Study Guide Chapter 15 -Chromosomal Basis of Inheritance-Answers
15.1 Mendelian Inheritance and chromosome theory______________________________
1. Thomas Hunt Morgan identified the first solid evidence associating a specific___gene_____ on a specific chromosome.
2. Why did Morgan choose Drosophila as his experimental organism? (List 3 reasons)
They reproduce quickly, a new generation of adults forms every two weeks!
Prolific (single matting = hundreds of offspring)
Only 4 chromosome pairs = simple genetics
3A. The normal phenotype for a character (phenotype most common in nature) is called___wild type_____.
3B. Provide at least two examples this phenotype in Drosophila.
Red eyes
gray body
4A. An alternative phenotype for a character (phenotype not common in nature) is called____mutant____.
4B. Provide at least two examples of this phenotype in Drosophila.
White eyes
Black body
5. Morgan and his students invented a notation to symbolize alleles in Drosophila that differed from the notation Mendel used to represent alleles. Describe how Morgan’s Drosophila characters are named and the symbol used for the allele type.
You can think of Morgan’s wild-type allele as equivalent to the dominant allele in Mendel’s naming system. And you can think of Morgan’s mutant allele as equivalent to Mendel’s recessive allele. So whenever you have one wild-type allele and one mutant allele, that organism will have the wild-type phenotype.
Mendel
Used the first letter of the dominant character name to represent the dominant allele. This letter was capitalized for the dominant allele, lower case for the recessive allele
Ex: purple flower allele dominant to white flower allele: P= dominant allele, p=recessive allele
Morgan
-Used the first letter of the mutant character name to represent the wild-type allele. The letter for the wild-type and mutant alleles are both lower case. The wild-type allele gets a + sign and the mutant does not.
Ex: red eye allele wild-type to white eye mutant: w+ = wild-type allele, w= recessive allele.
6. Morgan and his students invented a notation to symbolize alleles in Drosophila. Which of the following genotypes would produce a fly that is wild-type for eye color (red vs. white eyes)?
w+ w+
w+ w
w w
w+w+ and w+w
7. Morgan performed an experiment that yielded a 3:1 ratio of offspring in the F2 generation; however, only the males of this F2 generation had white eyes.
White- eye females DO EXIST, so why were only white-eye males observed in this cross?
Complete the following chart and describe why Morgan observed these results and how it allowed him to conclusively determine that the gene for eye color was located on the X chromosome.
Morgan’s experiment (see Figure 15.4) Use notation developed by Morgan and his students
If the gene for eye color is located on the X chromosome….
P generation
Red eye Female genotype for eye color = w+w+
White eye Male genotype for eye color= w
F1 generatio.
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1. Study Guide Chapter 15 -Chromosomal Basis of Inheritance-
Answers
15.1 Mendelian Inheritance and chromosome
theory______________________________
1. Thomas Hunt Morgan identified the first solid evidence
associating a specific___gene_____ on a specific chromosome.
2. Why did Morgan choose Drosophila as his experimental
organism? (List 3 reasons)
They reproduce quickly, a new generation of adults forms every
two weeks!
Prolific (single matting = hundreds of offspring)
Only 4 chromosome pairs = simple genetics
3A. The normal phenotype for a character (phenotype most
common in nature) is called___wild type_____.
3B. Provide at least two examples this phenotype in Drosophila.
Red eyes
gray body
4A. An alternative phenotype for a character (phenotype not
common in nature) is called____mutant____.
4B. Provide at least two examples of this phenotype in
Drosophila.
White eyes
Black body
5. Morgan and his students invented a notation to symbolize
alleles in Drosophila that differed from the notation Mendel
used to represent alleles. Describe how Morgan’s Drosophila
characters are named and the symbol used for the allele type.
2. You can think of Morgan’s wild-type allele as equivalent to the
dominant allele in Mendel’s naming system. And you can think
of Morgan’s mutant allele as equivalent to Mendel’s recessive
allele. So whenever you have one wild-type allele and one
mutant allele, that organism will have the wild-type phenotype.
Mendel
Used the first letter of the dominant character name to represent
the dominant allele. This letter was capitalized for the dominant
allele, lower case for the recessive allele
Ex: purple flower allele dominant to white flower allele: P=
dominant allele, p=recessive allele
Morgan
-Used the first letter of the mutant character name to represent
the wild-type allele. The letter for the wild-type and mutant
alleles are both lower case. The wild-type allele gets a + sign
and the mutant does not.
Ex: red eye allele wild-type to white eye mutant: w+ = wild-
type allele, w= recessive allele.
6. Morgan and his students invented a notation to symbolize
alleles in Drosophila. Which of the following genotypes would
produce a fly that is wild-type for eye color (red vs. white
eyes)?
w+ w+
w+ w
w w
w+w+ and w+w
7. Morgan performed an experiment that yielded a 3:1 ratio of
offspring in the F2 generation; however, only the males of this
3. F2 generation had white eyes.
White- eye females DO EXIST, so why were only white-eye
males observed in this cross?
Complete the following chart and describe why Morgan
observed these results and how it allowed him to conclusively
determine that the gene for eye color was located on the X
chromosome.
Morgan’s experiment (see Figure 15.4) Use notation developed
by Morgan and his students
If the gene for eye color is located on the X chromosome….
