1. Introduction to Genetics
Chapter 11
Introduction to Genetics

2. 1. Genetic information passes from parent to offspring during meiosis when gametes, each containing one representative from each chromosome pair, unite.

3. 11.1 The Work of Gregor Mendel
2. genetics (308) - scientific study of heredity
3. fertilization (309) - result of male and female reproductive cells combining during sexual reproduction

4. 4. traits (309) - Characteristics that are inherited
5. hybrid (309) - offspring of crosses between parents with different traits

5. The Experiments of Gregor Mendel
The modern science of genetics was founded by an Austrian monk named Gregor Mendel.
Mendel was in charge of the monastery garden, where he was able to do the work that changed biology forever.

6. Mendel chose to study pea plants.
Contrasting characters- green & yellow
wrinkled & round
Reproduce sexually
Crosses can be controlled
Short life cycles
Produce large number of offspring

7. 6. true breeding- plant consistently produces offspring with only one form of a trait. Either the trait is dominant (TT) or recessive(tt)

8. Cells can sexually reproduce

9. 7. cross pollination - transferring a male gamete from the flower of one pea plant to the female reproductive organ in a flower of another pea plant

10. The Role of Fertilization
Mendel knew that the male part of each flower makes pollen, which contains sperm—the plant’s male reproductive cells.

11. 8. self fertilization - when a male gamete within a flower combines with a female gamete in the same flower
9. p generation - parent generation

12. The Role of Fertilization
Mendel decided to “cross” his stocks of true-breeding plants—he caused one plant to reproduce with another plant.

13. Alleles in this situation are the color of the pea.
Cross between parents with different forms of a trait
Pure breeding

14. 10. f1 generation- The offspring of the P cross are called the first filial (F1) generation; filius is Latin for son
11. f2 generation- The offspring of the f1 generation

15. Genes and Alleles

16. In Mendel’s experiment he observed that in each cross, the nature of the other parent, with regard to each trait, seemed to have disappeared.
The offspring of crosses between parents with different traits are called hybrids.

17. From these results, Mendel drew two conclusions.
12. An individual’s characteristics are determined by factors that are passed from one parental generation to the next.
13. gene (310) - segments of DNA located on chromosomes that control

18. 14. alleles (310) - different forms of a gene
15. principle of dominance (310) - Mendel’s discovery that some alleles are dominant and others are recessive.

19. Allele – Alternative(different) form that a single gene may have for a particular trait We use letters to Represent each form. Example P=purple p=pink

20. Adding alleles to Mendel’s experimentyy YY
All are Yy
Now some are not just Yy. The green ones are yy. How?

21. The same thing was happening when he examined all of the traits
The same thing was happening when he examined all of the traits. The recessive trait returned in the F2 generation.

22. The key to understanding what was happening was the gametes.
Gametes are the sex cells from each parent

23. Explaining the F1 Cross
Why did these alleles separate or segregate?
Mendel suggested that the alleles for tallness and shortness in the F1 plants must have segregated from each other during the formation of the sex cells, or gametes. Known as Mendel’s Law of Segregation

24. 16. segregation (312) - Mendelian law stating that two alleles for each trait separate during meiosis; explains how different forms of a gene are distributed to offspring
17. gamete (312) - sex cell; female egg; male sperm

25. Gametes are formed during meiosis.

26. 18. During gamete formation, the alleles for each gene segregate from each other so that each gamete carries only one allele for each gene.

27. 11.2 Applying Mendel’s Principles
19. probability (313) - the likelihood that a particular event will occur

28. 20. homozygous (314) - having two identical alleles for a particular gene

29. 21. heterozygous (314) - having two different alleles for a particular gene

30. 22. phenotype (315) - physical characteristics of an organism
Ex. Yellow or green peas
23. genotype (315) - genetic makeup of an organism
Ex. YY, Yy or yy

31. 24. Punnett square (315) - diagram that can be used to predict the genotype and phenotype combinations of a genetic cross.
25. Punnett squares use mathematical probability to help predict the genotype and phenotype combinations in genetic crosses.

