Notes: Probability and Heredity

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# Notes: Probability and Heredity - PowerPoint PPT Presentation

Notes: Probability and Heredity. Read pgs. 162-167. Objective: Be able to perform a simple Punnett square. Genetics. Heredity: the passing of traits/characteristics from parents to offspring.

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### Notes: Probability and Heredity

Objective: Be able to perform a simple Punnett square.

Genetics
• Heredity: the passing of traits/characteristics from parents to offspring.
• Genes: the part of the DNA that controls a certain trait or characteristic. Hair color, eye color, freckles, etc.
Alleles
• The different forms of a gene, represented by capital and lower case letters.
• TT, Tt, tt.
Traits
• Dominant Trait: Capital Letter. A trait that always shows up in an organism when it is present.
• Recessive Trait: Lower-case Letter. A trait that only shows up in an organism when a dominant trait is not present.

Video: Testcross

Dominant and Recessive

T=Tall

t=Short

H=no hair

h=hair

F=Fan

f=non fan

Genotype
• Genotype: An organism’s genetic makeup or allele combinations, TT, Tt, tt.
• These are the actual genes in your DNA.
Phenotype
• Phenotype: an organisms physical appearance or visible traits, tall or short.
• This is what you look like or what you see.
Homozygous
• Homozygous/Purebred: When an organism has two identical alleles for a trait, TT or tt.
Heterozygous
• Heterozygous/Hybrid: when and organism has different

alleles for the same trait, Tt.

Donkey

Video: Zygous

Mule

Horse

Codominance
• Codominance is when alleles are neither dominant nor recessive, but both are expressed.
• This helps to explain mixed traits such as a black chicken and a white chicken mating and their offspring are black and white.

Video: Codominance

Punnett Square
• Punnett Square: A chart that shows all of the possible combinations of alleles from a genetic cross.

Video: Punnett Squares

Probability
• Probability is a number that describes how likely it is that a certain event will occur.
• When flipping a coin, the probability of it landing on heads is 50% and tails is 50%.
Probability
• In a Punnett square, each box represents a 25% chance of the offspring receiving that genotype.
• Each box represents a 25% chance and there are 4 boxes. 4X25%=100%.
Punnett Square

Cross a homozygous tongue roller with a heterozygous tongue roller.

Dominant Allele=

Recessive Allele=

Genotype for homozygous tongue roller=

Genotype for heterozygous tongue roller=

Genotype outcomes=

Phenotype outcomes=

Punnett Square

Cross a homozygous tongue roller with a homozygous non-tongue roller.

Dominant Allele=

Recessive Allele=

Genotype for homozygous tongue roller=

Genotype for homozygous non-tongue roller=

Genotype outcomes=

Phenotype outcomes=

Punnett Square

Cross a heterozygous tongue roller with a heterozygous tongue roller.

Dominant Allele=

Recessive Allele=

Genotype for heterozygous tongue roller=

Genotype for heterozygous tongue roller=

Genotype outcomes=

Phenotype outcomes=