1. IB Biology II Van Roekel 1/15/14
Genetics
IB Biology II
Van Roekel
1/15/14

2. What can you tell me about this individual based on its Karyotype
What can you tell me about this individual based on its Karyotype. When finished, read the article.

3. Topic 4.1 Notes
4.1.1 State that eukaryote chromosomes are made of DNA and proteins.
4.1.2 Define gene, allele and genome.
4.1.3 Define gene mutation .
4.1.4 Explain the consequence of a base substitution mutation in relation to theprocesses of transcription and translation, using the example of sickle-cell anemia.

4. Background Info Somatic Cells – typical body cell (non-sex cell)
Gamete – Egg and sperm cells
Haploid – a cell containing a single set of chromosomes (N)
Diploid – in an organism that reproduces sexually, a cell that contains 2 homologous sets of chromosomes.

5. Meiosis Meiosis is for the reproduction of sex cells. (sperm and egg)
It makes 4 daughter cells
They are Haploid (half the number of chromosomes as the parent cell)
They are not identical

7. Chromosome Refresher Chromosomes are made of DNA and Protein.
Unwinding DNA is similar to unwinding a ball of string…the proteins help keep it organized (histones).

8. Chromosome Refresher
In eukaryotes, chromosomes always come in homologous pairs in somatic cells (one from mother, one from father)
Humans have 23 pairs of chromosomes, or 46 total

10. What is a gene?
A gene is a heritable factor that controls a specific characteristic (hair color, eyes, etc.)
Humans have roughly 30,000 genes.
Many genes have variations of forms called ALLELES.

11. Alleles cont. One specific form of a gene.
Different alleles typically only differ by a few base pairs (nucleotides).
Alleles of the same gene occupy the same LOCUS on each chromosome pair. Locus is a corresponding region on chromosome.

13. Genome
The complete set of an organism’s base sequences is called it’s genome

14. Mutation
A mutation, by definition, is a change in the genetic material. (typically rare)
Types of mutations:
Insertion/DeletionFrameshift mutations
Base substitutionMissense mutations

15. Insertion/Deletion Additions or losses of nucleotide pairs in a gene
Has disastrous effect on resulting protein
Results in Frameshift mutation because reading frame (codon grouping) is altered, usually results in nonfunctional proteins

17. Base Substitution
A single base substitution may or may not have an effect on the overall gene (and ultimately protein). Why?
A base substitution would be like guanine changing to adenine in the parent sequence.
Missense mutation: altered codon still codes for an amino acid, although it may not be planned amino acid

19. Base Substitutions-Sickle Cell Anemia
DNA is mutated from CTC to CAC, so codon GAG converted to GUG
Valine is added instead of Glutamic Acid to growing polypeptide.
Ultimate mutation is a “sickle” shaped cell.
Oxygen is ultimately not carried as efficiently throughout the body.

20. Define the following terms
Chromosome:
Bundled packages of DNA and protein
Gene:
Heritable factor that controls a specific characteristic
Allele:
Specific forms of a gene
Mutation:
Random, rare change in the genetic material

21. Topic 4.3 Theoretical Genetics
4.3.1 Define genotype , phenotype , dominant allele , recessive allele, codominant
alleles , locus, homozygous, heterozygous, carrier and test cross.
4.3.2 Determine the genotypes and phenotypes of the offspring of a monohybrid
cross using a Punnett grid.
4.3.3 State that some genes have more than two alleles (multiple alleles).
4.3.4 Describe ABO blood groups as an example of codominance and multiple
alleles.
4.3.5 Explain how the sex chromosomes control gender by referring to the
inheritance of X and Y chromosomes in humans.
4.3.6 State that some genes are present on the X chromosome and absent from the
shorter Y chromosome in humans.
4.3.7 Define sex linkage.
4.3.8 Describe the inheritance of colour blindness and hemophilia as examples of
sex linkage.
4.3.9 State that a human female can be homozygous or heterozygous with respect
to sex-linked genes.
Explain that female carriers are heterozygous for X-linked recessive alleles.
Predict the genotypic and phenotypic ratios of offspring of monohybrid
crosses involving any of the above patterns of inheritance.
Deduce the genotypes and phenotypes of individuals in pedigree charts.

