Download Ch 11 Mendel STUDENT lecture notes

Video: Basics of genetics total 35 min , parts Bill Nye Genetics (16 min)
Chapter 11-1, 2, 3
Mendel and Genetics
A monk named Gregor Mendel spent several years gardening, along with teaching math and science.
His hobby of gardening experiments changed biology forever. Mendel grew peas. He noticed that
there were several traits of peas, such as color, smoothness, height, and flower color. Sometimes
he would allow the flower to ___________ pollinate. Most flowers have both sperm (sperm) and egg.
He called this________ ___________________. The offspring of this true breeding always brought
about offspring that looked ________________________ to parents. Other times he would take the
pollen from one variety of pea plant and brush the pistil (female flower part). He called this crosspollination. (pg 264)
When Mendel cross pollinated plants he noticed that some of the traits showed up more often and
some of the traits seemed to disappear, and then show up again in a later breed. This is when he
began to start collecting data.
P= parent generation. This is the first breeding generation
F1 = this is the offspring of the parent breeding. F1 means first filial (first family)
F2= Second generation from Self pollinating of F1 generation. (Grandkids)
Mendel noted that when crossing yellow pea plants and green pea plants (Parents were pure breed
yellow and pure breed green), that all the F1 generation was yellow. He indicated that yellow must
be dominant color to green. He knew that these yellow F1 plants were not pure, so he called them
hybrids.
Mendel’s First Conclusions
1. Inheritance determines traits that are passed to the next generation. These traits are called
___________________
2. Each form of a trait is called an __________________. Yellow is one type of color allele and
green is another.
Principle of Dominance: Some alleles are dominant and others are recessive. The dominant
allele will cover the recessive allele trait.
Mendel’s next question was: What happened to the green pea gene?
In his next experiment, he self pollinated a hybrid F1 plant. Most of the peas were still yellow but a
few were green. He repeated this experiment several times and ended up with a ratio of
____:_____. 25% of peas will be green, and 75% will be yellow in the F2 generation.
Mendel associated letters for these traits, where a _____________letter indicates a dominant trait.
Based on the above experiments:
P generation: = YY x yy (Pure breed yellow dominant is YY) (Pure breed green recessive is yy)
F1 generation = 100% yellow Yy hybrid
F2 generation = Yy x Yy 75% yellow YY or Yy , 25% green yy
Principle of Probability is used to determine a certain outcome of genetic crosses.
Homozygous: Both alleles are the same, and called pure breed, _______or _______
TT = homozygous dominant, tt = homozygous recessive
Heterozygous: The alleles for a trait are different ______ _________________
Genotype: genes or alleles represented by letters, where capitals indicate dominant, and lower
case represent recessive
Phenotype: The ___________________trait expressed, what it looks like
Tall is dominant to short plants
TT= homozygous dominant, phenotype is tall
Tt = heterozygous, phenotype is tall
tt = homozygous recessive, phenotype is short
Punnett Squares are used to help determine genotypes and phenotypes in breeding.
One allele from one parent goes to the left side of each box, and one allele from the other parent
goes on top.
It doesn’t matter which parent is on the top squares, or side of the square.
The capital letter is always placed first, since it is dominant.
Cross a Pure breed Tall with a Pure Breed Short TT x tt
F1 Generation
F2
Generation
F1 Genotypes__________
F1 Phenotypes_____________
Cross F1 generation Tt x Tt
F2 Genotypes
__________
_________
F2 Phenotypes
__________
__________
___________
______ are Pure breed short. _______Pure breed tall______are hybrid tall
When crossing two hybrids, there will always be a 3:1 phenotypical ratio. The larger the test
population, the more closely this will occur.
Mendelian Genetics pg 270
Law of Independent Assortment
Mendel began looking at more than one gene. He began experiments on peas that were yellow and
round, and peas that were green and wrinkled. He observed that almost all of the peas were yellow
and smooth. He began cross breeding to determine if he could create a smooth green pea, or a
yellow wrinkled pea. In the first test, he crossbred pure yellow, pure smooth with a pure green pure
wrinkled plant.