P generation
Red eye Female genotype for eye color = w+w+
White eye Male genotype for eye color= w
F1 generation
Genotype of offspring =
Red eye females w+w
Red eye males w+
F2 generation (F1 M crossed to F1 F)
Genotypes of offspring:
Red eye females w+w+
Red eye females w+w
Red eye males w+
8. If the eye-color gene locus in Drosophila was located on an
autosome what would you expect to observe in the F2 offspring
produced by the crosses in the Morgan’s experiment described
in the previous question?
He would have observed equal numbers of white -eye males and
females.
4. 15.2 Sex-linked genes inheritance
patterns______________________________________
9. Compare the X an Y chromosomes in Mammals.
X = larger, has more genes, two found in females, one in males
Y = smaller, has fewer genes, one in males, none in females
10A. Following Meiosis in mammals, each ovum (egg) contains
one __X_____(X or Y) sex chromosome, whereas following
meiosis in males each sperm cell has either an X OR Y
chromosome.
10B. Which gender M/F determines the sex of offspring in
mammals? Male
11. Your friend Bill has a “sex-linked” disease. Which
chromosome, X or Y, is more likely to contain the mutant allele
that is responsible for Bill’s disease Why?
X-because it is bigger than the Y, it has many more genes. For
this reason, if a person has a “sex-linked disease” it is most
likely on the X chromosome. It is so rare to have a sex-linked
disease as a result of a mutant gene on the Y chromosome that
sex-linked diseases are also called X-linked diseases.
12. In mammals, sex-linked genes are passed from Father’s to
__daughters__(daughters/son) only. Mother’s can pass sex-
linked genes to sons OR daughters.
13A. Name at least two sex-linked disorders found in humans.
Colorblindness, hemophilia
13B. Why are sex-linked disorders more common in males?
More common in males because males only have one X
chromosome, whereas females have two X chromosomes. If a
male inherits an X chromosome from his mom with a diseased
allele, he will have the disease because he has only one X
chromosome and does not have another X chromosome to
inherit a good (non-diseased allele). Females, because they have
two X chromosomes, have two chances to inherit a non-diseased
allele.
5. 14. Define the term “Hemizygous”. When is this term used?
How does it differ from the term “carrier”?
The term “hemizygous” is used to describe a male who has a
mutant allele for a gene on his X chromosome. Being a male, he
does not have another X chromosome. Therefore, a male
CANNOT be a “carrier” for a sex-linked disease…he either has
the disease or he does not have the disease.
15. If a female homozygous dominant for the normal form of a
sex-linked gene mates with a male who is hemizygous for the
mutant form of the gene…
MAKE A PUNNETT SQUARE FOR THIS CROSS!
A. What fraction of the total offspring from this mating will
have the disease?
0/4 = 0 (When asked for total offspring, look at the ENTIRE
punnett square...0 out of the 4 offspring will have the disease.)
B. What fraction of the total offspring from this mating will be
carriers for the disease? 2/4 = 1/2 (When asked for total
offspring, look at the ENTIRE punnett square...2 out of the 4
offspring will be carriers.)
C. What fraction of the female offspring from this mating will
be carriers for the disease? 2/2 =1, (When asked about the
female offspring, look at the females ONLY…All females will
be carriers.)
D. What percentage of the female offspring from this mating
will have the disease?
0/2 = 0 (look at the females ONLY…0 out of the 2 females will
have the disease)
E. What percentage of the male offspring from this mating will
be carriers for the disease? NONE, Males CANNOT be
“carriers” for a sex-linked disease!
F. What percentage of the male offspring from this mating will
have the disease?
0/2 = 0 (When asked about the male offspring, look at the males
ONLY…0 out of the 2 males will have the disease.)
16. If a female heterozygous for a sex-linked disease mates with
a male who is hemizygousfor the mutant form of the gene…
6. MAKE A PUNNETT SQUARE FOR THIS CROSS!
A. What fraction of the total offspring from this mating will
have the disease?
2/4 = 1/2 (When asked for total offspring, look at the ENTIRE
punnett square...2 out of the 4 offspring will have the disease.)
B. What fraction of the total offspring from this mating will be
carriers for the disease? 1/4 (When asked for total offspring,
look at the ENTIRE punnett square...1 out of the 4 offspring
will be a carrier.)
C. What fraction of the female offspring from this mating will
be carriers for the disease? 1/2 (When asked about the female
offspring, look at the females ONLY…one out of the two
females will be a carrier.)
D. What percentage of the female offspring from this mating
will have the disease?
1/2 (look at the females ONLY…1 out of the 2 females will
have the disease.)
E. What percentage of the male offspring from this mating will
be carriers for the disease? NONE, Males CANNOT be
“carriers” for a sex-linked disease!
F. What percentage of the male offspring from this mating will
have the disease?
1/2 (When asked about the male offspring, look at the males
ONLY…1 out of the 2 males will have the disease.)
17. During embryogenesis, one of the X chromosomes in every
female cell becomes inactivated. What is the name given to this
inactivated X chromosome? Barr body
18A. Random inactivation of one of the X chromosomes (X
inactivation) occurs in every body cell of female mammals. In a
particular breed of cat (tortoiseshell cat) the gene for fur color
is located on the X chromosome. Two alleles exist, orange fur
allele and black fur allele. A female with a heterozyougous
genotype will be tortoiseshell (orange and black). Male
tortoiseshell cats do not exist. Explain this finding.
The heterozygous fur color genotype female cat has one X with
7. the orange fur allele, other X has black fur color allele. X with
orange allele is active in some cells, inactive (Barr body) in
other cells. X with black
patches of orange and patches of black fur.
