Warm- Up # 4
1. What is a dominant trait?2. What is a recessive trait?3. Is “Bb” genotype or phenotype?4. Is black hair genotype or phenotype?5. Which of these is heterozygous:
A. TT B. Tt C. tt
Learning Target 1/31
• I can determine the genotype and phenotype of a monohybrid cross using a Punnett Square
Vocab Review
• Genotype - the genetic make-up of an organism
HH: homozygous dominantHh: heterozygous dominanthh: homozygous recessive
• Phenotype: the way an organism looks or behaves based on the genotype (trait)
Examples: left-handed, brown eyes, long nose
CH 11 Punnett Squares Notes
Mendel’s Law of Segregation
Rr
R r
R r SpermSperm
Alleles separate during meiosis
Mendel’s Law of Independent Assortment
RrGg
RG Rg rG rg
An individual can give lots of combinations of alleles
Punnett Squares
• Punnett Square - a tool used to predict the genotype of an organism’s offspring
Bb
Bb
Male
Female
Example Punnett Square• Trait: Body Color
dominant = green body (G)recessive = blue body (g)
Parent #1: GgParent #2: Gg
G g
G
g
GG Gg
Gg gg
Example Punnett Square• Possible Offspring Genotypes:
1 GG 25%2 Gg 50%1 gg 25%
G g
G
g
GG Gg
Gg gg
dominant = green body (G)recessive = blue body (h)
Possible Offspring Phenotypes:3 green body 75%1 blue body 25%
Practice Problem #1• Trait: Human Eye Color
dominant = brown eyes (B)recessive = blue eyes (b)
Parent #1: BBParent #2: Bb
B B
B
b
BB
Bb
BB
Bb
Practice Problem #1• Possible Offspring Genotypes:
2 BB 50%
2 Bb 50%
Possible Offspring Phenotypes: 4 brown eyes 100%0 blue eyes 0%
B B
B
b
BB BB
Bb Bb
Practice Problem #2
• In many animals black fur is dominant (B) and brown fur is recessive (b).
• Complete the Punnett Square for Female dog-BbMale dog- bb
B
b
b
b
Bb bb
Bb bb
Practice Problem #2
• Possible genotypes:2 Bb 50%2 bb 50%
• Possible phenotypes: 2 Black fur dog 50%2 Brown fur dog 50%
B
b
b
b
Bb bb
Bb bb
Practice Problem #3
• In people right-handed is dominant (R) and left-handed is recessive (r)
• Complete the Punnett Square for:Heterozygous parentHomozygous recessive
parent
R
r
r
r
Rr rr
Rr rr
Practice Problem #3
• Possible genotypes:2 Rr 50%2 rr 50%
• Possible phenotypes: 2 Right-handed 50%2 Left-handed 50%
R
r
r
r
Rr rr
Rr rr
Monohybrid cross
• Homozygous dominant + homozygous recessive• Example: BB x bb, HH x hh
B
b
b
B
Bb Bb
Bb Bb