22. Gregor Mendel Father of Genetics.
Used pea plants to construct crosses between different types of pea plants.
Crossed tall with tall; tall with short; etc. for generations of pea plants

23. Genotype
The symbolic pair of alleles possessed by an organism…represented by two letters.
Bb, GG, tt

24. Phenotype The physical characteristic or trait of an organism.
Hair color, shell color, eye color, etc.
“PHysical characteristic”

25. Dominant vs. Recessive
Dominant alleles are always expressed in phenotype when present in genotype.
BB, Bb
Recessive are only expressed when they are homozygous. bb

27. Codominance
Pair of alleles that both affect the phenotype when present in a heterozygote.

28. Homozygous vs. Heterozygous
Homozygous- having two identical alleles of a particular gene (ex. AA rather than Aa)
Heterozygous – having two different alleles of a particular gene (ex. Aa rather than AA)

29. Carrier
An individual with a recessive allele that does not effect phenotype of the individual.
Ex. – Aa individual is a carrier for the albinism gene.

30. Test Cross
Testing a suspected heterozygote plant with a known homozygous recessive (aa).
It is very difficult to tell just by phenotype whether or not an individual is AA or Aa until a test cross is done.

31. Setting up a Punnett Grid for monohybrid crosses

32. Steps of setting up Punnett Square
Choose and indicate a letter to show alleles.
Determine the parents’ genotypes
Determine possible gametes
Draw and complete Punnett grid
Determine percentages of genotypes and phenotypes

33. In dogs, the gene for fur color has two alleles
In dogs, the gene for fur color has two alleles. The dominant allele (F) codes for grey fur and the recessive allele (f) codes for black fur.
The female dog is heterozygous. The male dog is homozygous recessive. Figure out the phenotypes and genotypes of their possible puppies by using a Punnett Square.
The female dog has black fur. The male dog has black fur. Figure out the phenotypes and genotypes of their possible puppies by using a Punnett Square.

34. In fruit flies, red eyes are dominant (E). White eyes are recessive (e).
If both flies are heterozygous, then what are the possible phenotypes and genotypes of their offspring?
If the female fly has white eyes and the male fly has homozygous dominant red eyes, what are the possible phenotypes and genotypes of their offspring?

35. Using CR and CW as alleles for incomplete dominance in snapdragon flower color, show how two plants could have some white-flowered offspring, pink-flowered offspring, and red-flowered offspring within one generation?

36. Having a widow’s peak is dominant to not having a widow’s peak
Having a widow’s peak is dominant to not having a widow’s peak. Look at the pictures of Jay Z and Beyonce. If these two have more children, could they have widow’s peak? Why or Why not? Use a Punnett Square to explain your answer.

37. Multiple Alleles
Occurs when there are three of more alleles for one gene, which results in more than two possible phenotypes.
Example: Blood Type in humans
Type A, B, AB, or O

38. Blood Type Three alleles for gene
IA – Allele for type A
IB – Allele for type B
i – Allele for type O
Crossing these together can create 6 possible genotypes and 4 phenotypes

39. Blood Type IAIA or IAi = Type A IBIB or IBi = Type B IAIB = Type AB
ii = Type O

40. Determine the possible blood types of a child whose mother has type A blood, and whose father has type O blood. The child’s maternal grandparents had type A blood and type O blood.

41. Sex chromosomes 23rd chromosomes are the sex chromosomes XX = Female
XY = Male
X chromosome is longer and contains more genes than Y chromosome

42. Sex Chromosomes Females - all gametes carry the X chromosome
Males – 50 % of gametes carry X chromosomes, 50% carry Y chromosome
Always a 50/50 chance of male or female

43. Sex-Linked Traits
Any genetic trait whose allele has its locus (location) on the X or Y chromosome.
Examples:
Color Blindness
Hemophilia

44. Sex-Linked Alleles Color Blindness Hemophilia
Xb = recessive allele for color blindness
XB = allele for ability to distinguish colors
Hemophilia
Xh = allele for hemophilia
XH = allele for ability for blood to clot

45. Sex Linked Traits
XBXB = phenotype for non-affected female
XBXb = phenotype for non-affected female
XbXb = phenotype for affected female
XBY = phenotype for non-affected male
XbY = phenotype for affected male
Rare in females because require two recessive alleles, whereas males only require one

46. Sex-Linked Carriers
Only females can be carriers of sex-linked traits

47. Autosomes vs Sex Chromosomes
Autosomes: any chromosome that is not a sex chromosome. 22 pairs in humans
Genes can be autosomal or sex-linked
Autosomal means they are found on any of the 22 autosomes
Sex-linked means the genes loci are on the X or Y chromosome.