A male has only ONE X chromosome, so he can only have the
orange fur color allele on his X OR the black fur color allele on
his X. He can only be orange OR black.
B. A Female orange (tortoiseshell species) cat mates with a
black male (tortoiseshell species) cat.
Orange allele= b
Black allele =B
What are the fur color genotypes of the parent cats
(REMEMBER…this allele is on the X chromosome!) ?
Female: Xb Xb
Male: XB Y
C. What are the possible genotypes of their offspring?
(construct a punnett square)
XB Xb
Xb Y
D. What are the offspring phenotypes associated with the
genotypes listed in the previous question?
XB Xb tortoiseshell female
Xb Y orange male
disorders
19. Describe how nondisjunction can occurs during meiosis.
Meiosis I = homologous chromosomes do not separate
Meiosis II = sister chromatids do not separate
20. If a gamete with an abnormal number of chromosomes
(produced as a result of nondisjunction) unites with a normal
21. Peas are available in many varieties, and he could strictly
control which plants mated with which. Many of the pea plant
traits (flower color, height, etc.) varied in an “either-or”
manner.
2. Mendel tracked only those characters of the pea plants that
varied in an “either-or” manner. What does this mean? For
example, the pea plants he studied had purple OR white flowers;
there was no phenotype intermediate (light purple) between
these two varieties.
3A. Alleles: Alternative versions of genes are called alleles. For
each character, an organism inherits __2__(number) alleles for
each trait, __1___(number) from each parent.
3B. What is a dominant allele vs. a recessive allele? Give an
example.
P vs p purple flower color is dominate to white flower color
allele
3C. If an organism has one of each allele type (one dominant
and one recessive) then the __dominant__(dominant/recessive)
allele determines organism’s appearance
4. Genotypes: Homozygous dominant, Homozygous recessive
and Heterozygous Provide at least one example of each
genotype.
Homozygous dominant (Two dominant alleles) = AA
Heterozygous recessive (Two recessive alleles) = aa
Heterozygous (One dominant, One recessive allele)= Aa
5. Phenotype vs. genotype
Long fur (L) is dominant to short fur (l). Provide an example of
the three possible genotypes and the phenotype of each
genotype.
22. Homozygous dominant Genotype = LL, Phenotype = Long fur
Heterozygous recessive Genotype = ll, Phenotype = short fur
Heterozygous Genotype –Ll, Phenotype – Long fur
6. Describe the Typical Mendel experiment. Use the following
terms:
True-breeding
Parental (P) generation
Hybridization
Hybrids (Heterozygotes)
F1 generation
F2 generation
3:1 phenotype ratio
-Mendel always started with two homozygous (one homozygous
dominant one homozygous recessive) true-breeding organisms
in the P generation.
-He crossed P generation true-breeders (hybridization) to get F1
generation, Hybrid offspring.
-Mendel crossed plants from F1 to produce F2 generation
offspring = 3:1 phenotype offspring ratio observed
7. Construct punnett squares for the following crosses and
determine the probability of offspring genotypes and
phenotypes.
A. Rr X Rr
Genotypes: ¼ RR, ½ Rr, ¼ rr
Phenotypes: RR= dominant, Rr = dominant, rr = recessive
¾ dominant, ¼ recessive
23. B. AA X Aa
Genotypes: ½ AA, ½ Aa
Phenotypes: AA dominant, Aa dominant
ALL dominant
C. Dd X dd
Genotypes: ½ Dd, ½ dd
Phenotypes: Dd dominant, dd recessive
½ dominant, ½ recessive
8. What is a testcross and when is this method utilized?
The breeding of a homozygous recessive organism (aa) with an
organism of dominate phenotype but unknown genotype (AA?
or Aa?)
EX: Used when you don’t know the genotype of a dominant
phenotype organism (AA or Aa? = cross it with an organism of
KNOWN genotype = homozygous recessive organism, aa)
CROSS 1 Aa X aa
Offspring = ½ aa and ½ Aa
CROSS 2 AA X aa
Offspring = ALL Aa
So…
if you do the cross and get ½ dominant phenotype offspring and
24. ½ recessive phenotype offspring, then you know the dominant
parent MUST have a Heterozygous genotype.
if you do the cross and get ALL dominant phenotype offspring,
then you know the dominant parent MUST BE Homozygous
dominant.
9. Explain the difference between a monohybrid and a dihybrid.
Monohybrid = follow one character P( F1 will be hybrids for
one trait (have one dominant allele, one recessive allele) (EX:
Pp)
Dihybrid = follow two characters P and R( F1 will have one
dominant allele, one recessive allele for each character (EX:
PpRr)
14.2 Laws of probability and Mendelian
inheritance______________________________
10. Multi-hybrid Cross Calculation
3 characters = trihybrid cross
Parent 1: Purple flowers (PP), Yellow (Yy), Wrinkled (rr)
Parent 2: Purple flowers (Pp), Green (yy), Round (Rr)
Parents: PPYyrr X PpyyRr
Question: What percentage of the offspring from this cross
would be predicted to have the following genotypes: PpyyRr
and PPyyRr (phenotype: purple flowers and green and round
seeds)?
Step 1. Consider each character separately (make a punnett
square for each character)
Parents: PPYyrr X PpyyRr:
25. PP X Pp = ½ PP, ½ Pp
Yy X yy = ½ Yy, ½ yy
rr X Rr = ½ Rr, ½ rr
Step 2. Calculate Genotype: Calculate probability for the
genotype using the Rule of Multiplication
State the Rule of multiplication:
Probability that two or more independent events will occur
together.
