Mendel and Heredity

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

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

Section 11-1

Go to Section:

ParentsLong stems short stems

Red flowers white flowers

Green pods yellow pods

Round seeds wrinkled seeds

Yellow seeds green seeds

First GenerationAll long

All red

All green

All round

All yellow

Second Generation787 long: 277 short

705 red: 224 white

428 green: 152 yellow

5474 round: 1850 wrinkled

6022 yellow: 2001 green

Mendel and Heredity

Heredity: The transmission of traits from parents to offspring.

Who was Gregor ____________?

Austrian monk and high school teacher born in ___________.

Father of _______________(1800’s) study of_______________

Modern genetics is a core theme___________.

Mendel and Heredity

Mendel’s data revealed patterns of inheritance.

• Mendel made ____________________in his experiments.– use of ________plants– control over __________=observation of seven

“either-or” traits

Mendel and Heredity

• 4 stock plants:• Tall/Short Green/Yellow seeds• The peas were self pollinating and producing

an exact copy of the parent plant. (True Breeding)

• Mendel cross bred the seeds and got hybrid pea plants.

• How ? He took pollen from the male structures (anthers) of a tall plant and placed it on the female structures (pistil) of a short plant.

• All of the offspring were hybrid tall (F1).

•

•

Mendel and Heredity

5

A. Mendel’s Peas

Chose garden peas to test.

Why?1.Grow ___________________in very little space.

2.True-breeding peas - all offspring show the same ______________after generation (homozygous).

3.Variety of _______________to study (tall v short, white v purple, etc.)

4.Easy to ____________because closed flower doesn’t let random sperm/pollen in!

Mendel and Heredity

6

4. Easy to control breeding• male & female parts are in a closed flower –

other plant pollen can’t get in.

a) self-pollinate – fertilization in a single plant using ________(sperm) and ____to make a zygote (seed!)

Mendel and Heredity

7

Mendel wanted to study the results of breeding 2 different plants, so he had to prevent self-pollination.

b) cross-pollination breeding

___________plants

Mendel and Heredity

8

B.Mendel’s experiments

Mendel studied__________________.

What is a trait?

A specific________________________.

P Generation are the parent plants.

F1 Generation are the 1st generation plants.

F2 Generation are the 2nd generation plants.

__________________and studied the results using math.

Can’t study them all at once

Mendel studied _______________(1 variable) = good science!

Mendel and Heredity

F1 –first filialF2 –second filial 9

a) P = ______________parents (homozygous)– Tall x short

b) F1 = ____________(offspring of P, heterozygous)

– all tall

1. Bred true breeding plants.True tall to true short.

P - parent

Mendel and Heredity

F1 –first filial F2 –second filial

F2 = ______________(offspring of F1)

– 3 tall:1 short

2. Bred F1 x F1

P - parent

Mendel and Heredity

• Mendel’s work led to 2 laws.• _________________: Members of each pair

of alleles separate when the gametes are formed. (Homologous Chromosomes separate)

• ___________________: Pairs of alleles separate independently of one another during gamete formation.

Mendel and Heredity

What do the results mean?

1. _______________are passed unchanged as a unit

12

No blending!

Genes – DNA sequence on a chromosome that codes for specific protein(s) that determine traits (The ____________that determine traits.)

Alleles - different expressions of same gene for same trait Ex: one allele codes for tall, one allele codes for short but both the same ______________for height

Mendel and HeredityWhat do the results mean?

2. _________________– during gamete formation, alleles separate so you only inherit one copy of each gene from each parent

– F1 had to have both alleles to get a short plant in F2, so the allele for shortness had to be separated from the allele for tallness when passed to the F2.

– homologous chromosomes must separate• When does this happen during sexual reproduction???

MEIOSIS! Anaphase I

Mendel and Heredity

What do the results mean?

3. ____________of Dominance – one allele can mask another allele.

Tall allele dominated short allele.

____________– allele or trait that is seen when present, masks recessive allele. Capital letters: A

_____________– allele or trait that is only seen if the dominant trait is NOT present. Lower case letters: a

14

Mendel and Heredity

• Mendel drew three important conclusions.

