1. Pick up the 2 handouts as you come in
Pick up the 2 handouts as you come in!! Complete the Warm Up—on your notes
Why do our bodies use mitosis?
Why do our bodies use meiosis?

2. Genetics
SB2c: I can analyze how biological traits are passed on to successive generations.

3. Guiding Questions: What determines an organism’s physical appearance?
How do parents pass traits to their offspring?
How can predictions be made about the genetics of an organism?

4. Genetics What is Genetics? Heredity
The modern science that studies the mechanisms for the transmission of hereditary information in the resulting organism.
Heredity
Transmission of traits causing the offspring to resemble their parents.

5. What is genetics? Genetics: Is the science of heredity
Mendel is considered the “Father of Genetics”
Mendel was a monk who experimented with pea plants to study heredity
Traits:Flower color, seed color, seed shape, pod color,
pod shape, flower position, plant height

6. Why did Mendel study peas?
Peas reproduce and grow quickly
They had easy to observe traits
Can reproduce using 2 different plants or using 1 plant
True-Breeding: Can produce offspring with only 1 parent
Cross Pollination – 2 parents self-fertilizing/true-breeding

8. Genetics Definitions
Genes - sections of chromosomes that code for a trait
Trait - characteristic that can be passed from parent to offspring
Allele - distinct form of a trait – one from each parent
Dominant - fully expressed gene
Recessive - gene expressed when not in the presence of a dominant allele
Traits

9. What are examples of traits?
Trait: Is a notable feature or characteristic in an organism
Physical traits
Examples - Hair color, eye color, & height
Behavioral traits
Example – Sheepdog has herding instincts
Medical conditions
Examples – Cancer, Sickle cell, cystic fibrosis

10. But what color will the offspring show?
More about alleles
Allele: Alternative form that a single gene may have for a particular trait.
A gene in a particular place on a particular chromosome will express a particular trait….like flower color
Purple is an Allele coming from mom
But what color will the offspring show?
Chromosome from MOM
Chromosome from DAD
White is an Allele coming from dad

11. How do alleles determine what traits will show?
Some alleles are dominant and others are recessive
Do you have to remember which traits are dominant and which are recessive?...
Dominant: A trait that will appear (show)
* Represented with a CAPITAL letter
Example: Tall (T), Black (B), Brown (B)
NO…
Punnett Square questions will give you clues or will tell you in the question! You HAVE TO READ!
Recessive: A trait that is masked (hidden) if a
dominant allele is present, but will show if both
alleles are recessive
* Represented with a lower case letter
Example: short (t), blond (b), blue (b)

12. How do you know if a trait will show or not?
Rule #1: If there is a dominant trait present, it will always show that trait.
Tall is dominant over short
Capital “T” bosses the little “t”
T T
T t
Dominant
Dominant
Dominant
Recessive
Shows Tall
Shows Tall

13. I do you know a trait will show or not?
Rule #2: If there is NOT a dominant trait present, then the recessive trait will always show.
Tall is dominant over short
t t
Recessive
Recessive
Shows Short

14. Who is considered the “Father of Genetics”? Darwin Hooke Mendel Paquin
Review Question #1
Who is considered the
“Father of Genetics”?
Darwin
Hooke
Mendel
Paquin

15. Review Question #2
These plants were used in Mendel’s experiments because they grow & reproduce quickly:
Peas
Corn
Wheat
Roses

16. What is true-breeding? 2 parents reproduce offspring
Review Question #3
What is true-breeding?
2 parents reproduce offspring
2 offspring with three parents
Self fertilizing plants
Cross pollinating plants

17. Tall is dominant over short
Review Question #4
If a girl has Tt, she will show:
Short
Tall
Both (a) & (b)
None of the above
Tall is dominant over short

18. Before we start Punnett Squares, we have a few more things to learn…

19. What are some terms that will help with understanding Punnett Squares?
Homozygous: Organism with 2 of the same alleles for a particular trait. Also called “pure”.
Examples – TT tt DD dd
Same sized letters!
Same sized letters!
Same sized letters!
Same sized letters!
Same
Homo means: ________
Think: Same SIZED letters

