1. Genetics

2. Heredity: the passing of characteristics (traits) from parents to offspring
Trait: specific characteristic
Genetics: the study of heredity

3. Traits

4. Gregor Mendel
first person to predict how traits are transferred from parent to offspring
“Father of Genetics”
Austrian monk , 1830s , in charge of the monastery garden
Decided to study how traits were passed in pea plants
Kept meticulously accurate records

5. Pea Plants

6. Seven Contrasting Traits
Reproduce sexually
Crosses can be controlled
Short life cycle
Large # offspring

7. Fertilization: the uniting of male and female gametes
Pollination is the process by which pollen is transferred from the anther (male part) to the stigma (female part) of the plant, thereby enabling fertilization and reproduction
Cross: combining gametes from parents with different traits

8. Self Pollination “True breeding” = self pollination (one parent)
Results in identical offspring

9. Cross Pollination

10. Cross Pollination
Mendel called the original pair of plants the (Parental) P generation.
He called the offspring the (1st filial)
F1 generation
The offspring of crosses between parents with different traits are called hybrids.

11. ??? P Generation F1 Generation F2 Generation Tall Short Tall Tall Tall

12. Genes Control Traits

13. Alleles: Different forms of a Gene

14. Mendel Discovered the principles that govern heredity Law of Dominance
Law of Segregation
Law of Independent Assortment

15. Genotype vs. Phenotype Genotype = genetic makeup
Phenotype = physical characteristics

16. Compare phenotype and genotype
Phenotype: appearance of the organism ex: short, tall, green, yellow
Genotype: gene combination of organism ex: tt, TT, Tt, GG, gg

17. Homozygous vs. Heterozygous
Homozygous: 2 identical alleles for particular trait
Heterozygous: 2 different alleles

18. Compare heterozygous and homozygous alleles
Heterozygous: the two alleles are different, can be called hybrids
Ex: Tt, Gg
Homozygous: the two alleles are the same
Ex: TT: homozygous dominant
tt: homozygous recessive aa

19. Genotype determines phenotype

20. 1. Law of Dominance Some alleles are dominant and others are recessive
Dominant traits appear even if only one copy of the allele is present
Dominant alleles are represented by uppercase (capital) letters
Recessive traits are hidden whenever a dominant allele is present
Recessive alleles are represented by lowercase letters
In order to display a recessive trait, two recessive alleles must be present

21. Dominant and Recessive
An organism with a dominant allele for a particular trait (height-tall) will always show that trait.
An organism with a recessive allele for a trait will only show that trait (height-short) when the dominant allele is not present.

22. ???

23. For example, the F1 plants (Yy) were all green because the allele for green pod color (Y) was dominant over the allele for yellow pod color (y)

24. GENOTYPE = the genes present in the DNA of an organism; GG, Bb, tt
Homozygous = both alleles are identical (ex: GG or tt)
Heterozygous = the two alleles (found on homologous chromosomes) are different (ex: Bb)
PHENOTYPE = how the trait physically shows-up in the organism; green seed coat, curly hair
ALLELES = alternative forms of the same gene
alleles for a trait are located at corresponding positions on homologous chromosomes A b C D E f
homologous chromosomes A B C d E f

25. Law of Dominance

26. Punnett Square Diagram that shows possible gene combinations
Parental alleles are on the outside of the square
Offspring alleles will be on the inside of the square

27. Punnett Squares
Monohybrid cross = Cross that involves a single trait Ex: Tall plant crossed with Short plant

28. Parent Generation

29. Monohybrid Crosses Crosses that differ by a single trait
Ex: tall plant X short plant
Male alleles are on top
Female alleles are on side
Each box in the square is 25% probability (all 4 boxes equal 100%)

30. Probability: the chance of a trait being exhibited
The probability of a coin landing heads-up when you flip it is 50-50, one out of two, ½, ( 50%) What is the probability of getting tails if you flip it again? - It is still ½ (50%) The two events do not affect each other. They are independent!

31. Probability The chance or percent chance of a trait being exhibited
Principles of probability can be used to predict the outcomes of genetic crosses

32. 2. Law of Segregation
inheritance is determined by factors passed from parent to offspring (today these are called GENES)
The different forms of genes are called alleles
(ex: for tongue rolling; two possibilities: one for “rollers” and one for “non-rollers”)
Mendel’s Law of Segregation states that allele pairs separate (or segregate) during gamete formation, and randomly unite at fertilization

33. Law states that the alleles for a trait separate (or segregate) when gametes are formed
These allele pairs are then randomly united at fertilization Tt
TT Duplicated tt
in S phase
T T t t

34. Law of Segregation
During the formation of gametes (eggs or sperm), the two alleles responsible for a trait separate from each other.  Alleles for a trait are then "recombined" at fertilization, producing the genotype for the traits of the offspring.

35. Mendel performed experiments on monohybrid crosses
He cross-pollinated pea plants that differed in one trait (ex: pod color)
When he cross-pollinated a true-breeding yellow pod plant with a true-breeding green pod plant, he noticed all the resulting offspring (F1 generation) were green

36. Result = 3:1 ration in pod color
Mendel self-pollinated all of the green F1 plants (referred to as the F2 generation)
Result = 3:1 ration in pod color
¾ of the plants had green pods
¼ had yellow pods

37. 3. Law of Independent Assortment

38. 3. Law of Independent Assortment
Genes for different traits assort independently during the formation of gametes
Each pair of homologous chromosomes assorts independently of all 22 pairs of remaining homologous pairs
Gives different traits an equal opportunity of occurring together

40. Tail Length & Fur Color