32. Punnett Squares 10.2 Mendelian Genetics Chapter 10
Sexual Reproduction and Genetics
10.2 Mendelian Genetics
Punnett Squares

33. 26. monohybrid cross- involves only one trait; Punnett square will have 4 squares
dihybrid cross – involves two traits; Punnett square will have 16 squares.
Remember 1 letter represents 1 gamete from the parent

34. Independent Assortment
Mendel wondered if the segregation of one pair of alleles affects another pair so he performed an experiment that followed two different genes as they passed from one generation to the next.
Because it involves two different genes, Mendel’s experiment is known as a two- factor, or dihybrid, cross. .

35. Chapter 10
Sexual Reproduction and Genetics .

36. 27. independent assortment (317) - one of Mendel’s principles that states that genes for different traits can segregate independently during the formation of gametes

37. Crosses involving 2 traits
Dihybrid Crosses
Crosses involving 2 traits

38. “FOIL” Method used to determine gametes in a dihybrid
F = first of each pair
O = outer two
I = inner two
L = last of each pair
BbTt = gametes would be BT,Bt,bT,bt
Remember to keep homologous pairs of chromosomes together when combining gametes to form offspring.
BbTt NOT BTbt
Always place the dominant allele first in a homologous pair of chromosomes.
BbTt NOT bBtT

39. Phenotype ratio __________________________

40. 28. The principle of independent assortment states that genes for different traits can segregate independently during the formation of gametes.
29. Mendel’s principles of heredity, observed through patterns of inheritance, form the basis of modern genetics.

41. 11.3 Other Patterns of Inheritance EXCEPTION ALERT
30. Some alleles are neither dominant nor recessive. Many genes exist in several different forms and are therefore said to have multiple alleles.

42. 31. incomplete dominance(319) - situation in which one allele is not completely dominant over another allele 
Big hint: incomplete dominance problems always have 3 phenotypes

43. In this case, neither allele is dominant.
the heterozygous phenotype lies somewhere between the two homozygous phenotypes.

44. codominance (319) - situation in which the phenotypes produced by both alleles are completely expressed
Hint: the heterozygote you will be able to see both phenotypes

45. Codominance
For example, in certain varieties of chicken, the allele for black feathers is codominant with the allele for white feathers.

46. CODOMINANCE in the heterozygous condition Ex. checkered chicken
Both alleles are expressed
in the heterozygous condition
Ex. checkered chicken
8. black chicken X white chicken  checkered chicken
BB X WW  BW

47. Roan cattle another example of codominance
RR red hair, RR’ roan(pinkish brown),
R’R’ white
Type AB blood type is an example of codominance

48. 32. Many genes exist in several different forms and are therefore said to have multiple alleles.
33. multiple allele (320) - a gene that has more than two alleles

49. Blood types A, B and O are
Examples of multiple alleles.

50. Blood types are examples of multiple alleles;
IA Codes for type A blood
IB Codes for type B blood
i Codes for type O blood

51. 34. Many traits are produced by the interaction of several genes.
35. polygenic trait (320) - trait controlled by two or more genes
Hint: there will show a wide range of phenotypes

52. polygenic traits: Hair color, Skin color, Eye color, Fingerprint pattern, height

53. 36. Environmental conditions can affect gene expression and influence genetically determined traits.
The phenotype of an organism is only partly determined by its genotype.

54. Genes and the Environment
For example, consider the Western white butterfly. Western white butterflies that hatch in the summer have different color patterns on their wings than those hatching in the spring.
Scientific studies revealed that butterflies hatching in springtime had greater levels of pigment in their wings than those hatching in the summer.
In other words, the environment in which the butterflies develop influences the expression of their genes for wing coloration.

56. 11.4 Meiosis
37. homologous (323) - term used to refer to chromosomes in which one set comes from the male parent and the other from the female parent.
Same in length, position of centromere and location of genes

58. Sister chromatids - either of the two identical copies (chromatids) formed by the replication of a single chromosome
Centromere - region of a chromosome where the two sister chromatids attach

59. 38. diploid (323) - term used to refer to a cell that contains two sets of homologous chromosomes
39. The diploid cells of most adult organisms contain two complete sets of inherited chromosomes and two complete sets of genes.

60. 8, which can be written as 2N = 8,
Diploid Cells
For the fruit fly,
the diploid number is
8, which can be written as 2N = 8,
where N represents twice the number of chromosomes in a sperm or egg cell.

