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Ch 10.1
Mendel’s Laws
of Heredity
Take 5: 11/11/10
► Round
Seeds (R) are dominant to wrinkled
seeds. Finish the following crosses:
► Rr x rr : what percentage of the offspring
would be round?
► Rr
x Rr : What percentage of the offspring
would be round?
Take 5
►
Which phase in meiosis do the tetrads break and are
pulled to opposite poles of the cell?
►
Which phase in meiosis do the chromosomes (paired
chromatids) line at the equator of the cells?
►
Which phase results in formation of 4 haploid cells?
►
A haploid cell has ___________ as many chromosomes
than a diploid cell.
► Austrian
monk of the
mid 19th century who
studied pea plants:
_______________ aka
“Father of Modern
Genetics”
► Mendel
studied
__________ (the
passing on of
characteristics from
parents to offspring)
► ________
are inherited
characteristics
► Mendel
was the first
person to succeed in
predicting how traits are
transferred from one
generation to the next.
► This
branch of biology
that studies heredity is
called ___________
► Mendel
studied
_____________
► Garden
pea plants
reproduce sexually
(this means that
they produce both
male and female sex
cells) called
________
► The
male gamete of
a plant is referred to
as _______
► The
process by where male
gametes unite with female
gamete is called
_________________
► In
plants, the transfer of
pollen to female reproductive
organ is called
________________
►A
fertilized cell is known as a
_______ and in plants it
later develops into a seed
Mendel’s Monohybrid Crosses
► Mendel
experimented with many different traits
of pea plants and he recorded this information
and …
 For example, he looked at seed shape, seed color,
flower color, flower position, pod color, pod shape,
and plant height.
► Let’s
look at one example:
_____________
► Pea
plants came in two varieties:
_____& _______
► Mendel
noticed that when
he crossed a short (Mom)
plant and a tall (Dad)
plant, that all the offspring
(Children) were _______
► Then
X
when he crossed
two of the offspring
(children plants) with each
other, ___ out of 4 were
tall and ___ out of 4 where
short.
► Mendel
began noticing patterns like this and began
developing ideas for explanations.
first law is the LAW OF SEGREGATION:
which states that every individual has two alleles
for each gene and when gametes are produced,
each gamete receives one of these alleles
► The
second law (LAW OF INDEPENDENT
ASSORTMENT) states: each allele of any one pair
is free to combine with any allele from each of the
remaining pairs during the formation for the
gametes. This developed while Mendel examined
dihybrid crosses.
► The
Now let’s explore the terminology:
► The
parent generation is
P
called: ___
first born generation is
called: ___
F1
X
► The
► The
second generation is
F2
called: ___
X
you are crossing (breeding) organisms
and only looking at ONE characteristic, you
are conducting a ______________ cross
► When
you are crossing (breeding) organisms
and only looking at TWO characteristics, you
are conducting a ___________ cross
► When
you are crossing (breeding) organisms
and only looking at THREE characteristics,
you are conducting a ___________ cross
► When
►We
now know that genes are found on
_____________. Genes exist in
alternative forms. We call these
different gene forms _______. An
organism has two alleles for each trait
and these two alleles are found on
different copies of the chromosome
(one from Mom and one from Dad).
Alleles are often represented by
_________.
The Allele
►A
capital letter indicates a ___________
trait (what is observed)
►A
lowercase letter indicates a ___________
trait (often hidden)
► There
are three different combinations that
can arise from having only a capital and a
lowercase letter: ____, ____, ____.
Alleles for the height trait
Tall
Tall
Short
► Each
of these letter combinations has a
science description that corresponds with it.
►
_____ is called homozygous dominant
►
_____ is called homozygous recessive
►
_____ is called heterozygous
►When
talking about the genes of an
organism, these letter (allele)
combinations are referred to as the
___________.
►When
talking about the physical
appearance of an organism, we use
the term ___________.
How to use and complete a Punnett
Square:
1)___________________________________
_________________________________
How to use and complete a Punnett
Square:
2)________________________________
______________________________
How to use and complete a Punnett
Square:
3)__________________________________
__________________________________
How to use and complete a Punnett
Square:
4)_________________________________
_________________________________
How to use and complete a Punnett
Square:
5)__________________________________
__________________________________
How to use and complete a Punnett
Square:
6)__________________________________
__________________________________
How to use and complete a Punnett
Square:
7)__________________________________
__________________________________
How to use and complete a Punnett
Square:
8)__________________________________
__________________________________
Starting with the Parent
Generation….
IV. Mendel’s Dihybrid Crosses
A.
Mendel performed another set of crosses in which he used
peas that differed from each other in ________________
2
traits.
The first generation
B.
The second generation
►
Round Yellow
1. Mendel took true-breeding pea plants that had __________________
seeds (RRYY) and crosses them with true-breeding pea plants that had
_____________________
Green Wrinkled seeds (rryy).
2. F1 Generation all had __________________________
Round Yellow (RrYy) seeds.
1. Mendel let the F1 plant __________________
Pollinate
themselves.
2. In the F2 generation, he found that hey appeared in a definite ratio of
9
phenotypes _______
round yellow ____
3 wrinkled
3 round green, ____
yellow, _____
1 wrinkled green.
V. Punnett Squares
Dihybrid Crosses
* A Punnett square for a dihybrid cross
four
will need to be ________
boxes on
16
each side for a total of ________
boxes.
B.
Dihybrid cross: RrYy X RRyy
► Round
is dominant to wrinkled and Yellow is
Dominant
To Green
Genotypic Ratio:
______________
Phenotypic Ratio:
______________
VI. Probability
► Punnett
squared are good for showing
combinations
all the possible ______________
of
gametes and the likelihood that each
will occur.
► It is important to remember that the
results predicted by probability are
more
____________
likely to be seen when
large
there is a ___________
number of
offspring.