Download How do you write 23 using only the number 2?

How do you write 23 using only the number
2?
34 using only the number 3?
56 using only the number 5?
100 using only the number 9?
How do you write 23 using
only the number 2?
34 using only the number 3?
56 using only the number 5?
100 using only the number
9?
By using fractions. 22+2/2=23, 33+3/3=34, 55+5/5=56, 99+9/9=100
Genetics
A study of inheritance
Basic Genetics
Gregor Mendel: curious about physical
characteristics of plants
 Physical Characteristics = traits
 Heredity = passing of traits from one
parent to another

Gregor Mendel



Father of modern
genetics
Researched with
pea plants
Developed ideas of
dominance and trait
segregation
Phenotypes & Genotypes
Phenotype = physical characteristics =
visible traits
 Genotype = genetic makeup or allele
combinations
 Homozygous = two identical alleles for a
trait
 Heterozygous = two different alleles for a
trait

– the different forms
of a gene
 Genotype – combination of
alleles
 Phenotype – organism’s
appearance
 Alleles
dominant –
two dominant alleles
 Homozygous recessive –
two recessive alleles
 Heterozygous – one
dominant, one recessive
allele
 Homozygous
Dominant and Recessive
Alleles






Genes = factors that control traits
Allele = different form of a gene
Ex: Pea = stem height - one allele for short and
one allele for tall
Individual alleles control the inheritance of traits
Some alleles are dominant and some recessive
Dominant allele: trait always show
Recessive allele: masked, covered up when
dominant allele is present
Ex: In pea plants, the tall stem allele is dominant
over the short stem
Phenotype

Phenotype

Physical
characteristics
Phenotype
Notice the similarities:






Facial structure
Eyes
Smile
Ears
Nose
Neck
Genotype

Phenotype


Physical
characteristics
Genotype

Genes we inherit from
our parents
Mendel’s Experiments






Purebred plants: always have the same
form of a trait as the parent; Ex: Purebred
short pea = short pea
Mendel cross purebred tall plants with
purebred short plants
Parent plants = P generation
Offspring = F1 generation
F1 Generation = all tall
F2 Generation = 3 tall and 1 short
Mendel’s Crosses





P generation had two identical alleles for stem
height
Purebred tall pea = 2 alleles for tall
Purebred short pea = 2 alleles for short
F1 generation = received one allele for tall and
one allele for short
F1 plants = hybrids = had two different alleles for
a trait
Mendelian Genetics
Mendel studied a number of characteristics in pea
plants including:
•Height - short or TALL
•Seed color - green or YELLOW
•Seed shape - wrinkled or ROUND
Mendelian Genetics
Mendel studied a number of characteristics in pea
plants including:
•Height - short or TALL
•Seed color - green or YELLOW
•Seed shape - wrinkled or ROUND
•Seed coat color - white or GRAY
Mendelian Genetics
Mendel studied a number of characteristics in pea
plants including:
•Height - short or TALL
•Seed color - green or YELLOW
•Seed shape - wrinkled or ROUND
•Seed coat color - white or GRAY
•Pod shape - constricted or SMOOTH
•Pod color - yellow or GREEN
Mendelian Genetics
Mendel studied a number of characteristics in pea plants
including:
•Height - short or TALL
•Seed color - green or YELLOW
•Seed shape - wrinkled or ROUND
•Seed coat color - white or GRAY
•Pod shape - constricted or SMOOTH
•Pod color - yellow or GREEN
•Flower position - terminal or AXIAL
Mendelian Genetics
We will work with the following three:
•Height - short or TALL
•Seed color - green or YELLOW
•Seed shape - wrinkled or ROUND
•Seed coat color - white or GRAY
•Pod shape - constricted or SMOOTH
•Pod color - yellow or GREEN
•Flower position - terminal or AXIAL
Mendel & Probability