61. 40. haploid (323) - term used to refer to a cell that contains only a single set of gene

63. The gametes of sexually reproducing organisms are haploid.
Haploid Cells
The gametes of sexually reproducing organisms are haploid.
For fruit fly gametes, the haploid number is 4, which can be written as N = 4.

64. 41. meiosis (324) - process in which the number of chromosomes per cell is cut in half through the separation of homologous chromosomes in a diploid cell

65. Meiosis Reduces the genetic material by half Why is this necessary?
from mother
from father
child
too
much!
meiosis reduces genetic content

66. Before Meiosis I
Just prior to meiosis I, the cell undergoes a round of chromosome replication called interphase I.

67. Meiosis I Interphase 10.1 Meiosis Chapter 10
Sexual Reproduction and Genetics
10.1 Meiosis
Meiosis I
Interphase

68. Chapter 10
Sexual Reproduction and Genetics
10.1 Meiosis
Meiosis I
42. In prophase I, replicated chromosomes pair with corresponding homologous chromosomes.

69. 43. tetrad (324) - structure containing four chromatids that form during meiosis

70. 44. crossing-over (324) - process in which homologous chromosomes exchange portions of their chromatids during meiosis

71. 45. At metaphase I, paired chromosomes line up across the center of the cell.

72. 46. In anaphase I, chromosome pairs move toward opposite ends of the cell.

73. When anaphase I is complete, the separated chromosomes cluster at opposite ends of the cell.

74. 47. In telophase I, a nuclear membrane forms around each cluster of chromosomes.
48. Cytokinesis then forms two new cells.

75. Meiosis I
Notice that the two cells produced by meiosis I have sets of chromosomes and alleles that are different from each other and from the diploid cell that entered meiosis I.

76. 49. Meiosis II – second round of division but this time neither of the two cells undergo chromosome replication.

77. 50. As the cells enter prophase II, their chromosomes become visible.

78. Metaphase II
During metaphase of meiosis II, chromosomes line up in the center of each cell.

79. As the cell enters anaphase, the paired chromatids separate.
Anaphase II
As the cell enters anaphase, the paired chromatids separate.

80. Telophase II, and Cytokinesis
Each of the four daughter cells produced in meiosis II receives two chromatids.

81. 51. The final four phases of meiosis II result in four haploid daughter cells.

82. The haploid cells produced by meiosis II are gametes.
Gametes to Zygotes
The haploid cells produced by meiosis II are gametes.
In male animals, these gametes are called sperm.
The female gamete is called an egg in animals.

83. 52. zygote (325) - fertilized egg

84. 53. In mitosis, when the two sets of genetic material separate, each daughter cell receives one complete set of chromosomes.

85. In meiosis, homologous chromosomes line up and then move to separate daughter cells.

86. 54. Mitosis does not normally change the chromosome number of the original cell.
Meiosis reduces the chromosome number by half.

87. 55. Mitosis results in the production of two genetically identical diploid cells, whereas meiosis produces four genetically different haploid cells.

88. Mendel was one smart guy!
Tying Mendel’s laws back to meiosis
Mendel didn’t even know the process of meiosis, chromosomes or DNA!
But he was right in his theories!
Future research proved them!

89. Law of segregation - Mendelian law stating that two alleles for each trait separate during meiosis; explains how different forms of a gene are distributed to offspring

90. Sexual Reproduction and Genetics
*Mendel’s Law of Segregation states that two alleles for each trait separate during meiosis.

91. Where does the law of segregation occur in Meiosis?
Anaphase I

92. Law of independent assortment – one of Mendel’s principles that states that genes for different traits can segregate independently during the formation of gametes

94. Mitosis Meiosis Number of division phases Replication time
Mitosis
Meiosis
Number of division phases
Replication time
Sister chromatids
Homologous chromosomes
Synapsis/Crossing over
Number of cells as a result
Daughter cells
Occurs in what kinds of cells
Purpose

95. Another exception to Mendelian Genetics
56. Genetic linkage is the tendency of DNA sequences that are close together on a chromosome to be inherited together during the meiosis phase of sexual reproduction.

96. 57. Gene mapping is the process of determining where genes are located on individual chromosomes

97. 58. Alleles of different genes tend to be inherited together from one generation to the next when those genes are located on the same chromosome.