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Unit 2 Genetics Study Guide - KEY
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Genetics Vocabulary – Match the genetics vocabulary with the definitions.
1. Chromosome:
8. Heterozygous:
a threadlike structure of nucleic acids and protein found in the nucleus
of most living cells, carrying genetic information in the form of genes.
deoxyribonucleic acid, a self-replicating material present in nearly all
living organisms as the main constituent of chromosomes. It is the
carrier of genetic information.
Any characteristic that can be passed be inherited from parent to
offspring.
Section of chromosome (DNA) that codes for a specific trait.
Reproductive cell.
A diagram of the genetic history of an individual: can show how a trait is
inherited over several generations of a family. (a genetic family tree)
Any one of two or more alternative forms of a gene that may occur
alternatively at a given site on a chromosome. Alleles may occur in
pairs, or there may be multiple alleles affecting the expression of a
particular trait. If paired alleles are the same, the organism is said to be
homozygous for that trait; if they are different, the organism is
heterozygous.
Genotype of an individual with two different alleles for a given trait.
9. Homozygous:
Genotype of an individual with two of the same alleles for a given trait.
10. Dominant Allele:
Masks the recessive allele in a heterozygous individual.
11. Recessive Allele:
13. Punnett Square:
Allele that is masked by the dominant allele in a heterozygous
individual
If two alleles in a gene pair are different, then one allele can control the
expression of the trait and the other can be hidden.
A model used to show the probabilities of the results of a genetic cross.
14. Autosomes:
All chromosomes with the exception of the sex chromosomes.
15. Sex Chromosomes:
The pair of chromosomes that determine the gender of an individual.
16. Incomplete Dominance:
17. Genome:
Occurs when neither allele is dominant. They both have an affect on
the heterozygous individual which shows a phenotype between the two
homozygous phenotypes.
The complete genetic material contained in an individual.
18. Genotype:
The genetic make-up of an organism.
19. Phenotype:
The external appearance of an individual determined by it’s genotype.
20. Carrier:
An individual who has the allele for a trait or disease but does not have
the disease or outwardly express the trait.
2. DNA:
3. Trait:
4. Gene:
5. Gamete:
6. Pedigree:
7. Alleles:
12. Law of Dominance:
II. Key People and Discoveries in Genetics:
Greatest Discoveries in Genetics (with Bill Nye) http://www.youtube.com/watch?v=vIrrtM47Wio
This is the link to the video we watched in class. You only need to watch up to 23:00 to review the key
discoveries we focused on in this unit.
Video watched ________ / 10 points Partner/ Parent Signature: _____________________________________________________
* Video Review Study Strategies – Read and highlight your original notes pages – > Class # ______: Greatest Discoveries in Genetics.
Then, put your notes aside, and simply watch the video. Pause after each segment to add your own notes about anything you found interesting
or noticed for the first time as you watched the video a second time. Let yourself get engaged, draw pictures in the margins, enjoy learning. 
Fill-in-the Blank & Match the scientists with their contributions by lightly color coding the columns.
31. “Father of Genetics” -- Worked with pea plants.
Mendel's First Law of Genetics (Law of Segregation):
 A gene that can exist in more than 1 form (e.g. a gene for round or
wrinkled peas) is called an allele.
 When gametes are produced (by meiosis) in the parent, allele pairs
separate leaving each gamete with one allele for each trait.
 At fertilization, organisms inherit 2 alleles for each trait – 1 from
each parent.
 When the two alleles of a pair are different, one is dominant and the
other is recessive.
32. Genes are Located on Specific Chromosomes. Worked with
drosophila (fruit flies) because they have a short life cycle and produce
many off-spring  giving him a chance to study many generations for
inheritance patterns
 Genes are located at specific locations on a chromosome which
allows them to cross with each other
37. Avery, Pauling,
Chargaff
#35
38. Gregor Mendel
#31
33. Genes Control Biochemical Events – Worked with bread mold
 “one gene on enzyme concept”
 enzyme = A protein (or protein-based molecule) that speeds up a
chemical reaction in a living organism
 How does this relate to lactose intolerance or PKU?
