Mendenlian GeneticsHeredity and traits

Bellringer- Remediation

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2 minutes per slide

1. Which of the following accurately states the difference between plant and animal cells?

A. Animal cells have stomata that allow for gas exchange

B. Plant cells have chloroplasts that are sites of chemical reactions

C. Plant cells have stromal cells that make up connective tissue

D. Animal cells have chloropplasts that turn glucose into ATP

2. If you examined a cell under a microscope and found it had a

nucleus and other organelles, how would you classify it?

A. It is a plant cellB. It is an animal cellC. It is a eukaryotic cellD. It is a prokaryotic cell

3. Bacterial are prokaryotic cells, while multicellular and more sophisticated single-celled

organisms are eukaryotic. Which of these describes a prokaryotic cell

and NOT a eukaryotic cell? A. Sunlight is absorbed by chloroplasts in

the cell

B. Molecules join together to assemble a permeable cell membrane

C. The nuclear membrane dissassembles and chromosomes align in a cell

D. DNA is distributed loosely within the cell rather than in chromosomes

4. Because of the function of most plant leaves is to carry out

photosynthesis, their cells contain many more of what organelle than

any other part of the plant?A. ChloroplastsB. MitochondriaC. NucleiD. vacuoles

5. Which statement is true for both prokaryotes and

eukaryotes?

A. They can only reproduce asexually

B. Their DNA is found within a nucleus

C. Their DNA is found within the mitochondria

D. Their DNA is replicated during reproduction

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Gregor Mendel(1822-1884)Responsible for the Laws governing Inheritance of Traits

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Gregor Johann MendelAustrian monkStudied the inheritance of traits in pea plants

Developed the laws of inheritance

Law of segregationLaw of independent assortmentLaw of dominance

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Gregor Johann MendelBetween 1856 and 1863, Mendel cultivated and tested some 28,000 pea plantsHe found that the plants' offspring retained traits of the parentsCalled the “Father of Genetics"

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Genetic Terminology Trait - any characteristic

that can be passed from parent to offspring

Heredity - passing of traits from parent to offspring

Genetics - study of genes & heredity

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Mendel Chose Pea plants to test his theories

Pea plants expressed different traits (i.e) green or yellow seed

Genes are factors that are passed on to offspring to parents Genes are found on DNA

Alleles are different forms of a gene 2 alleles = a Gene

Alleles: alternative versions of a gene. The gene for a particular inherited character resides at a specific locus (position) on homologous chromosome.

For each character, an organism inherits two alleles, one from each parent

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Applying the Law of Segregation

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Principle of Dominance

In simple mendelian genetics, alleles can be either dominant or recessive

Dominant alleles: expresses the trait it represents; masks over recessive traits Represented by a capital letter (ex. R)

Recessive alleles: only is expressed when it is not paired with the dominant allele Represented by a lower-case letter (ex. r)

Hybrid (heterozygous) Gene: a gene with both a dominant and recessive allele Ex. Rr

Homozygous genes: have the same trait for both alleles Ex. (RR) or (rr)

bb

WW or Ww

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More Terminology Genotype - gene

combination for a trait (e.g. RR, Rr, rr)

Phenotype - the physical feature resulting from a genotype (e.g. red, white) i.e.- what you see

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Example: Eye color

-Genotype: bb

-Phenotype: Blue

color

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Eight Pea Plant Traits Seed shape --- Round (R) or Wrinkled (r) Seed Color ---- Yellow (Y) or  Green (y) Pod Shape --- Smooth (S) or wrinkled (s) Pod Color ---  Green (G) or Yellow (g) Seed Coat Color ---Gray (G) or White (g) Flower position---Axial (A) or Terminal

(a) Plant Height --- Tall (T) or Short (t) Flower color --- Purple (P) or white (p)

Principle of Segregation

If Maternal genotype (mom) has Bb and Paternal genotype (dad) has BB, how does the offspring end up with Bb? Or BB?

During the formation of gametes (meiosis) the alleles will separate or segregate into different gametes

B b

Bb B

B

Traits are passed down from generation to

generationP generation (parental generation)

F1 generation (first filial generation, the word filial from the Latin word for "son") are the hybrid offspring.Allowing these F1 hybrids to self-pollinate produces:F2 generation (second filial generation). It is the analysis of this that lead to an understanding of genetic crosses.

Probability and Punnett Squares Punnett square: diagram showing the probabilities of the possible outcomes of a genetic cross

Punnett squares - probability diagram illustrating the possible offspring of a mating.

Ss X Ss

gametes

A Testcross is designed to reveal whether an organism that displays the dominant phenotype is homozygous or heterozygous.

