IA4 Genetics

1/8/14

• BR6: Using the Carbon Cycle poster next to the board, describe the flow of carbon through the cycle. Use the words: carbon dioxide, photosynthesis, respiration, combustion, plants, animals, atmosphere.

• Agenda:– Human Genetics Survey

Grades are due tomorrow:The only thing that I haven’t putin are your projects. I am working on them today.

Darwin’s Point

1/10/14

• Pretest IA4Sharpen pencils, have IA numbers readyMark E if you don’t know/have to guessPick up Vocab/I Can sheet when you turn in scantron/test

Agenda:PIA4Look up traits on Human Genetics homework – what is the “dominant trait”Vocab/I Can for Genetics

1/13/14

• sub - Mythbusters

1/14/14

• BR 7:What factors affect whether or not children look

like their parents?

Agenda:Blue People!!Vocab Notes

Vocabulary

• Genetics – the study of heredity• Heredity- the passing of genes or traits from

parent to offspring• Genes – segments of DNA along chromosomes

that contain the chemical message that governs a trait

• Trait- an inherited characteristic

Blue People of Troublesome Creek

Vocabulary

• alleles – different forms of a gene in a gene pool

• genotype – genetic makeup of an individual• phenotype – physical characteristics of an

individual• homozygous – two identical alleles for a trait• heterozygous – two different alleles for a trait

1/15/14

• BR 8: In humans, the allele for free hanging ear lobes is dominant (F) over attached earlobes (f). Predict the genotypic ratio of offspring produced by crossing two heterozygous for this trait. Draw a punnett square to illustrate your prediction.

• Agenda:– Genetic Scientists’ Contributions

I can recognize the contributions of Redi, Needham, Spallanzani, and Pasteur.

Pedigree of Methemoglobinemia – The Blue People Pedigree Chart

Pedigree information graciously provided by Mary D. Fugate, publisher of The Fugate Family Newsletter.

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People/Scientist Belief/contribution to Genetics

Greeks -Both Male and Female contribute a fluid to create children-Each body part contributes fluid to create that part in children

Leeuwenhoek -Made improvements to microscope-First to observe sperm

Mendel -Developed law of heredity-Father of modern genetics-Worked with pea plants

Middle Ages -Thought there was spontaneous generation

Harvey -Women have eggs b/c chickens have eggs-Proposed epigenesis Fusion b/w egg and sperm

Spontaneous Generation Beliefs

• Maggots and worms came from decaying food, urine, and manure

• Animals that lived in mud (salamanders, frogs, etc.) were generated by the mud

• Rats were spontaneously generated in piles of garbage or created from magical recipes. One seventeenth-century recipe even called for the creation of mice from sweaty underwear and wheat husks placed together in a jar for twenty-one days.

• pieces of cheese and bread wrapped in rags and left in a dark corner, for example, were thus thought to produce mice, because after several weeks there were mice in the rags

I can recognize the contributions of

Redi, Needham, Spallanzani, and Pasteur.

• Open book to pages 9-12 and read about the 4 remaining scientists.

• Using the descriptions and pictures in the book I want you to make a table showing their ideas/contributions to genetics, and then draw a picture of their experiment for each of the scientists.

Scientist Ideas/Contributions to Genetics

How Experiment was set up

Redi

Needham

Spallanzani

Pasteur

1/16/14

• BR9: For each image, record which scientist created the experiment.

• Agenda:– Mendelian Genetics Notes – Anyone not read “Desiree’s Baby”?

Keep working on NovelStar if you didn’t finish. We have another week or so! See me for questions…

Gregor Mendel

• Austrian monk• garden peas – why?

– small– easy to grow– short growing season– lots of results quickly– more results = ???

Pollination/Fertilization in Peas

• Pea flowers are normally self-pollinating, which means that sperm cells fertilize egg cells from within the same flower.

• true-breeding - self-pollinating plants that would produce offspring with identical traits to themselves generation after generation (purebred)

Recall from elementary science classes: What are the male and female parts of the flower called? male _______________ female _____________

The Role of Fertilization

• Mendel decided to “cross” his stocks of true-breeding plants—he caused one plant to reproduce with another plant.

