how do you write 23 using only the number

How do you write 23 using only the number

2?

34 using only the number 3?



How do you write 23 using

only the number 2?



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

Alleles – the different forms

of a gene

Genotype – combination of

alleles

Phenotype – organism’s

appearance

Homozygous dominant –

two dominant alleles

Homozygous recessive –

two recessive alleles

Heterozygous – one

dominant, one recessive

allele

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

Facial structure

Eyes

Smile

Ears

Nose

Neck

Notice the similarities:

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


•Height - short or TALL •Seed color - green or YELLOW •Seed shape - wrinkled or ROUND •Seed coat color - white or GRAY

Mendelian Genetics


•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


•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 are used to represent dominant genes. lowercase letters are used to represent recessive genes.


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.


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!

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.


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


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

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.

Tt x tt

Predictions?

___% Tall

___% Short

50

50

Punnett Squares

Tt Tt

Tt Tt

The genes from one parent go here.

The genes from the other parent go here.

Punnett Squares

T T

t Tt Tt

t Tt Tt

Punnett Squares

T T

t Tt Tt

t 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 TT Tt

t Tt tt

F2 generation

Punnett Squares

T t

T TT Tt

t Tt tt

Next, give the genotype and phenotype ratios of the offspring (F2 generation).

Punnett Squares

T t

T TT Tt

t Tt tt

Genotype ratio: TT - 1

Punnett Squares

T t

T TT Tt

t Tt tt

Genotype ratio: TT - 1, Tt - 2

Punnett Squares

T t

T TT Tt

t Tt tt

Genotype ratio: TT - 1, Tt - 2, tt - 1

Punnett Squares

T t

T TT Tt

t Tt tt


Phenotype ratio: Tall - 3

Punnett Squares

T t

T TT Tt

t Tt tt


Phenotype ratio: Tall - 3, short - 1

Punnett Squares

T t

T TT Tt

t Tt tt

This is a monohybrid cross. We worked with only one trait. The height of the plant.

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.

9 spherical, yellow

3 spherical, green

3 dented, yellow

1 dented, green

how do you write 23 using only the number

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