PpyyRr = ½ x ½ x ½ =1/8 (rule of multiplication) chance of
offspring having this genotype
PPyyRr = ½ x ½ x ½ = 1/8 (rule of multiplication) chance of
offspring having this genotype
Additional Multiplication Rule Example
Rr Female X Rr male for a character:
Eggs = ½ will have the R allele and the other ½ will have the r
allele
Sperm = ½ will have the R allele and the other ½ will have the r
allele
-Chance of RR offspring from this cross = ½ chance of having R
egg X ½ change of R sperm fusing = multiplication rule = ¼
chance!
-Chance of rr offspring from this cross = ½ chance of having r
egg X ½ change of r sperm fusing = multiplication rule = ¼
chance!
-Chance of Rr offspring from this cross = ½ chance of having r
egg X ½ change of R sperm fusing = multiplication rule = ¼
chance!
26. -Chance of Rr offspring from this cross = ½ chance of having R
egg X ½ change of r sperm fusing = multiplication rule = ¼
chance
Step 3. Calculate Phenotype: Use the Rule of Addition to
determine the probability of offspring that have the genotype
ppyyrr (phenotype: white flowers and green and wrinkled
seeds)?
State the rule of addition:
Probability that any one of two or more exclusive events will
occur.
PpyyRr = ½ x ½ x ½ =1/8
PPyyRr = ½ x ½ x ½ = 1/8
Add them together to get the chance of having offspring with
this PHENOTYPE
=2/8 =reduce to 1/4
Additional Addition Rule Example:
There are two ways to get a Rr offspring from the cross
described in the answer for the previous step. So we will use the
addition rule to determine the fraction of Heterozygotes
expected from this cross. Chance Rr offspring from that cross =
¼ + ¼ =1/2 (addition rule)
11. Pea plants heterozygous for pea shape and color (YyRr) are
allowed to self-pollinate. What fraction of the offspring would
be predicted to have the genotype yyrr? green and wrinkled
phenotype.
(to calculate use the method for calculating offspring
probability outlined in the previous question)
Parents= YyRr X YyRr
27. Step 1. monohybrid cross for each character (construct a
punnett square for each)
Yy X Yy = 1/4YY, 1/2 Yy,1/4 yy
Rr X Rr = 1/4Rr, 1/2 Rr, ¼ rr
Step 2.Multiplication rule:
yyrr= 1/4 X 1/4 = 1/16
1/16 of the offspring will be both green and wrinkled
Step 3: Does not apply to this question because there is only
one possible offspring genotype.
14.3 Inheritance patterns are more complex than predicted by
Mendel________________
12. Describe how complete dominance differs from both co-
dominance and incomplete dominance. Provide and example of
each.
Complete = Menelian characteristics where one allele is totally
dominant over another allele. Phenotypes of homozygous
dominant and heterozygous individual are indistinguishable (Ex:
PP vs. Pp)
Codominance = when both alleles for a character are dominant
(Ex: M and N molecules on RBC. MM genotype = M molecules
only, NN genotype = N molecules only, NM genotype = BOTH
N and M molecules on RBC)
Incomplete Dominance = one allele is not completely dominant
over the other allele. Resulting in a combined or mixed
phenotype in the heterozygotes.
28. For example, if you cross-pollinate homozygous red and
homozygous white carnation flower plants, the dominant allele
that produces the red color is not completely dominant over the
recessive allele that produces the white color. The resulting
offspring are pink.
Cross true-breeding parents in P generation (RR red and WW
white)
F1 = hybrid offspring (RW pink) because in these flowers the
red allele only contributes ½ the amount of red pigment needed
for a red flower. So to have a red flower, 2 Red alleles are
required.
F2 = take two F1 organisms (RW x RW) and cross = ¼ RR red,
¼ WW white, and ½ RW pink offspring.
13. How many alleles determine human blood type? How many
different blood type phenotypes are possible?
3 alleles: A, B and O
4 phenotypes B, A, AB, O
6 genotypes BB, BO, AA, AO AB, OO
14. Can a person with type A blood receive blood from a person
with type B blood? WHY/WHY NOT?
No, B type blood has B carbohydrates molecules on its surface.
A person with type A blood will not recognize these B
carbohydrates and their immune system will think they are
foreign invaders = blood clumps
15. A woman with type O blood has a child with type B blood.
If the “father” has Type O blood, could he be this child’s
father? NO! If the mother has type O blood, her genotype must
be OO and she can only give her child an O allele. The same is
true for a father with type O blood, he can only give the child
an O allele. The child would have to have O type blood for this
29. man to possibly be the father….so “He is NOT the father!”
If the “father” had type AB blood, could he have fathered this
child?
Again, Mom give the child an O allele. This man can give the
child an A allele OR a B allele. If he gave the child the B
allele, the child would have the BO genotype, giving him type B
blood. So it is possible that he could be the father of this child.
14.4 Human traits and Mendelian
inheritance___________________________________
16. Construct a pedigree following the trait for free earlobe F
(dominant) vs. attached earlobe ff (recessive) for the following
family:
Grandparents: Ed and Lucy
Children: Peggy, Sue, Dave, Martha
Peggy marries Alec
Sue marries Dan
Dave marries Lisa
Martha is single
Grandchildren:
Peggy and Alec have two boys: Jim and Bob
Sue and Dan have no children
Dave and Lisa have one girl: Betty
Ed, Peggy and Bob have attached earlobes. Everyone else has
54. Analysis
Chapter 13 Study Guide Meiosis-ANSWERS
13.1 Chromosomes are
inherited_____________________________________________
1. Chromosomes are made of segments of DNA called
__GENES_____, which are found at specific places along the
chromosome called a___LOCUS________.
