Download Mutations and Genetic Variability 1. What is occurring in the diagram

Mutations and Genetic Variability
1. What is occurring in the diagram below?
A. Sister chromatids are separating.
B. Alleles are independently assorting.
C. Genes are replicating.
D. Segments of DNA are crossing over.
2. The chart below shows the codons that make up the genetic code and the sequence of nucleotides that
corresponds to them.
A mistake during DNA replication leads to a mutation in the nucleotide sequence shown below.
This mutation results from the insertion of two nucleotides into the original sequence, which causes the reading
frame of the sequence to change. This kind of mutation is known as
A. a nonsense mutation.
B. a silent mutation.
C. a chromosomal mutation.
D. a frame shift mutation.
3. Dr. Stevens is examining the DNA sequences of a group of mice. He notices that in one of the mice, one
nucleotide pair is substituted with another in the part of the DNA sequence that codes for fur color. However,
despite the substitution, the mouse still has the same fur color as the other mice with the correct DNA
sequence.
Why doesn't the substitution of nucleotides in the mouse change its phenotype, or physical characteristics?
A.
B.
C.
D.
The mouse has a completely different DNA sequence than the other mice.
The substituted nucleotide has the same directions as the original nucleotide.
Substitutions in the nucleotides of a mouse's DNA never affect their phenotypes.
DNA sequences don't determine the color of a mouse's fur.
4. Which of the following is a source of genetic variation in sexually-reproducing organisms?
A. mitosis
B. translation
C. meiosis
D. all of these
5. Most heritable differences are due to
A. the insertion of incorrect sequences of DNA by faulty polymerases.
B. point mutations that occur during mitosis.
C. the inability to form proper DNA sequences due to poor nutrition.
D. gene shuffling that occurs during the production of gametes.
6. The chart below shows the codons that make up the genetic code and the sequence of nucleotides that
corresponds to them.
A mistake during DNA replication leads to a mutation in the nucleotide sequence shown below.
What kind of mutation will result from the mistake made during DNA replication in the nucleotide sequence
above?
A. a frame shift mutation
B. a nonsense mutation
C. a silent mutation
D. a chromosomal mutation
7. A frame shift mutation is a genetic mutation that is caused by the insertion or deletion of a specific number of
nucleotides that shifts the reading frame of the sequence.
The insertion or deletion of how many nucleotides would cause a frame shift mutation?
A. 3
B. 2
C. 9
D. 6
8. How do mutations lead to genetic variation?
A. by changing the organism's appearance
B. by changing the way that the organism reproduces
C. by changing the organism's behavior
D. by producing random changes in an organism's genetic code
9. How could an apple farmer increase the number of genotypes and phenotypes present in his next apple
crop?
A. Cross plants that have the same characteristics.
B. Cross plants that have very different characteristics.
C. Make genetic clones of plants using asexual reproduction.
D. It would be impossible for a farmer to increase the genetic variation of plants.
10. Down syndrome is a genetic disorder that is typically caused by an extra copy of chromosome 21 in a
person's genome. In a small number of cases, however, Down syndrome occurs because a section of
chromosome 21 becomes fused onto another chromosome.
The type of Down syndrome that occurs because a section of chromosome 21 attaches to another
chromosome is an example of a genetic disorder caused by
A. chromosome deletion.
B. chromosome translocation.
C. a recessive allele.
D. a frame shift mutation.
11. Triple X syndrome, or trisomy X, occurs when a female has an extra X chromosome in each of her cells.
This results when the mother's reproductive cells divide improperly, and two X chromosome are moved into
one gamete. When that gamete is fertilized and the father's DNA and X chromosome are combined with the
mother's, that gives the cell three X chromosomes instead of two.
Triple X syndrome occurs because of _______.
A. deletions
B. crossing over
C. point mutations
D. nondisjunction
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13. During meiosis, the process of crossing over results in new combinations of alleles because
A. genetic material always mutates randomly during this process.
B. genetic material is added by a third chromosome during this process.
C. genetic material is removed during this process.
D. genetic material is exchanged between chromosomes during this process.
14. Organisms are able to reproduce either sexually or asexually. Which of the following statements is true of
these reproductive processes?
