1. Genetics

2. Heredity: is the passing of traits from parent to offspring.
Every organism is a collection of traits, all from its parents
Trait: are physical or genetic characteristics of an individual organism

3. Genes control the traits by producing proteins.
A Gene is a small section of DNA that codes for certain proteins.
An alternative form of genes are called alleles
Organisms have at least two genes for every trait.
They receive at least one from each parent.
The study of how traits are inherited through action of genes is the science of GENETICS.

4. Gregor Mendel
Gregor Mendel is often referred to as the “father of genetics”.
He was a monk that was born in Austria in 1822.
He was experimenting in garden with peas.

5. Mendel studied heredity with pea plants
Why pea plants? (was it luck?)
1. Small
2. Easy to grow
3. Produces large numbers of offspring
4. Matures quickly
5. Plants can self or cross fertilize
6. Many varieties
7. Each trait has two forms
Tall/short purple/white flowers
green/yellow seeds colored/white seed coat
green/yellow seed pods inflated/narrowed seed pod
wrinkled/smooth seed

6. - Mendel’s Work
Cross-fertilization

7. To begin, Mendel self fertilized to create pure breeding plants
all pure purple
Purple
white
all pure white

8. First Cross: pure purple with pure white
Cross fertilized P (Parental) generation
Pure purple with pure white
P Generation F1 Generation
purple
white X
All purple

9. Second Cross: Cross 2 F1 plants
Cross fertilized two of the offspring of the F1 generation
purple
purple
purple
purple X
purple
white
These were the F2
This was always 3:1 ratio
or out of 929, 705 : 224

10. Monohybrid Cross
A pairing in which the parent plants differ in only one trait .

11. Mendel’s Experiments led him to 3 Laws of Inheritance
The Law of Dominance
The Law of Segregation
The Law of Independent Assortment

12. Through his experiments he discovered that some genes were either dominant or recessive.
Dominant because it dominated or is always shows itself (D, a capital letter)
Recessive because it was hidden when the dominant gene was present (d, lowercase)
Freckles
No Freckles
Dimples
No dimples
Tongue roller
Non-roller
From Mom
From Dad

13. Law of Segregation
Segregation is the separation of alleles during gamete formation.
Since only one egg or one sperm will contribute to the new offspring, only one allele for a trait is passed on
The chance that any allele will be passed on is 50%

14. - Mendel’s Work
Segregation

15. Explaining the F2 Generation
When each F1 plant flowers and produces gametes, the two alleles segregate from each other so that gamete carries only a single copy of each gene. Therefore, each F1 plant produces two types of gametes – those with the allele for tallness and those with the allele for shortness.

16. Law of Independent Assortment
the inheritance of alleles for one trait doesn’t affect the inheritance of alleles for another trait
-accounts for the many genetic variation observed in plants, animals and other organism.

17. Genotype:
Genotype is the actual genes for a particular trait expressed with letters
Homozygous dominant:
TT - two capital letters
Heterozygous (hybrid)
Tt - one of each letter (big and small)
Homozygous recessive
tt - two lower case letters

18. Phenotype: Phenotype is physical expression of the genotype
Genotype Phenotype
TT tall plant
Tt tall plant
(dominant allele always is expressed over the recessive allele)
tt short plant
(recessive trait is expressed only if there is no dominant gene)

19. If R = red, and r = white What is the genotype of homozygous dominant?
What is the heterozygous genotype? Rr
What is the homozygous recessive genotype? rr

20. If R=red and r =white What is the phenotype of of RR?
What is the phenotype of Rr?
What is the phenotype of rr?
White

21. Predicting Traits
A tool used to predict and compare the genetic variations that will result from a cross is a Punnett Square.

22. If two parents are crossed (TT X tt), what are the resulting offspring?
You can determine phenotypes using a Punnet square. T T
parent Tt Tt t
Genotypes:
4 Tt Tt Tt
Phenotypes:
4 Tall t
This is the first or parent generation
parent

23. Now try on your paper a cross of two of the offspring from the parent generation. This is called the first generation or the F1. T t T Tt TT Tt tt t
Genotypes:
1TT: 2Tt : 1tt
Phenotypes:
3 Tall: 1 Short.

24. Take a few minutes and study for your Vocabulary quiz 51-60 Please turn in any work from Friday

25. Dihybrid Crosses
A two-factor cross follows two different genes as they pass from one generation to the next.
Explains the Law of Independent Assortment

26. Let’s Solve Together
In guinea pigs, the allele for short hair (S) is dominant to long hair (s), and the allele for black hair (B) is dominant over the allele for brown hair (b). What is the probable offspring phenotype ratio for a cross involving two parents that are heterozygotes for both traits?