20. What are some terms that will help with understanding Punnett Squares?
Heterozygous: Organism with 2 different alleles for a particular trait. Also called “hybrid”.
Examples – Tt Dd Gg Bb
Different sized letters!
Different sized letters!
Different sized letters!
Different sized letters!
Different
Hetero means: __________
Think: Different SIZED letters

21. Allele Representation
Homozygous Dominant Allele HH
Homozygous Recessive Allele hh
Heterozygous Dominant Allele Hh

22. What are some terms that will help with understanding Punnett Squares?
Phenotype: The observable characteristic or outward expression of an allele pair (genotype)
Characteristics you can see with your eyes!
Think: Phenotype -- Physical
Black Hair
Blond Hair
Red Hair
Brown Hair

23. What are some terms that will help with understanding Punnett Squares?
Phenotype
Characteristics you can see with your eyes!
Multi color Butterfly
Blue Butterfly
White Butterfly
Orange Butterfly

24. What are some terms that will help with understanding Punnett Squares?
Genotype: The organism’s allele pairs
Characteristics you can NOT see with your eyes!
Think: Genotype – Genetic Code HH GG bb Gg Hh Bb hh gg BB

25. Another term for heterozygous is:
Review Question #5
Another term for heterozygous is:
Allele
Same
Hybrid
Pure

26. tt is an example of: homozygous heterozygous hybrid all of the above
Review Question #6
tt is an example of:
homozygous
heterozygous
hybrid
all of the above

27. tt is an example of: phenotype heterozygous hybrid genotype
Review Question #7
tt is an example of:
phenotype
heterozygous
hybrid
genotype

28. Tall is dominant over short
Review Question #8
If a boy has tt, he will show:
tall
short
both (a) & (b)
none of the above
Tall is dominant over short

29. Tall is an example of: phenotype Heterozygous pure genotype
Review Question #9
Tall is an example of:
phenotype
Heterozygous
pure
genotype

31. Total # of Students= ______
Trait
Form 1
Form 2
Earlobe
Dimples
Chin
Hairline
Finger Hair
Thumb

32. DAY 2
Take Out Notes from Yesterday!

33. Monohybrid Cross: The use of Punnett Square for 1 trait
Punnett Square: A diagram used to predict the possible outcomes (offspring) of a particular cross or breeding.
Monohybrid Cross: The use of Punnett Square for 1 trait
(will have 4 boxes)
A cross that studies one set on contrasting traits. Each cross produces a new generation.
First generation: F1 Second generation: F2

34. Do the Punnett Squares to see the ratios. PP, pp

35. Explaining Mendel’s Results
His results showed that inheritance follows a simple pattern.
This pattern follows simple rules
Law of Segregation:
When an organism produces gametes, each gamete has an equal chance of receiving either one of the alleles.

37. Mendel’s 1st Law
Mendel’s 1st law: law of segregation -- a child inherits one allele from each parent
Each gamete (sex cell) receives only one copy

39. Explaining Mendel’s Results
Mendel looked for patterns and for a lack of patterns.
The lack of patterns helped him develop
Law of Independent assortment:
Alleles of each gene are passed on independently during gamete formation.
Ex. Round seeds may or may not be yellow. The traits are not linked.
Inheritance of one trait has no effect on the inheritance of another trait

40. Mendel’s 2nd Law
Mendel’s 2nd law: law of independent assortment - alleles of different genes are passed to offspring independently of each other during gamete formation
Independent assortment means that new combinations of genes present in neither parent are possible

41. 3rd Law: Degrees of Dominance
Dominance occurs in varying degrees
Complete dominance
occurs when phenotypes of the heterozygous and homozygous dominant are identical
Incomplete dominance
the phenotype is somewhere between the phenotypes of the two parental varieties
Codominance
two dominant alleles affect the phenotype in separate, distinguishable ways

42. Sometimes two traits can be dominant at the same time

43. What’s the difference between incomplete dominance and co-dominance?
Incomplete Dominance: Complex inheritance pattern in which the heterozygous phenotype is intermediate between those of the two homozygous parent organisms…
Mixes like paint! R R W RW RW W RW RW

44. Incomplete Dominance

45. What’s the difference between incomplete dominance and co-dominance?
Co-Dominance: Complex inheritance pattern that occurs when neither allele is dominant and both alleles are expressed. B B BW BW W BW BW W