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Trait: Seed Shape Alleles: R – Round r – Wrinkled Cross: Round seeds x Wrinkled seeds RR x rr

P1 Monohybrid Cross

R

R

rr

Rr

RrRr

Rr

Genotype: RrPhenotype: RoundGenotypicRatio: All alikePhenotypicRatio: All alike

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P1 Monohybrid Cross Review

Homozygous dominant x Homozygous recessive

ALL Offspring Heterozygous (hybrids) and thus round

Offspring called F1 generation Genotypic & Phenotypic ratio

is ALL ALIKEcopyright cmassengale

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Trait: Seed Shape Alleles: R – Round r – Wrinkled Cross: Round seeds x Round seeds

F1 Monohybrid Cross

R

r

rR

RR

rrRr

RrG.Ratio: 1:2:1P.Ratio: 3:1

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Cross 2 heterozygous round seeds

Welcome Back!

Get Ready for your remediation bellringer!

1. Over time, the climate of an island became drier, which resulted in changes to

the populations of various island finch species. Finch populations with a certain

beak shape thrived, while those not having that beak shape decreased. Which of the following describes a necessary condition for these changes in the finch populations

to occur? A. fewer mutations B. limited food resources C. limited beak variations D. overproduction of offspring

2. Which of these would have the least effect on natural selection in a

subspecies of giraffes that is geographically isolated from other

subspecies of giraffes?

A. available niches B. existing predators C. chromosome number D. available food resources

3. Mutations within a DNA sequence are

A. natural processes that produce genetic diversity

B. natural processes that always affect the phenotype

C. unnatural processes that always affect the phenotype

D. unnatural processes that are harmful to genetic diversity

4. Which of the following best illustrates natural selection?

A. An organism with favorable genetic variations will tend to survive and breed successfully. 

B. A population monopolizes all of the resources in its habitat, forcing other species to migrate.

C. A community whose members work together utilizing all existing resources and migratory routes.

D. The largest organisms in a species receive the only breeding opportunities.

5. In his book On the Origin of the Species, Charles Darwin described how species change over time. Which of the

following is NOT part of his observations that describes the mechanisms of natural

selection? A. Organisms produce more offspring

than can survive. B. Disease and natural disaster will limit

population growth. C. Species today descended with

modifications from ancestral species. D. Organisms with advantages will

survive and reproduce.

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Summary of Mendel’s laws

LAW PARENT CROSS OFFSPRING

DOMINANCE TT x tt tall x short

100% Tt tall

SEGREGATION Tt x Tt tall x tall

75% tall 25% short

INDEPENDENT ASSORTMENT

RrGg x RrGg round & green x round & green

9/16 round seeds & green pods 3/16 round seeds & yellow pods 3/16 wrinkled seeds & green pods 1/16 wrinkled seeds & yellow podscopyright cmassengale

Law of Independent assortment and Dihybrid

crosses Genes for a different trait can segregate independently during gamete formation

Dihybrid CrossExample: pea COLOR and Texture can be cross together

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Dihybrid Cross A breeding experiment that tracks

the inheritance of two traits. Mendel’s “Law of Independent

Assortment” a. Each pair of alleles segregates

independently during gamete formation b. Formula: 2n (n = # of heterozygotes)

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Question:How many gametes will be

produced for the following allele arrangements?

Remember: 2n (n = # of heterozygotes)

1. RrYy

2. AaBbCCDd

3. MmNnOoPPQQRrssTtQq

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Answer:1. RrYy: 2n = 22 = 4 gametes

RY Ry rY ry

2. AaBbCCDd: 2n = 23 = 8 gametesABCD ABCd AbCD AbCdaBCD aBCd abCD abCD

3. MmNnOoPPQQRrssTtQq: 2n = 26 = 64 gametes

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Dihybrid Cross Traits: Seed shape & Seed color Alleles: R round

r wrinkled Y yellow y green

RrYy x RrYy

RY Ry rY ry RY Ry rY ry

All possible gamete combinationscopyright cmassengale

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Dihybrid CrossRY Ry rY ry

RY

Ry

rY

rycopyright cmassengale

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Dihybrid Cross

RRYY

RRYy

RrYY

RrYy

RRYy

RRyy

RrYy

Rryy

RrYY

RrYy

rrYY

rrYy

RrYy

Rryy

rrYy

rryy

Round/Yellow: 9

Round/green: 3

wrinkled/Yellow: 3

wrinkled/green: 19:3:3:1 phenotypic ratio

RY Ry rY ry

RY

Ry

rY

rycopyright cmassengale

We Do: Dihybrid Practice Problems

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Incomplete Dominanceand

Codominance

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Incomplete Dominance

Some traits are neither dominant nor recessive

So what happens to the Hybrid? (Rr) Incomplete Dominance results in an

intermediate phenotype for the hybrid species

Example: RR-WHITE rr- RED Rr- PINK

Co-Dominance (multiple alleles)

Some traits are both, in a sense, dominant

Therefor, the hybrid of the two traits will result in both traits being expressed

Example: BB- White bb-Brown Bb- brown and white

Roan Cow

Blood Type and Co-dominance

Another example of a co-dominant trait is blood type

Blood type A and B are both dominant (O is recessive) AA- homozygous type A BB homozygous type B AB- type AB AO- Type A BO- Type B OO- Type O