– Traits are inherited as_________________.– Organisms inherit_________________, one from each

parent.– The two copies_______

during ________formation.– The last two conclusions are

called the law of segregation.purple white

Mendel and Heredity

1. Assuming that you expect 5 heads and 5 tails in 10 tosses, how do the results of your tosses compare? How about the results of your partner’s tosses? How close was each set of results to what was expected?

2. Add your results to those of your partner to produce a total of 20 tosses.

Assuming that you expect 10 heads and 10 tails in 20 tosses, how close are these results to what was expected?

3. If you compiled the results for the whole class, what results would you expect?

4. How do the expected results differ from the observed results?

Section 11-2Interest Grabber continued

Go to Section:

Mendel and Heredity

Genes and Physical Traits• __________– genetic makeup of alleles

– Geno = “genes” – Ex: AA, Aa or aa; dominant or recessive,

heterozygous or homozygous• _____________– physical expression of traits or what

organism looks like!– Pheno = “to show”– Ex: tall or short, green or yellow, blue eyes or brown

eyes

17

Mendel and Heredity

What is homozygous?

Having two identical alleles for a trait.Homozygous Dominant –________________= AA

Homozygous Recessive –________________= aa

What is heterozygous?

Having _____________alleles for a trait. = Aa

Mendel and Heredity

The same gene can have many versions.

• A gene is a piece of DNA that directs a cell to make a certain protein.

• Each gene has a______, aspecific position on a pair of___________chromosomes.

Mendel and Heredity

• An allele is any _____________________occurring at a specific locus on a chromosome.

– Each parent donates one allele for every gene.

– Homozygous describes two alleles that are the same at a specific locus.

– Heterozygous describes two alleles that are different at a specific locus.

Mendel and Heredity

• Alleles can be represented using letters.

– A dominant allele is expressed as a phenotype when at least one allele is dominant.

– A recessive allele is expressed as a phenotype only when two copies are present.

– Dominant alleles are represented by _________ letters; recessive alleles by _______________ letters.

Mendel and Heredity

• Both ________________________________ genotypes yield a dominant phenotype.

• Most traits occur in a range and do not follow simple dominant-recessive patterns.

Mendel and Heredity

23

Probability and Punnet Squares• Whenever Mendel crossed two hybrid plants (F1), he got

3:1 ratio or ¾ dominant and ¼ recessive.• Mendel realized that the

principles of probability

(MATH!!) could be used

to explain the_________

_____________________

Mendel and Heredity

Genetics and Probability

• Ex: coin flip – probability of heads is 1 chance out of 2 possible outcomes = 1/2, or 50%.

• Does heads on the first flip change the probability of heads on the next? What if heads 10 times in a row – will next flip be more likely tails?

_____________do not affect future ones

Probability - the likelihood that any particular event(s) will occur

Mendel and Heredity

Genetics and Probability

What is the probability that we will flip heads three times in a row?

Because each event is independent :

(probability of event)N = number of events

or

½ x ½x ½ = (½)3 = 1/8

1 in 8 chance that 3 heads flipped in a row

Mendel and Heredity

26

Genetics and Probability

How is this related to genetics?Allele segregation is ______________and each event______________________

_____________________a given allele from a heterozygous parent = 50% or 1/2

If parent, T or t – you have a 50% chance of either, same as heads or tails

Mendel and Heredity

Probability and Gender

Females = ________________What is the probability that you will inherit an X from your

mother?

Males =__________________.What is the probability that you will inherit an X from your

dad? Probability of a Y?What is the probability of having a boy? Having a girl?Which parent’s genes determine your gender?What is the probability that a family with three children will

have all girls?(probability of event)N = number of events

½ x ½x ½ = (½)3 = 1/8

Mendel and Heredity

• Why ________________squares?• Predicts the probability of a cross between two

organisms.• Rules:• Dominant allele represented by a Capital

letter.______________• Recessive allele represented by a lower case letter

_____________• The letters designate the two forms of one gene, the

two alleles for a monohybrid cross.• Every cell in your body has at least two alleles for

every trait, one from Mom and one from Dad)

Mendel and Heredity

29

Punnet Squares

Punnett square – grid showing possible gene combinations for offspring from a given genetic cross.