39. Barbara McClintock
34. Some Genes Can Jump! – Worked with corn plants
 While genes are usually located on specific locations, some
segments of genes called transposons can move to different location
on a chromosomes
 This can cause mutations
35. DNA is the Genetic Material
40. Watson & Crick
#36
36. DNA is a Double Helix - deoxyribonucleic acid
 Made up of 4 base pairs: guanine, adenine,
thymine, cytosine
All living things contain DNA
There are commonalities in DNA code across species genomes
DNA controls similar cell functions and reproduction
There are Laws of Inheritance
41. Thomas Hunt Morgan
#32
42. Beadle & Tatum
#33
43. Genetic factors that promote UNITY




#34
44. Genetic factors that promote DIVERSITY



During sexual reproduction, offspring receive ½ of their genetic
material from each parent w/ variations in dominance
Transposons & mutations
Independent assortment during meiosis
III. Dominant and Recessive Alleles and Traits.
45. The convention for writing a dominant genotype is: Upper case, first letter of dominant trait
46. The convention to writing a recessive allele is: Lower case, first letter of dominant trait
47. A homozygous gene has 2 of the same alleles for example AA or aa.
48. A heterozygous gene has 2 different alleles for example Aa
49. For each genotype, indicate whether it is heterozygous (HE) or homozygous (HO)
AA HO
Bb HE
Cc HE
Dd HE
Ee HE
ff HO
GG HO
HH HO
Ii HE
Jj HE
kk HO
Ll HE
Mm HE
nn HO
OO HO
Pp HE
50. For each of the genotypes below, determine the phenotype.
Purple flowers are dominant to white flowers
PP purple
Pp purple
pp white
Brown eyes are dominant to blue eyes
BB brown
Bb brown
bb blue
51. For each phenotype, list the genotypes. (Remember to use the letter of the dominant trait)
Straight hair is dominant to curly.
SS or Ss
straight
SS or Ss
straight
ss
curly
Pointed heads are dominant to round heads.
PP or Pp
pointed
PP or Pp
pointed
pp
round
52. One more vocabulary word … Purebreeding = also known as truebreeding, is when 2 organisms with
identical genotypes procreate an organism for the same traits.
53. Picture
54. Sentence
__________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
“Step 1: Who’s your mama and whose your daddy?” Name the parents for the Reebop crosses using
the following dominance and recessive relationships for guinea pig traits.
o Short hair (S) dominant over long hair
o Black (B) dominant over white hair
o Wacky hair (W) dominant over smooth hair
55. Homozygous short, heterozygous black
x
heterozygous short, heterozygous black
SS Bb
x
Ss Bb
56. Homozygous long, heterozygous black
x
homozygous short, homozygous white
ss Bb
x
SS bb
57. Homozygous smooth, homozygous white
x
heterozygous wacky, heterozygous black
ww bb
x
Ww Bb
58. Homozygous smooth, heterozygous black
x
heterozygous wacky, heterozygous black
ww Bb
x
Ww Bb
59. Homozygous long, homozygous white
x
heterozygous short, homozygous black
ss bb
x
Ss BB
60. Homozygous short, homozygous black
x
heterozygous short, homozygous white
SS BB
x
Ss bb
IV. Punnett Squares: Run video to 6:00. http://www.youtube.com/watch?v=Y1PCwxUDTl8
o
(R) Round is dominant and wrinkled seeds (r) are recessive.
61. Homozygous dominant x homozygous dominant
RR x RR
70. Homozygous recessive x homozygous recessive
rr x rr
62. Genotypic Ratios: 1 RR : 0
63. Phenotypic Ratios: 1 Round : 0
71. Genotypic Ratios: 1 rr : 0
72. Phenotypic Ratios: 1 wrinkled : 0
64. Homozygous dominant x homozygous recessive
RR x rr
73. Homozygous recessive x homozygous dominant
rr x RR
65. Genotypic Ratios: 1 Rr : 0
66, Phenotypic Ratios: 1 Round : 0
74. Genotypic Ratios: 1 : Rr
75. Phenotypic Ratios: 1 Round : 0
67.
76.