2. Compare and contrast asexual and sexual reproduction.
Asexual- parent produces identical cell by mitosis = offspring a
clone of parent
Sexual- egg or sperm produced by meiosis = offspring are not
clones of parents because they have a set of chromosomes from
each parent.
13.2 Meiosis and Fertilization alternate in sexual life
cycles________________________
3. What cells undergo Meiosis? Where are these cells located in
the human body?
Certain Diploid cells located in the male or female gonad
ONLY. These cells undergo meiosis to produce gametes or sex
cells, egg or sperm. NO OTHER CELLS IN YOUR BODY
UNDERGO THIS PROCESS!
4. A human has 46 chromosomes. How many of these
chromosomes were inherited from Mom? 23
5. What is a karyotype and at what stage in the cell cycle can
one be constructed?
Ordered representation of homologous chromosomes usually
constructed from a prophase cell. Chromosomes are ordered
from largest to smallest. The sex chromosomes (XX or XY) are
placed last, at the bottom right of the karyotype.
6. What are Homologous chromosomes? What is each
homologue composed of during mitotic phases of the cell cycle?
55. -2 chromosomes with same length, centromere position and
order of genes (although the type of gene may be different).
One homologue was inherited from mom, the other homologue
was inherited from dad.
-Each homologue is composed of 2 sister chromatids (when the
cell is preparing to divide) until anaphase of mitosis or
anaphase 2 of meiosis.
7. What is the difference between autosomes and sex
chromosomes?
Autosome- any homologue that is not an X or Y chromosome.
All autosomes have a homologue.
Sex chromosomes- X or Y chromosome that determines gender
of organism. If you are a female XX, you have a homologous
chromosome. If you are a male XY, you do not have a
homologus chromosome for this chromosome. The X
chromosome is very large and contains many more genes
compared to the Y chromosome. We will discuss this further in
chapter 15.
8. An organism has a diploid number of chromosomes 2n = 48.
What is the haploid chromosome number? 24
13.3 Meiosis reduces chromosome
number_____________________________________
9. Describe the major event(s) that occur in each stage of
Meiosis:
Interphase- cell grows, organelles produced, copy DNA
Prophase I- chromosomes condense, homologous chromosomes
come together to form tetrads, non-sister chromatids crossover
(exchange genetic material) places where these crossing over
events occur are called chiasmata
Metaphase I- Homologous chromosomes line up together (in
tetrads) on the metaphase plate.
56. Anaphase I- Homologous chromosomes move to opposite poles
of the cell
Telophase I and cytokinesis- 2 haploid daughter nuclei form
followed by division of cytoplasm (cytokinesis)
Prophase II- in each daughter cell, spindle forms,
Metaphase II- sister chromatids line up on metaphase plate
Anaphase II- sister chromatids move to opposite poles of the
cell
Telophase II and cytokinesis- 4 haploid nuclei form followed by
cytokinesis to form 4 haploid cells
10. How many cell division events take place during meiosis? 2
11A. How is metaphase of Meiosis I different from metaphase
in mitosis?
Metaphase Meiosis = homologous chromosomes line up together
on metaphase plate.
Metaphase Mitosis = homologous chromosomes do not line up
together on metaphase plate.
11B. Identify and describe at least 2 more events that
distinguish meiosis from mitosis.
1. Homologous chromosomes line up together on metaphase
plate during meiosis I
2. Non-sister chromatids of homologous chromosome pairs
cross over during prophase of meiosis I
3. During anaphase I of meiosis homologues separate, during
anaphase I of Mitosis sister chromatids separate
13.4 Genetic
70. 2. Each chromosome contains many ____Genes__________,
which are segments of the chromosome that codes for a certain
polypeptide (protein).
3A. In what stages of the cell cycle are chromosomes visible
under the microscope?
The chromosomes become visible during prophase and remain
visible through mitosis (prophase( metaphase( anaphase(
telophase) and begin to de-condense during telophase of
mitosis.
B. Why are they visible during these stages?
Chromosomes duplicate and condense during prophase of
mitosis making them visible under a microscope. They condense
in order to more easily distribute the correct amount of DNA
into each daughter cell.
4. Explain the basic differences between Mitosis and Meiosis.
Name a cell type that undergoes Mitosis. Name a cell type that
undergoes Meiosis.
Mitosis = results in two identical daughter cells ex: skin cell
Meiosis = results in four non-identical haploid cells ex: cells in
gonads
5. Starting with a fertilized egg (zygote), a series of four
mitotic cell divisions would produce an early embryo with how
many cells?
1 cell ( 2 cells ( 4 cells( 8 cells( 16 cells
Each arrow represents a mitotic cell division
6A.What is the name given to the duplicated chromatids of a
chromosome when they are still attached to one another during
the first half of mitosis?
71. sister chromatids
6B. What are these chromatids called after they split during
anaphase of mitosis?
Chromosomes
12.2 Mitotic
phases_______________________________________________
_________
7. Specific events occur during interphase to prepare the cell for
Mitosis. Interphase is divided into 3 sub-phases. Name each
sub-phase and describe the events that occur during each sub-
phase.
