Download BIO152 DiscussTerm Test 2 Term Test 2: inheritance

BIO152 DiscussTerm Test 2
Tutorial 9
November 24
Term Test 2: inheritance
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Statistics
Diagnosis
Next step
Questions + answers
1
How did you do?
730 students wrote the test
Cummulative %
Mark number
%
A
39 (10 A+)
5
B
66
9
≥ B =14%
C
159
22
≥ C =36%
D
184
25
≥ D = 61%
diagnosis
• Check your mark—STORM (course
webpage: Marks)
• Pick up the test questions (wooden boxes
outside 1087)
• Print the correct answers (NEWS on course
web page)
• Print the list questions you got wrong
2
How did you study? Did you…
• Do the Freeman tutorials ch 12 & 13 (CD or
online)?
• Work through the end of chapter problems?
• Work through the problems discussed in
tutorials & lectures?
• Draw out the chromosomes in all stages of
meiosis?
• Draw out the chromosomes if nondisjunction
occurred?
• Look at the answer AFTER you did the
problems?
Were you…
• At the lectures &
tutorials
• Awake
3
Possible problems DURING the
test
Did you read the question?
Some questions were very similar to the
study questions: many of you gave the
answer to the study question, not the
answer to the test question.
Possible problems DURING the
test
Time?
Time management is really hard, but
important
28 questions
7 about the figure—easy if you drew out
meiosis
8-9 concepts
12-13 problems-fast if you did lots before
except for the 3 hard ones.
4
What is the number of chromosomes in each of the
figures? C.
I 2; II 4; III 4; IV 4
• I
• II
• III
• IV
What is the amount of DNA in each figure?
b.
I 1n; II 4n; III 4n; IV 2n
• I
• II
• III
• IV
5
In which of the figures do the chromosomes have both
sister and nonsister chromatids?
e.
II and III
• I
• II
• III
• IV
What is the 2n number of chromosomes for
this organism?
b. 4
• I
• II
• III
• IV
6
What is the stage of division for Figure I?
d. telophase II – meiosis
• I
• II
• III
• IV
What is the stage of division for Figure III?
a. metaphase I – meiosis
• I
• II
• III
• IV
7
Arrange the figures in the correct ORDER so that
the stages are listed from first to occur to last
to occur. c.
• I telophase II
• III metaphase I
III II
IV
I
• II anaphase I
• IV anaphase II
8. Which of the following statements is true?
[at the beginning of Prophase I] 52%
a. Alleles on sister chromatids must be the
same.
b. Alleles on non sister chromatids must be the
same.
c. Alleles on homologs must be the same
d. Alleles on sister chromatids may be the
same.
e. a, b and c
8
11. In a cross between peas heterozygous for two
traits , the probability of the offspring exhibiting
both recessive traits is 1/16. If the parents
were heterozygous for THREE traits, what is
the probability that each offspring exhibited all
three dominant traits?
[hint for one trait 3:1 or 3/4]
3 traits = ¾ x ¾ x ¾ = 27/64 [24%]
Exhibited all 3 recessive traits? ¼ x ¼ x ¼ =
1/64 [61%]
13. A man and woman are both of normal
pigmentation, but both have one parent who is
albino (without melanin pigmentation).
Albinism is an autosomal recessive trait. Their
first child is a girl with albinism. What is the
probability that their second child is a
boy and has albinism?
[just like the one in class for a girl]
= ¼ [albino] x ½ [boy] = 1/8 b. 41%
9
16. A recessive allele on the X chromosome is responsible for redgreen color blindness in humans. A woman with normal vision
whose father is color-blind marries a color-blind male. What is
the probability that this couple's first son will be color-blind?
why is b. 50% correct this time?
Boys get X from mom
Girls get X from dad
Mom is heterozygous (1/2 chance to give X with
colour blindness to sons)
First son is not the same as the first child being a
son
This one is hard [45%]
17. Hemophilia is caused by several genetic factors; one,
a sex-linked recessive gene, is the subject of this
problem. Assume that (1) a man with
hemophilia marries a (2) normal woman
whose father had hemophilia. What is
the probability that they will have a
daughter with hemophilia?
Dad and mom give an X to daughters
½ (mom is heterozygous) x ½ (girl) = 1/4
10
This is the other hard question
this form of sex determination gives
predictable, but “reversed” results.
Do a Punnett square
Female = ZW female gametes Z or W
Male = Z- Z
ZZ [male gametes]
Z
Z Z- ZZ male offspring
W W Z- WZ female offspring, but W Z- die
A lethal recessive allele that causes death of the
embryo occurs on the Z chromosome in pigeons so
W Z- die
e. 2:1 male to female [25%]
11
20. If a diploid cell undergoes meiosis and
produces two gametes that are normal, and
one with n – 1 chromosomes, and one with
n + 1 chromosomes, what type of error
occurred?
Nondisjunction but WHEN?
See tutorial Ch 12; draw it out; see
figure 12.14 for the OTHER type
of nondisjunction
21. Suppose 64% of a remote mountain village can taste
phenylthiocarbamide (PTC) …what percentage of the population
must be homozygous dominant for this trait?
p2 + 2pq + q2 = 1
tasters = p2 + 2pq = 64%
q2= 1-.64 = .36 q=.6
p=1-0.6= 0.4
Homozygous dominant = 0.42 = 0.16
Heterozygous? = 2pq = 2(0.4 x 0.6) or 0.64 - 0.16
12
25. In tomatoes, tall is dominant to short, and smooth fruit is dominant
to hairy fruit. A plant homozygous for both dominant traits is crossed
with a plant homozygous for both recessive traits. The F1 progeny
are testcrossed with the following results:
78 tall, smooth fruit
parental
82 dwarf, hairy fruit
parental
22 tall, hairy fruit
recombinant
18 dwarf, smooth fruit recombinant
Total 200
Parental = 78+82= 160/200 = 0.8
Recombinants = (22+18)/200 = 0.20
Linked and 20 map units apart
13