P1 YYRR x yyrr
1. This type of a Punnett square must have 16 boxes.
2. Find each combination of both traits,
3. Place each combination on the side or above the 8 boxes.
Combinations of YYRR ____ ____ ____ ____ Combinations of yyrr ____ ____ ____ ____
F1 Generation
F1Genotype _________
YR
YR
YR
YR
F1 Phenotype_________
________ of the peas are yellow and round, but all of them are also __________________.
Cross F1 generation.
Combinations of YyRr ____ ____ ____ ____ Combinations of YyRr ____ ____ ____ ____
F2 Phenotype
_____________
______________ _______________ _______________
Ratio ____:____:____:____
Mendel concluded that these genes (color and shape of pea) can be separated from each other
during gamete (sperm or egg) formation. This is called The Law of Independent Assortment.
Mendel’s Principles
1. Inheritance of biological characteristics is determined by genes. Genes are passed from
parents to offspring.
2. When there are two or more genes for a single trait, some genes may be dominant and some
recessive.
3. The parent has two copies of each gene, one from each of their parents. These are
separated, when meiosis occurs. Only one gene is in each gamete.
4. Alleles for genes segregate independently.
Beyond Recessive and Dominant pg 272
There are other possibilities that Mendel didn’t address. Not all genes are dominant or recessive.
Many traits are controlled by multiple alleles and even multiple genes.
Incomplete Dominance
When cross breeding two pure breeds, both traits are blended, and neither is dominant.
Crossing a pure breed red and pure breed white 4’Oclock flower will result in all pink F1 generation.
F1
F2
P1 geno/phenotypes _____ x ______
F1 geno/phenotype_________
F2 geno/phenotypes_______________ _______________ ________________
Co-dominance: both traits are equally expressed.
When you cross a white feathered chicken (male or female) with a black feathered chicken, the F1
generation has both black and white feathers.
Multiple Alleles: when there are more than two alleles for a gene (trait). Rabbit fur has only one
gene for fur, but 4 alleles for each rabbit. There are 4 combinations of alleles that allow for different
fur color. Blood type and eye color are another example. Pg 273
Cross a Chinchilla Hair cchc, with a Himalayan Hair chc
F2 geno/phenotypes____________
____________
_____________
_______________
Polygenic Traits: traits controlled by two or more genes. They show a wide variety of phenotypes.
Skin color is an example.
Mendel did not know about chromosomes containing genes. Luckily, in his pea plant tests, the traits
(genes) happened to be on different _________________________. Therefore, they could assort
independently. If traits are on the same chromosome, they may not separate. The closer the gene is
to another gene, the more likely it will be linked. Gene B and C are more closely linked (less likely to
separate) than gene A and F. In crossover of meiosis, gene B and C are more likely to cross over
together.
Chapter 11 MENDEL Vocab
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3:1
9:3:3:1
Alleles
Co-dominance
Dihybrid cross
Dominance
F1
F2
Genotype
Example of Heterozygous alleles
Example of Homozygous alleles
Hybrid (definition)
Incomplete Dominance
Independent Assortment
Monohybrid cross
Multiple Alleles
P
Phenotype
Polygenic Traits
Probability
Recessive
1. ____2__ Ratio in a Dihybrid Cross
2. ____14__ Genes from separate traits can segregate separately from each other
3. __3____ Different forms of genes (such as looking at a tall or short trait)
4. __16____ Genes having more than 2 alleles, such as rabbit fur
5. __10____ Tt
6. __15____ Testing one hybrid trait such as Tt x Tt
7. __19____ Traits controlled by 2 or more genes, such as skin color.