G (Growth) 1= growth, manufacture organelles and proteins
S (synthesis) phase= Chromosome duplicate
G (Growth) 2 = growth, manufacture organelles and proteins
8. List (in order) starting with Interphase, the 5 phases of the
cell cycle and give a brief description of the major events that
occur in each phase. (Use the powerpoint slides as a guide for
the amount of detail you need to know about each stage)
Interphase-
G (Growth) 1= growth, manufacture organelles and proteins
S (synthesis) phase= Chromosome duplicate
G (Growth) 2 = growth, manufacture organelles and proteins
Prophase
-Duplicated Chromosomes appear as 2 sister chromatids
connected at the centromere
-Mitotic spindle forms in cytoplasm from centrosomes
Metaphase
72. -Mitotic spindle fully formed
-Duplicated Chromosomes line up on metaphase plate located in
middle of the cell
-Each sister chromatid is attached to a spindle fiber
Anaphase
-Sister chromatids are pulled apart and taken to opposite poles
of the cell by the spindle fibers
-Cell elongates
Telophase
-Roughly opposite prophase:
-Nuclear envelopes begin to reform around chromosomes
-Chromosomes begin to uncoil
-Mitotic spindle disappears
-Mitosis complete!
9. The average human cell can complete the cell cycle in
approximately 24hrs. The cell spends most of its time in one
phase of the cell cycle. Identify this phase and explain why so
much time is spent in this phase.
Interphase- Much needs to be accomplished before a cell can
divide. The cell spends nearly the entire cell cycle in interphase
for this reason.
Interphase events:
73. G (Growth) 1= growth, manufacture organelles and proteins
S (synthesis) phase= Chromosome duplicate
G (Growth) 2 = growth, manufacture organelles and proteins
10. Identify the function of centrosomes in mitosis.
Located outside nucleus, microtubules extend from centrosomes
to form the spindle
11. A spindle is considered complete when…? (i.e. What major
events must occur/structures form?)
Spindle microtubules are attached to sister chromatids, asters
extend from centrosomes attaching to cell membrane
12. We discussed an experiment that explained how the
chromosomes move to opposite poles of the dividing cell during
anaphase. Two hypothesis were made:
Hypothesis #1:chromosomes are pulled to the poles: spindle
fibers shorten at their spindle pole (centrosome) ends. The
spindle fiber pulls the chromosome to the spindle pole, like a
horse (chromosome) being lassoed by a rope (spindle fiber).
Hypothesis #2: chromosomes walk to the spindle poles: spindle
fibers shorten at their kinetochore (part of chromosome that is
attached to the spindle fiber) ends. The chromosome “walks
down” the spindle fiber and the spindle fiber dismantles behind
the chromosome.
A. Describe this experimental design and the experimental
results.
Experimental Design: The spindle was tagged with a fluorecent
marker. Florecence was then removed from a specific region of
the splindle at time A. (the spindle fibers in this region were
still present, only the fluorecent tag was removed). Mitosis
proceeded and another picture was taken at a later time B. The
74. two pictures were then compared. The region of the spindle
where the fluorescence had been removed had not moved, but
the chromosome attached to the spindle fiber had moved closer
to the spindle pole. This tells us that the spindle fiber was
shortening (dismantling) at the kinetichore (chromosome) end
and not the spindle pole (centrosome) end. If the region of the
spindle where the fluorescence had been removed had moved
closer to the spindle pole at time B compared to time A, then we
would have concluded that the spindle fiber was shortening
(dismantling) at the spindle pole (centrosome) end
B. Which hypothesis was accepted? #2
13A. Define: Cytokinesis (Hint: break this word down into
“cyto” and “kinesis”…what do these words mean?)
Cyto- as in “Cytoplasm”
Kinesis- means “ to cut”
Cytoplasm cutting!
13B. How do the processes of Mitosis and Cytokinesis differ?
Mitosis = duplicate chromosomes
Cytokinesis = divide cell into two daughter cells
13C. How does cytokinesis in animal cells and plants cells
differ?
Animal- microfilaments form ring around center of dividing cell
and contract to form two new cells
Plant- golgi vesicles containing cell wall material migrate to
center of dividing cell to form cell plate
14A. Prokaryotes reproduce by a process called ____binary
fission___________.
75. 14B. Describe the process of prokaryote cell division using the
following terms:
origin of replication, genome replication, cell elongation, cell
division (cytokinesis)
1. Origin of replication is duplicated
2. One copy of origin of replication moves to opposite end of
cell
3. Genome Replication
4. Cell elongates
5. Cell divides
15. List at least 1 structural similarity and at least 2 structural
differences between bacterial (prokaryotic) chromosomes and
eukaryotic chromosomes
Structural Similarities:
Both are made of DNA and associated proteins
Structural Differences:
Eukaryotic chromosomes are linear, many chromosome are
present in a nucleus.
Prokaryotic chromosome circular, single chromosome NOT
surrounded by nucleus
16. List at least 1 functional similarity and at least 1 functional
difference between bacterial (prokaryotic) chromosome and
76. eukaryotic chromosome behavior during cell division.
Functional Similarities:
Both duplicate their DNA before the cell divides
Both divide into two cells
Functional Differences:
Eukaryotic chromosomes move to opposite poles of cell by
spindle fibers
Prokaryotic chromosome do not use spindle to move to opposite
poles of the cell
12.3 Cell Cycle
Regulation____________________________________________
______
17. Name the three checkpoints in the cell cycle. How do they
function (in general) to control the cell cycle?
G1, G2, M
The cell must have certain molecules available in certain
quantities in order to pass the checkpoint and proceed to the
next stage of the cell cycle.
