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mendel notes and puppy dog.notebook
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November 19, 2013
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Genetics and InheritanceChapter 10: Section 1
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PuppyDog Creations…
Choose BLUE or YELLOW paperFEMALE or MALESQUARE eyes or ROUND eyesOVAL nose or TRIANGULAR nosePOINTED teeth or SQUARE teeth
***The rest is up to you!***
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In this section vocabulary is extremely important. It leads the way to the rest of your understanding.
As always, ask questions if you do not understand!
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VOCABULARY• TRAITS a genetic (inherited) characteristic
• HEREDITY The passing of traits from parent to offspring
• GENETICS the branch of biology that studies heredity (inherited traits)
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Gregor Mendel
Who? Monk (priest)
What? Curious gardener trained in math and science
When? 1851 is when it all began…
Where? Austria (central Europe)
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Curiosity Leads the Way• He was curious as to why plants, specifically garden pea plants, had different physical characteristics (short/tall, yellow seeds/green seeds, purple/white flowers, etc.)
• Observed that TRAITS were often similar to those of their parents
• Spent over 10 years experimenting with the thousands of pea plants to understand HEREDITY
• He was the first person to succeed in predicting how traits are transferred from one generation to the next.
• His work formed the foundation of GENETICS
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Why Pea Plants?• Easy to grow
• Grow quickly
• Produce large number of offspring in one generation (lots of data available at one time)
• They have many traits that exist in only two forms (makes it easier to study them)
• Pea plants have both male and female parts on the same flower; so fertilization can be controlled.
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Plant Vocabulary• Gametes male and female sex cells
• Fertilization male gamete unites with the female gamete
• Zygote the fertilized cell that develops into a seed.
• Pollination transfer of pollen grains from male reproductive organ to female reproductive organ.
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• Pistilfemale sex cells
• Stamenmale sex cells (pollen)
• NOTE in nature these plants would be selfpollinating
• Mendel developed a way to crosspollinate pea plants• Remove pollen from a flower on one plant and brush it on a
flower of a second plant• To prevent selfpollination he carefully removed the
stamens from the flowers on the second plants
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FIGURE 10.1
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Vocabulary Continued
1. taking the male gamete and combining it with the female gamete of the same plant
2. Taking the male gamete of one plant and combining it with the female gamete of another plant
3. A plant (organism) that can only provide one type of allele during reproduction (EE, ee; not Ee)
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Let the Experiment Begin!• Mendel crossed PUREBRED plants with opposite forms of the same trait. For example he crossed a purebred tall plant with a purebred short plant.
• Why purebreds??? Because those were the plants that he knew what to expect from the offspring.
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Experiment #1• Characteristic: Tall Plant vs Short Plant
• NOTE: The parent plants were called the parent generation or P generation and the offspring from this cross were called the F1 generation.
• Results: ALL F1 generation plants were tall! The short trait had “disappeared”.
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Quick Vocabulary
1. Parent generation; first cross TTxtt
2. First generation; offspring of P1
3. One of each allele
4. One of each allele for just trait.
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Experiment #2• He then allowed all of the F1 generation to selfpollinate.
• This generation was called the F2 generation.
• Results: He discovered that about ¾ of them were tall and ¼ were short. Short trait had returned!
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Experiment #3???
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ConclusionsIndividual factors must control the inheritance of traits in peas.Factors exist in pairsFemale contributes one trait and the male contributes the otherOne factor can mask/hide the other factor
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Vocabulary…cont.
“Factors” that control traits are called GENES, they are located on chromosomes.
Different forms of a gene are called ALLELESex: two alleles for height: short and tall, purple vs. white
An organism's two alleles are located on different copies of a chromosome one from mom and one from dad.
Individual alleles control the inheritance of traits. Some alleles are dominant while others are recessive.
*Dominant alleles will always show up if they are present.
*Recessive alleles are covered up when dominants are present.
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Take out your puppydogs!
Answer Questions 12
Dominant alleles are: B (blue skin), R (round eyes), T (triangular nose), and P (pointed teeth)
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Always use the same letter for different alleles of the same gene.
Capital Letters stand for dominant alleles.
Lower case letters stand for recessive alleles
Dominant allele is always written first.