• This process, known as cross-pollination, produces a plant that has two different parents.

• The offspring of crosses between parents with different traits are called hybrids.

Genes and Alleles• When doing genetic crosses, we call the original pair of

plants the P, or parental, generation.

• Their offspring are called the F1, or “first filial,” generation.

• For each trait studied in Mendel’s experiments, all the offspring had the characteristics of only one of their parents, as shown in the table.

Mendel’s Laws of Genetics

1. Law of Dominance

2. Law of Segregation

3. Law of Independent Assortment

Dominant and Recessive Traits

• Mendel’s principle of dominance states that some alleles are dominant and others are recessive.

• An organism with at least one dominant allele for a particular form of a trait will exhibit that form of the trait. Dominant “masks” recessive.

• An organism with a recessive allele for a particular form of a trait will exhibit that form only when the dominant allele for the trait is not present.

Dominant and Recessive Traits

• In Mendel’s experiments, the allele for tall plants was dominant and the allele for short plants was recessive.

• Likewise, the allele for yellow seeds was dominant over the recessive allele for green seeds

Dominant and Recessive Human Traits

Dominant Recessive

Cheek Dimples No Dimples

Cleft Chin Smooth Chin

Freckles No Freckles

Free Earlobes Attached Earlobes

Wet Ear Wax Dry Ear Wax

Straight thumb Hitchhiker's thumb

Widow's peak Straight hairline

Polydactyly 5 fingers/toes

Mendel’s Laws of Genetics

1. Law of Dominance

2. Law of Segregation

3. Law of Independent Assortment

Segregation

• Mendel wanted to find out what had happened to the recessive alleles.

• Mendel allowed all seven kinds of F1 hybrids to self-pollinate. The offspring of an F1 cross are called the F2 generation.

• One fourth of the F2 generation were short.

• Mendel suggested that the alleles for tallness and shortness in the F1 plants must have segregated from each other during the formation of the sex cells, or gametes.

• Each gamete carries only one allele for each gene.

Explaining the F1 Cross -The Formation of Gametes

The Formation of Gametes

• A capital letter represents a dominant allele.

• A lowercase letter represents a recessive allele.

• Assume each F1 plant had a T(Tall) allele and a t(short) allele or gametes.

• When they crossed, they produced three different mixed pairs…

TT, Tt, and tt.

The Formation of Gametes

Whenever the pair was TT (both dominant)…the plant was tall.

When the pair was Tt (one dominant, one recessive) …the plant was tall.

When the pair was tt (both recessive)…the plant was short.

Mendel’s Laws of Genetics

1. Law of Dominance

2. Law of Segregation

3. Law of Independent Assortment

Independent Assortment

• Mendel wondered if the segregation of one pair of alleles affects another pair.

• Mendel performed an experiment that followed two different genes as they passed from one generation to the next.

• Because it involves two different genes, Mendel’s experiment is known as a two-factor, or dihybrid, cross. Single-gene crosses are monohybrid crosses.

• The principle of independent assortment states that genes for different traits can segregate independently during the formation of gametes.

The DiHybrid (Two-Factor) Cross: F1

• Lets look at pea color (green or yellow) and shape (round or wrinkled.

• The round yellow peas had the genotype RRYY, which is homozygous dominant.

• The wrinkled green peas had the genotype rryy, which is homozygous recessive.

• The Punnett square shows that the genotype of each F1 offspring was RrYy, heterozygous for both seed shape and seed color.

The Two-Factor Cross: F2

In the F2 offspring:

Mendel observed that the alleles for seed shape segregated independently of those for seed color.

Genes that segregate independently—such as the genes for seed shape and seed color in pea plants—do not influence each other’s inheritance.

Mendel’s experimental results were very close to the 9:3:3:1 ratio that the Punnett square shown predicts.

Mendel had discovered the principle of independent assortment. The principle of independent assortment states that genes for different traits can segregate independently during gamete formation.