48. Pedigree Charts
Pedigree – refers to the record of an organism’s ancestry
Constructed to show biological relationships, specifically how traits pass from generation to generation

49. Pedigree Charts – Is this trait dominant or recessive? Is it sex linked? Explain your answer.

50. Topic 10 (Genetics Continued)
Describe the behavior of the chromosomes in the phases of meiosis.
Outline the formation of chiasmata in the process of crossing over.
Explain how meiosis results in an effectively infinite genetic variety in gametes through crossing over in prophase I and random orientation in metaphase I.
State Mendel’s law of independent assortment.
Explain the relationship between Mendel’s law of independent assortment and meiosis.

51. 10.2 Dihybrid crosses and gene linkage Assessment statements
Calculate and predict the genotypic and phenotypic ratio of offspring of 3 dihybrid crosses involving unlinked autosomal genes.
Distinguish between autosomes and sex chromosomes.
Explain how crossing over between non-sister chromatids of a homologous
pair in prophase I can result in an exchange of alleles.
Define linkage group .
Explain an example of a cross between two linked genes.
Identify which of the offspring are recombinants in a dihybrid cross involving linked genes.

52. Mendel’s Law of Independent Assortment
What does it state?
The separation of one pair of alleles is independent of the separation of another pair of alleles, provided that they are on separate chromosomes (unlinked)

54. Dihybrid crosses
Consider two traits on separate chromosomes (unlinked genes)
Example: Seed color (yellow-Y; green- y)
Seed shape (round-R; wrinkled-r)

55. Two parents each of which are heterozygous for each trait mate, what are the possible offspring’s genotypes?
R Y
R y
r Y
r y
R Y
RR YY
RR Yy
Rr YY
Rr Yy
R y
RR Yy
Rr Yy
Rr yy
RR yy
r Y
Rr YY
Rr Yy
rr YY
rr Yy
r y
Rr Yy
Rr yy
rr Yy
rr yy

56. Dihybrid Crosses
When two heterozygous parents mate, the following phenotypic ratio is expected:
9:3:3:1
9 represents both dominant traits expressed
3 represents one dominant one recessive trait
1 represents both recessive traits

57. Dihybrid Practice
A pea plant with round yellow seeds is crossed with a pea plant that has wrinkled green seeds, what are the possible genotypes of their offspring?

58. Dihybrid Cross
In man, assume that spotted skin (S) is dominant over non-spotted skin (s) and that wooly hair (W) is dominant over non-wooly hair (w). Cross a marriage between a heterozygous spotted, non-wooly man with a heterozygous wooly-haired, non-spotted woman. Give genotypic and phenotypic ratios of offspring.

59. Dihybrid Cross
In horses, black is dependent upon a dominant gene, B, and chestnut upon its recessive allele, b. The trotting gait is due to a dominant gene, T, the pacing gait to its recessive allele, t. If a homozygous black pacer is mated to a homozygous chestnut trotter, what will be the appearance of the F1 generation?

60. Autosomes vs Sex Chromosomes
Autosomes: any chromosome that is not a sex chromosome. 22 pairs in humans
Genes can be autosomal or sex-linked
Autosomal means they are found on any of the 22 autosomes
Sex-linked means the genes loci are on the X or Y chromosome.

61. Linked Genes
Any two genes found on the same chromosome are said to be linked to each other.
Linked genes usually pass from generation to generation together.
Any set of genes inherited together because they are on the same chromosome are referred to as a linkage group.

62. Linked Genes Linked Genes are represented as
G L
Linked Genes are represented as
Horizontal bars represent homologous chromosomes, with G & L being on the same chromosome
Genotype is read by pairing vertical alleles, i.e. GGLL
G L

64. Linked Genes
Crossing over still produces genetic variations of linked genes.
Offspring can have different combinations of alleles of linked genes by crossing over, new forms of chromosomes are referred to as recombinants

65. Practice Problems
Pg. 282 questions 2-5

66. Pg. 282, #2
The diagram below shows chromosomes during prophase 1 of meiosis. How many chromosomes are visible? How many chiasmata?
2 chromosomes, 2 chiasmata

67. Pg. 282 # 3
Explain how meiosis results in great genetic variety among gametes? (5 marks)
Homologous chromosomes pair up during prophase I
Crossing over- exchange of genetic material between paternal and maternal chromosomes. Results in different combinations of alleles
Bivalents randomly align on equator during metaphase I, random homologous chromosomes separate and move towards each pole
Law of independent assortment leads to 2n possible gametes because of the possible arrangements of sister chromatids during meiosis II

