Download uh-lee-uls

• What are some of the things you already
know about heredity and genetics?
• (STAR book)
• What are some things you want to learn?
Chapter 5.1
• Have you ever wondered why some family
members look very similar while others look
very different?
Section 1:
Mendel’s Work
What were the results of Mendel’s experiments, or
crosses?
What controls the inheritance of traits in organisms?
Heredity
• Is the passing of physical characteristics from
parent to offspring.
Trait
• Each different form of a characteristic is called
a trait.
Fertilization
• The process of a new organism beginning to
form due to the joining of a sperm and an egg
cell.
Purebred
• The offspring of many generations that have
the same trait.
Hybrid
• Is an organism that has two different alleles
for a different trait.
Hybrid
• Is an organism that has two different alleles
for a different trait.
Genes vs Alleles
• Genes are the factors that control a trait
• Alleles are the different forms of a gene
Dominant vs Recessive Alleles
• Dominant always shows up
• Recessive is hidden by a dominant allele
• The only was a recessive allele shows up is if the
organism has TWO recessive alleles for a particular
trait.
Black is dominant and white is
recessive in bunnies
Symbols for Alleles
• Geneticists use Letters
• Capital letters are used for dominant alleles
• Lower case are used for recessive alleles
Crossing Pea Plants
• Gregor Mendel crossed pea plants that had
different traits. The illustrations show how
he did this.
Mendel’s Experiments
• In all of Mendel’s crosses, only one form of the trait
appeared in the F1 generation. However, in the F2
generation, the “lost” form of the trait always
reappeared in about one fourth of the plants.
Dominant and Recessive Alleles
• Mendel studied several traits in pea plants.
Mendel's final Conclusions
• Each of the selected garden pea traits is
controlled by a pair of alleles (uh-lee-uls)
Mendel's final Conclusions
• Each of the selected garden pea traits is
controlled by a pair of alleles (uh-lee-uls)
• For each trait, the offspring receives one allele
from each parent
Mendel's final Conclusions
• Each of the selected garden pea traits is
controlled by a pair of alleles (uh-lee-uls)
• For each trait, the offspring receives one allele
from each parent
• The chance of each offspring receiving one or
the other allele is equal (50/50 chance)
Mendel's final Conclusions
• Each of the selected garden pea traits is
controlled by a pair of alleles (uh-lee-uls)
• For each trait, the offspring receives one allele
from each parent
• The chance of each offspring receiving one or
the other allele is equal (50/50 chance)
• The expression of a dominant trait only
requires one dominant allele, recessive
requires two recessive alleles.
End of Section: Mendel’s Work
HW: Please complete the
Questions on page 159 (1abc2abc) in your STAR book