Answer Key__
Name: __
43
Pretest Score: _
_/43
Post test score: _____/43
Ch 11 & 14.1 Pretest: Genetics
Match the definition on the left with the vocab word on the right.
L__ has two different alleles; another
1. __
word for heterozygous
A. allele
B. carrier
controlling it
C. codominance
D. cross-pollinate
S__ something that has more than one gene
2. __
A__ different form of a gene
3. __
E__ genetic cross where two traits are
4. __
E. dihybrid cross
F. dominant
examined at once
G. F1 generation
H. gene
the other, the phenotypes mix
I. genotype
J. heterozygous
meiosis, thus genes are randomly
distributed
K. homozygous
L. hybrid
M. incomplete dominance
M__ one allele does not completely suppress
5. __
N__ chromosomes line up randomly during
6. __
B__ one who has the gene for a trait, but
7. __
does not show it
V__ trait on the X or Y chromosome
8. __
F__ an allele that suppresses the expression
9. __
of another allele
G__ “children” from a genetic cross
10. __
I
11. __ __ the alleles that are present in an
individual; uses letters
K__ having two of the same alleles; another
N. law of independent
assortment
O. monohybrid cross
P. P generation
Q. pedigree
R. phenotype
S. polygenic trait
T. pure-bred
U. recessive
V. sex linked trait
12. __
word for pure bred
C__ two alleles are both expressed together
13. __
U__ an allele does not get expressed because of another allele
14. __
H__ piece of a chromosome that is a code for one trait
15. __
P__ the organisms you start a genetic cross with
16. __
Q__ a diagram that tracks genetic characteristics
17. __
T__ an organism that has two copies of the same allele; another word for
18. __
homozygous
D__ taking gametes from two different parents and examining the results
19. __
J__ having two different alleles; another word for hybrid
20. __
O__ genetic cross where only one trait is examined
21. __
R__ a description of how an organism looks; uses words
22. __
23. – 26. In guinea pigs, short hair (S) is dominant to long hair (s). Cross a
heterozygous short haired guinea pig with a homozygous long haired guinea
pig. Show the parents genotypes as well as the genotypic and phenotypic ratios
for the offspring.
23. Parents genotypes: short haired: _
24. Punnett Square:
25. Genotypic ratio:
50% Ss
50% ss
Ss_
S
ss__
long haired: __
s
Ss
s
ss
s
Ss
ss
26. Phenotypic ratio:
50% short haired
50% long haired
27. If this were a case of codominance, what would the results be?
Same genotypes, but the Ss would have long
and short hair… some parts long, some parts
short.
28. If this were a case of incomplete dominance, what would the results be?
Same genotypes, but the Ss would have
medium length hair… in between long and
short.
29. How are crosses with sex linked traits written differently?
Using X and Y with the letters for the allele,
e.g. XS Xs or Xs Y
30. What two pieces of information do you get phenotypically from a cross involving a
sex linked trait?
Gender of offspring (male or female) and
trait
31. – 34. Left handedness is a sex linked trait found on the X chromosome. Right
handed (R) is dominant to left handed (r). Cross a left handed male with a
female carrying the trait for left handedness. Show the parents genotypes as
well as the genotypic and phenotypic ratios for the offspring.
r
R
r
31. Parents genotypes: Father: _
_
Mother: _
_
32. Punnett Square:
r
X Y
X X
X
33. Genotypic ratio:
R
25 % X Xr
25 % Xr Xr
25 % XR Y
25% Xr Y
Y
XR XR Xr XR Y
Xr Xr Xr Xr Y
34. Phenotypic ratio:
25 % female, right handed
25 % female, left handed
25 % male, right handed
25% male, left handed
35. – 38. In pea plants, Tall (T) is dominant to short (t) plants and purple flowers (P)
are dominant to white (p). Cross a pure bred tall plant with white flowers to a tall
plant with purple flowers that is a hybrid for both traits. Show the parents genotypes
as well as the genotypic and phenotypic ratios for the offspring.
TTpp_
Tall, purple flowers: _TtPp_
35. Parents genotypes: Tall, white flowers: _
36. Punnett Square:
37. Genotypic ratio:
25%
25%
25%
25%
TTPp
TTpp
TtPp
Ttpp
Tp
Tp
Tp
Tp
TP TTPp TTPp TTPp TTPp
Tp TTpp TTpp TTpp TTpp
tP TtPp TtPp TtPp TtPp
tp Ttpp Ttpp Ttpp Ttpp
38. Phenotypic ratio:
50% Tall, purple flowers
50% Tall, white flowers
To the right is a diagram called a pedigree.
Squares represent males and circles represent
females. Ones that are colored in represent
individuals with the trait in question.
39. – 40. Is this trait autosomal or sex linked?
How can you tell?
Autosomal. Roughly
equal numbers of males
and females have it. (proportion very uneven
between males and females, usually more in
males = sex linked)
41. – 42. Is this trait dominant or recessive? How can you tell?
Dominant. For every child that has it, at
least one parent does, too. (recessives skip
generations)
43. What are the genotypes for person I-1, and III-2? Use B for the dominant allele,
and b for the recessive.
I-1 is Bb (heterozygous) … you can tell
because if he was BB, all his kids would have
the trait. If he was bb, he would not have the
trait.
III-2 is bb (homozygous) … you can tell
because if he was BB or Bb, he would have the
trait.