Download BB - Life Science Classroom

KEY CONCEPTS
1. Definition
2. Revision from gr 11:
• Homologous chromosomes
• Paternal/maternal chromosomes
• Diploid/haploid
• Somatic cell/body cell
1
Genetics
• Genetics is the study of heredity
• It deals with the similarities and
differences between parents and their
offspring
• In Genetics we look at how
characteristics are passed from one
generation to the next.
• Genes carry the hereditary information on
chromosomes.
WHAT IS GENETICS
4
JESSICA ALBA GETS MARRIED
Chromosomes, DNA & Genes
KEY CONCEPTS
1. Locus(i)
2. Alleles
3. Genome
4. Dominance & Recessiveness
5. Karyotype
6. Genotype
7. Phenotype
8. Homozygous
9. Heterozygous
2
Genetics
• Let us look at the human characteristic of
having a free or attached earlobe
• Click on the attached lobe
YES This ear is attached
This lobe is FREE
3
Genetics
Attached lobe
Free lobe
4
Attached lobe
e e
•Genes occur in pairs
•If we represent the gene for
attached ear lobe as little “e”
•Then this persons gene pair will
be “ee”
5
Genetic Terms
e e
PHENOTYPE
The characteristic
expressed by the gene
e.g. attached ear lobe
ALLELE
genes are partners
of each other:“e”
is an allele of “e”
GENOTYPE
The genes that code
for a characteristic e.g.
ee
6
Looking at the genes on Chromosomes
Attached lobe
e
e
The genes occur in
pairs on
chromosomes
Free lobe
E
E
The gene for free
lobe is “E”
7
Attached lobe
e
e
Free lobe
E
E
The genes occur at special positions on
chromosomes called loci.
One version of the gene is inherited from the
father , the other from the mother
If the two genes are the same e.g. ee or EE
they are homozygous.
8
E
e
There can be a mixture of attached and free
ear lobe genes (Ee)- heterozygous.
One gene, in this case (E) is dominant over
unattached lobe (e) which is called recessive
In this case the E gene completely supresses
the expression of e gene so this persons will
have free ear lobes
9
Summary Three possible genotypes…
PHENOTYPE
Free lobe
Attached lobe
GENOTYPE
e
e
Homozygous
recessive
E
E
E
e
Heterozygous dominan
Homozygous dominant
Alleles
Alleles
Bb
BL**DY IMPORTANT DEFINITIONS
1. The two genes on homologous chromosomes
that code for the same characteristic are found
on identical locations on the pair of
chromosomes, called loci (singular: locus) pg 5
2. Alleles are alternate forms of a gene located on
the same locus of homologous chromosomes.
3. It seems that sometimes, one gene dominates
the other of the pair. We say that the one gene
is dominant, while the one that is dominated, is
called the recessive gene (pg5).
4. A genotype Bb is called HETEROZYGOUS (or
hybrid). Here the paired genes (ALLELS) for a
particular trait (characteristic) are different (pg
6).
5. A genotype BB or bb is HOMOZYGOUS. Here
the paired genes (ALLELES) for a particular
trait (characteristic) ore identical (7)`
BL**DY IMPORTANT DEFINITIONS
1. The characteristics that we can see in
an individual, for example, brown
eyes, is known as the PHENOTYPE (pg
6).
2. The letters Bb indicate to us the
GENOTYPE for eye colour, that is, its
genetic makeup (pg 6).
1
Looking at our example of earlobes.
What possible offspring can be produced if:
The male parent has
The female parent has
ATTACHED lobes
FREE lobes
(ee)
(EE)
2
Firstly we need to look at
the formation of sperm
cells (male gametes in the
testes) to see the different
types of sperm cell that
can be produced from this
ee parent.
3
Looking at one cell in the testes dividing by meiosis
e
e e
e
Cell with double stranded
chromosome pair with egenes
4
Cell divides by meiosis
e
e e
e
5
e
e
e
e
End of the first MEIOTIC
division Chromosomes
have separated
6
e
e
e
e
Second MEIOTIC division
7
End of the second MEIOTIC division
– FOUR sperm cells are produced,
each with a e-gene
e
e
e
e
8
E
ee
EE
e
e
e
e
e
In the same way, the female
will produce egg cells in the
ovary.