A.
B.
C.
D.
The sorting of genes during sexual reproduction results in a large amount of genetic variation.
During every cell division in sexual reproduction, the number of chromosomes is reduced by half.
During every cell division in asexual reproduction, the number of chromosomes is reduced by half.
The sorting of genes during asexual reproduction results in a large amount of genetic variation.
15. The diagram below illustrates a process that can occur during cell division and results in an alteration in the
composition of a chromosome. Each letter in the diagram represents a specific gene on the chromosome.
The diagram shows that a section of the chromosome was broken out and reinserted backwards. This is
known as
A. chromosome translocation.
B. chromosome insertion.
C. chromosome inversion.
D. chromosome deletion.
16. The diagram below shows a process that can result in the alteration of the composition of chromosomes.
A piece of each chromosome in the diagram has broken off and been reattached to the other chromosome,
resulting in an exchange.
The process that occurs when a section of a chromosome breaks off and reattaches to another chromosome is
known as _______.
A. chromosome nondisjunction
B. chromosome deletion
C. chromosome inversion
D. chromosome translocation
17. A genetic mutation that causes a codon that should code for a specific amino acid to be changed into a
stop codon results in a shortened protein product and is known as
A. a frame shift mutation.
B. a silent mutation.
C. a nonsense mutation.
D. a chromosomal mutation.
18. Technology Enhanced Questions are not available in Word format.
Disease
Characteristics
Cause
Cri-du-chat
Syndrome
(Cry of the Cat)





improperly developed larynx
babies cry like distressed cats
severe mental retardation
small round faces
small cranium
deletion of parts of chromosome 5
Edward's
Syndrome
(Trisomy 18)





extra chromosome 18

severe mental retardation
elongated skull
very narrow pelvis
feet with round bottoms
two central fingers grasped by thumb and
little finger
death in early infancy







mild to severe retardation
short height
broad hands
stubby fingers and toes
round face
large protruding tongue
speech difficulties
extra chromosome 21
Down Syndrome
(14-21
Translocation)

same as Trisomy 21
extra chromosome 21 attached to
chromosome 14
Turner's Syndrome
(XO)


female appearance
infertility
lack of a second sex chromosome
Klinefelter's
Syndrome
(XXY)


female characteristics
infertility
extra X chromosome
Down Syndome
(Trisomy 21)
19. A cat's coloring is mostly determined by genes on their X chromosomes, which contain alleles for colors,
such as black, orange, gray, and cream. The allele for white fur is located on a different gene.Calico cats, by
definition, must display three different colors in their fur - white plus two of the other colors. This is easily
possible in female cats, because females normally possess two X chromosomes. However, this occurs rarely
in male cats, because males typically possess only one X chromosome plus one Y chromosome.What must be
the genetic make-up of a male calico cat, and what type of chromosome disorder does this most resemble?
A. XO, Turner's syndrome
B. XX, Down's syndrome
C. XYY, Cri-du-chat syndrome
D. XXY, Klinefelter's syndrome
20. Errors that are made during DNA replication may result in
A. a viral infection.
B. mutations.
C. identical twins.
D. radioactive decay.
21. Technology Enhanced Questions are not available in Word format.
22. A genetic mutation that does not result in a change in the amino acid sequence of the resulting protein is
called
A. a silent mutation.
B. a frame shift mutation.
C. a nonsense mutation.
D. a chromosomal mutation.
The table below shows various DNA codons and their corresponding amino acids.