68. Pg 282 # 4
In Peas, the allele for round seed (R) is dominant to wrinkled seed (r) and yellow seed (Y) is dominant to green (y). IF YyRr and Yyrr are crossed, what ratio of phenotypes is expected?
C- 3 round yellow, 1 round green, 3 wrinkled yellow, 1 wrinkled green

69. Pg. 282 # 5 A) CcWw all colored starchy seeds
B) 1 CcWw; 1 ccWw; 1 Ccww; 1 ccww
1 colored starchy; 1 colorless starchy;
1 colored waxy; 1 colorless waxy
C) Genes are linked, so they are located on same chromosome therefore independent assortment has not occurred. Offspring will have higher chance of containing parental phenotypes

70. 10.3 Polygenic inheritance Assessment statement
Define polygenic inheritance
Explain that polygenic inheritance can contribute to continuous variation using two examples, one of which must be human skin color.

71. Polygenetic inheritance
Characteristics are influenced by two or more genes.
Large number of possible genotypes and phenotypes
Most human traits are considered polygenetic
eye color, skin color, height, susceptibility to certain illnesses, etc…

72. Continuous Variation
Occurs in traits with large number of possible genotypes, which leads to an array of possible phenotypes that transition from one to the next.
Continuous variation results because of the interaction between multiple genes
Affected by genetics, as well as the environment
Results in a bell shaped distribution curve

73. Beak Depth in Finches

74. Skin Color

75. Discontinuous Variation
Occurs when there are no transitions between phenotypes for specific traits.
Distinct phenotypes that can be easily separated

76. BILL
What is the difference between continuous and discontinuous variation?
Continuous variation occurs in polygenetic genes and shows a transition between phenotype. Discontinuous variations occur in single gene traits, and the phenotype is either present or it is not.

77. Genetic Engineering & Biotechnology
How can I use genetics in useful, real life applications?
DNA Profiling
The Human Genome Project
Gene Transfer
Genetically Modified Organisms
Cloning

78. DNA Profiling
Use polymerase chain reaction (PCR) to make millions of copies of DNA
Often amounts of DNA collected are limited
Using PCR, forensics experts can obtains millions of copies of DNA in order to have enough to analyze it.

79. DNA Profiling
Gel electrophoresis separates fragments of DNA in order to identify its origin
DNA is broken into pieces by enzymes and placed in the gel
Gel is Introduced to an electrical current
Largest particles don’t move far
Smaller particles pass through gel
Results in unique banded patterns for each individual based on DNA composition

81. What to do with DNA Profiling?
Match unknown samples of DNA with known sample to see if they correspond to determine:
Paternity cases
Analyze crime scenes
Study ecosystems to see which individuals are related

83. The Human Genome Project
Started in 1990, project set out to determine the order of all the bases A, T, C, & G in human DNA.
Completed in 2003, now deciphering what sequences represent which genes
Used to:
Determine which chromosomes carry specific genes
Produce beneficial medications
Compare ancestries

84. Gene Transfer
Takes a gene out of one organisms and places it in another organism
Possible because DNA is universal, meaning that A,T,C,& G are used in all organisms to code for protein
Tomatoes resistant to cold
Proteins used by fish to resist icy temps are now produced in modified tomatoes
Bt-corn
Produces toxins that kill bugs which attack it, thanks to gene from a soil bacterium that produces a protein fatal to certain larvae

85. Gene Transfer – Cutting and Pasting
Cut specific sequences of DNA using enzyme endonuclease
Paste sequences using DNA ligase
Sequences can be copied using host cells such as E. coli
Splice sections of DNA into plasmids (small circles of extra copies of DNA), place host cells in ideal conditions to grow and replicate

86. Genetically Modified Organisms
Genetically modified organisms (GMO) is one that has had an artificial change using techniques of genetic engineering
Transgenic plants: undesirable genes are removed or replaced with desired sequences of DNA
Tomatoes that can grow in high salinity soil
Rice plants that produce beta carotene
Transgenic animals
Use animals to produce substances for medical treatment, i.e. transgenic sheep produce Factor IX

87. Cloning
Clone: genetically identical organism artificially derived from a single parent
Usually done using an undifferentiated, but fertilized egg cell
Dolly, sheep whose genetic material did not originate from egg cell

88. How Dolly was made

89. Therapeutic Cloning Interested in cloning only cells.
Stem Cell research, aka culturing stem cells in order clone healthy cells to be used for medical treatment

91. Genetics Test Thursday, 1/30 Covers: Chapter 4 & 10 Meiosis Genetics
Genetic Engineering & Biotechnology