1. Genes, Heredity, & Gregor Mendel

2. Your unique combination of your characteristics are known as traits.
Inherited traits: from your parents
Acquired traits: developed during your life
(ex: riding a bike, ability to read and write, interaction with the environment)

3. Genes
Gene: a unit of heredity that occupies a specific location on a chromosome and codes for a particular trait.
Heredity: the passing of genes from parents to offspring

4. Alleles Different form of the same gene
2 alleles for each gene, 1 on each chromosome
Get 1 allele from each parent, because you get one set of chromosomes from each parent

5. Alleles So… Genes tell us the type of trait
Hair color, eye color, etc.
Alleles tell us the SPECIFIC trait
Different forms of the same gene
Blonde hair, blue eyes

6. DO NOW Homework out on your desk
Notebooks open to continue notes on Heredity
Answer this question: what is the difference between a GENE and an ALLELE?

7. Traits Phenotype Genotype The way an organism looks on the outside.
Physical appearance
Red hair, green eyes, etc.
Genotype
The combination of your genes
Always listed as two letters, because two alleles
Ex/ AA, Aa, aa

8. Genotype Homozygous Heterozygous Each allele is the same
Ex/ each allele says brown eyes.
Heterozygous
Each allele is different
Ex/ One allele says brown eyes, the other says blue eyes

9. Genotype: What Happens if I’m heterozygous?
Some alleles are DOMINANT to others.
Recessive allele:
Represented by a LOWER CASE letter
Must be homozygous recessive to display the phenotype of a recessive allele
Dominant allele:
Represented by an UPPER CASE letter
Determines the phenotype
Dominates the recessive allele in a heterozygous organism

10. Genetic first started when an Austrian monk, named Gregor Mendel, performed a series of experiments on garden peas.
Mendel observed qualitative information about the traits of the pea plants. He then tried to quantify how those traits were passed from one generation to another.
Mendel developed purebred lines of pea plants. He recorded the results of his experiments and made statistical notes about how the traits were passed down.
The results of Mendel’s studies were so important that he is considered: Father of Genetics

11. WHY PEAS? Structure of the pea flowers Presence of distinctive traits
Rapid reproduction cycle
Grow quickly
Produce large number of offspring
Cheap and easy to grow and maintain
Pea plants normally self-pollinate but can cross-pollinate if the anthers (the male parts) are removed when the flower is young

12. The Pea Plant Experiment
Mendel studied characteristics in the parents and offspring of pea plants. The plants displayed several easily-observed characters in one of two contrasting traits or forms

13. The Pea Plant Experiment Studied and tracked one trait at a time over multiple generations.

14. Mendel observed that there were two different types of pea plants
plants that, when self-pollinated, produce the same form of a trait in all offspring
Example: white flower plants that produce offspring with white flowers
Purebred Plants
plants that, when self pollinated, produce more than one form of a trait in their offspring
Example: Purple flower plants that produce some purple and some white flowered offspring
Hybrid Plants

16. Mendel Concluded…
Parent transmits information about traits to their offspring
Gamete production and fertilization
Each parent must contribute a form of a gene to the offspring
Homozygous vs. heterozygous
Symbols can be used to represent alleles
Dominant vs. recessive
Genetic make-up and observed characteristics are not always the same
Genotype vs. phenotype

17. Law of Independent Assortment Law of Segregation
As a result of his many years of careful study, Mendel’s work was summarized into three main laws.
Law of Dominance
Law of Independent Assortment
Law of Segregation

18. Example: Green pod color is seen in plants with the genotype Gg
Law of Dominance
States that if two alleles in a gene pair are different, then one allele can control the trait and the other one can be hidden.
Example: Green pod color is seen in plants with the genotype Gg

19. Law of Independent Assortment
States that gene pairs segregate into gametes randomly and independently of each other. At what stage of meiosis does this occur? Metaphase I and Anaphase I of meiosis: homologous chromosomes randomly lineup and separate

20. Law of Segregation
States that each pair of genes segregates, or separates, during meiosis and each gamete contains one gene from each gene pair.
What is the chance that a gamete will end up with a maternal homolog at any one chromosome pair?
½ or 50%
The chance that all 23 homologs from one parent will end up in a single gamete is 1 in 8 million (1/2)23

21. DO NOW: In your notebooks… Heterozygous or Homozygous?
AA _______________
Bb _______________
ff _______________
Jj _______________
OO _______________
Ll _______________

22. Determine the Phenotype
Purple flowers are dominant to white
1. PP ________________
2. Pp ________________
3. pp ________________

23. Determine the Phenotype
Wrinkled seeds are recessive to round seeds
1. RR ________________
2. Rr ________________
3. rr ________________

24. Determine the Genotype
Straight hair is dominant to curly hair
1. Straight _____________
2. Straight _____________
3. Curly _____________

25. Determine the Genotype
Blue eyes are recessive to brown eyes
1. Brown _____________
2. Brown _____________
3. Blue _____________

26. Applying the Laws
Knowing the genotype and phenotypes of the parents allows us to predict the POSSIBLE genotypes and phenotypes of the offspring…
Use a Punnett Square
P = Purple, dominant
p = white, recessive

27. Applying the Laws: Punnett Squares
Used to predict the outcome of genetic variation that results from sexual reproduction.
Uses the genotypes of the parents to predict the genotypes (and thereby phenotypes) of the offspring
Gives POSSIBLE outcomes IF the two parents were to mate

28. Punnett Squares Genotype of parent Individual Alleles are separated
Represents the separating of chromosomes into gametes after meiosis Tt Tt tt tt
Genotype of offspring

29. Punnett Square Practice
Round seeds are dominant to wrinkled seeds
A heterozygous parent is mated with a homozygous recessive parent.
What percentage of the offspring will be round?
________ x ________