Amino Acid
DNA Codon(s)
Alanine
GCT, GCC, GCA, GCG
Arginine
AGA, AGG, CGT, CGC, CGA, CGG
Asparagine
AAT, AAC
Aspartic Acid
GAT, GAC
Cysteine
TGT, TGC
Glutamic Acid
GAA, GAG
Glutamine
CAA, CAG
Glycine
GGT, GGC, GGA, GGG
Histadine
CAT, CAC
Isoleucine
ATT, ATC, ATA
Leucine
CTT, CTC, CTA, CTG, TTA, TTG
Lysine
AAA, AAG
Methionine (Start) ATG
Phenylalanine
TTT, TTC
Proline
CCT, CCC, CCA, CCG
Serine
TCT, TCC, TCA, TCG, AGT, AGC
Threonine
ACT, ACC, ACA, ACG
Tryptophan
TGG
Tyrosine
TAT, TAC
Valine
GTT, GTC, GTA, GTG
Stop
TAA, TAG, TGA
23. In the DNA strand below, two nucleotides were reversed during replication.
What will happen when the replicated DNA strand is translated into proteins?
A. No proteins will be formed at all.
B. Nothing will happen.
C. The same protein, isoleucine, will be formed.
D. Tyrosine will be formed instead of isoleucine.
24. An organism's genotype describes its specific combination of alleles. For example, an Aa genotype is
heterozygous for the A allele.
An organism's phenotype describes a visible trait, such as tall height, brown eyes, or black fur.
How does genotypic variation occur?
A.
B.
C.
D.
Genotypic variation occurs when alleles are randomly sorted during asexual reproduction.
Genotypic variation occurs when alleles are randomly sorted during sexual reproduction.
Genotypic variation only occurs when genetic mutations occur.
Genotypic variation only occurs during binary fission.
25. The chart below shows the codons that make up the genetic code and the sequence of nucleotides that
corresponds to them.
A mistake during DNA replication leads to a mutation in the nucleotide sequence shown below.
What kind of mutation will result from the mistake made during DNA replication in the nucleotide sequence
above?
A. nonsense mutation
B. silent mutation
C. frame shift mutation
D. chromosomal mutation
26. When environmental conditions change, it is more likely that at least some members of a species will
survive if
A. the species reproduces asexually.
B. the members are genetically identical.
C. there is variation among the members.
D. the species requires very specific environmental conditions.
27. During meiosis, homologous chromosomes frequently exchange portions of their DNA. This process
increases the number of different genotypes that an offspring can inherit. What is the name of this process?
A. genetic transfer
B. transduction
C. crossing-over
D. mutation
28. During normal meiosis, homologous chromosomes pair up and separate so that each gamete receives a
copy of every chromosome.
Sometimes an error is made during this separation and homologous chromosomes fail to separate. This
results in one gamete that has two copies of the chromosome, and another gamete that does not have the
chromosome at all.
This type of error is known as _______ and usually results in zygotes that either do not develop to term or
have severe abnormalities.
A. chromosome translocation
B. chromosome insertion
C. chromosome inversion
D. chromosome nondisjunction
29. ______ is a source of genetic variation that involves the swapping of sections of chromosomes during
meiosis.
A. Fertilization
B. Transcription
C. Translation
D. Crossing over
30. Technology Enhanced Questions are not available in Word format.
Answers
1. D
2. D
3. B
4. C
5. D
6. B
7. B
8. D
9. B
10. B
11. D
12. -13. D
14. A
15. C
16. D
17. C
18. -19. D
20. B
21. -22. A
23. D
24. B
25. B
26. C
27. C
28. D
29. D
30. -Explanations
1. In the diagram, segments of DNA from homologous chromosomes are crossing over. This process,
which occurs during Prophase I of meiosis, happens randomly and frequently. In fact, it can even occur at
more than one place along the same chromosome.
Meiosis and crossing-over are important processes because they contribute to the genetic variation found in
organisms that undergo sexual reproduction.
2. Frame shift mutations cause the reading frame of the sequence to be shifted. Since a codon is a sequence
of three nucleotides that code for a specific amino acid, any insertion or deletion that is not a sequence of three
causes a frame shift mutation.
Insertions or deletions in multiples of 3 will cause a protein to be shorter or longer than normal, but the entire
sequence of the amino acids will not be shifted.
