The Origin of GeneticsThe Origin of Genetics

Gamete:Gamete: Reproductive cells (sperm & egg)Reproductive cells (sperm & egg)

Chromosomes:Chromosomes: Coiled up DNA, looks like an “X”Coiled up DNA, looks like an “X”

Genes:Genes: A segment of DNA that codes for a A segment of DNA that codes for a proteinproteinGenes:Genes: A segment of DNA that codes for a A segment of DNA that codes for a proteinprotein

Autosome:Autosome: Any chromosome that isn’t a sex Any chromosome that isn’t a sex chromosomechromosome

Sex chromosome:Sex chromosome: A chromosome that determines A chromosome that determines the sex of an individualthe sex of an individual

Heredity:Heredity: The passing of traits from The passing of traits from parents of an individualparents of an individual

Genetics:Genetics: Science of heredity and how Science of heredity and how traits are passedtraits are passed

Genetics developed from Genetics developed from curiositycuriosity

Offspring traits are a combination of the traits of the parentsof the traits of the parents

Trait –A variation of a specific characteristic

Gregor Mendel: The Father of Genetics!Gregor Mendel: The Father of Genetics!

�� Born in AustriaBorn in Austria

�� Entered a seminary then ordained a priestEntered a seminary then ordained a priest

��Went to the University of Vienna and then Went to the University of Vienna and then taught high schooltaught high schooltaught high schooltaught high school

Experiments:Experiments:

�� Used garden peas and their featuresUsed garden peas and their features

�� Pea plants have both male and female partsPea plants have both male and female parts

�� So to stop selfSo to stop self--fertilization he cut either the male fertilization he cut either the male or female parts off each plantor female parts off each plantor female parts off each plantor female parts off each plant

Male parts

Female parts

�� This allowed for This allowed for crosscross--fertilizationfertilization

�� With this technique, Mendel was able to With this technique, Mendel was able to combine male gametes from the pollen of one combine male gametes from the pollen of one flower to fertilize the ovules in the flower of a flower to fertilize the ovules in the flower of a different plantdifferent plant

�� Used crossUsed cross--fertilization to look at traits fertilization to look at traits �� Used crossUsed cross--fertilization to look at traits fertilization to look at traits (characteristics) like tall plants or green pods(characteristics) like tall plants or green pods

Findings:Findings:

When he crossed parent plants, he saw 1 parent When he crossed parent plants, he saw 1 parent trait being seen in each of the F1 generationtrait being seen in each of the F1 generation

When he crossed the F2 generation, he When he crossed the F2 generation, he discovered traits being seen that were only in discovered traits being seen that were only in discovered traits being seen that were only in discovered traits being seen that were only in the parent generation!the parent generation!

P GENERATION:P GENERATION: PARENT GENERATIONPARENT GENERATION

F1 GENERATION:F1 GENERATION: FIRST GENERATIONFIRST GENERATION

F2 GENERATION:F2 GENERATION: SECOND GENERATIONSECOND GENERATION

PARENT GENERATION

F1 GENERATIONGENERATION

F2

GENERATION

Traits Mendel used:Traits Mendel used:

Parents

Long stems × short stems

Red flowers × white flowers

Green pods × yellow pods

Round seeds × wrinkled seeds

Yellow seeds × green seeds

First Generation

All long

All red

All green

All round

All yellow

Second Generation

787 long: 277 short

705 red: 224 white

428 green: 152 yellow

5474 round: 1850 wrinkled

6022 yellow: 2001 green

1.1. In the first generation of each experiment, how do the In the first generation of each experiment, how do the characteristics of the offspring compare to the parents’ characteristics of the offspring compare to the parents’ characteristics?characteristics?characteristics?characteristics?

2.2.How do the characteristics of the second generation How do the characteristics of the second generation compare to the characteristics of the first generation?compare to the characteristics of the first generation?

All of the 1st generation expresses the characteristics of just one parent

¾ of 2nd generation offspring keep the traits of the 1st generation, but ¼ have a different characteristic that has not been seen since the parent generation

On your notes sheet where we left off, please On your notes sheet where we left off, please answer these 3 questions…answer these 3 questions…

1. Give 2 examples of human traits.1. Give 2 examples of human traits.

2. What method did Mendel use to combine the 2. What method did Mendel use to combine the sperm from pollen of one flower to fertilize the sperm from pollen of one flower to fertilize the sperm from pollen of one flower to fertilize the sperm from pollen of one flower to fertilize the

eggs in the flower of a different plant?eggs in the flower of a different plant?

