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Heredity
2011-2012
Mav Mark 10/11/11
• In pea plants, purple flowers (P) are
dominant over white (p). A purple
flowered plant pollinates a white flowered
plant. As a result, two purple flowered
plants and one white flowered plant are
produced. Using a Punnett square, show
how these results are possible.
Mav Mark 10/12/11
• In pea plants, yellow peas (Y) are
dominant over green peas (y). Use a
Punnett square to predict the phenotypes
and genotype that result from a
heterozygous (Yy) pea plant and
homozygous recessive (yy) pea plant.
Mav Mark 10/13/11
• What biological process produces sex
cells?
• How do sex cells differ from body cells?
• Explain why it is necessary to make sex
cells through a process separate from
mitosis.
Mav Mark 10/14/11
1. Physical appearance of
traits
2. Inherited combination of
alleles
3. Process that produces sex
cells
4. Process through which
bacteria reproduce
5. The chances that an event
will occur
A.
B.
C.
D.
E.
Probability
Genotype
Binary Fission
Phenotype
Meiosis
Mav Mark 10/17/11
• Define a genetic disorder.
• What can cause a genetic disorder?
• Are genetic disorders typically the result
of dominant or recessive genes?
• Give an example of a genetic disorder.
Mav Mark 10/18/11
• Here is a pedigree for
an inherited lung
disease. Provide the
genotypes of each of
the individuals
marked with lower
case letters.
Determine if they are
male or female.
Mav Mark 10/19/11
• Compare and contrast hybrid and
purebred organisms.
Mav Mark 10/20/10
1. Two forms of the same
gene
2. Each allele has its own
degree of influence
3. Structure of DNA
4. Process produces sex
cells
5. Mutation in these cells
can be passed down to
offspring
A.
B.
C.
D.
E.
F.
Meiosis
Double Helix
Alleles
Sex Cells
Body Cells
Incomplete
Dominance
Mav Mark 10/21/10
• Test Day!
• Clear Desk except for sheet of notebook
paper and a pencil.
I. What is Genetics?
• Genetics is the study of genes
• Heredity is the passing of traits from a
parent to an offspring
II. Gregor Mendel
• Gregor Mendel is the “Father of Genetics”
• He spent 7 years researching the
inheritance patterns of pea plants
A. The Pea Plants
• Mendel used pea plants because
– They reproduce quickly
– They could self-pollinate
– They had several different traits (7)
• Height, Flower Color, Seed Texture, etc.
• Mendel’s work was successful because he
studied one trait at a time!!!
B. The Experiments
First we need to know a few important terms
• Self-pollinate- one plant- fertilizes its own
flowers
• Cross-pollinate- two plants- pollen from
one fertilizes the other
• P1 (parent) – original plant
• F1 (offspring) – 1st generation after the
parents
• F2 (offspring) – 2nd generation after the
parents
1. The 1st Experiment – Cross
Pollination
• Mendel made sure to begin
with purebred plants
– Example: Tall always makes tall,
Purple flowers produced
purple
flowers
• Mendel cross-pollinated the
purebred plants to see what
would happen
– Example: Tall X Short = ?
2. The Results
• P1 (Tall) X P1 (short) = F1 (All Tall)
• He concluded that tall is a dominant trait
and short is a recessive trait:
– Dominant: more likely to appear; represented
by capital letters (T)
– Recessive: usually hidden; represented by
lower-case letters (t)
3. The 2nd Experiment
• Mendel allowed his new
plants to self-pollinate
• He noticed the short trait
reappeared
4. His Conclusions
• After years of research, Mendel found
that:
– Information for traits were located on genes
– Each parent contributes this information to its
offspring
– Traits are not connected (Tall plants don’t
always have purple flowers)
III. Chromosomes and Genes
• Genes control particular hereditary traits
• Genes are located ON chromosomes
• An allele is a form of a gene
– Two alleles = 1 gene
– One is from mom; one is from dad
IV. Genetic Crosses
• Genotype- is an organism’s genetic makeup; represented by letters (TT, Tt, tt)
• Phenotype- is a physical description of the
organism; Tall or short
• Homozygous- When both alleles of a gene
are the same; TT or tt
• Heterozygous- When the alleles of a gene
are different; Tt
A. The Punnett Square
•Developed by
Rudolph
Punnett
•Makes genetic
predictions a
lot easier!
Examples
1. What offspring would result if a plant
that is homozygous dominant for height
is crossed with a plant that is homozygous
recessive for height?
Examples
2. What offspring would result if a plant
that is homozygous recessive for flower
color is crossed with a plant that is
heterozygous for flower color?
Examples
3. What offspring would result if a plant
that is heterozygous for seed texture is
crossed with another plant that is
heterozygous for seed texture?
V. Incomplete Dominance
• When one trait is not completely dominant
over another. The result is a combined
phenotype.
– Ex. Snap dragons: Red X White = Pink
VI. Codominance
• Occurs when both alleles for a gene are
expressed equally.
– Ex. Blood Type
VII. Probability
• Probability is the mathematical likelihood
that something is the case or will happen
• May be expressed as a fraction or as a
percentage
– Ex. Flipping a coin
• ½ chance of coin landing on heads and ½ chance of
coin landing on tails
• 50% chance of coin landing on heads and 50%
chance of coin landing on tails