• predicts ______________and their probability

• Shows phenotype &__________________________

Mendel and Heredity

Setting up a Punnett Square

1. Determine _________genotype.

2. _______for dominant, lower case__________.

3. Top and left letters =____________________

4. Bring down from top and over from left to create possible ______________________for offspring.

30

Tt

tt

Tt

tt

Short plant x

Tall heterozygote

Mendel and Heredity

31

Ratios and Punnett Squares

________________– number of each type of offspring genotype predicted by punnett square

• For a single trait (_________________) –homozygous dominant: heterozygous: homozygous recessive

#TT : #Tt : #tt

________________– number of each type of offspring phenotype predicted by a punnett square

____________________traits#Tall : #short

Mendel and Heredity

• Monohybrid Cross: • Provided data for one pair of contrasting traits.

• What are the possible genotypes that can result?

• What are the possible phenotypes that can result?

• What is the ratio of tall to short plants in a hybrid cross?

• Does this ratio agree with Mendel’s result in the F2 generation?

Mendel and Heredity

A monohybrid cross involves one trait.

• Monohybrid crosses examine ____________________ specific trait.– homozygous dominant-homozygous recessive: all

heterozygous, all dominant

Mendel and Heredity

– heterozygous-heterozygous—___________________ dominant: heterozygous:homozygous recessive; 3:1 dominant:recessive

Mendel and Heredity

• heterozygous-homozygous recessive—1:1 heterozygous:homozygous recessive; 1:1

• __________________________• A testcross is a cross between an organism with an

unknown genotype and an organism with the recessive phenotype.

Mendel and Heredity

_____________________involves two traits.

• Mendel’s dihybrid crosses with heterozygous plants yielded ________________phenotypic ratio.

• Mendel’s dihybrid crosses led to his second law,the law of independent assortment.

• The law of independent assortment states that allele pairs separate independently of each other during meiosis.

Mendel and Heredity

Law of Independent Assortment

• genes for different traits can ____________________during the formation of gametes.

• Independent assortment =____________________

• Mendel concluded that the inheritance of one trait does not influence the inheritance of a second trait

Mendel and Heredity

Independent Assortment occurs in __________________

38

R = roundr = wrinkled

Y = yellowy = green

R

R

R RR R

R

R

yY

r r

r

rr

r

r

Y

YYYY

Y

y

yy

y

yy

Mendel and Heredity

Heredity patterns can be calculated with probability.

• Probability is the likelihood that something will happen.• Probability predicts an average number of occurrences, not

an exact number of occurrences.

• Probability =number of ways a specific event can occur

number of total possible outcomes

• Probability applies to random events such as meiosis and fertilization.

Mendel and Heredity

Probability and Punnett Square

– Probabilities predict averages,

– _____________

– outcomes

– Probability is more accurate when you have more chances

Mendel and HeredityDIHYBRID CROSS

Crossing organisms with genes for two different traits = _______________possible gametes.

If we cross RRYY with rryy – what are the possible gametes?

41

Mendel and Heredity

DIHYBRID CROSS : punnett square for true breeding or homozygous parents.

R = roundr = wrinkledY = yellowy = green

Mendel and Heredity

43

heterozygous

Offspring have combinations of alleles ________in earlier generations = ______________

independently

Mendel and HeredityDIHYBRID CROSS

___________________from dihybrid cross of heterzygotes = 9:3:3:1

44

Mendel and Heredity

45

Summary of Mendel’s Principles1. Traits come from your__________________.

2. _____________________________allele and some are dominant.

3. Your two copies of each gene (one from each parent) are _________________when gametes form.

4. Alleles for different genes usually segregate

__________________________of one another.

Mendel and Heredity

Height in Humans

Height in pea plants is controlled by one of two alleles; the allele for a tall plant is the dominant allele, while the allele for a short plant is the ecessive one. What about people? Are the factors that determine height more complicated in humans?

Section 11-3Interest Grabber

Go to Section:

Mendel and Heredity

KEY CONCEPT Phenotype is affected by many different factors.

Mendel and Heredity

Genetics can be affected by 5 other different heredity patterns.

1.__________________Dominance

2.___________________

3._________ Traits (Multiple Genes)

4._____________ Influences

Mendel and Heredity

Phenotype can depend on________________________.