46. Codominance White = WW Red = RR Roan (spotted) = WR

47. Dihybrid Cross Involves two traits and two allele pairs.
Yellow peas – Y Green peas – y
Round peas – R Wrinkled peas – r
So if I have a yellow, round pea; what is a possible genotype?
YyRr or YYRR

48. Dihybrid Cross
Since we have 4 alleles, our square is now going to have 4 boxes on each side.

49. Dihybrid Cross: The use of Punnett Square for 2 traits
(will have 16 boxes)

50. Each gamete has only one allele for a trait because of:
Review Question #10
Each gamete has only one allele for a trait because of:
recessive
Law of segregation
dominance
phenotype

51. Review Question #11
When a white flower & a red flower have pink offspring, this is because of:
Co-dominance
Law of segregation
Law of Independent assortment
Incomplete dominance

52. In speckled chickens, both alleles are express because of:
Review Question #12
In speckled chickens, both alleles are express because of:
Co-dominance
Law of segregation
Law of Independent assortment
Incomplete dominance

53. The cross with one trait is called:
Review Question #13
The cross with one trait is called:
Dihybrid
Trihybrid
Monohybrid
All of the above

54. A dihybrid cross will have how many squares?
Review Question #14
A dihybrid cross will have how many squares? 4 16 18 20

55. Patterns of Heredity
READING A PEDIGREE Genetic disorder: a disease that is caused by a mutation in a gene Can be dominant or recessive

56. Genetic disorders caused by a recessive allele
Recessive disorders
Genetic disorders caused by a recessive allele
Only shows up in people that are homozygous recessive
EXAMPLES:
Cystic fibrosis: thick mucus builds up in lungs and digestive system due to a defective protein in the cell membrane
Tay-Sachs disease: certain lipid cannot be broken down and builds up in the central nervous system
Phenylketonuria: phenylalanine amino acid cannot be broken down and builds up in the central nervous system

57. Genetic disorders caused by a dominant allele
Dominant disorders
Genetic disorders caused by a dominant allele
Shows up in people that are homozygous dominant or heterozygous
EXAMPLE:
Huntington’s disease: certain parts of the brain break down

58. Multiple alleles More than 2 alleles exist for a trait
However, an organism can only have 2 of these alleles for a trait

59. Example: alleles for hair color are blond, brown, red
Blood type is controlled by multiple alleles (A, B, and O)
O is recessive, A and B are codominant

60. AA, AO or IAIA, IAi Type A blood BB, BO or IBIB, IBi Type B blood
Genotype Phenotype
AA, AO or IAIA, IAi Type A blood
BB, BO or IBIB, IBi Type B blood
OO or ii Type O blood
AB or IAIB Type AB blood (A and B are codominant )

61. Sex determination Humans have 46 chromosomes
44 of these chromosomes are autosomes (do not determine the sex of an organism)
2 of these chromosomes are sex chromosomes (determine the sex of an organism)
Sex chromosomes are X and Y
Females are XX, Males are XY

62. Females can only make eggs with the X chromosome
Males make sperm with the X or Y chromosome, so it is the males that determine the sex of a baby

63. Sex-linked traits
Traits controlled by genes on the sex chromosomes, X or Y

64. Example: Hemophilia (h) is a recessive disorder in which you cannot clot your blood. Normal blood clotting (H) is dominant. These genes are located on the X chromosome.

65. For sex-linked traits, you must write genotypes like:
XhXh : female with hemophilia
XHXh : female carrier
XhY : male with hemophilia
XHY : normal male without hemophilia
Example: XHXh x XhY

66. Example: Red-green color blindness: an individual cannot tell the difference between red and green
XcXc : female with color blindness
XCXc : female carrier
XcY : male with color blindness
XCY : male with color vision
Example: XcXc x XCY

67. Key Vocabulary Allele Carrier Dominant Pedigree Genetics Codominance
Genotype
Incomplete dominance
Heterozygous
Polygenic trait
Homozygous
Sex chromosome
Hybrid
Sex linked trait
Law of independent assortment
Multiple alleles
polyploidy
Law of segregation
Phenotype
Recessive