Genetics and InheritanceChapter 10: Section 1
Puppy-Dog CreationsChoose BLUE or YELLOW paperFEMALE or MALESQUARE eyes or ROUND eyesOVAL nose or TRIANGULAR nosePOINTED teeth or SQUARE teeth
***The rest is up to you!***
Note to Students: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!
VOCABULARYTRAITS- a genetic (inherited) characteristic
HEREDITY- The passing of traits from parent to offspring
GENETICS- the branch of biology that studies heredity (inherited traits)
Gregor MendelWho? Monk (priest)
What? Curious gardener trained in math and science
When? 1851 is when it all began
Where? Austria (central Europe)
Curiosity Leads the WayHe 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
Why Pea Plants?Easy to grow
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.
Plant VocabularyGametes- 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.
Pistil-female sex cells
Stamen-male sex cells (pollen)
NOTE- in nature these plants would be self-pollinating
Mendel developed a way to cross-pollinate pea plantsRemove pollen from a flower on one plant and brush it on a flower of a second plantTo prevent self-pollination he carefully removed the stamens from the flowers on the second plants
Vocabulary ContinuedSelf-pollinating- The pollen of one flower lands on the pistil of the same flower
Cross-Pollinating- The pollen of one flower is placed on the pistil of a different flower.**To prevent self-pollination Mendel removed the stamen from the flowers on the second flower.**
Pure bred- always produces offspring with the same form of a trait as the parent.its pure!
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.
Mendel carefully controlled his experiments making sure that he studied only one trait at a time to control the variables.
Experiment #1Characteristic: 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.
Experiment #2He then allowed all of the F1 generation to self-pollinate.
This generation was called the F2 generation.
Results: He discovered that about of them were tall and were short. Short trait had returned!
Experiment #3-???He tested all of the other main traitsFlower color, Seed shape, seed color, seed coat color, pod shape, pod color, and flower position.
Results: All of the traits had the same results as plant height!
Hybrids- offspring of parents that have different forms of a trait.
Monohybrid- Mendels first experiments were monohybrids because they differed only by a single trait.
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
Vocabularycont.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.
Mendel concluded that every plant in the F1 generation had one allele for Tall height and one allele for short height.
Take out your puppy-dogs!
Answer Questions 1-2
Dominant alleles are: B (blue skin), R (round eyes), T (triangular nose), and P (pointed teeth)
The Law of SegregationRecall the results of Mendels 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 P-generation 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.
Another Rule from Mendel:
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.
History Rap-upMendel tried to present his results to other scientists; however, some felt that he had over-simplified 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
Question of the DayWhy do you think people often look very similar to other family members, but also different?
How genetically similar are you to your classmates???Class Traits activityCompareNotesFinish Activity
Vocabulary Once morePhenotype- its physical appearance (visible traits)
Genotype- genetic makeup or allele combinations.
Homozygous (pure bred)- organism with two identical alleles for a trait (purebred)Homozygous dominant (TT)Homozygous recessive (tt)
Heterozygous (hybrid)- two different alleles for the same trait (hybrid)Notice: two genotypes for tall-cant tell the difference by looking at them.
Finish Class Survey Activity
Bell Work: 11-8Take out your simple genetics practice problems that you picked up on Friday.
Complete the front page, using your notes to help you.
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 upBUT 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 youll be.
Probability in GeneticsMendel, mathematician and scientist, was the first to recognize that the principles of probability can be used to predict the results of genetic crosses.
Mendel carefully counted the offspring from every cross. Every time he crossed two hybrid plants (Tt) of the F1 generation would be tall and would be short.
Mendel could say that the probability of such a cross producing a tall plant was 3 in 4 chances.
PUNNET SQUARESUsed to relate probability to genetics.
Shows all of the possible outcomes of a genetic cross
Allows you to determine the probability of a particular outcome (possible genotypes in the offspring)
You can predict probabilities of the offspring IF you know the genotypes of the parents.
Monohybrid CrossesYou need a 2x2 box
Each parent can produce two kinds of gametes or alleles for this trait.
Once the boxes are filled in you have all of the possible genotypes for a particular trait
From that information you can determine the phenotypes.
Understanding the CrossesAlways 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.
Meaning Behind the Symbols T T
tP-generation: 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.
Punnet Squares Practice Sheet
Mendels Dihybrid CrossesHe 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?
Dihybrid Cross Experiment
Characteristics: True-bred round, yellow seeds and a true-bred wrinkled, green seeds
He already knew: Round and Yellow were dominant from his monohybrid crosses.
Results: All Seeds were round and yellow.
Dihybrid Cross Experiment #2Allow 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)
Conclusions to Dihybrid Cross ExperimentsMendel was able to express his second Law from the results and he called it: The Law of Independent AssortmentGenes 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.
Dihybrid Punnet Squares4x4 box because each combination must be considered.
2 traits per box
See Figure 10.8 in your book (pg 261).
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 non-tongue roller?
Due to Mendels 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.
Practice: Foil the following genotype: BbWw (F) _____, (O) ______, (I) _____, (L) ____
Now were ready to tackle the example problem above.
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??
Dads Genotypes: _________________________
Possible Sperm Alleles: ______ or _______ or ______ or _______
Moms Genotypes: __________________________
Possible Egg Alleles: ______ or _______ or _______ or _________
What is the chance their child will be a blue-eyed non-tongue roller?______ out of _____ or ______%
Dad: Homozygous blue eyes AND Heterozygous Widows Peak ____________
Mom: Heterozygous brown eyes AND Heterozygous Widows Peak ___________
Genes Discovery WorksheetDihybrid Cross WorksheetPuppy Dog madness ActivityOompa Loompa Activity.Quiz
**TT with tt