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Genetics . Probability and Punnet Squares. Objectives. By the end of class you will know: How to indicate the difference between dominant and recessive alleles The definitions of heterozygous and homozygous The definitions of genotype and phenotype. Vocabulary . Gene : - PowerPoint PPT Presentation
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Genetics Probability and Punnet Squares
ObjectivesBy the end of class you will know: 1. How to indicate the difference
between dominant and recessive alleles
2. The definitions of heterozygous and homozygous
3. The definitions of genotype and phenotype
• Gene:
• Found on a chromosome in a specific location called a locus
• Allele:
• Example: the gene for pea height has two alleles: Tall or Short
Vocabulary
A dominant allele will always mask a recessive allele.
Vocabulary• Dominant: Alleles that are always expressed.
A CAPITAL LETTER used to show a dominant allele• Example: Tongue Rolling
• Tongue Rolling: Dominant • Non-Tongue Rolling: Recessive
When a person has both alleles, Tongue Rolling and Non-Tongue Rolling, the person will always be a ____________________________
Vocabulary• Recessive: Alleles that are only expressed
when paired with another recessive allele. A lowercase letter represents the recessive allele.• Example: Hitchhiker’s thumb
• Straight thumb = Dominant• Hitch-hiker’s thumb = Recessive
When a person has both recessive alleles, the person will have a _____________________ thumb.
VocabularyAll organisms have two copies of each
gene, one contributed by the father, the other contributed by the mother.
• Homozygous: • Example:• Heterozygous:
• Example:
Two different alleles are present (heterozygous) for pea shape, round and wrinkled. Round is dominant and wrinkled is recessive.
• Using the letter R/r to show pea shape. How would this be written?
• Genotype:
• Describing an organism in terms of the individual’s genes• Example: Pea Shape - Wrinkled (R) or Non-
wrinkled (r) • Genotype Possibilities:
RR – wrinkled pea
Rr – wrinkled pea Heterozygous
rr – non-wrinkled
Vocabulary
• Phenotype:
• Example: Pea Shape (Wrinkled or Non-Wrinkled)• Phenotype Possibilities
• Wrinkled • Round
** Use the genotypes to determine the phenotypes
Vocabulary
Genetics and Probability
• The likelihood that a particular event will occur is called probability.
Example: Consider flipping a coinLanding: Heads UP or Tails UPThe probability of landing heads?
The probability of landing 3 heads in a row?
Penny Flipping Lab