8. _5_____ Testing two hybrid traits such as TtRr x TtRr
9. ___6___ Some traits are dominant over others, indicated by a capital letter
10. __20____ Likelihood that a trait will show up
11. __17____ Parent generation
12. __7____ First generation
13. ___8___ 2nd generation
14. __12____ Genetic makeup of an individual having one capital allele and one lower case allele
15. __11____ TT, tt
16. __1____ Ratio in a monohybrid Cross
17. ___13___ Blending of two traits, such a red flower and white flower producing a pink flower
18. ___4___ Both alleles are expressed equally, such as checkered chicken feathers (black hen, white rooster,
making a black and white feathered chick)
19. ___21___ Trait masked by dominant gene
20. __18____ Physical characteristics of an organism, what it looks like
21. __9____ Genetic make up of an organism, indicated by letters, such a Yy, YY, or yy.
In mice, running mice are dominant to waltzing mice(mice that run in circular patterns). Brown fur is dominant
to black fur. Create table that shows the crosses between a heterozygous running, homozygous black mouse as
one parent and the other parent is homozygous waltzing heterozygous brown mouse. “R” is run, “B” is brown.
1. List All the allele combinations of independent assortment of the Heterozygous running-homozygous
black mouse. (Some may be repeated)
__________
__________
__________
__________
2. List All the allele combinations of independent assortment of the homozygous waltzing-heterozygous
brown mouse. (Some may be repeated)
__________
3.
__________
__________
__________
Create a Table that shows all the possible combinations of genotypes for the 16 offspring
Genotypes
4. List all the phenotypes (some lines may not be filled in depending upon the test cross)
Running Brown__________________/16 Waltzing Brown________________/16
Running Black____________________/16 Waltzing Black_________________/16
5. A florist wants to guarantee that the seeds she sells will produce only pink flowered 4 O’clock plants. These
types of flowers are incomplete dominance. What should she do to get only pink seeds?
Yellow peas are dominant to green peas and purple flowers are dominant to white flowers in a pea plant. Create a table
that shows a cross between a heterozygous yellow pea-homozygous white flower for one parent and the other parent as
homozygous green pea-homozygous white flower. “Y” for yellow ‘y’ is for green and “P” for purple and ‘p’ is white.
1. List All the allele combinations of independent assortment of the Heterozygous yellow -homozygous
white plant (Some may be repeated)
__________
__________
__________
__________
2. List All the allele combinations of independent assortment of the homozygous green-homozygous white
flower plant. (Some may be repeated)
__________
3.
__________
__________
__________
Create a Table that shows all the possible combinations of genotypes for the 16 offspring.
Genotypes
4. List all the phenotypes (some lines may not be filled in depending upon the test cross)
Yellow pea-White Flower_________/16 Yellow pea-Purple Flower_________/16
Green pea-White Flower_________/16
Green pea-Purple Flower__________/16
5. A florist wants to guarantee that the seeds she sells will produce only pink flowered 4 O’clock plants. These
types of flowers are incomplete dominance. What should she do to get only pink seeds?
Blue corn is dominant to yellow corn. “B” is used for dominant and ‘b’ is used for recessive. Hard kernels are
dominant to recessive kernels. “H” will be used to illustrate hard and “h” will be used to illustrate soft. You
will be crossing a heterozygous blue, homozygous soft corn plant with a homozygous yellow, homozygous soft
plant.
1. List All the allele combinations of independent assortment of the a heterozygous blue-homozygous soft
corn (Some may be repeated)
__________
__________
__________
__________
2. List All the allele combinations of independent assortment of the homozygous yellow, homozygous soft
plant.(Some may be repeated)
__________
3.
__________
__________
__________
Create a Table that shows all the possible combinations of genotypes for the 16 offspring.
Genotypes
4. List all the phenotypes (some lines may not be filled in depending upon the test cross)
Blue Corn Hard Kernel_________/16 Yellow Corn-Hard Kernel_________/16
Blue Corn Soft Kernel_________/16
Yellow Corn-Soft Kernal__________/16
5. A florist wants to guarantee that the seeds she sells will produce only pink flowered 4 O’clock plants. These
types of flowers are incomplete dominance. What should she do to get only pink seeds?