Heredity -- Chapter 5
1. Gregor Mendel (1822-1884)
The Father of Genetics
2. Gregor Johann Mendel
 Austrian monk
 Studied the inheritance of traits in pea plants
 Developed the laws of inheritance
 Mendel's work was not recognized until the turn of the 20th century
3. Gregor Johann Mendel
 Between 1856 and 1863, Mendel cultivated and tested thousands of pea
plants
 He found that the plants' offspring retained traits of the parents
4. Particulate Inheritance
 Mendel stated that physical traits are inherited as “particles”
 Mendel did not know that the “particles” were actually Chromosomes &
DNA
5. Why peas, Pisum sativum?




Can be grown in a small area
Produce lots of offspring
Produce pure plants when allowed to self-pollinate several generations
Can be artificially cross-pollinated
6. Traits to Track
• Mendel tested 7 traits:
1. Flower color
Heredity -- Chapter 5
2.
3.
4.
5.
6.
7.
Flower position
Seed color
Seed shape
Pod shape
Pod color
Plant height
7. Mendel and His Peas
• Mendel crossed flowers that were true-breeding for each characteristic.
• He crossed a purple (PP) flowered plant with a white (pp) flowered plant.
(Parent Generation)
Heredity -- Chapter 5
8. Mendel and His Peas
• The first generation (F1) of plants all had purple flowers.
• Where did the white color go??
Drawing
9. Mendel and His Peas
• Mendel took two of his first generation (F1 x F1) purple flowered plants
and crossed them together.
• In the second generation (F2) he had 3 purple flowered plants, and 1
white flowered plan
Drawing
10. Mendel and His Peas
• Mendel noticed in the first generation, all of the white flowers seemed to
disappear.
Heredity -- Chapter 5
• He called this a recessive trait.
• The white color faded into the background at first.
• It showed up in the next generation when he pollinated the flowers.
11. Mendel and His Peas
• The color (purple) that seemed to mask over the recessive color was
named the dominant trait.
12. Mendel and His Peas
• Mendel was responsible for figuring out that each plant carried two sets
of instructions for each characteristic (one from the “mom” and one from
the “dad”).
• Like many scientists, his work was not accepted until after his death.
13. Let’s Recap:
1. If you crossed a true-breeding black rabbit with a true-breeding white rabbit,
all of the offspring would be black. Which trait is dominant in rabbits: black
fur or white fur?
2. Which trait is recessive?
14. Answer
• The trait for black fur is dominant over the trait for white fur. The white
fur trait is recessive.
Draw
15. Google’s tribute to Mendel July 2011
Heredity -- Chapter 5
16. Science Humor
17. Vocabulary
1. Heredity- the passing of traits from parent to offspring.
2. Self-pollinate- A plant is often able to pollinate by itself because it contains
both the male and female reproductive structures. This only requires 1 parent.
3. True-breeding- all of the offspring will have the same trait as the parent
when self-pollinated
4. First-generation- the very first set of offspring from two parents
Heredity -- Chapter 5
5. Dominant trait- the trait observed when at least one dominant allele for a
characteristic is inherited
6. Recessive trait- a trait that is apparent only when two recessive alleles for
the same characteristic are inherited
7. Genes- a segment of DNA that carries hereditary instructions and is passed
from parent to offspring
8. Alleles- multiple forms of the same gene
9. Genotype- is organisms inherited combination of alleles
10. Phenotype- is organisms inherited appearance
11. Probability – the mathematical chance that something will happen.
Heredity -- Chapter 5
1. Gregor Mendel (1822-1884)
The Father of ______________
2. Gregor Johann Mendel
 Austrian monk
 Studied the inheritance of __________ in pea plants
 Developed the ________ of ________________
 Mendel's work was not recognized until the turn of the 20th century
3. Gregor Johann Mendel
 Between 1856 and 1863, Mendel cultivated and tested thousands of pea
plants
 He found that the plants' offspring retained ___________ of the parents
4. Particulate Inheritance
 Mendel stated that physical traits are _______________ as “particles”
 Mendel did not know that the “particles” were actually
___________________ & ________
5. Why peas, Pisum sativum?
 Can be grown in a small area
 Produce lots of offspring
Heredity -- Chapter 5
 Produce pure plants when allowed to _________-_______________ several
generations
 Can be artificially cross-pollinated
6. Traits to Track
• Mendel tested 7 traits:
1.
