Download Chapter 6: Introduction to Genetics

Chapter 6:
Introduction to Genetics
Section 6-1:
The Science of Inheritance and
Gregor Mendel
Parents and Offspring
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Heredity = biological inheritance
An organism’s heredity is the set of
characteristics it receives from its parents.
Genetics is the study of heredity.
Heredity IS NOT just a blend of characteristics
from both parents – look at page 124
Gregor Mendel
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Born in 1822, became a monk, but also studied
science and math in Vienna
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In the monastery, Mendel’s job was to take care
of the garden (monasteries are self-sustaining)
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He took an interest in pea plants – he began
with true-breeding stock
True-Breeding Stock
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True-breeding stock refers to individuals that
always pass on their characteristics to the next
generation (ex. a tall pea plant with green pods
will ALWAYS produce tall pea plants with green
pods)
Reproduction in Pea Plants
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Peas use their flowers to reproduce (p.125)
Male sex cell = pollen
Female sex cell = egg
Pea plants normally self-pollinate, meaning the
pollen and egg come from the same plant
(basically only one parent)
True-breeding stock results from generations of
self-pollination
Mendel and Pea Plants
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Mendel wanted to see what would happen if he
crossed true-breeding stock with different
characteristics
Mendel removed all the male plant parts so that
he could control pollination, making sure that
pollen and egg came from different plants
This is called cross-pollination
Mendel’s Seven Traits
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Trait = characteristic that identifies one
individual from another
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Mendel focused on seven traits, each with two
contrasting forms
Mendel’s Seven Traits
Trait
Form 1
Form 2
Seed shape
Round
Wrinkled
Seed color
Yellow
Green
Seed coat color
Gray
White
Pod shape
Smooth
Constricted
Pod color
Green
Yellow
Flower position
Axial
Terminal
Plant height
Tall
Short
Mendel’s Seven Traits
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Mendel used true-breeding stock to create
hybrids – offspring of parents with different
characteristics
The hybrids were called the first filial generation
(F1 generation) and the true-breeding stock
were called the parental generation (P
generation)
Mendel’s Seven Traits
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Mendel noticed the traits seen in the F1
generation were not a blending of the P
generation’s traits
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The traits of only ONE parent appeared in the
offspring while the traits of the other parent
seemed to disappear