Transcript the series uno dos tres

Monocross and Dicross Genetics
Problems
Begins
Keep polishing the lamp.
I’m telling you, nice to be back, ladies and gentlemen. Hi. Where
you from? What’s your name?
Uh..A-A-Aladdin
Aladdin! Hello, Aladdin. Nice to have you on the show. Can
we call you Al, or maybe just Din? Or, how about Laddie?
No wait, that sounds too much like a Scottish dog.
Speaking of nuts, you should have known my last
master. Say you’re a lot smaller than him. Either
that, or I’m getting bigger. Look at me from the
side. Do I look different to you?
Why did I
have to rub
that lamp.
This genie is
nuts!
It sure feels god to get out of that lamp. Oi! Ten
thousand years will give you such a crick in the neck.
Anyway, I am a genie and I am here to teach you the
magic of genetics( Get it? Genie teaching genetics) at
the request of my master Aladdin.
I also want the princess, Jasmine to fall
in love with me.
You understand , Aladdin, that these are two
of your three wishes, to be exact. And nay on
the wishing for more wishes. That's all.
Three. Uno, dos, tres. No substitutions,
exchanges or refunds.
Okay, well first things first. I’ve gotta
teach these students about genetics!
I understand
In order to tackle genetics problems, you must first learn the simple techniques
and you must master the series of steps. These steps are essential to your
understanding at the beginning of the genetics section. Less emphasis on these
steps will occur at the end, but for now – the steps are essential!!
For out first problem, let’s look at a lonely tall pea plant. He is a pure
breeding variety, meaning that any time he self pollinates, (plants do that
sort of stuff), he produces only more tall pea plants.
Pure bred (homozygous) tall mated with pure bred (homozygous) dwarf.
Analyze the F1 (first generation) offspring phenotypes and genotypes
STEP #1 STATE LETTER REPRESENTATIONS
Remember to use
only one letterupper and lower case
Let T represent the dominant tall allele
Let t represent the recessive dwarf allele
STEP #2 SHOW THE PARENTAL CROSS
Ô = male
Ю = female
P1 Ô T T X Ю t t
STEP #3 SHOW THE
Male
sperm
T
T
GAMETES
Female
egg
t
t
STEP #4 COMPLETE THE PUNNETT SQUARE AND ANALYSIS
Bring the gametes from step 3 to the sides of the punnett square
Identify
sexes
T
Ô
T
Phenotype analysis
Ю
t
4/4 are all tall
Tt
Tt
Genotype analysis
t
Tt
Tt
4/4 are heterozygous tall
Wasn’t that easy. Just
make sure your
capitals in the punnett
are always before the
lower case
Okay good. So lets try another problem. This time
lets use the characteristic of flower colour. In pea
plants purple colour is dominant to white.
If two heterozygous purple flowers are mated, analyze
the F1 phenotypes and genotypes
STEP #1 STATE LETTER REPRESENTATIONS
Let B represent the dominant purple flower colour allele
Let b represent the recessive white flower colour allele
STEP #2 SHOW THE PARENTAL CROSS
P1 Ô B b X Ю B b
STEP #3 SHOW THE
Male
sperm
B
b
GAMETES
Female
egg
B
b
Letter B was
chosen here but a
better pick would
have been to use
the letter P
STEP #4 COMPLETE THE PUNNETT SQUARE AND ANALYSIS
Phenotype
¾ purple flower pea
plants
¼ white flower
pea plant
Genotype
¼ homozygous
purple flower
½ heterozygous
purple flower
PHENOTYPE RATIO IS 3:1 – That is the
Mendelian ratio
¼ homozygous white
flower
Now lets try to work out a problem that requires us to
determine an F2 generation. That means we start with parents
-- go to children – then to grandchildren.
In pea plants yellow pea colour is dominant to green.
A pure bred Yellow pea plant is mated to a green pea plant. Analyze F1 and F2 phenotypes
STEP #1 STATE LETTER REPRESENTATIONS
Let Y represent dominant yellow pea colour
Let y represent recessive green pea colour
STEP #2 SHOW THE PARENTAL CROSS
P1 Ô YY X Ю yy
STEP #3 SHOW THE
Male
sperm
Y
Y
GAMETES
Female
egg
y
y
STEP #4 COMPLETE THE PUNNETT SQUARE AND ANALYSIS
Y
male
Y
F1 analysis
Pnenotype
female
Yy
y
Yy
4/4 yellow seeds
Genotype
Yy
Y
Yy
4/4 heterozygous
yellow seeds
STEP #5 SHOW MATING OF OFFSPRING
f1 Ô Y y X Ю Y y
STEP #6 SHOW GAMETES
MALE GAMETE
Y
y
FEMALE GAMETE
Y
y
STEP #7 COMPLETE THE PUNNETT SQUARE AND ANALYSIS
Y
y
F2 analysis
Pnenotype
Y
YY
Yy
¾ yellow seeds
¼ green seeds
Genotype
y
Yy
yy
¼ homozygous yellow
seeds
½ heterozygous
yellow seeds
This shows the Mendelian Phenotype
ratio of 3:1. Note that it is a
monohybrid cross used to generate this
punnett square.
¼ homozygous
green seeds
Hum. Time to get
Aladdin his date.
Princess Jasmine, you are very........
Punctual?
Punctual
Okay!
Uh, uh beautiful
Say lets go together on a magic carpet ride.
Thank you for choosing “Magic
Carpet” for all your travel
needs. In case of emergency,
the exits are here, here, here
and anywhere. Keep your
hands and arms inside the
carpet!
Wonderful, glorious, magnificent, ..
punctual
Nice recovery.
