WELCOME BACK!
Time to jump start your brain!
• What’s the purpose of mitosis?
• What’s the purpose of meiosis?
• How many chromosomes do somatic cells
have?
• How many chromosomes do gametes have?
Heredity and Genetics
Mendel and Our Understanding of
the Gene Pool
Gregor Mendel
• Gregor Mendel was an Augustinian friar who
enjoyed gardening and science
• Though people had an idea about how traits
were passed from parent offspring, it was
Gregor Mendel who proved it using science
• Between 1856 and 1863, he raised pea plants,
which he used to study genetic inheritance
• He is now known as the “Father of Genetics”
What did Mendel prove?
• The Law of Segregation - The two members of a
gene pair (alleles) segregate (separate) from each
other in the formation of gametes. Half the gametes
carry one allele, and the other half carry the other
allele.
• The Law of Independent Assortment - Genes
for different traits assort independently of one
another in the formation of gametes.
The Experiment
• There are three things that Mendel paid
attention to in his experimental design:
– He controlled over breeding
– He used purebred plants
– He observed only either/or traits, or traits that
manifest in only two forms
• He followed 7 traits: pea shape, pea color,
flower color, flower position, pod shape, pod
color, plant height
Vocab Check
• A gene is a piece of DNA that provides a set of
instructions to a cell to make a certain protein.
• An allele is any of the alternative forms of the
gene that may occur.
• A genome is all of an organism’s genetic
information.
Punnett Squares
Types of Crosses
• Monohybrid Cross – involves the crossing of
only one trait
– Test Cross – A cross between an unknown
genotype and a recessive phenotype
Types of Crosses
• Dihybrid Cross – involves the crossing of two
different traits
Mendel’s Second Law
• The Law of Independent Assortment – states
that allele pairs separate independently of
each other during gamete formation (meiosis)
Heredity Probabilities
• Probability is the likelihood that an event will
occur
Genetic Variation
• One of the benefits of sexual reproduction
(over asexual reproduction) is that it provides
for abundant variation.
• There can be 8 million different combinations
of chromosomes produced through meiosis.
• Crossing over occurs when homologous
chromosomes exchange segments during
meiosis.
Genetic Variation
• Each chromosomes contains hundreds of
genes
• How do genes show independent assortment
if they are on the same chromosome?
• Genes located close together on the same
chromosome are said to display genetic
linkage.