3. A mutation (substitution, insertion, deletion, etc.) can cause changes in the phenotype of an organism.
These changes may be beneficial and produce organisms that are better suited to their environments, or they
may be detrimental. However, in some cases, there is no effect, and a change of phenotype does not occur. If
a mutation occurs that does not dramatically change the DNA sequence, it is possible that it can be translated
properly into proteins.
In this example, the substituted nucleotide provides the same directions as the original nucleotide. This
occurs when one nucleotide is replaced with another, but the resulting nucleotide group (codon) still codes for
the same protein. If the protein that is made is the same as it would normally be, the mutation is called a silent
mutation, and the organism's phenotype will be normal.
4. In sexually-reproducing organisms, meiosis helps contribute to genetic variation. Meiosis is the process by
which sexually-reproducing organisms produce gametes, or sex cells. Meiosis produces gametes that are
unique from each other and from the "parent genome". The gametes will be passed on to future offspring.
5. Many factors can cause a change in a gene over time. However, most heritable differences are due to gene
shuffling that occurs during the production of gametes. Gametes are produced when cells undergo
meiosis.
Mutations or changes in DNA sequences can occur spontaneously, but this happens infrequently.
6. As shown in the chart, UGU codes for cysteine (Cys), but the mutated mRNA codon, UGA, is a stop codon,
which signals the end of transcription. This is a nonsense mutation, which is a mutation that changes a codon
that codes for a specific amino acid into a stop codon.
If the mutation occurs during DNA replication, the mRNA strand that is produced will result in a shortened
protein product. The earlier in a nucleotide sequence that this mutation occurs, the shorter the resulting protein
will be.
7. Frame shift mutations cause the reading frame of the sequence to be shifted. Since a codon is a sequence
of three nucleotides that code for a specific amino acid, any insertion or deletion that is not a sequence of three
causes a frame shift mutation. Therefore, the insertion or deletion of 2 nucleotides would cause a frame shift
mutation.
Insertions or deletions in multiples of 3 will cause a protein to be shorter or longer than normal, but the entire
sequence of the amino acids will not be shifted.
8. A mutation is a random change in a cell's genetic code due to a variety of causes. The change can be
small and insignificant, or it can be major. Mutations can be passed on to offspring through reproduction, thus
increasing the genetic variation within a population.
9. Farmers can enhance the genotypic variety of their crops by crossing crops with very different
characteristics, resulting in new combinations of alleles. This genotypic variety will result in phenotypic
variety.
10. Chromosome translocation is caused when material is exchanged between two chromosomes or part of
one chromosome becomes fused onto another chromosome. Some human disorders are caused by
chromosome translocation, such as cancer, infertility, and translocation Down syndrome.
Translocation Down syndrome is caused by a piece of chromosome 21 fusing onto another chromosome. It
accounts for less than 5% of the total cases of Down syndrome reported.
11. Syndromes such as triple X syndrome, Turner's syndrome, Down syndrome, and Klinefelter's syndrome
occur because of nondisjunction, or the improper separation of the chromosomes during division. In each of
these cases, an extra chromosome (X chromosome for triple X, chromosome 21 for Down syndrome, etc.)
causes symptoms in the offspring. In some syndromes, such as triple X syndrome, the symptoms are often not
very noticeable.
12. -13. During meiosis, the process of crossing over results in new combinations of alleles because genetic
material is exchanged between homologous chromosomes during this process.
When crossing over occurs, different parts of chromosomes are exchanged, meaning that genes (and their
alleles) are transferred to new chromosomes. When meiosis separates these chromosomes, the new
combination of alleles is transferred to the offspring, resulting in a new combination of traits.
14. Binary fission, budding, and spore formation are all examples of asexual reproduction. This form of
reproduction is prevalent among single-celled organisms and some plants and fungi. Although asexual
reproduction is faster and requires less energy than sexual reproduction, offspring are almost always
genetically identical to their parents; there is little to no genetic variation.
Sexual reproduction requires the formation of gametes (e.g. sperm and egg) during the process of meiosis.
The advantage of sexual reproduction is that a great variety of possible gene combinations can be
produced in the offspring of any two parents. This variety is due to the sorting and recombination of genes
that occurs during meiosis.