27. Example 1: Dihybrid Short hair = dominant = SS or Ss
Long Hair = recessive = ss
Black coat = dominant = BB or Bb
Brown coat = recessive = bb
SsBb x SsBb (gametes done by the FOIL method)
SB, Sb, sB, sb and SB, Sb, sB, sb

28. Example 1: Punnett Square Parents: SsBb x SsBb

29. Example 1: Answer the Question
What is the probable offspring phenotype ratio for a cross involving two parents that are heterozygotes for both traits?
9/16 Black, short coats
3/16 Black, long coats
3/16 Brown, short coats
1/16 Brown, long coats

30. A Pedigree
- Human Genetic Disorders
A pedigree is a chart or “family tree” that tracks which members of a family have a particular trait.

31. Pedigree analysis
Pedigree analysis reveals Mendelian patterns in human inheritance; tracks certain traits through a family
data mapped on a family tree
= male
= female
= male w/ trait
= female w/ trait

32. Simple pedigree analysis1 2 3 4 5 6 1 2 3 4 5 6

33. Genetic counseling
Pedigree can help us understand the past & predict the future

35. Incomplete Dominance – in which one allele is not completely dominant over another; a blending in the heterozygous
Pink flowers
RR = red
RW = pink
WW = white

36. Codominance – can see both alleles at the same time.
Feathers in chickens
FWFW – White Feather
FBFB – Black Feather
FWFB – Half Black Half White

37. Multiple Alleles – three or more alleles of the same gene.
Blood Types in Humans
Single gene, but four phenotypes
Type A  can be IAIA or IAi
Type B  can be IBIB or IBi
Type AB  only IAIB (codominant pattern here)
Type O  only ii (both recessive)
All 3 blood types are dominant to O

38. Polygenic Traits Traits controlled by two or more genes Examples
Eye color
Skin color
Hair color

39. The importance of the environment
An individual phenotype depends on environment as well as on genes.
Temperature
Nutrition
The product of a genotype is generally not single, rigidly defined phenotype but a range of possibility influenced by the environment.

40. Human Genetic Diseases1 2 3 4 5 6

41. Human Genetics Disorders
Genetic Disorder: is an abnormal condition that a person inherits through genes or chromosome.
Caused by mutations in the DNA of genes, or the overall structure and number of chromosomes

42. Recessive disorders Your genotype is homozygous recessive (aa)
Heterozygotes (Aa) have a normal phenotype because one “normal” allele produces enough of the required protein
A carrier is a person who doesn’t have the disease but carry the gene for the disease

43. Heterozygote crosses Aa x Aa A a Aa A a AA Aa AA Aa A a A a Aa Aa aa
Heterozygotes as carriers of recessive alleles
Aa x Aa A a Aa A a
male / sperm AA Aa AA Aa A a
female / eggs
carrier A a Aa Aa aa Aa aa
carrier
disease

44. Cystic Fibrosis
The body produces abnormally thick mucus in the lungs and intestines.
This mucus makes it hard to breathe
Caused by a removal of 3 bases from DNA

45. Tay-Sachs
Primarily Jews of eastern European (Ashkenazi) descent & Cajuns (Louisiana)
non-functional enzyme fails to breakdown lipids in brain cells
fats collect in cells destroying their function
symptoms begin few months after birth
seizures, blindness & degeneration of muscle & mental performance
child usually dies before 5yo

46. Sickle-Cell Disease
Affects hemoglobin, a protein in red blood cells that carries oxygen
Cells have an unusual sickle-shape
They clog blood vessels, make it difficult for blood flow

47. Huntington’s disease 1872 Dominant inheritance
repeated mutation on end of chromosome 4
build up of “huntingtin” protein in brain causing cell death
memory loss
muscle tremors, jerky movements
starts at age 30-50
early death
10-20 years after start
Testing… Would you want to know?

48. Sex-linked traits
Are traits that are controlled by the X or Y chromosomes.
Sex-linked disorders, which are disorders caused by abnormal sex chromosomes.
Occurs more often in men than women.
Most are recessive
Two common disorders
Colorblindness and hemophilia

49. Colorblindness Test

50. Hemophilia A person’s blood clots very slowly or not at all.
Danger from small bumps and cuts
A recessive gene on the X-chromosome
Occurs more in males than females