18. What molecules control the G2 Checkpoint?
Cyclin dependent kinase (cdk) and cyclin. When the two
molecules join it is called MPF- Maturation Promoting Factor
19. How do cyclins and Cdk’s interact to control the G2
checkpoint?
Cdk’s are present throughout the cell cycle, whereas cyclins
accumulate just before the G2 checkpoint. Cdk’s are inactive
without cyclins. If MPF (the cdk-cyclin complex) is not present
77. before the G2 checkpoint, the cell cycle will not proceed. The
cell will be held in Interphase and not permitted to enter the
Mitotic phases of the cell cycle.
20A. According to the graph in the figure below, MPF activity
reaches its highest concentration at what stage in the cell cycle?
MPF concentration sharply increases just before the mitotic
phases of the cell cycle and reaches its highest point during the
mitotic phases.
20B. How does this correlate with MPF’s functions during that
stage in the cell cycle?
MPF phsophorylates (activates) proteins/molecules that have a
role in the events of mitosis. As a result, it is found in highest
concentration during this phase of the cell cycle!
Some events of Mitosis that MPF facilitates: dismantling the
nuclear membrane, building the spindle, sister chromatids
walking down the spindle fiber to the cell pole, etc.
21A. Describe how Platelet Derived Growth Factor (PDGF)
controls the cell cycle of fibro.
PDGF is released from Platelets in the area of an injury.
(Platelets are a type of blood cell present in the blood stream.
They also have a role in blood clotting.) PDGF binds to
fibroblast cells (connective tissue cells) at the site of the injury,
which causes these cells to divide. This will allow the injured
tissue to eventually heal.
21B. Is this control present in cancer cells? Why/Why not?
No. Cancer cells do not respond to normal cell cycle signals
22. Distinguish among benign, malignant and metastatic tumors.
Benign = cancer cells localized to one part of an organ or
tissue. The cells are tightly bound to one another. Due to its
structure, this type of tumor is more easily removed compared
99. Review!Ch. 12:Cell Cycle Control
Molecular signals
Internal
G2 = MPF (cyclin +CdK)
ExternalCancer
DATE___________________
Chapter 12- Cell Cycle
1. Phases of the cell cycle- An organism’s body cells have 4
chromosomes.
A. Identify the major characteristics of each phase.
B. OPTIONAL-Draw a picture to illustrate these characteristics.
Cell Cycle Phase
A. Characteristics of phase
B. OPTIONAL-Illustration of phase
Interphase
G1-
S-
G2-
Prophase
Metaphase
Anaphase
100. Telophase
Cytokinesis
-A researcher treats cells with a chemical that prevents DNA
synthesis. This treatment traps the cells in which part of the cell
cycle?
#2 OPTIONAL PRACTICE
2. Phases of the cell cycle- An organism’s body cells have 2
chromosomes
A. Identify the major characteristics of each phase.
B. Draw a picture to illustrate these characteristics.
Cell Cycle Phase
A. Characteristics of phase
B. Illustration of phase
Interphase
G1-
S-
G2-
Prophase
Metaphase
Anaphase
101. Telophase
Cytokinesis
3. During anaphase, do kinetochore microtubules:
Hypothesis #1: shorten at their spindle pole ends?
Hypothesis #2: shorten at their kinetochore ends?
EXPERIMENTAL RESULT:
-CONCLUSION:
-What observation would have to have been made to support the
OTHER hypothesis?
4A. Cyclin combines with Cyclin Dependent Kinase (CdK) to
form Maturation Promoting Factor (MPF). The Cyclin
concentration and MPF activity during the cell cycle are shown
in the figure below. Describe where a line on the graph would
be drawn to represent the CdK concentration through the cell
cycle.
B. Using your understanding of the molecules that control the
G2 checkpoint and the graph above, make at least one statement
about when these molecules are present & absent during the cell
cycle and how this results in cell cycle control.
5. Tumors
Benign
Malignant
102. Metastatic
Describe basic structure of this tumor.
Cancerous cells?
Localized to single tissue/organ?
Prognosis (good/fair/poor)
Typical treatment?
Chapter 13-Meiosis and Sexual Life Cycles
1. Important Terminology: Match the terms listed below with
the appropriate letter in the figure below.
Sister chromatids
Nonsister chromatids
Homologous pair
Centromere
104. Anaphase I
Telophase I & cytokinesis
Prophase II
Metaphase II
Anaphase II
Telophase II & cytokinesis
#4 OPTIONAL PRACTICE
4. Phases of Meiosis- An organism’s body cells have 2
chromosomes (1 pair)
A. Identify the major characteristics of each phase that differs
from Mitosis.
B. Draw a picture to illustrate these characteristics.
Meiosis Phase
A. Characteristics of phase that differs from Mitosis
B. Illustration of phase
Interphase
Prophase I
105. Metaphase I
Anaphase I
Telophase I & cytokinesis
Prophase II
Metaphase II
Anaphase II
Telophase II & cytokinesis
5. Fruit flies have a diploid number of 8, and honeybees have a
diploid number of 32. Assuming no crossing over, is the genetic
variation among offspring from the same two parents likely to
be greater in fruit flies or honeybees? Explain.
Chapter 14-Mendel and the Gene Idea
1. Genetics Terminology
Match each commonly used genetics term with its appropriate
definition or example.
