Download Ch11 Mendelean Genetics

Graded notes
Review Meiosis
2 mitosises, chromosomes replicated in interphase 1, homologous pairs,
crossing over, 4 haploid daughter cells
Review Meiosis
Pair of homologous
chromosomes vs. homologous
chromosomes….s phase…..
Gregor Mendel: Austrian
Monk who studied pea
plants
Pea plants
(1st Mendel did this: )
True-breeding: if self-pollinate,
produce offspring identical to
themselves
Cross pollinate: male sex cells in
pollen from one plant fertilize egg
cells of flower in another plant
(Then he tested flowers together w/2 different
characteristics; purple/white)
Traits: specific characteristics
(seed color, height, texture)
Monohybrid Cross
Mono = one trait
(flower color)
Hybrid = Offspring of
two different breeding
varieties
Mendel reasoned that F1 plants carried two
factors for the flower color trait
(Purple and White).
“Factors” called genes
Mendel’s crosses:
P: Parental generation
F1: Offspring or 1st generation
Hybrids: Offspring of crosses
between parents with different traits
Testing of other
traits…one trait
disappears in F1,
Reappears in F2
Conclusions of Mendel’s crosses:
Genes: Chemical factors that
determine traits passes on from
one generation to another
Alleles: Different forms of genes
for trait
Ex. Plant height has two forms
produces tall plants & short
ones
Alleles on Homologous
chromosomes
Principle of Dominance:
states that some alleles
are dominant and other
are recessive
Dominant: Trait will always
show up; Shown with
capital letters
Recessive: Trait does not
show up; Shown with
lower case letters
Homozygous: (TT)
organism has 2 identical
alleles for particular trait
Heterozygous: (Tt)
organism has 2 different
alleles for particular trait
Phenotype: physical
characteristics you see
(yellow, round)
Genotype: genetic makeup
(Tt); what we write
Don’t Copy
What are alleles?
Different forms of gene
Where do alleles come from?
One from each parent
Since one allele is inherited from each parent,
two letters are needed to represent the alleles of a gene
GENOTYPE?
-two letters that represent the alleles of a gene
EX. RR, Rr, rr
Don’t copy
Phenotype?
the outward appearance of an
organism (what it looks like)
If a farmer has a red flower (RR) give
genotype and phenotype
- the genotype is RR
- the phenotype is red
1. A brown dog (bb)
the genotype ________
the phenotype _______
2. A long haired cat (Hh)
the genotype _______
the phenotype _______
(Review)
Mendel learned that the
alleles of each
Replication of
individual separate chromosomes
and end up in
gametes because of
MEIOSIS!!
Ex. A female pure brown dog (bb)
Dominant or Recessive?
bb
b
b
PRACTICE on paper
A hybrid male yellow canary (Yy)
Dominant?
Yy
Y
y
Practice!
A pure female white flower (rr)
Dominant? Recessive?
rr
r
r
If a male red flower (Rr) and a female pure
white (rr) flower from above got their
gametes together (fertilization)
What kind of combinations could be formed?
X
Practice on own paper before showing next slide! Write out male=Rr, female=rr.
Which is dominant, recessive? What are we crossing? (Write Genotypes)
Male red flower (Rr)
Female white flower (rr)
Rr
R
Sperm 1
rr
r
Sperm 2
Answers? Write out alleles for each
gamete of cross.
r
Egg 1
r
Egg 2
Show possible offspring of crossing
different alleles.
Genotype
R
+
1
r
=
1
R
+
r
1
2
r
2
r
2
+
r
=
=
1
+
r
2
=
Phenotype
A punnet square is a chart
that helps us predict the
probability that an offspring
with a particular genotype
and phenotype will be
produced
Punnett Squares show the
chances that one male’s
sperm & one female’s eggs
can make certain offspring
Create a punnett square using male red (Rr)
and female white (rr) flowers.
To Make a punnet square there are a few
simple steps to follow:
1) Draw a box and divide it into four parts
2) Label the left hand side of the box with
the genotype of male parent
(R=Red, r=White)
R
r
3) Label the top of the box with the genotype
of the female parent
r
R
r
r
4) In the middle boxes place 2 alleles. One letter
comes from the left side and one from the top
R
r
r
r
Rr
Rr
rr
rr
R= Red
You have predicted
what kind of
offspring these 2
parents could
have!!!
r= White
Red______%
White______%
You now know the possible genotypes
for the offspring of these two parents.
• The genotypes of the offspring are:
2: Rr, 2: rr
Red=50% White=50%
R
•The phenotypes of the
offspring are:
r
2: Red, 2: White
r
r
Rr
Rr
rr
rr
1. A cross between a female with straight
hair (SS) and a male with curly hair (ss).
Draw out punnett square:
genotypes_____________
phenotypes______________
Straight______% Curly_______%
2. A cross between a black dog (Bb) and a
brown dog (bb). Draw out Punnett Square.
genotypes_____________
phenotypes_______________
Black_______% Brown________%
Ratio_____:______
3. A cross between a yellow corn (Yy) and
another yellow corn (Yy) (y = white corn).
Draw out Punnett Square.
genotypes_________________
phenotypes_________________
Yellow corn_______% White corn________%
Ratio_____:______