15. Chromosome inversion occurs when a section of the chromosome breaks out and is reinserted
backwards. Inversions usually do not cause physical or mental abnormalities in an individual as long as no
genetic information is lost during the inversion.
16. Chromosome translocation occurs when a section of a chromosome breaks off and is added to a
different chromosome. The type of chromosome translocation shown in the diagram is known as reciprocal
translocation, which involves the exchange of material between two chromosomes. Reciprocal translocations
are the most common type of translocation and do not result in a loss of genetic information.
17. A nonsense mutation is a mutation that changes a codon that codes for a specific amino acid into a stop
codon. This results in a shortened protein product. The earlier in a nucleotide sequence that this mutation
occurs, the shorter the resulting protein will be.
18. -19. As mentioned in the question, a calico pattern can only result if a cat has two X chromosomes, but in order
for a cat to be male, it must also possess a Y chromosome. So, a male calico cat must have XXY
chromosomes.
This pattern is also possessed by humans with Klinefelter's syndrome.
20. Errors that are made during DNA replication may result in mutations.
Mutations are a source of variation within species. Some mutations are harmless, while others may be harmful
to an organism.
21. --
22. A silent mutation is a mutation that does not result in a change in the amino acid sequence of the
resulting protein.
Most amino acids are coded by several different codon sequences. Therefore, a mutation can occur that
changes the nucleotide sequence, but does not change the resulting amino acid. These mutations are referred
to as silent because they do not change the product of protein translation and cannot be detected without
sequencing the gene.
23. If two or more nucleotides are reversed, it is possible for the same protein to be translated, or a different
protein may be translated. In this case, ATT codes for isoleucine, whereas TAT codes for tyrosine. So,
tyrosine will be formed instead of isoleucine.
If the T in the 5th position and the T in the 6th position had been reversed, however, the same codon (ATT)
would have resulted, and the same protein would have been translated. When a mutation occurs that does not
affect the amino acid sequence of a protein, it is known as a silent mutation.
24. Genotypic variation occurs when alleles are randomly sorted during sexual reproduction. Since
each offspring receives a different combination of alleles from the parent organisms, phenotypic diversity
results. Genotypic and phenotypic traits can be predicted using Punnett squares.
25. As shown on the chart, both CCU and CCC code for proline (Pro). This means that the mistake made
during DNA replication in the nucleotide sequence in the question will result in a silent mutation, which is a
mutation that does not result in a change in the amino acid sequence of the resulting protein.
Most amino acids are coded by several different codon sequences. Therefore, a mutation can occur that
changes the nucleotide sequence, but does not change the resulting amino acid. These mutations are referred
to as silent because they do not change the product of protein translation and cannot be detected without
sequencing the gene.
26. When environmental conditions change, it is more likely that at least some members of a species will
survive if there is variation among the members. This is because the variant organisms within the species
are able to respond differently to the environmental changes.
27. Crossing-over is a process that typically occurs during prophase I of meiosis. During this phase,
homologous chromosomes are held tightly together which enables the exchange of segments of DNA.
Crossing-over is an important process because it introduces more genetic variation into a species.
28. Chromosome nondisjunction occurs when homologous chromosomes fail to separate during meiosis.
The result of chromosome nondisjuction is the formation of one gamete that does not have the chromosome
and another gamete that has two copies of the chromosome.
Zygotes that have a gamete lacking a chromosome usually do not develop to term. Zygotes that have a
gamete with two copies of a chromosome, along with a normal gamete, have a total of three copies of a
chromosome and sometimes do develop, although they often have severe abnormalities.
Examples of genetic conditions caused by the presence of three chromosomes (also known as a trisomy)
include triple X syndrome, Turner's syndrome, Down syndrome, and Klinefelter's syndrome.
29. Crossing over, which occurs in prophase I of meiosis, is a process by which homologous chromosomes
swap homologous segments of DNA. This helps produce gametes that are unique from the "parent genome",
thus increasing genetic variation.
30. --