1. Chapter 8
Genetics

3. Father of Genetics Austrian monk named Gregor Mendel
Did experiments on pea plants
Heredity-the passing of characters from parent to
offspring
Genetics- the branch of biology that focuses on heredity
Character- inherited characteristic
(example: flower color)
Trait- single form of character
(example: purple flowers)

4. Pea reproduction True- breeding- always produce the same trait when
self-pollinating
Cross-pollinate- removing the male part of the flower
and dusting with pollen from a flower.
Hybrids- offspring of crosses between parents with
different traits

5. Mendal’s 1st cross
Crossed white flowered plants with purple flowered plants All the offspring were purple- why??

6. Principal of Dominance
For most simple traits there are 2 possible versions of the gene (alleles)
Each organism gets 2 alleles for a simple trait (one from the Mom and one from its Dad)
Dominant alleles mask the other allele and are UPPERCASE
Recessive alleles are masked by the dominant allele and are LOWERCASE

7. Purple is dominant over White
The offspring of Mendel’s first cross were all purple but they had a purple allele (P) from one parent and a white allele (p) from the other parent
Genotype- which alleles are present (letters)
The genotype of the offspring was Pp

8. Phenotype Which trait is actually seen
The phenotype of the 1st cross offspring was purple

9. Other Traits Mendal Tested

10. Example Problem 1
A pea plant has round seeds and has an allele for round and an allele for wrinkled.
Genotype-?
Phenotype-?

11. Example Problem 2 A pea plant has white flowers. Genotype-?
Phenotype-?

12. Mendal’s 2nd Cross
Crossed the offspring of the first cross with each other.
Why had the white flowers reappeared?

14. Segregation Segregation- alleles for the same gene separate from
each other during gamete formation so that
each gamete cell gets only 1 type
Homologous chromosomes separate during Prophase I!

15. Biological Inheritance
Genes- chemical factors that determine traits
Pieces of DNA that code for proteins
Different alleles produce different shaped proteins

16. Homozygous and Heterozygous
Homozygous- individual with 2 dominant alleles or 2 recessive alleles.
Example: TT or tt
Heterozygous- individual with one dominant allele and one recessive allele
Example: Tt

17. Review Questions Who is the father of genetics?
What type of plant was used in the first genetics experiments?
What does true-breeding mean?
What is meant by the term F1? Hybrid?
Define the terms “gene” and “allele”.
Explain the principle of segregation.

18. Probability Likelihood that an event will occur
Probability can be used to predict outcomes of genetic crosses

19. Punnett Squares
Used to predict and compare the genetic variations that will result from a cross

20. Independent assortment
-Genes assort independently during
gamete formation
Having one trait doesn’t increase
the chance of having the other

21. Incomplete dominance
Heterozygous organisms have intermediate trait (combination of dominate and
recessive trait)

22. Codominance
Heterozygous organisms have both dominant and recessive trait
Example- animals with speckled fur

23. Multiple alleles
More than 2 alleles exist for a certain trait, but each organism can still only have 2
-- Example: Blood type has 3 alleles
(A, B, and O)

25. Sex Linked Traits Gene occurs on the X or Y chromosome
Males cannot be heterozygous because they only have 1 X!!!
Example: genes for baldness and colorblindness occur on the X chromosome so men are more likely to be affected
Heterozygous female X
normal male

26. Polygenetic traits
Produced by interaction of several genes