Don’t stand until the rug has
come to a complete stop.
Thank you. Goodbye.
Goodbye, thank you. Goodbye
You know, I’m sitting here reading this book thinking “Why don’t
we try to calculate two characteristics at once with the punnett
square?” That would mean four different traits all at once!
In the pea plant, Green pod is dominant to yellow pod and round
seed are dominant to wrinkled. Perform an analysis of the f1 and
f2 genotypes if a Pure bred green pod, round seed plant is mated
with a yellow pod, wrinkled seed plant.
STEP #1 STATE LETTER REPRESENTATIONS
Let G represent the green dominant pod
Let g represent the yellow recessive pod
Let R represent the dominant round seed
Let r represent the recessive wrinkled seed
STEP #2 SHOW THE PARENTAL CROSS
P1 Ô GGRR
STEP #3
SHOW THE
GAMETES
X Ю ggrr
gr
GR
GR
Observe
carefully how
the gametes
are formed!
GR
GR
gr
gr
gr
Notice that this time we have made four gametes! That
means we need a punnett square with four boxes one each
side. That makes a 16 box punnett square. That sure is a lot
bigger and more complicated than the old four box variety
STEP #4 COMPLETE THE PUNNETT SQUARE AND ANALYSIS
GR
gr
GgRr
GR
GR
GR
Phenotype
GgRr
GgRr
GgRr
GgRr
GgRr
GgRr
GgRr
gr
GgRr
gr
GgRr
GgRr
GgRr
gr
GgRr
GgRr
GgRr
GgRr
16/16 green pods
round seeds
Genotype
16/16 heterozygous
green pods
heterozygous round
seeds
STEP #5 SHOW MATING OF OFFSPRING
f1 Ô G g R r X Ю G g R r
STEP #6 SHOW
GAMETES
GR
Gr
gr
gR
GR
Gr
gR
gr
STEP #7 COMPLETE THE PUNNETT SQUARE AND ANALYSIS
GR
GR
Gr
gR
gr
GGRR
GGRr
Gr
GGRr
GGrr
GgRR
GgRr
GgRr
Ggrr
gR
GgRR
GgRr
gr
GgRr
Ggrr
ggRR
ggRr
ggRr
ggrr
Phenotypes
9/16 green pod
round seed
3/16 green pod
wrinkled seed
3/16 yellow pod
round seed
1/16 yellow
pod wrinkled
seed
Just like magic, the punnett square
gives a Mendelian ratio 9:3:3:1
So in summary if you have a cross
such as Rr x Rr you will end up with
a ratio of 3 dominant to 1 recessive
3:1 This is a monohybrid cross.
4 box punnett square
If you have a cross such as BbTt x BbTt it is called a
dihybrid cross and you will end up with a ratio of
9:3:3:1 . 9 double dominant - 3 dominant at one
allele and recessive at the other – 3 recessive at
one allele and dominant at the other – 1 recessive
at both alleles.
16 box punnett square
Hi there. Who are you?
Hi there. I am Reginald Punnett.
Recognize me from my last name?
You probably do not realize my significance to the study of
modern genetics. I together with my colleague William
Bateson, contributed much of the study of modern
Mendelian genetics. Bateson had Mendel’s work translated
into English in 1900 after the rediscovery of his work by Hugo
de Vries and others.
My book Mendelism brought genetics into popular publication
in 1905.
Together with Bateson, we developed the concept of gene
linkage using peas and chickens. You will learn more about
this in a future power-point presentation
Also, I played cricket with Hardy and helped to inspire him to
formulate his Hardy-Weinberg principle. Again you will learn
more about this in a future power point presentation.
This time you get the punnett. Can you determine
the parents and the question?
P1 Yy x yy
Yellow is dominant to
green pod. A
heterozygous yellow
plant is mated to a
homozygous green
pod plant.
Phenotype
½ yellow pod
½ green pod
Try this one.
P1 AA x aa
Homozygous dominant red
crossed with homozygous
recessive blue
Phenotype
4/4 dominant red
Genotype
4/4 heterozygous dominant red
Now you might have noticed that if you have a
subject with a dominant allele, you cannot be sure
of its genotype. For example if B represents the
dominant Brown eye and b represents the
recessive blue eye, the brown eye subject could be
BB or Bb homozygous or heterozygous.
You can use the test cross to determine the
genotype!
Hey remember me. I have
brown eyes and I don’t
know if I’m homozygous
or heterozygous.
We could do a test
cross on you to find
out.
B
If I am BB my
punnett will look like
the following.
BB
x
bb
b
Bb
Bb
b
Bb
Bb
B
If I am Bb my
punnett will
look like the
following
Bb
x
bb
I f I have no blue eyed
children I am BB
B
b
b
Bb
Bb
100% of my
children will
be brown eyes
even though
my husband
has blue eyes.
b
bb
bb
50% of my
children will be
blue eyed and
50% will be
brown eyed
So if I have a blue eyed child with my blue
eyed husband, I know that I am heterozygous
brown eye.-- Bb
People are not good experimental subjects
for the test cross, but if we used plants or
bugs this cross would be more practical.
Well you should be able to handle genetics
problems now. I’ll get back to my reading. Oh
yes, you probably are wondering how Jasmine
and Aladdin are coming along. Let’s take a
look.
I guess that magic carpet ride got
you two off to a good start!
It took us to a
wonderous
place
It’s a whole
new world!
You have been a fabulous
audience! Tell you what,
you're the best audience in
the whole world. Take care
of yourselves! Good night,
Alice! Good night,
Agrabah! Adios, amigos!
MONOCROSS AND DICROSS
GENETICS PROBLEMS
ENDS