Mendel = 1st scientist to recognize the principles of
probability can be used to predict the results of a
genetic cross
Punnett Square = a chart that shows all possible
combinations of alleles that can result from a genetic
cross
Predicting Inheritance
To determine the chances of inheriting a given
trait, scientists use Punnett squares and
symbols to represent the genes.
UPPERCASE letters
dominant genes.
lowercase letters
recessive genes.
are
are
used
used
to
represent
to
represent
Predicting Inheritance
For example:
T = represents the gene for TALL in pea plants
t = represents the gene for short in pea plants
So:
TT & Tt both result in a TALL plant, because T is
dominant over t. t is recessive.
tt will result in a short plant.
Remember there are two genes for every trait! One
from each parent.
Predicting Inheritance
Mendels’ Principle of Dominance
Some genes (alleles) are dominant and others are recessive. The
phenotype (trait) of a dominant gene will be seen when it is paired with
a recessive gene.
For example:
T = represents the gene for TALL in pea plants
t = represents the gene for short in pea plants
So:
TT & Tt both result in a TALL plant, because T is
dominant over t. t is recessive.
tt will result in a short plant.
Remember there are two genes for every trait!
Predicting Inheritance
Let’s cross a totally dominant tall plant (TT) with a
short plant (tt).
Each plant will give only one of its’ two genes to
the offspring or F1 generation.
TT x tt
T
T
t
t
Predicting Inheritance
Mendels’ “Law” of Segregation
Each gene (allele) separates from the other so that the offspring get
only one gene from each parent for a given trait.
Let’s cross a totally dominant tall plant (TT) with a
short plant (tt).
Each plant will give only one of its’ two genes to
the offspring or F1 generation.
TT x tt
T
T
t
t
Tt x tt
Predictions?
50
___%
Tall
___%
Short
50
Punnett Squares
Tt
Tt
The genes from one parent go here.
The genes from the other parent go
here.
Tt
Tt
Punnett Squares
T
T
t
Tt
Tt
t
Tt
Tt
Punnett Squares
T
T
t
Tt
Tt
t
Tt
Tt
Punnett Squares
T
T
t
Tt
Tt
t
Tt
Tt
Punnett Squares
T
T
t
Tt
Tt
t
Tt
Tt
Punnett Squares
T
T
t
Tt
Tt
t
Tt
Tt
Punnett Squares
t
t
T
T
Tt
Tt
Tt
Tt
F1 generation
Interpreting the Results
The genotype for all the offspring is Tt.
The genotype ratio is:
Tt - 4/4
The phenotype for all the offspring is tall.
The phenotype ratio is:
tall - 4/4
Punnett Squares
T
t
T
??
??
t
??
??
Punnett Squares
T
t
T
t
TT
Tt
Tt
tt
F2 generation
Punnett Squares
Next, give the genotype and phenotype
T (F2 generation).
t
ratios of the offspring
T
TT
Tt
t
Tt
tt
Punnett Squares
Genotype ratio: TT - 1
T
t
T
TT
Tt
t
Tt
tt
Punnett Squares
Genotype ratio: TT - 1, Tt - 2
T
t
T
TT
Tt
t
Tt
tt
Punnett Squares
Genotype ratio: TT - 1, Tt - 2, tt - 1
T
t
T
TT
Tt
t
Tt
tt
Punnett Squares
Genotype ratio: TT - 1, Tt - 2, tt - 1
T
t
T
TT
Tt
t
Tt
tt
Phenotype ratio: Tall - 3
Punnett Squares
Genotype ratio: TT - 1, Tt - 2, tt - 1
T
t
T
TT
Tt
t
Tt
tt
Phenotype ratio: Tall - 3, short - 1
Punnett Squares
This is a monohybrid T
cross. We worked
with
t
only one trait. The height of the plant.
T
TT
Tt
t
Tt
tt
Punnett Squares
This is a monohybrid T
cross. We worked
with
t
only one trait. The height of the plant.
T
TT
Tt
t
Tt
tt
Dihybrid Crosses: Crosses that involve 2
traits.
For these crosses your punnet square needs
to be 4x4
In any case where the parents are
heterozygous for both traits (AaBb x AaBb)
you will get a 9:3:3:1 ratio.
If you cross other combinations, you will
need to do a square. Try RrYy x rryy
Determine all possible
combinations of
alleles in the
gametes for each
parent.
Half of the gametes get
a dominant S and a
dominant Y allele;
the other half of the
gametes get a
recessive s and a
recessive y allele.
Both parents produce
25% each of SY, Sy,
sY, and sy.
List the gametes for
Parent 1 along one
edge of the punnett
square.
List the gametes for
Parent 2 along one
edge of the punnett
square.
Fill out the
squares with the
alleles of Parent
1.
Fill out the squares with the alleles
from Parent 2.
The result is the prediction of all
possible combinations of genotypes
for the offspring of the dihybrid
cross, SsYy x SsYy.
There are 9 genotypes for spherical,
yellow seeded plants. They are:
SSYY (1/16)
SSYy (2/16)
SsYY (2/16)
SsYy (4/16)
Two recessive alleles result in green
seeded plants.
There are 2 genotypes for spherical,
green seeded plants. They are:
SSyy (1/16)
Ssyy (2/16)
Two recessive s alleles result in
dented seeded plants.
There are 2 genotypes for dented,
yellow seeded plants. They are:
ssYY (1/16)
ssYy (2/16)
A ssyy plant would be recessive for
both traits.
There is only 1 genotypes for
dented, green seeded plants. It is:
ssyy (1/16)
A phenotypic ratio of 9:3:3:1 is predicted for the offspring of a SsYy x SsYy dihybrid
cross.
3 spherical, green
9 spherical, yellow
1 dented, green
3 dented, yellow