As she is EE she will only
In this
only one type of sperm cell
produce
onecase
typethere
of eggis cell
that can be produced – all have e-gene
with the E-gene
9
e
E
ee
EE
E
e
The sperm and
egg cells fuse to
form a new child
All the offspring from these parents will have a Ee
genotype – They will ALL have Free ear lobes
Punnett Square
GAMETES
E
E
e
Ee
Ee
e
Ee
Ee
1
Now what if both parents are heterozygous (Ee)
What are the possible offspring?
The male parent has
The female parent has
ATTACHED lobes
ATTACHED lobes
(Ee)
(Ee)
2
Looking at one cell in the testes dividing by meiosis
E
E e
e
Cell with double stranded
chromosome pair with E
and e genes
3
Cell divides by meiosis
E
E e
e
4
E
E
e
e
End of the first MEIOTIC
division Chromosomes
have separated
5
E
E
e
e
Second MEIOTIC division
6
End of the second MEIOTIC division: FOUR
sperm cells are produced, TWO with an Egene and TWO with e-gene
E
E
e
e
7
E
E
e
e
Two types of sperm cells can be produced- ONE
with a e-gene and one with a E-gene
8
Looking at one cell in the ovary dividing by meiosis
E
E e
e
9
E
E e
e
10
E
E
e
e
11
E
E
e
e
12
E
E
e
e
13
E
E
e
e
Two types of egg cells can be produced- ONE with
a e-gene and one with a E-gene
14
E
e
15
E
E
e
e
What possible offspring can be produced
when these sperm and egg cells fuse?
16
e
E
E
e
E
E
E
e
If a E-sperm
If a e-sperm
fuses with a E- fuses with a Eegg, the child
egg, the child
will be EE -Free will be Ee -Free
Lobe
Lobe
17
e
E
E
e
E
E
e
E
In the same
way …
E
e
e
e
To simplify this we use a Punnett square to
show possible offspring
male gametes
E
female gametes
18
E
e
EE
Ee
e
Ee
ee
Possible offspring
3 out of 4 free
lobes
1 out of 4
attached lobe
If for example
marries
P1 (first parental generation) Bb
x
(Brown-eyed male)
Meiosis
Meiosis
B
b
Male gametes (sperm)
♀
GAMETES
b
b
Female gametes (egg cells)
Male gametes ♂ (symbol for male)
We use what is called a PUNNET SQUARE
Female
gametes
bb
(blue-eyed female)
B
b
b
Bb
bb
b
Bb
bb
Punnett Square
GAMETES
B
b
b
Bb
bb
b
Bb
bb
Male gametes ♂ (symbol for male)
We use what is called a PUNNET SQUARE
GAMETES
B
b
b
Bb
bb
b
Bb
bb
• Phenotype: Half are Brown-eyed, half
are blue-eyed (1:1)
• Genotype: half are heterozygous
brown (Bb) and half are homozygous
blue (bb): 1Bb:1Bb
Why can two brown-eyed parents have a blue-eyed child?
P1
Bb
x
Bb
P1
Meiosis
B
Fertilisation
F1
or
GAMETES
b
B
or
B
b
ratio of gametes
b
B
BB
Bb
b
Bb
bb
1 homozygous brown (BB)
2 heterozygous brown (Bb)
1 homozygous blue (bb)
(F1 = first filial generation, in other words, the possible types of eye-colour of
children the parents may have)
The PHENOTYPIC RATIO: 3 brown-eyed child:1 blue-eyed child
The GENOTYPIC RATIO:
1 homozygous brown (BB): 2 heterozygous brown (Bb): 1 homozygous blue (bb)
1BB:2Bb:1bb or
25%BB:50%Bb:25%bb
e.g., Tall Plants x Short Plants
Let T = gene for tallness
Let t = gene for shortness (note: you must use the same letter for a
characteristic)
P1
TT
x
T
T
tt
t
P1 (crossed 2 homozygous plants)
t
(Gametes)
Fertilisation
F1 (Punnet square)
GAMETES
t
t
T
Tt
Tt
T
Tt
Tt
All the offspring of F1 will be Tt (heterozygous tall)
Thus, Mendel said that when two characteristics meet in an individual, one
dominates over the other, called the recessive
(LAW OF DOMINANCE AND RECESSIVENESS).
