1. Mendel’s Laws of Heredity
Chapter 10.1
Mendel’s Laws of Heredity

2. Explain fertilization.
Fertilization = male gamete (sperm) + female gamete (egg)
Resulting cell is now called a zygote
In plants, its called pollination
Self-pollination = one plant
Cross-pollination = two plants

4. Compare and contrast phenotype and genotype
Phenotype = physical expression of genes
Ex: Brown hair vs blonde hair
Genotype = actual gene combination
Ex: BB, Bb, bb
Homozygous = BB (dominant), bb (recessive)
Heterozygous = Bb

5. Phenotypes
Genotypes

6. Punnett squares. Parent’s alleles go on side and top
Carry alleles across or down
Monohybrid Cross = one trait
Dihybrid Cross = two traits

7. Why is Mendel the “Father of Genetics”?
Mendel studied heredity of traits among pea plants
Study of heredity = genetics
He came up with the basic laws and understanding of genetics
mendel.imp.ac.at/mendeljsp/images/mendel2.jpg

8. Explain the results of Mendel’s Monohybrid Cross.
Some terms
True breeding = many generations carrying the same trait
P = parent
F = filial (son or daughter)

9. Explain the results of Mendel’s Monohybrid Cross.
Mendel’s cross pollination
TALL plant x short plant (P1 generation)
Result: Hybrids
ALL offspring TALL (F1 generation)
Self pollination of F1
F1 TALL X self (TALL)
Result
3/4 TALL and 1/4 short (F2 generation)
We refer to this as a ratio of 3:1

10. Mendel continued to test this with each of 7 traits
Mendel continued to test this with each of 7 traits. Every time the same ratios appeared…
Conclusion: Each organism has 2 factors (genes) that control each of its traits.
Different versions of each factor (gene) is now called an allele
Ex. Gene for height has a tall and short allele

11. Describe dominant and recessive alleles.
Rule of dominance: in F1 generations the trait that is observed in 100% of the offspring is considered to be the dominant allele.
Dominant alleles (TALL) mask the other form
Recessive alleles (short) get masked by the dominant form
ONLY ONE dominant allele is needed for the form to be expressed! Tt = TALL

12. Dom. alleles are always written first
Dom. alleles are always given a capital letter, recessive get the lower case letter
EX: for Height
TALL = T or H or Z
Short = t or h or z

13. Describe Mendel’s Law of Segregation.
Every individual has 2 alleles for each gene
Gametes are produced to carry only 1 from you parents
When fertilization occurs you now have 2 alleles, 1 from mom, 1 from dad.
4 possible combinations
ghs.gresham.k12.or.us/.../lawofsegregation.gif

14. Explain the results of Mendel’s Dihybrid Cross.
P1: Round, Yellow x Wrinkled, Green
RRYY x rryy
F1: 100% Round, Yellow (dihybrids)
F2: 9 Round, Yellow: 3 Round, Green :
3 Wrinkled, Yellow : 1 Wrinkled,
Green

16. Describe Mendel’s Law of Independent Assortment.
Genes of different traits are inherited independently when found on different C.
Ex: Not all Blondes have blue eyes

17. fig.cox.miami.edu/.../150/mitosis/sf9x5b.jpg