Hero Blood When receiving blood

transfusions, people must receive blood that matches their own blood types The body will reject a foreign

blood type Because type O(-) is recessive, it

can be given to any other blood type

Downside of being O(-): You can only receive O(-) Only 9% of the population is O(-)

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Sex-linked Traits Traits (genes) located on the

sex chromosomes Sex chromosomes are X and Y

XX genotype for females XY genotype for males

Many sex-linked traits carried on X chromosome

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Sex-linked Traits

Sex Chromosomes

XX chromosome - female Xy chromosome - male

fruit flyeye color

Example: Eye color in fruit flies

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There are NO ALLELES on the Y-chromosome

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Sex-linked Trait Problem Example: Eye color in fruit flies

(red-eyed male) x (white-eyed female) XRY x XrXr

Remember: the Y chromosome in males does not carry traits.

RR = red eyed Rr = red eyed rr = white eyed XY = male XX = female

XR

Xr Xr

Y

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Sex-linked Trait Solution:

XR Xr

Xr Y

XR Xr

Xr Y

50% red eyed female

50% white eyed male

XR

Xr Xr

Y

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Female Carriers

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Sex-linked trait facts1. Y-chromosome carries NO traits2. Male offspring always show the

trait of their mother3. Females can be carriers of the

recessive trait herterozygotes

4. Males are never carriers They either have the trait or the

don’t

Polygenic Traits• Polygenic traits, or

continuous traits, are governed by alleles at two or more loci, • each locus has some

influence on the phenotype.

• Hair, eye and skin color, height, face shape are polygenic traits

• So, several genes influence the outcome of the trait

Environmental Influence on Gene

Expression For some traits, a particular

environment can influence the expression of the gene

Examples: Temperature and Light

Himalayan Rabbit fur color Drugs and chemicals

Cyclopean fish Gender

Baldness

You Do: Patterns of Inheritance Practice

Problems

Bellringer- Human Impact Remediation

1. New fuels are being produced by converting corn and grasses into

compounds containing alcohols that can be broken down for energy in

various engines. The purpose of this research is to

A. reduce the use of nonrenewable resources.

B. increase the rate of air pollution. C. reduce the rate of homeostasis in

organisms. D. cause a loss of biodiversity in the

rain forests.

2. The presence of wastes, such as plastic bags and motor oil, in lakes and

streams miles away from developed areas suggests that

A. ecosystems are interconnected and human action can alter ecosystem equilibrium.

B. recycling programs have failed to conserve biotic resources.

C. natural processes can alter ecosystem stability.

D. direct harvesting practices have led to irreversible destruction of ecosystems.

3. The northern elephant seal was almost hunted to extinction in the 1800s.

By the late 1890s, approximately one hundred seals were left, reducing the

gene pool of the population. What will be the consequence of this reduction?

A. Competition within the population will increase.

B. The surviving elephant seals will be better able to adapt.

C. Inbreeding will be less frequent among the remaining population.

D. The elephant seals will be more vulnerable to environmental change.

4. When fertilizers run off farmland into streams and ponds, the nitrogen content of the water increases. This can lead to rapid

growth of algae in a process called eutrophication. How can this process affect

other organisms in the water? A. Oxygen is used up as algae is decomposed,

reducing the amount available to other organisms.  B. The water becomes better able to support

aerobic organisms. C. The algae provide food for fishes and other

organisms, leading to decreased algae populations. 

D. The extra nitrogen provides additional food for the other organisms, increasing their population

What is a Pedigree? A pedigree is a chart

of the genetic history of family over several generations.

Scientists or a genetic counselor would find out about your family history and make this chart to analyze.

Pedigree Analysis

Goals of Pedigree Analysis 1. Determine the mode of

inheritance: dominant, recessive, partial dominance, sex-linked, autosomal, mitochondrial, maternal effect.

2. Determine the probability of an affected offspring for a given cross.

Pedigree Symbols

• Half shaded shapes signify carriers (heterozygotes)

Interpreting a Pedigree Chart

1. Determine if the pedigree chart shows an autosomal or X-linked disease.

If most of the males in the pedigree are affected the disorder is X-linked

If it is a 50/50 ratio between men and women the disorder is autosomal.

Example of Pedigree Charts

Is it Autosomal or X-linked?

Answer: Autosomal

Interpreting a Pedigree Chart

2. Determine whether the disorder is dominant or recessive.

If the disorder is dominant, one of the parents must have the disorder.

If the disorder is recessive, neither parent has to have the disorder because they can be heterozygous.

Example of Pedigree Charts

Dominant or Recessive?

Answer: Dominant

Example of Pedigree Charts

Dominant or Recessive?

Answer: Recessive

Summary Pedigrees are family trees that

explain your genetic history. Pedigrees are used to find out the

probability of a child having a disorder in a particular family.

To begin to interpret a pedigree, determine if the disease or condition is autosomal or X-linked and dominant or recessive.

Pedigree Chart -Cystic Fibrosis