It does NOT matter where each parent is placed. One on top, one on the left side.
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Tt Tt
Tt Tt
T T
t
t
• Pgeneration: Tall Purebred (TT) and Short Purebred (tt)
• All four possibilities posses a tall gene so in every case the recessive, short gene, will be hidden.
• All F1 plants are considered to be hybrids they have two different alleles for the same trait, rather than being purebreds.
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The Law of Segregation• Recall the results of Mendel’s cross between F1 plants
• Rules: Each tall plant in the F1 generation carried one dominant allele for tallness and one unexpressed recessive allele for shortness. (F1 plants received 1 allele from each Pgeneration parent)
• The Law: Every individual has two alleles of each gene. When gametes are produced, each gamete receives one of these alleles at random. There are a total of four combinations of alleles.
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Two more Rules from Mendel:
• Rule of Unit Factors there are two different ‘factors’ or alleles that control each trait.
• Rule of Dominance Only one of the two alleles (dominant allele) for each trait actually determines the trait that will show up. The alternate form of the trait (recessive allele) is only present if the dominant trait is not.
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History Rapup• Mendel tried to present his results to other scientists; however, some felt that he had oversimplified inheritance while others would not even read his findings.
• It took 34 years before people began to realize how important his work really was.
• Today Mendel is often referred to as the FATHER OF GENETICS
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Question of the Day…
Why do you think people often look very similar to other family members, but also
different?
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How genetically similar are you to your classmates???
• Class Traits activity• Compare• Notes• Finish Activity
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Vocabulary Once more…
Phenotype Genotype
Tall TT
Tall Tt
Short tt
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• Finish Class Survey Activity
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• Take out your simple genetics practice problems that you picked up on Friday.
• Complete the front page, using your notes to help you.
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What is probability?• The likelihood that a particular event will occur.
• For example we would say that any coin that is tossed will have a 1 in 2 chances of landing heads up…BUT if you were to toss a coin 20 times you might expect it to be 10 heads and 10 tails but that might not be the case.
• Laws of probability PREDICT what is likely to occur not necessarily what WILL occur. However, the more tosses you make, the more accurate you’ll be.
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Probability in Genetics
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PUNNET SQUARES
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Monohybrid Crosses
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• Punnet Squares Practice Sheet
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• He used Peas that differed from each other by 2 traits instead of just one.
• The question he was asking: Will the two traits stay together in the next generation or will they be inherited independently of each other?
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Dihybrid Cross Experiment
• Characteristics: Truebred round, yellow seeds and a truebred wrinkled, green seeds
• He already knew: Round and Yellow were dominant from his monohybrid crosses.
• Results: All Seeds were round and yellow.
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• Allow the F1 generation to self pollinate.
• Results were that F2 varied greatly: round/yellow seeds, wrinkled/green seeds, round/green seeds, and wrinkled/yellow seeds.
• In the F2 generation he again counted a definite ratio of physical characteristics: 9 round/yellow, 3 round/green, 3 wrinkled/yellow, and 1 wrinkled/green (9:3:3:1)
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Conclusions to Dihybrid Cross Experiments
• Mendel was able to express his second Law from the results and he called it: The Law of Independent Assortment
• Genes of different traits are inherited independently
• Why was he able to make this conclusion? Because if the alleles for seed shape and color were inherited together only 2 kinds of pea seeds would have been produced instead of variations of all combinations.
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• 4x4 box because each combination must be considered.
• 2 traits per box
• See Figure 10.8 in your book (pg 261).
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Dihybrid Cross Punnet Square
Example: What happens if a man who is heterozygous brown eyes AND heterozygous tongue roller has children with a woman who is homozygous blue eyes AND heterozygous tongue roller?? What is the chance that their child will be a blue eyed nontongue roller?
Due to Mendel’s Law of Independent Assortment, we must look at all possible allele combinations that can go into sperm and egg. We will use a method of distribution you may have seen in math class called FOIL. FOIL stands for First, Outside, Inside, Last.
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What is the chance their child will be a blueeyed nontongue roller?______ out of _____ or ______%
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Genes Discovery WorksheetDihybrid Cross WorksheetPuppy Dog madness ActivityOompa Loompa Activity.Quiz
