Download Chapter 4: Genetics The Science of Heredity Section 1: Mendel*s

Chapter 4: Genetics The
Science of Heredity
Section 1: Mendel’s Work
What were the results of
Mendel’s experiments, or
crosses?
• Mendel discovery of genes and
alleles eventually changed
scientists’ ideas about heredity.
What controls the
inheritance of traits in an
organism?
• An organism’s traits
are controlled by the
alleles it inherits
from its parents.
Some alleles are
dominant, while other
alleles are
recessive.
Heredity
• The passing of
physical
characteristics
from parent to
offspring.
Trait
• Each different
form of a
characteristic
such as stem
height or seed
color is called a
trait.
• In humans it
would be eye
color, or hair
color as traits.
Genetics
• The scientific
study of
heredity.
Fertilization
• A new organism
begins to form
when an egg and a
sperm join.
Purebred
• A purebred
organism is the
offspring of many
generations that
have the same
trait.
P Generation
• Scientists call
the parent plants
the P Generation
F 1 or First Filial
• The first group
of offspring from
the P generation
are known as the
first filial or
F1 generation.
(Filius and Filia
mean daughter or
son in Latin)
F2 or Second Filial
• The second group of
offspring (crosses
of the F1
generation) are
known as the second
filial or F2
generation
• It is at this point
that traits from the
P generation being
to reappear even
though they were not
seen in the F1
generation
Gene
• The factors that
control a trait.
Alleles
• The different
forms of a gene.
Dominant Allele
• An allele whose
trait always
shows up in the
organism when the
allele is
present.
Recessive Allele
• A recessive
allele is always
hidden whenever
the dominant
allele is
present.
Hybrid
• A hybrid is an
organism that has
two different
alleles for a
trait.
• Tt a dominant and
recessive allele
for a trait.