Heterozygous x homozygous dominant
Rr x RR
68. Genotypic Ratios: 1 RR : Rr
69. Phenotypic Ratios: 1 Round : 0
heterozygous x homozygous recessive
Rr x rr
77. Genotypic Ratios: 1 Rr : 1 rr
78. Phenotypic Ratios: 1 Round : 1 wrinkled
Sex-linked Punnett Squares: Short 2:49 video http://www.youtube.com/watch?v=j35OALtS3Bk
B = Normal sight
b = color blindness
79. XBXB x XbY
Xb
a. What proportion/percent of the male children
are colorblind? 0%
XB
b. What proportion/percent of the female children
are colorblind? 0%
XB
80. XBXb x XBY
Y
XB Xb
XB Y
XB Xb
XB Y
XB
a. What % of the male children are
colorblind? 50%
XB
b. What % of the female children are
colorblind? 0%
Xb
Y
XB XB
XB Y
XB Xb
Xb Y
Dihybrid Punnett Squares: Start video at 6:00 http://www.youtube.com/watch?v=Y1PCwxUDTl8
o Tall (T) and short (t)
Green (G) and white (g)
81. A tall green pea plant (TTGg) is crossed with a tall green pea plant (TtGg)
TT Gg x Tt Gg
TG
TG
TG
Tg
tG
tg
82. Genotypic Ratios
Tg
Tg
TG TT GG
1
TTGG:
2 TTGg: 1 TtGG: 2 Tt Gg:
TT Gg Tt GG Tt Gg
tG
TT gg
Tt Gg Tt gg
tg
Tg TT Gg
1 TT gg: 1 Tt gg
83. Phenotypic Ratios: 6 Tall/Green : 3 Tall/White or 3 Tall/Green : 1 Tall/White
84. A tall green pea plant (TtGg) is crossed with a Short white pea plant (ttgg).
Tt Gg X tt gg
TG
tg
tg
85. Genotypic Ratios
Tg
1 TtGg: 1 Tt gg: 1 tt Gg: 1 tt gg
tG
TG Tt Gg
tg
Tg Tt gg
tG
tg
tt Gg
tt gg
86. Phenotypic Ratios: 1 Tall/Green : 1 Tall/white : 1 short/Green : 1 short/ white
Analyze the following dihybrid crosses for the phenotypic and genotypic ratios.
Example 1: Guinea Pigs
B = Black hair b = white hair
S = short
s = long
87. Genotypic Ratios
1BBSS: 2BBSs: 2BbSS: 4BbSs: 1BBss: 2Bbss:
1 bbSS: 2bb Ss: 1 bb ss
88. Phenotypic Ratios
9 black short: 3 black long; 3 white short; 1 white long
Example 2: Naked Mole Rats
T = long tails t = short tails
Z = fuzz z = no fuzz
89. Genotypic Ratios
1 TTZZ: 2 TTZz: 2 TtZZ: 4 TtZz:
1 TTzz : 2Ttzz: 1 ttZZ: 2ttZz: 1 ttzz
90. Phenotypic Ratios
9 long/ fuzz: 3 long/ no fuzz: 3 short/ fuzz: 1 short/ no fuzz
Describe
Example
Incomplete Dominance
91. Neither allele is completely
dominant
Co-Dominance
93. Both alleles are equally dominant
92. white and red parents ->
pink off-spring
94. white and red parents -> white and red
striped off-spring
V Pedigrees: Introductory Video (2:40 minutes) http://www.youtube.com/watch?v=Wuk0W10EveU
95. The pedigree to the right shows a family’s pedigree
for colorblindness. Which sex can be carriers of
colorblindness and not have it? females
96. With this in mind, what kind of trait is
colorblindness (use your notes)? Sex-linked recessive
**half-shaded = carrier of
disease
I
II
97. Which IV females are carriers? IV 3, IV 6
III
98. Why do all the daughters in generation II carry the
colorblind gene? Father has recessive gene, mother is
homozygous dominant  girls are heterozygous
99. Name 2 IV generation colorblind males. IV 1, IV 5
100. Relationship between IV 1 and IV 7? 2nd cousins
IV
1
2
3
4
5
6
7
8