2.
3.
4.
5.
6.
7.
Flower __________
Flower position
Seed _________
Seed shape
Pod shape
Pod color
Plant height
Heredity -- Chapter 5
7. Mendel and His Peas
• Mendel crossed flowers that were true-breeding for each
________________________ .
• He crossed a_______________ (PP) flowered plant with a
_________(pp) flowered plant. (Parent Generation)
8. Mendel and His Peas
• The first generation _________ of plants all had purple flowers.
• Where did the white color go??
Draw
Heredity -- Chapter 5
9. Mendel and His Peas
• Mendel took two of his first generation (F1 x F1) purple flowered plants
and crossed them together.
• In the second generation _______ he had 3 purple flowered plants, and 1
____________ flowered plan
Draw:
10. Mendel and His Peas
• Mendel noticed in the first generation, all of the ___________ flowers
seemed to disappear.
• He called this a ______________ trait.
• The white color faded into the background at first.
• It showed up in the next generation when he pollinated the flowers.
Heredity -- Chapter 5
11. Mendel and His Peas
• The color (purple) that seemed to mask over the recessive color was
• named the _______________ trait.
12. Mendel and His Peas
• Mendel was responsible for figuring out that each plant carried ________
sets of instructions for each characteristic (one from the “mom” and one
from the “dad”).
• Like many scientists, his work was not accepted until after his death.
13. Let’s Recap:
1. If you crossed a true-breeding black rabbit with a true-breeding white rabbit,
all of the offspring would be black. Which trait is dominant in rabbits: black
fur or white fur?
2. Which trait is recessive?
Heredity -- Chapter 5
14. Answer
• The trait for black fur is dominant over the trait for white fur. The white
fur trait is recessive.
15. Google’s tribute to Mendel July 2011
16. Science Humor
Heredity -- Chapter 5
17. Vocabulary
1. Heredity- the passing of traits from parent to offspring.
2. Self-pollinate- A plant is often able to pollinate by itself because it contains
both the male and female reproductive structures. This only requires 1 parent.
3. True-breeding- all of the offspring will have the same trait as the parent
when self-pollinated
4. First-generation- the very first set of offspring from two parents
5. Dominant trait- the trait observed when at least one dominant allele for a
characteristic is inherited
6. Recessive trait- a trait that is apparent only when two recessive alleles for
the same characteristic are inherited
7. Genes- a segment of DNA that carries hereditary instructions and is passed
from parent to offspring
8. Alleles- multiple forms of the same gene
9. Genotype- is an organism’s inherited combination of alleles
10. Phenotype- is an organism’s inherited appearance
11. Probability – the mathematical chance that something will happen.
Heredity -- Chapter 5
Mendel’s Conclusions
Each plant must have two “factors” for
each possible trait, one factor from each
parent
Some forms of a trait can be masked
Traits able to be masked can only be seen
if both the plant’s factors are for that
form of the trait
Mendel’s “factors” are now known as
genes and alleles Alleles interact to produce t
Alleles interact to produce traits
Phenotype
describes the physical
characteristic that is displayed by your
genes; observable (eye color, hair color)
Genotype
describes the actual genes
that you have on your DNA; not always
obviousTwo forms of every gene
Mendel found that we have two copies of
each allele (one from mom, one from dad)
Alleles can be
Dominant
•
Physically expressed
regardless of what other
Heredity -- Chapter 5
allele it is paired with
•
Always expressed as a
capital letter (T)
•
Ex: tallness is the
dominant trait for pea plant
height
Recessive
•
Physically expressed
only when paired with
another recessive allele
•
Always expressed as a
lower-case letter (t)
•
Ex: dwarfism is the
recessive trait for pea
plant height
Heredity -- Chapter 5