your mom has a set of two genes for each trait, too, because she had her own mom and dad.
Same with your pop.
YOUR MOM
Got the:
“Can Roll Tongue”
gene from her Dad.
Got the:
“Can’t Roll Tongue”
gene from her Mom.
YOUR DAD
Got the:
“Can’t Roll Tongue”
gene from his Dad.
Got the:
“Can Roll Tongue”
gene from his Mom.
Mendel explained that your mom donates only 1 of her 2 tongue rolling genes to you. Likewise,
your dad donates only 1 of his 2 tongue rolling genes to you. Each “choice” is completely
random.
#17 Continued
YOUR MOM
Got the:
“Can Roll Tongue”
gene from her Dad.
Got the:
“Can’t Roll Tongue”
gene from her Mom.
YOUR DAD
Got the:
“Can’t Roll Tongue”
gene from his Dad.
Got the:
“Can Roll Tongue”
gene from his Mom.
Mendel explained that your mom donates only 1 of her 2 tongue rolling genes to you. Likewise,
your dad donates only 1 of his 2 tongue rolling genes to you. Each “choice” is completely
random.
…you can’t…
YOU
Can’t Roll Tongue
So even though mom
can roll her tongue
and dad can, too…
Can’t Roll Tongue
#18 Genetics, wrapped up
There are all sorts of rules, vocabulary terms, and tools used by scientists to make predictions of
these types. For now, just remember this:
•Each of your cells has long strands of DNA.
•Half of your DNA came from Mom, half came from Dad.
•On each strand of DNA are codes for 30,000 traits in your body. These codes are genes.
•Mom and Dad gave you different combinations of dominant and recessive genes. These mix
and sort out to determine your physical make-up and more.
•You are a completely unique combination of genes (unless you have an identical twin). Your
brothers and sisters have unique combinations of your mom’s and dad’s genes—similar, but
different from yours.
#19 On another note…
There’s a certain beauty about being a unique individual.
If all humans were clones of one individual, how boring would that be?
#20 Not only would that be boring
sameness…
…any defects in that one individual’s genes would be shared by all of the clones, too. If the
person’s genes made it extremely likely that “it” would get cancer by age 30, then all of the
clones would share that weakness, too.
Now, if all of the individuals were cloned after a perfect physical specimen, like your science
teacher, well then…that’s different. 
Reproduction where genes are combined from two unique parents, so that the offspring show
diversity of traits, is called sexual reproduction.
Most animals
reproduce
this way.
Even fungi reproduce
sexually
Plants, too.
#21 Let’s Write.
II. Genetics – Science of results of half your genes
coming from mom, half from dad.
•Dominant gene – “wins out” and is likely to be
shown
•Recessive gene – “loses out” in a conflict with
a dominant gene
III. Reproductive Strategies
A. Sexual Reproduction – combines genes from
genetically unique parents to make unique
offspring.
•Results in greater diversity for the species
•Done by most complex organisms
#22 On the other hand…
Many organisms do not reproduce sexually. Instead of a “mom” and “dad” combining genes
together to make unique “children,” the individuals reproduce asexually. The prefix “a” is
another way to say “not.”
Some organisms reproduce asexually by simply splitting in half, very much like the cells in your
body do.
Budding is a different way to reproduce asexually…in this
manner, small bits of a large organism break off and regrow
into full-size adults.
Go, paramecia, go!
A potato like this is able
to be cut up and grown
into several genetically
identical complete plants
A hydra bud ready to fall off.
#23 Write.
III. Reproductive Strategies
A. Sexual Reproduction – combines genes from
genetically unique parents to make unique
offspring.
•Results in greater diversity for the species
•Done by most complex organisms
B. Asexual Reproduction – does not create diverse
offspring (they are genetically identical to the
parent).
•Results in identical generations (no diversity)
•Done by many simple organisms (very easy)
#24 In Conclusion…
It’s a good thing we humans combine genes together to make offspring. I like the variety. And
it’s what makes us all unique, special one-of-a-kind individuals.
And it’s a LOT easier to draw this in powerpoints:
…than either of these:
#25 And That’s…