Download 11-1 The Work of Mendel

Introduction
On a 3 x 5 card write down a description of
yourself using only your inherited traits.
For example, you can describe your hair
color or texture but not your hair style that
day. The description will be read aloud to
the class. The class will try to figure out if
they could identify the student based on the
description.
11-1 The Work of Mendel
• What does every living thing inherit from
their parents?
• Genetics – the study of heredity
Look around at your classmates and make a
list of some of the traits that are inherited.
Gregor Mendel’s Peas
Read about Mendel on p. 308 – report some
findings about his life.
• What was Mendel in charge of at the
monastery? Garden
• What did he grow and study? Pea Plants
What did Mendel already know
…
• Each flower produces pollen and egg cells
• Cross fertilization (sexual) – male and
female cells join
• Self-pollination (asexual) – pollen fertilizes
eggs from same plant
• Mendel’s pea plants were true-breeding
– A tall plant with green seeds would produce a
tall plant with green seeds
How Mendel started his experiment
• Cross-pollinated the pea plants
• Had to prevent self-pollination in order to
do this…HOW?
Cut away the male parts of the plant
• How did Mendel cross-pollinate the plants?
Dusted the female reproductive part with
pollen from another plant
How Mendel started his experiment
• What did crosspollination produce?
Hybrid Plants
• What did this make
possible?
To study the
inheritance of certain
traits
Genes and Dominance
• Trait – specific characteristic
– Mendel studied 7 different pea plant traits
• What are some examples? Plant Height, Seed
Shape, Pod Color
Mendel crossed plants to study offspring
• The original plants = P generation
• The offspring = F1 generation
• Hybrid – offspring of crosses btwn parents
w/ diff. traits
Mendel crossed plants to study offspring
• Mendel expected a blend of traits HOWEVER
• Offspring had characteristic of one parent
• The character of the other parent seemed to
disappear
Mendel crossed plants to study offspring
• Genes – the chemical factors that determine
traits
• Alleles – different forms of a gene
– Ex. From pea plants:
gene = plant height
alleles = tall and short
Mendel crossed plants to study offspring
• Principle of dominance: some alleles are
dominant and others are recessive
• Dominant allele – the trait is always shown
– Capital letter
• Recessive allele – the trait that will only
show if there is no dominant allele
– Lower case letter
Segregation
• Mendel’s next question…Where had the
recessive allele gone?
• P generation – (parents, originals) – Tall x short
• F1 generation – (offspring of P) tall x tall
• F2 generation – (offspring of F1) 3 tall, 1 short
The F1 Cross
• Shows the F2 generation
• Recessive alleles had reappeared!!!
Questions
1. Genetics is the study of ________.
2. Alternate characteristics of an organism
such as height, hair color, eye color, etc.
are called _______.
3. Why did pea plants make such a good
subject for Mendel to study?
4. Pea plants are self pollinating. Why did
mendel cross pollinate?
5. What does “true breeding” mean?
Considering the allele related to
short and tall pea plants.
1. Plants of the P generation (tall) will
produce only_____________ if not
crossed with plants having other alleles.
2. Describe the phenotype (what we can see)
of Mendel’s F1 Generation.
3. What was the genotype (use letters “T”
and “t”) for Mendel’s F1 generation?
4. How did the F2 generation suggest that
genes were simply segregated, not lost?