Mendel took the offspring from F1 (Tt) and crossed them
P2
Tt
x
Tt
P2 (2nd Parental generation)
Meiosis
T
t
T
t
gametes
Fertilisation
F2
GAMETES
T
t
T
TT
Tt
t
Tt
tt
1 homozygous tall (TT)
2 heterozygous Tall (Tt)
1 homozygous short (tt)
Mendel’s law:
INDEPENDENT ASSORTMENT
• Independent assortment occurs
during meiosis I, specifically
metaphase I of meiosis, to produce
a gamete with a mixture of the
organism's maternal and paternal
chromosomes. Along with
chromosomal crossover, this
process aids in increasing genetic
diversity by producing novel genetic
combinations.
3
MEIOSIS – Prophase I
Crossing Over
As
This happens
homologous
when
partner
pairs line up,
chromosomes
crossing
over
swop
pieces
of
occurs
chromatid
Chromatids
This
mixesof
Pieces
from
partner
genetic
chromosome
material
chromosomes
are
andswopped
brings
cross
over
variety
4
Crossing Over brings Variation
Instead of
Four different
types of
chromatids
Two
5
MEIOSIS – Metaphase I -
The
Homologous
chromosome
pairs
can line
chromosomes
up in different
line up
combinations –
IN
this PAIRS
atbrings
the equator
variety
6
How many possible combinations are there ?
With 2
chromosome
pairs (2) there
are 4 possible
combinations
22 = 4
This is called
independent
assortment
7
How many possible combinations are there ?
What possible
combinations are
there with 23 pairs?
223 = ?
8 388 608
Remember this is without
crossing over and just in
a sperm or egg cell!!
Mendel’s law:
INDEPENDENT ASSORTMENT
• In independent assortment the homologous
•
chromosomes separate randomly during
Anaphase I of Meiosis I. Chromosomes that
end up in a newly-formed gamete are randomly
sorted from all possible combinations of
maternal and paternal chromosomes.
Because gametes end up with a random mix
instead of a pre-defined "set" from either
parent, gametes are therefore considered
assorted independently. As such, the gamete
can end up with any combination of paternal or
maternal chromosomes.
INCOMPLETE DOMINANCE
• In Gauteng, we often see cosmos
flowers on the side of roads at the
end of summer. We see red, white
and purple flowers. Why?
1
Incomplete Dominance
Incomplete Dominance occurs when the
offspring show a combination of recessive and
dominant characteristics
Pure Red flowers crossed with White flowers
produce all pink flowers in the F1 generation.
INCOMPLETE DOMINANCE
• Let R
• Let W
= gene for red snapdragons
= gene for white snapdragons
GENOTYPE PHENOTYPE
CRCR
Red Flowers
CRCW
Pink flowers
CWCW
White flowers
INCOMPLETE DOMINANCE
P1
CRCR
x
CWCW P1 (crossed 2 homozygous plants)
CR
CR
Fetilisation
F1 (Punnet square)
GAMETES
CW
CW
CW
CW
CR
CR
CRCW
CRCW
CRCW
CRCW
(Gametes)
INCOMPLETE DOMINANCE
If CRCW is crossed with CRCW the result will be
F2
GAMETES
CR
CW
CR
CRCR
CRCW
CW
CRCW
CWCW
• Phenotype: 1 red: 2 pink: 1 white
• The genes are unaltered by this
phenomenon
CO-DOMINANCE
PARENTS
Phenotype: Red
Genotype: IRIR
x
x
White
IWIW
Key: R – Red coat W – White coat
MEIOSIS
GAMETES
IR IR
IW IW
FERTIISATION
GAMETES
IW
IW
IR
IR
IR IW
I RI W
IRIW
IRIW
Looking at co-dominance when pure bred
(homozygous) red and white cattle are bred.
2
P1
Genotype
Red Bull
IRIR
White cow
IW IW
Gametes
CR
CW
F1
All IRIW (Roan) Offspring are produced
GAMETES
W
W
GENOTYPE:
PHENOTYPE:
R
R
RW
RW
RW
RW
ALL HETEROZYGOUS RW
ALL ROAN
CO-DOMINANCE
P2 (F1)
Phenotype:
Roan
IR I W
x
MEIOSIS
GAMETES IR IW
FERTIISATION
GAMETES
Roan
IR I W
IR I W
IR
IW
IR
IR IR
IR IW
IW
IR IW
IW IW
• F2Genotype: 1 IR IR: 2 IR IW: 1 IW IW
• F2 Phenotype: 1 RED: 2 ROAN: 1 WHITE
GAMETES
R
W
Genotype:
Phenotype:
R
W
RR
RW
RW
WW
1 RR: 2 RW: 1 WW
1 RED: 2 ROAN: 1 WHITE
WHAT ARE THE CHANCES OF HAVING A BOY OR GIRL ON THIS BASIS ALONE?