PUNNETT SQUARE – DIHYBRID CROSS

– Separate the alleles inall possible combinationsYYRR YR YR YR YR

YyRr YR Yr yR yr

– Set up the square

YR YR YR YR

YR        

Yr        

yR        

yr        

YYRR x YyRr

YR YR YR YR

YR YYRR   YYRR YYRR  YYRR 

Yr  YYRr YYRr  YYRr   YYRr

yR  YyRR YyRR  YyRR  YyRR 

yr  YyRr  YyRr YyRr   YyRr

Mendel’s Principles continued…

Before long, Morgan and other biologists had tested every one of Mendel’s principles and learned that they applied not just to pea plants but to other organisms as well.

At the beginning of the 1900s, American geneticist Thomas Hunt Morgan decided to use the common fruit fly as a model organism in his genetics experiments because it could produce plenty of offspring, and it did so quickly in the laboratory.

Beyond Dominant and Recessive Alleles

In most organisms, genetics is more complicated, because the majority of genes have more than two alleles.

Some alleles are neither dominant nor recessive.

Mendel’s principles alone cannot predict traits that are controlled by multiple alleles or multiple genes.

Other Inheritance Patterns

• Incomplete Dominance –

Flower Color • Polygenic -

Skin Color• Codominance -

Speckled Feathers

• Multiple Alleles - Blood Type

• Sex-Linked-Color blindness

Incomplete Dominance

• A cross between two four o’clock plants shows a common exception to Mendel’s principles.

• The F1 generation produced by a cross between red-flowered (RR) and white-flowered (WW) plants consists of pink-colored flowers (RW), as shown.

• In this case, neither allele is dominant. Cases in which one allele is not completely dominant over another are called incomplete dominance.

• In incomplete dominance, the heterozygous phenotype lies somewhere between the two homozygous phenotypes.

Codominance

• Cases in which the phenotypes produced by both alleles are clearly expressed are called codominance.

• For example, in certain varieties of chicken, the allele for black feathers is codominant with the allele for white feathers.

• Heterozygous chickens have a color described as “erminette,” speckled with black and white feathers.

Multiple Alleles

• A single gene can have many possible alleles.

• A gene with more than two alleles is said to have multiple alleles.

• Many genes have multiple alleles, including the human genes for blood type. This chart shows the percentage of the U.S. population that shares each blood group.

http://www.redcrossblood.org/learn-about-blood/blood-types

American Red Cross Info on Blood Types

Polygenic Traits

• Traits controlled by two or more genes are said to be polygenic traits. Polygenic means “many genes.”

• Polygenic traits often show a wide range of phenotypes.

• The variety of skin color in humans comes about partly because more than four different genes probably control this trait.

Genes and the Environment

• Environmental conditions can affect gene expression and influence genetically determined traits.

• Genes provide a plan for development, but how that plan unfolds also depends on the environment.

• For example, consider the Western white butterfly. Western white butterflies that hatch in the summer have different color patterns on their wings than those hatching in the spring.

Genes and the Environment

• Scientific studies revealed that butterflies hatching in springtime had greater levels of pigment in their wings than those hatching in the summer.

• In order to fly effectively, the body temperature of the Western white butterfly needs to be 28–40°C.

• More pigmentation allows a butterfly to reach the warm body temperature faster. Similarly, in the hot summer months, less pigmentation prevents the butterflies from overheating.

1/17/14Bellringer 10: (Turn in when done) Fill in the blanks using vocabulary words. Just write the word.

1. The _________ is used to describe the physical traits shown in the punnett square.

2. The _________ is used to describe the genes shown in the punnett square.3. The allele type that will usually mask or “cover up” the effect of another allele

is called _____________.4. The allele type that is usually not expressed when masked or “covered up” is

called ____________.

Agenda:“Desiree’s Baby”

1/27/14

BR 1:Use this Word Bank to complete the

sentences on the right.Word Bank:• Independent assortment• Sex-linked• Polygenic traits• Codominance• Laws of segregation

Agenda:Desiree’s BabyWork on Spongebob Genetics Assignment

1. When both traits show up, like black

with white spots, it is called ______________________.

2. Traits that are found on the X or Y chromosome are called __________.

3. Traits controlled by two or more genes are______________________.

4. The independent segregation of genes is ____________________________.

5. The defined separation of alleles is called_________________________.

Desiree’s Baby

• Summary of the story?