Transcript Analyzing heredityx

Analyzing heredity
Probability
• The likelihood that a chance event will occur.
• Probability = # of one kind of outcome
Total # of outcomes
• Ex- Probability of a coin landing on heads.
• ½ = 50%
• Ex- probability of a baby being a boy.
• ½ = 50%
• The results of one event do not effect the
other.
Punnett Squares
• A special chart used to predict genetic probabilities.
• Ex- BB pure black guinea pig X bb pure white guinea
pig
• The parent genes go across top and side.
• The small squares the middle are the predicted genotypes
of offspring
Related vocab
• Pure- organism with 2 of the same genes for a
trait; homozygous (Ex- tt)
• Hybrid- organisms with 2 different genes for a
trait; heterozygous (Ex- Tt)
Monohybrid cross
• A cross that shows 1 pair of opposite traits.
• Ex- BB X bb(black fur x white fur) or
• FF X ff ( 6 fingers X 5 fingers)
Ex- If 2 hybrids are crossed
Punnett
Ratios (classic Mendelian ratio)
• Genotype ratio
• Phenotype ratio
5 steps to solving genetics problems
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1. Write a key
2. Determine genotypes of parents
3. Punnett square
4. Genotype, phenotype ratios of offspring
5. Answer any questions
Dihybrid Cross
• Cross that involves 2 different sets of contrasting
traits.
• Ex- tall yellow seeds X short green seeds
• P generation TTRR X ttrr
• T= Tall/dominant R= Yellow/dominant
• t-= short/ recessive r= green/recessive
TTRR X ttrr
• Both pure parents produce all hybrids
• Phenotype ratio
• Genotype ratio
Cross 2 hybrids from F1: TtRr X TtRr
Ratios
Dihybrid cross phenotype ratio pattern
with both parents heterozygous for
both traits.
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9 Dominant and dominant
3 Dominant and recessive
3 Recessive and dominant
1 recessive and recessive