_______%
50%
MALE
PARENT
FEMALE
XY
BODY CELL
XX
MEIOSIS
GAMETES
X
Y
X
XX
XY
X
FERTILISATION
ZYGOTE
[OFFSPRING/PROGENY] XX
XY
SEX-LINKED INHERITANCE
Some Characteristics, like the gene for colour vision are found attached to the X
chromosome. This means that the gene for that characteristic is linked to the sex o
the individual.
X
X
X
Y
Do you notice that the male’s
X chromosome does not have
corresponding loci on the Y
chromosome because it is
shorter. Thus even a recessive
gene on the X chr. will be
expressed.
In humans, the gene for colour vision is sex-linked. The gene is linked to the X
chromosome. The gene for normal colour vision (B) is dominant over the gene for
colour blindness (b).
B
b
X
X
XBXb
b
X
Y
XbY
If the female parent (XX) has normal vision (Bb) and the male (XY) is colour blind (b
– only on the X)…
8
SEX-LINKED INHERITANCE
X
X
X
Y
If the female parent (XX) has normal vision (BB)
and the male (XY) is colour blind (b –only on
the X)…
How do we link the colour blind genes to the
sex chromosomes ?
9
SEX-LINKED INHERITANCE
B
B
X
b
X
X
Y
Normal Female
Colour Blind male
BB on the X
chromosomes
b on the X
chromosome only
10
Normal
Female
B
Colour
Blind
Male
b
B
XX
b
XY
X
B
Colour blind male
possible sperm cells
B
X
Y
X
Normal female
possible egg cells
Normal Female x Colour Blind Male
11
Normal
Female
B
Colour
Blind
Male
b
B
XX
b
XY
Y
X
B
X
B
b
B
X
X
Normal Female but
carries the (b) colour
blind gene
Normal Female x Colour Blind Male
X
Y
Normal Male
12 What are the possible offspring that would result
from a carrier female and normal male ?
Normal male gametes
Carrier female
gametes
XB
Y
1
2
XBXB
XB
4
XBXb
XbY
Possible GENOTYPE
1 Normal
female
2 Normal
male
XBY
3
Xb
PHENOTYPE
3 Carrier
female
4 Colour
blind male
What are the possible offspring that would result from a carrier female and
normal male?
P1
XBXb
x
XB Y
meiosis
gametes
XB
Xb
XB
Y
FERTIISATION
GAMETES
F2:
XB
XB
XB X B
Xb
XB X b
Y
XB Y
XbY
Genotype:
_____________________________________________
1
XBXB: 1XBXb: 1 XBY: 1 XbY
NORMAL: 1 FEMALE NORMAL CARRIER:
Phenotype: 1 FEMALE
_____________________________________________
1 MALE NORMAL: 1 MALE COLOURBLIND
_____________________________________________
BLOOD GROUPS
• CO-DOMINANCE
• MULTIPLE ALLELES


ABO blood groups in humans
Important because ABO blood groups affect blood transfusions
o Genes cause expression of sugar groups on surface of red blood cell
membrane; these carbohydrates act as antigens in immune reactions
o 3 alleles: A, B, O
o A & B dominant over O
o A & B co-dominant to each other
o Type O produces no sugar antigens
o 6 genotypes and 4 phenotypes
Phenotype
Genotypes
A
AA (IAIA) or AO (IAi)
B
BB (IBIB) or BO (Ibi)
AB
AB (IAIB)
O
OO (ii)
Blood Groups
e.g., Cross a homozygous group A man with a heterozygous group B women to
find the
F1
PHENOTYPE
A (I A I A)
x
B (I Bi)
GENOTYPE
GAMETES
F1
GAMETES
IA
IA
IB
IAIB
IAIB
i
IA i
IA i
50% = IA i 50% = IAIB
GENOTYPE: _______________________________________________________
50% = A 50% = AB
PHENOTYPE:_______________________________________________________
Blood Groups
Cross a homozygous group A man with a heterozygous group B women to find the
F1
PHENOTYPE
A
x
GENOTYPE
AA
B
BO
GAMETES
F1
GAMETES
A
B
AB
O
AO
GENOTYPE:
A
AB
AO
2 AB:2AO
PHENOTYPE: 50% GROUP A: 50% AB
BLOOD GROUPS
BLOOD TRANSFUSION
Before a person (recipient) receives blood, the
blood of the donor has to be first tested to ensure
that it is not infected and is of the right type.
