solving genetics problems : monohybrid crosses two organisms one characteristic complete dominance
TRANSCRIPT
Solving Genetics Problems : Monohybrid Crosses
• Complete dominance
• the dominant allele completely masks the effect of the recessive allele in heterozygous condition.
• Bb
Solving Genetics Problems : Monohybrid Crosses
• Incomplete dominance
• dominance occurring in heterozygotes in which the dominant allele is only partially expressed
– Pp – Sweet peas
Solving Genetics Problems : Monohybrid Crosses
• The problem involved two gerbils named Honey and Ritz.
Solving Genetics Problems : Monohybrid Crosses
• The gene in question is a fur color gene which has two alleles
• dominant brown (B) and recessive black (b)
An allele is one of two or more forms of a gene
Solving Genetics Problems : Monohybrid Crosses
• Step One: Figure out the genotypes of the parents. – address the question of all of
the possible kinds of babies they could produce
Solving Genetics Problems : Monohybrid Crosses
• Step Two: Figure out what kinds of gametes the parents can produce.– Now you need to determine all the possible ways
that his sperm can combine with her eggs.– Punnett Square
Solving Genetics Problems : Monohybrid Crosses
• Step Three: Set up a Punnett Square .– You need to create a chart
with one column for each of the female's egg types, and one row for each of the male's sperm types
Solving Genetics Problems : Monohybrid Crosses
• Step Four: Fill in the babies inside the table by matching the egg allele at the top of the column with the sperm allele at the head of the row.
Solving Genetics Problems : Monohybrid Crosses
Figure out the genotypic ratio for your predicted babies.
• So we have now figured out that, if Honey and Ritz have a lot of babies, we can predict that:
• 25% should be BB homozygous
• 50% should be Bb homozygous recessive
• 25% should be bb heterozygous
Solving Genetics Problems : Monohybrid Crosses
Step Five: Figure out the Phenotype ratio for your predicted babies.
• This is where dominance really enters the picture
• If B is completely dominant to b, all gerbils with at least one B will look pretty much alike, no matter what their second allele is