1. 4.2 Patterns in Heredity
Mrs. Leos
May 25, 2019

2. SO FAR…….. We have learned: NOW we will learn:
Genes are passed from parents to offspring
Offspring inherit genes in predictable patterns
NOW we will learn:
how punnett squares can be used to predict patterns in heredity
How ratios and probability can be used to predict patterns of heredity

3. Punnett Square illustrates how the parents’ alleles
might combine in offspring
Dominant & recessive alleles represented
by letter
Capital letter stands for dominant allele
Small letter stand for a recessive allele
Shows genetic make- up or genotype of organism

4. Punnett Square
T t
Letters of two alleles from one parent are written on top of square
Second parent on side of square T t

5. One allele per parent in square
Letters filling squares are genotype
T t TT Tt tt T t

6. Ratio
Compares, or shows the relationship between two quantities

7. Probability
Likelihood or chance of a specific outcome in relation to the total number of possible outcomes

8. Two alleles for a trait are different Tt
Heterozygous OR Hybrid
Two alleles for a trait are different Tt

9. Hybrid
Offspring may look the same or different
Genes are different

10. Homozygous
Organism always produces same trait in offspring tt TT

11. mutation
Any change made to DNA

12. On page 31
Punnett Square worksheet