The table below shows the safe donor for recipients
of the various blood types:
BLOOD TYPE OF
RECIPIENT
ANTIBODIES
A
B
AB
O
B
A
NONE
A&B
DONOR
A, O
B, O
A, B, AB, O
O
Blood Groups
BLOOD TYPE OF
PARENTS
AB
x
AB
AB
x
A
AB
x
B
AB
x
O
A
x
A
A
x
B
A
x
O
B
x
B
B
x
O
O
x
O
BLOOD TYPE OF
CHILDREN
A, AB, B
A, AB, B
A, AB, B
A, B
A, O
AB, A, B, O
A, O
B, O
B, O
O
AB
X AB = A, AB, B
GAMETES
A
A
(I )
B
B
(I )
A (IA)
AA (IAIA) AB (IAIB)
B (IB)
AB (IAIB) BB (IBIB)
BLOOD TRANSFUSION
recipient
donor
A
A or O
B
B or O
AB (UNIVERSAL RECIPIENT) A, B, AB, or O
O (UNIVERSAL DONOR)
O
The pedigree diagram below shows the blood groups of individuals of a
family. The blood groups are indicated inside the circle or square. The
blood groups of individuals W and X are not indicated.
Blood
group O
W
Blood Group
A
X
Write down al the possible
genotypes of individuals:
[a]
W
[b]
X
Blood
group B
(a)W = AB (IAIB)
(b) AO (IAi)
Blood
group O
Key:
Male
Female
X = AO (IAi)
OO (ii)
(8)
Haemophilia is a blood clotting disorder. Explain why
mainly males suffer from this disorder.
(4)
• It is a sex-linked disease caused by a recessive
•
•
•
•
allele carried on the X chromosome
Males need only one recessive allele to have the
disease because
they have XY combination,
while females have to have both recessive
alleles to have haemophilia
because they have an XX combination any (4)
DIHYBRID CROSSES
Let R = gene for round seeds
Let Y = gene for yellow seeds
r = gene for wrinkled seeds
y = gene for green seeds
If a Round, yellow seed is crossed with a wrinkled green seed:
Genotype of parents (P1)
RRYY
x
rryy
meiosis
Gametes
RY
Genotype of offspring (F1)
Phenotype of offspring:
RY
ry
ry
RrYy
All Round, Yellow seeds
Genotype of parents (P2)
RrYy
x
RrYy
meiosis
Gametes
RY
Ry
rY ry
RY
Ry
rY
Genotypes of the offspring (F2)
GAMETES
RY
Ry
rY
ry
RY
Ry
rY
ry
RRYY
RRYy
RrYY
RrYy
RRYy
RRyy
RrYy
Rryy
RrYY
RrYy
RrYy
rrYY
rrYy
Phenotype of offspring (F2):
Rryy
Round Yellow:
rrYy
9
………
………
3
Round Green:
............
Wrinkled Yellow: 3
…….....
Wrinkled Green: 1
……….
rryy
ry
Polygenic inheritance
• Some phenotypes determined by
additive effects of 2 or more genes on a
single character
– phenotypes on a continuum
– human traits
• skin color
• height
• weight
• eye color
• intelligence
• behaviors
Polygenic inheritance
ALBINISM
The woman must be Aa (because parents were aa x AA or aa x Aa)
Albino man
normal woman
X
aa
all
a
½
Aa
sperms x
Aa
Normal children
½
A
eggs ½
½
aa
Albino children
a
Albinism
albino
Africans
Johnny & Edgar Winter
DOWN’S SYNDROME
DOWN’S SYNDROME
• Individuals with Down syndrome tend to
have a lower-than-average cognitive
ability, often ranging from mild to
moderate disabilities.
• A small number have severe to profound
mental disability. The average IQ of
children with Down syndrome is around
50, compared to normal children with an
IQ of 100.
•
•
•
•
•
•
•
•
abnormally small chin
poor muscle tone
a flat nasal bridge
protruding tongue (due to small oral cavity,
short neck,
Mental retardation in the mild (IQ 50–70) to
moderate (IQ 35–50) range.
They also may have a broad head and a very
round face.