3. If you are the F2 generation in your family, who 3. If you are the F2 generation in your family, who would be the Parent and F1 generations? would be the Parent and F1 generations?

Homozygous

Heterozygous

Two identical alleles for a trait

Two different alleles for a

1,2, or more forms of a gene

Heterozygous

Dominant

Recessive

Two different alleles for a trait

Gene that masks another allele

Genes that are masked by another gene, but are still present

We use upper and lowercase letters We use upper and lowercase letters to represent traits. to represent traits.

Why don’t we use “s” for short?Why don’t we use “s” for short?

Because each is a characteristic of the same TRAIT Because each is a characteristic of the same TRAIT (height), so we have to use the same letter(height), so we have to use the same letter

Shorthand writing allelesShorthand writing alleles

Dominant

Recessive H = Hairh = No hair

Homozygous

Heterozygous

Homozygous

h = No hair

Genotype

Phenotype

Alleles in the genes

(What the genes look like)

Phenotype

Outward appearance

(What the organism physically looks like)

Principles of Segregation Principles of Segregation

Offspring of true-breeding parents

Cross that only looks at one characteristic

ProbabilityProbability -- the likelihood a particular the likelihood a particular event will occur/the percentage for the event will occur/the percentage for the event to occur (the number of trials)event to occur (the number of trials)

Punnett Square Punnett Square -- chart that shows a genetic chart that shows a genetic cross and the inheritance of specific allelescross and the inheritance of specific alleles

B = brown

b = blue

Problem: Cross a homozygous dominant puppy with a homozygous recessive puppy

If they have 4 puppies, how many puppies will be:

BrownBlue HomozygousHeterozygous

Red is dominant to white. Cross two heterozygous individuals. How many offspring are homozygous dominant, homozygous recessive, and heterozygous?

Red is dominant to white. Cross two heterozygous individuals. How many offspring are homozygous dominant, homozygous recessive, and heterozygous?

These ratios give you the odds on what will likely happen – like the odds on horseracing or something like that…

When flipping coins, what is the chance of getting heads? What about tails?

What about when you flip 2? What is the chance of getting 2 heads? A heads and a tails?

P

P

Blending of characteristics

Neither characteristic is dominant over the other

Intermediate Dominance

Do the Punnett square for the F1 cross to predict the offspring in the F2 generation

Dihybrid Cross:

a cross that looks at 2 characteristics

R = Roundr = wrinkledY = yellowy = green

at 2 characteristics

Multiple AllelesMultiple Alleles

�� When several When several allelesallelesexist for a gene.exist for a gene.–– Example: blood Example: blood

type in humanstype in humans

Multiple traits can be expressed!

Human Blood TypesHuman Blood Types�� Multiple alleles control the character of blood Multiple alleles control the character of blood type in humans.type in humans.

�� A person’s blood type may be A, B, AB, or O.A person’s blood type may be A, B, AB, or O.

�� Letters refer to proteins on the surface of the Letters refer to proteins on the surface of the red blood cells.red blood cells.

�� A person’s red blood cells may be coated with A person’s red blood cells may be coated with one protein (type A) or the other (type B), with one protein (type A) or the other (type B), with both (type AB), or with neither (type O).both (type AB), or with neither (type O).

More about Human Blood TypesMore about Human Blood Types

�� A (IA (IAA))

�� B (IB (IBB))

�� Neither A or B (i) Neither A or B (i)

�� Each person inherits one of these alleles Each person inherits one of these alleles from each parent (six possible ways to from each parent (six possible ways to pair alleles/six possible genotypes)pair alleles/six possible genotypes)

More About Human Blood TypesMore About Human Blood Types

�� Alleles IAlleles IAA and Iand IBB exhibit CODOMINANCE exhibit CODOMINANCE meaning that a heterozygote expresses meaning that a heterozygote expresses both traitsboth traits

Blood Types Determination

Co-dominanceBOTH traits are expressed…expressed…

Mate a person with blood type O with a person whose blood type is AB.

What is the probability of probability of getting an offspring with blood type:

A?B?O?

Genes found Genes found Genes found Genes found Genes found Genes found Genes found Genes found on the X on the X on the X on the X chromosomechromosomechromosomechromosome

Autosomal –genes found on non-sex chromosomes

What is the genotype that is needed in order to see an white eyed female?

Shows family relationships and traits that are passed through out a family

X

1. Is the trait being shown here dominant or recessive?2. Is the trait autosomal or sex-linked?3. What is the genotype for the infected individual?4. What is the genotype of the mother, the father?5. What is the probability that sister X is a carrier of the

trait?