• In incomplete dominance, neither allele is completely dominant nor completely recessive.– Heterozygous phenotype is intermediate between

the two homozygous phenotypes

– Homozygous parental phenotypes not seen in F1 offspring

Mendel and Heredity

50

1. Incomplete Dominance

• cross between red-flowered (RR) and white-flowered (WW) plants consists of pink-colored flowers (RW).

• What happens if you breed the pink flowers?

neither allele is completely dominant so

_________________________

Mendel and Heredity

• Codominant alleles will both be____________________.

– Codominant alleles are neither dominant nor recessive.

– The ABO blood types result from codominant alleles.

• Many genes have more than______________________

Mendel and Heredity

2. Codominance

• both alleles expressed in the phenotype –____________________.

Mendel and Heredity

What are ____________ alleles?

Genes that have more than two alleles for a trait. Example: ____ type in humans

What are ______________ traits?

Traits that are controlled by two or more genes. Example: _______in humans.

Mendel and Heredity

54

3. Multiple Alleles• Genes with more________________________

• This does not mean that an individual can have more than two alleles. It only means that more than two possible alleles exist in a population.

• One of the best-known examples is blood type in humans.

Mendel and Heredity

Human Blood Types

• _______type alleles gene: – A = makes A surface protein– B = makes B surface protein– O doesn’t make either.

• ____________alleles are codominant to each other & both __________over recessive O allele.

Is your blood type a genotype or phenotype?

55

Mendel and Heredity

56

4. Polygenic Traits

• Traits controlled by interaction of two or more genes

• _____________=“many genes.” • Ex: Hair color, eye color, skin color all the result of

several genes

Mendel and Heredity

Environmental Influence:

Phenotype can depend on conditions in the environment.

Conditions can cause a gene to _______

__________________ in coat color.

This allows the animal to blend in with its background.

Mendel and Heredity

58

ENVIRONMENT INFLUENCES ____________TRAITS

Environment factors like diet, exercise, exposure to

toxic agents, or medications can all influence our genes

and traits.

I got the “fat” gene.

13.1 Ecologists Study Relationships

concluded that

which is called the

which is called the

GregorMendel

Law ofDominance

Law ofSegregation

Peaplants

“Factors”determine

traits

Some alleles are dominant,

and some alleles are recessive

Alleles are separated during gamete formation

Section 11-3Concept Map

Go to Section:

experimented with

Mendel and Heredity

Linked Genes

• Mendel concluded that traits are assorted independently, but some traits are Linked

• Linked genes: Genes usually _________________because on same chromosome

Mendel and Heredity

Genes on the sex chromosomes are linked.

i. _________ genes Y has few genes – mostly gender determining (boy or girl). – Y only in males so these genes only affect males.

ii. _______________ Many genes on X chromosome– Affects mostly males because only________________– Male copy of _____________(Dad gave Y to son)– Females less affected because ______________= have to

inherit trait from both parents.– Heterozygous females are _____________________traits.– EX: baldness, colorblindness

Sex-Linked Genes

Mendel and Heredity

Crossing Over affects linked genes.

• Crossing over – exchanging DNA during prophase

• Genes _______on the chromosome _______ likely to be separated by crossing over.

Mendel and Heredity

Chromosome MappingThe farther apart genes are, the higher probability

that they will be separated by crossing over.– Scientists conduct experiments to determine how

frequently genes of a particular trait are separated from one another.

• Chromosome map - _______________sequence of genes on a chromosome.

• Two genes that are separated by crossing-over 1 percent of the time are considered to be one________________.

Mendel and Heredity

Summary of Mendel’s Principles1. Traits come from your__________________.

2. Genes may have ______________and some are dominant.

3. Your two copies of each gene (one from each parent) are ________________________when gametes form.

4. Alleles for different genes usually ______________

________________ of one another.

Mendel and Heredity

Beyond Mendel – Other Patterns of Inheritance

1. Most genes have more than two alleles.

2. Some alleles are neither dominant nor recessive (codominance & incomplete dominance)

3. many traits are controlled by multiple genes.

4. Some genes are linked and do not segregate independently - on the same chromosome so inherited together.