Language skills show a difference between
understanding speech and expressing speech,
and commonly individuals with Down syndrome
Nature vs. nurture
• Phenotype is controlled by
both environment & genes
Human skin color is
influenced by both genetics
& environmental conditions
Coat color in arctic
fox influenced by
heat sensitive
alleles
Color of Hydrangea
flowers is influenced by
soil pH
Non Inherited variations
ENVIRONMENTAL
VARIATIONS
• Birth Defects also called congenital
•
disorders due to factors affecting foetal
development, such as radiation, heat, chemicals
(booze, smoking), infectious agents or maternal
disease (e.g., measles)
Teratogen: “monster” “born”
Inherited Variations
• Mutations
A mutation occurswhen the
order of nucleotides in the
D.N.A. is changed.
X-rays, excessive exposure to
the sun’s heat, exposure to
harmful chemicals, radiation
form nuclear bomb
explosions are some of the
causes of mutated genes.
The offspring will inherit the
mutated gene
Hybridisation
Genetically modified (GM)
foods
GM foods
• Genetically modified organisms have had
specific changes introduced into their DNA
by genetic engineering,
• unlike similar food organisms which have
been modified from their wild ancestors
through selective breeding (plant breeding
and animal breeding) or mutation
breeding.
• GM foods were first put on the market in
the early 1990s.
GM FOODS – the positives
• GM foods have been modifies to:
increase the crop yield;
• make crops resistant to herbicides
(so that weeds can be eliminated);
resistance to insects which may eat
the crop;
• production of specific nutrients (like
vitamins);
• produce drought-resistance crops;
• improve the taste of certain foods;
GM FOODS – the negatives
• Critics have objected to GM foods on several
•
grounds, including perceived safety issues
(may cause diseases), ecological concerns
(genes from GM foods may mix with nonGM foods and cause unfvourable changes
in crops) and
economic concerns raised by the fact that
these organisms are subject to intellectual
property law (premium on price for these
seeds).
Human Genome
• The human genome is the
genome of Homo sapiens, which
is stored on 23 chromosome
pairs. Twenty-two of these are
autosomal chromosome pairs,
while the remaining pair is sexdetermining. The haploid human
genome occupies a total of just
over 3 billion DNA base pairs.
The Human Genome Project
(HGP) produced a reference
sequence of the euchromatic
human genome, which is used
worldwide in biomedical
sciences.
Human Genome
• The haploid human genome contains ca.
23,000 protein-coding genes, far
fewer than had been expected before its
sequencing. In fact, only about 1.5% of
the genome codes for proteins, while
the rest consists of non-coding RNA
genes, regulatory sequences, introns, and
(controversially named) "junk" DNA.
STEM CELLS
• Stem cells are cells found in all multi
cellular organisms. They are characterized
by the ability to renew themselves
through mitotic cell division and
differentiate into a diverse range of
specialized cell types.
• The two broad types of mammalian stem
•
•
•
cells are:
embryonic stem cells that are isolated from
the inner cell mass of blastocysts, and
adult stem cells that are found in adult
tissues.
In a developing embryo, stem cells can
differentiate into all of the specialized
embryonic tissues. In adult organisms, stem
cells and progenitor cells act as a repair system
for the body, replenishing specialized cells, but
also maintain the normal turnover of
regenerative organs, such as blood, skin, or
intestinal tissues.
AB
X A (AA OR AO) = A, AB, B
GAMETES
A
B
A
AA
AB
A (O)
AA (AO)
AB
(OB)
AB
X B (BB OR BO) = A, AB, B
GAMETES
A
B
B
AB
BB
B (O)
AB (AO)
AB
(OB)
AB
X O = A,B
GAMETES
A
B
O
AO
BO
O
AO
BO
AA (AO) X AA (AO) = A,O
GAMETES
A
A (O)
A
AA
AA
(AO)
A (O)
AA
(AO)
AA
(OO)
AA (AO) X BB (BO) = A, B, AB, O
GAMETES
A
A (O)
B
AB
AA
(BO)
B (O)
AB
(AO)
AB
(OO)
AA (AO) X OO = A,O
GAMETES
A
A (O)
O
AO
AO
(OO)
O
AO
AA
(OO)
BB (BO) X BB(BO) = B, O
GAMETES
B
B (O)
B
BB
BB
(BO)
B (O)
BB
(BO)
BB
(OO)
BB (BO) X OO = B,O
GAMETES
B
B (O)
O
BO
BO
O
BO
BO
(OO)