Happy Wednesday Bio-Ninjas
Bellwork: Scientists
have discovered a
new creature!
Seen to the right…
EE = Two Eyes, Ee = Two Eyes, ee = one eye
AA = Two horns, Aa = Two horns, aa = one horn
What are the possible genotypes for this
creature?
What are some creature phenotypes that can
be observed from the picture?
Set up today’s page in your journal…
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Page: 51
Title: Mendelian Genetics
Date: 11-18-14
Essential Question: Can genetic outcomes
be predicted with 100% accuracy?
**Do NOT leave a summary space on the
first page! We will be using multiple pages
today.**
Standard: predict possible
outcomes of various genetic
combinations (B.6F)
Trait: a specific characteristic that varies from
one individual to another
For example…
Inheritance is determined by
biological factors that are passed
from one generation to the next.
In other words, which traits you
pass on depends on what genes
you get from your parents.
Genes: chemical factors that
determine traits
(small sections of your DNA
strand…remember??)
Alleles: different forms of a gene
Principle of Dominance:
some alleles are dominant
and others are recessive
• the dominant allele will
always be expressed
when it is present
[
[
• a capital letter is used
to represent a
dominant allele
• the recessive allele will
only be expressed when
the dominant is not
present
• a lowercase letter
is used to represent
a recessive allele
Phenotype:
appearance
Genotype: the actual
gene code (letters)
*Two organisms can
have the same
phenotype but
different genotypes*
Homozygous = purebred
*Homo = same alleles
(both dominant or both
recessive)
Heterozygous = hybrid
*hetero = different alleles
(one dominant, one
recessive)
Principle of Independent Assortment: the way alleles
separate during meiosis is completely random and cannot
be predicted
**This is why you
never know for
sure which traits
will be passed on
to which
offspring!**
Probability: the
likelihood that a
particular event will
occur
We can predict
possible genetic
outcomes using
probability.
Punnett square:
a diagram that
shows the
probability of
certain traits
being passed on
to offspring
•The letters in the
Punnett square
represent alleles passed
on from parent to child.
Punnett squares are
used to predict and
compare the genetic
variations that will
result from a cross.
How to complete a Punnett Square
1st = Use information to IDENTIFY and
EXTRACT THE GENOTYPES
*”homo”/”hetero”, “dominant”/”recessive”, “pure”/”hybrid” are all
clues to the genotype
• Extract: remove or take out, especially by effort or
force.
How to complete a Punnett Square
2nd = Arrange the genotypes on the top and
side of the Punnett square.
*the male genotype is usually written on top and the female on the side
How to complete a Punnett Square
3rd = Cross the Genotypes to discover the
possibilities.
*the male genotype is usually written on top and the female on the side
How to complete a Punnett Square
3rd = Cross the Genotypes to discover the
possibilities.
*the male genotype is usually written on top and the female on the side
Let’s Pracice….
• You will need the worksheet you grabbed
when you came in.
Punnett Square practice…
1. What would be the possible outcomes for the offspring of a
cross between pink flower (PP) and a white flower (pp)?
p
p
P
P
Pp
Pp
Pp
Pp
P = Pink
p = White
DAD = PP
MOM = pp
**When using the letters like “P and p” OR “C and c”, draw the lowercase letter in
cursive or just make sure you make them look different. Otherwise, you might
confuse the dominant for the recessive **
2. Long fingers are dominant (F) to short fingers (f).
Complete the Punnett square for a homozygous
recessive mom and a heterozygous dominant dad.
f
f
F
f
Ff
ff
F = Long
f = Short
ff
DAD = Ff
MOM = ff
Ff
3. In a plant, long stems are dominant (L) to short stems (l). If a
homozygous dominant flower and a homozygous recessive plant are
crossed, what would be the phenotypic ratio of their offspring?
l
l
L
L
Ll
Ll
L = Long
l = Short
Ll
DAD = LL
MOM = ll
Ll
4. Straight hair (C) is dominant to curly hair (c). What would be
the probability that a child would have curly hair if both
parents are heterozygous dominant?
C
c
C
c
CC
Cc
Cc
cc
C = Straight
c = Curly
DAD = Cc
MOM = Cc
5. Having a hitchhiker's thumb is a dominant trait (T). If
a woman with a straight thumb has a child with a man
who is heterozygous for the trait, what are the chances
their child will have a hitchhiker's thumb?
T
t
t
Tt
tt
t
Tt
tt
T = Hitchhiker
t = Straight
DAD = Tt
MOM = tt
6. What would the phenotypic and genotypic ratios be
for two purple (Pp) flowers that were bred together?
P
p
P
p
PP
Pp
Pp
pp
P = Purple
p = White
DAD = Pp
MOM = Pp
Can you identify your own genotypes
and phenotypes?
Hairline:
Widow’s peak is dominant to
straight hairline
Eye Shape:
Almond eyes
is dominant to round eyes
Eyelash Length:
Long eyelashes is dominant to
short eyelashes
Tongue Rolling:
CAN roll the tongue
is dominant to cannot
Hitchhiker’s Thumb:
Hitchhiker’s thumb is dominant to
straight thumb
Lip Thickness:
Thick lips
are dominant to thin lips