TERMS:DEFINITIONS AND EXAMPLES:
106. __ heterozygous
a. Blue-eyed blonde mates with brown-eyed brunette
__ homozygous
b. BB or bb
__ monohybrid cross
c. not on sex chromosomes
__ autosomal
d. blue or brown eyes
__ genotype
e. Bb
___ phenotype
f. locus on a chromosome that codes for a given polypeptide
__ gene
g. Blonde mates with brunette.
__ allele
h. BB, Bb, or bb
__ dihybrid cross
i. Males have only one for each gene on the X chromosome
2. Make a punnett square using the following information.
Traits: Oval eyes = A, Round eyes = a
107. Parents: Mom Aa, Dad aa
-What eye shape does Mom have?
-What eye shape does Dad have?
-What fraction of the offspring will have oval eyes?
-What fraction of the offspring will have round eyes?
-What fraction of the offspring will have the Homozygous
Dominant genotype AA?
-What fraction of the offspring will have the Heterozygous
genotype Aa?
-What fraction of the offspring will have the Homozygous
Recessive genotype aa?
3. Make a punnett square using the following information.
Traits: Brown eyes = B, Blue eyes = b
Parents: Mom Bb, Dad Bb
-What eye color does Mom have?
-What eye color does Dad have?
-What fraction of the offspring will have brown eyes?
-What fraction of the offspring will have blue eyes?
-What fraction of the offspring will have the Homozygous
Dominant genotype BB?
-What fraction of the offspring will have the Heterozygous
108. genotype Bb?
-What fraction of the offspring will have the Homozygous
Recessive genotype bb?
4. Multi-hybrid cross #1:
3 characters = trihybrid cross
Parent 1: Purple flowers (Pp), Yellow (Yy), Round (Rr)
Parent 2: Purple flowers (Pp), green (yy), wrinkled (rr)
Parents: PpYyRr X Ppyyrr
Question: What percentage of the offspring from this cross
would be predicted to have the following genotypes: Ppyyrr,
PPyyrr
1. Consider each character separately (make a punnett square
for each character)
Parents: PpYyRr X Ppyyrr:
Pp X Pp =
Yy X yy =
Rr X rr =
2. Calculate probability for each genotype using the Rule of
Multiplication
Ppyyrr ½ x ½ x ½ = 2/16
PPyyrr
3. Use the Rule of Addition to determine the probability of
offspring that have the following genotypes:
Ppyyrr =2/16
109. PPyyrr =
5. Multi-hybrid Cross #2
3 characters = trihybrid cross
Parent 1: White flowers (pp), Yellow (Yy), Wrinkled (rr)
Parent 2: Purple flowers (Pp), Green (yy), Round (Rr)
Parents: ppYyrr X PpyyRr
Question: What percentage of the offspring from this cross
would be predicted to have the following genotypes: ppyyrr
(phenotype: white flowers and green and wrinkled seeds)?
1. Consider each character separately (make a punnett square
for each character)
Parents: ppYyrr X PpyyRr:
pp X Pp =
Yy X yy =
rr X Rr =
2. Calculate probability for the genotype using the Rule of
Multiplication
ppyyrr=
3. Use the Rule of Addition to determine the probability of
offspring that have the genotype ppyyrr (phenotype: white
flowers and green and wrinkled seeds)?
6. Pedigree for a recessive trait. Determine the genotype and
phenotype of each individual in the pedigree shown below. Use
A for dominant, a for recessive.
110. 7. Joan was born with six toes on each foot, a dominant trait
called polydactyly. Two of her five siblings and her mother, but
not her father, also have extra digits. Draw a pedigree inclucing
all family members mentioned in the question. Use D and d to
symboloze the alleles for this character. What is Joan’s
genotype for the “number-of-digits” character?
Chapter 15-The Chromosomal Basis of Inheritance
1. A heterozygous brown-eyed human female who is a carrier of
color blindness marries a blue-eyed male who is not color-blind.
Color blindness is a sex-linked trait. Assume that eye color is
an autosomal trait and that brown is dominant over blue. What
is the probability that any of the offspring produced have the
traits listed? Construct two punnett squares, one for hair color
and one for color blindness.
Eye color (autosomal trait):
B
b
b
b
Color blindness (sex-linked trait):
XA
Xa
XA
Y
111. a. Brown eyes
b. Blue eyes
c. Color blind OFFSPRING?
d. What fraction of the MALE OFFSPRING will be color-blind?
e. What fraction of the FEMALE OFFSPRING will be color-
blind?
f. What fraction of the FEMALE OFFSPRING will be carriers
for colorblindness?
g. What fraction of the MALE OFFSPRING will be carriers for
colorblindness?
h. What fraction of the TOTAL OFFSPRING will have Brown-
eyes and be color-blind?
i. Why do males show sex-linked traits more often than
females?
2A. Describe the process of X inactivation in female mammal
body cells.
2B. Why does this process not occur in male mammal body
cells?
2C. Discuss at least one possible reason for this phenomenon.
3. Construct a linkage map using the following gene
recombination frequencies.
112. The Recombination Frequency between characters:
A and B = 30%, A and C = 20%, and B and C = 10%.
4. Rip two long strips of paper from a piece of scrap paper. On
the end of each strip of paper write “A B C D”. These letters
represent gene alleles on non-sister chromosomes that are
crossing over during prophase I of meiosis. Rip one strip
between the B and C and Rip the other strip between the C and
D. Transfer the pieces you ripped off to the other non-sister.
Record the sequence of alleles on each non-sister below.
Sequence on non-sister 1:
Sequence on non-sister 2:
-What type of chromosome alterations have occurred?
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A
B
C
D