5.2 Probability and Heredity

1

• 5.2 Probability and Heredity
• A. Punnett Squares
• 1. It is used to show
• a. all possible ___________combinations of the
  offspring that result from a mating for a
  particular trait
• b. ______________of each allele combination
  showing up in the offspring
• each square inside the punnett square equals
  _______ probability
• 2. Example- Using a punnett square
  figure out the possible allele _________ of the
  _________ and the probability of each
  genotype showing up in the offspring. Lets say
  that the gene for dwarfism in guinea pigs has 2
  alleles.
• The dominant allele (G) has the instructions
  for normal sized guinea pig and the recessive
  allele (g) has the instructions for dwarf sized
  guinea pig. Cross or mate a hybrid guinea pig
  with another hybrid guinea pig.

allele
probability
25
combos
offspring
G
g
G
g
Distribute the females alleles into the boxes
below them
Put in the alleles that the female parent has to
give to the offspring along the top and the males
alleles on the side of the punnett square
G
G
G
g
g
g
G
g
G
G
g
g
Distribute the males alleles into the boxes to
the right of them
Each box represents a possible allele combo for
an offspring
G
G
G
G
G
G
g
G
G
g
g
g
g
G
G
g
g
g
g
g
2

• Lets do a couple of things using the results of
  the punnett square
• a. First we can list the genotypes and
  phenotypes of the possible offspring for that
  given trait- dwarfism
• b. Now we can figure the probabilities of
  each of the offspring

Genotypes
Phenotypes
Probability
GG
Normal
25
Gg
Normal
50
gg
Dwarf
25
4. Codominance or incomplete dominance
3

• More incomplete dominance or codominance visuals

x
4

• B. Pedigrees
• 1. Family tree that tracks the movement of a
  __________________ within a family
• female male Male carrier of
  trait
• Female w/trait
  marriage children
• C. Diagnosing Genetic Disorders
• 1. Amniocentisis- removing of ________________
  that surrounds a developing baby
• a. How is it done?

trait
fluid
Needle is inserted into the abdomen of pregnant
mother then into amniotic sac
Genetic disorder
cells
chromosomes
Karyotype
5

• Try This Activity- text page 164.
• Comparing a coin toss to percentages of what
  Mendel found in his resulting offspring s