Download ch 12 quick check answers

Chapter 12
Answers
1
QUICK-CHECK questions
Identify the following statements as true or false.
a
Restriction enzymes cut DNA molecules at random sites along their length.
False: Cuts made by restriction enzymes do not occur randomly, but occur at
specific recognition sites along a double-stranded DNA molecule.
b
The restriction enzyme Aha I produces DNA fragments with sticky ends.
False: The restriction enzyme Aha I produces fragments with blunt ends (see
figure 12.5).
c
Target DNA must be denatured before it can be located with a probe.
True: Target DNA must be denatured (made single stranded) before it can be
located with a probe. The probe is single stranded and it can pair with a
complementary base sequence in the single-stranded target DNA.
d
An enzyme that can act on human DNA would not be able to act on mouse
DNA.
False: DNA has an identical composition in all living organisms and so an enzyme
that can act on DNA from one source can also act on DNA from any other source.
2
Where does in situ hybridisation occur?
In situ hybridisation occurs at a normal location in a cell. In the case of DNA, for
example, in situ hybridisation would take place at the chromosomal location of DNA
within the cell nucleus.
3
Give an example of a vector.
Vectors are carriers used to transport particular compounds. Examples of vectors used
to transport DNA into a cell include plasmids and modified viruses.
4
What raw materials are needed to build a DNA segment using a DNA
synthesiser?
Raw materials needed to build a DNA chain using a DNA synthesiser include the four
different kinds of nucleotides that differ in their base component, with the four different
bases in nucleotides found in DNA being adenine, guanine, cytosine and thymine.
(Note: The statement above reflects a highly simplified version of the chemical
synthesis of DNA. In reality, the chemical reactions that occur in a DNA synthesiser
are very complex but the end result is the production of a linear chain of nucleotides
joined in a particular order.)
5
a
Name the starting point for making copy DNA (cDNA).
The starting point for making copy DNA (cDNA) is mRNA.
b
Name the enzyme needed to make cDNA.
The enzyme needed to make cDNA is reverse transcriptase.
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Chapter 12: QUICK-CHECK answers
6
Give an example of a protein made by recombinant DNA technology.
Proteins made by recombinant DNA technology include:
 rec human insulin
 rec human growth hormone
 rec human follicle-stimulating hormone
 rec factor 8.
(See table 12.2.)
(Note: Other examples include rec human antithrombin, rec human lactoferrin and
recombinant plasma proteins additional to factor 8, including rec factor IX and rec
factor VIIa.
7
What is meant by the term ‘TGO’?
TGO means transgenic organism. This term refers to an organism that has had DNA
from another species artificially added to its genome.
8
Give an example of a plant crop that:
a
is a source of GM food in overseas countries
Genetically modified (GM) plants that are a source of food include corn and soya
beans.
(Note: At present, some GM foods that are grown overseas are approved for
consumption in Australia as ingredients of processed food; these include GM corn,
GM soya beans, and GM potato. This is a changing field; for a recent update from
CSIRO, see www.csiro.au/news/ps3nu.html.
b
has been engineered to contain the Bt toxin gene.
The Bt toxin gene has been engineered into cotton that is grown in Australia.
9
Name the legislation that governs gene technology in Australia.
The Federal legislation is the Gene Technology Act 2000. In addition, Australian states
have enacted complementary legislation, such as Victoria's Gene Technology Act
2001.
10
One method of introducing a foreign gene to a species is micro-injection of a
fertilised egg. List one disadvantage of this procedure.
A disadvantage of micro-injection of a fertilised egg is that the procedure is
unpredictable. The location where the injected foreign gene inserts is random and
uncontrolled, and, in some cases, it may insert within an essential gene disrupting the
function of that gene so that the egg does not develop.
11
If Jane’s fetus had shown a RFLP pattern identical with that in Tom, what
conclusion may have been drawn about this fetus?
If Jane’s male fetus showed the same RFLP pattern as Tom, it would be reasonable to
conclude that the fetus had inherited the haemophilia allele (c) from Jane and that it
would be affected by this disorder.
12
What is meant by the term ‘predictive testing’?
Predictive testing refers to procedures used to test for the presence or absence of an
allele responsible for an inherited disorder in a person who is at risk of having inherited
that allele but who shows no signs of the disorder in their phenotype.
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Chapter 12: QUICK-CHECK answers
13
What does the abbreviation RFLP denote?
The abbreviation RFLP stands for restriction fragment length polymorphism.
14
If a person at risk of HD has 56 CAG repeats in one of the HD alleles, what
conclusion can be drawn?
Based on the number of CAG repeats in this allele, it is reasonable to conclude that
the person has inherited the HD allele that is responsible for Huntington disease from
an affected parent.
15
Identify the following statements as true or false.
a
The current technique of identification by DNA is known as DNA
fingerprinting.
False: The current technique for identification by DNA is called DNA profiling and
is based on detection of variation in regions of DNA known as short tandem
repeats (STRs).
b
A minisatellite is also known as a short tandem repeat.
False: A short tandem repeat can also termed a microsatellite. Minisatellites are
another kind of variable region of DNA but they differ from microsatellites.
c
The length of the repeated unit in an STR is from two to five base pairs.
True (Note: The label ‘short’ in STRs is in contrast to minisatellites where the
repeating unit is typically much longer.)
d
Chromosomal DNA gives more precise identification than mtDNA.
True: DNA profiles based on chromosomal DNA give far more precise
identification than that obtained using mitochondrial DNA (mtDNA). This occurs
because mtDNA is inherited generation after generation without recombination
from maternal ancestors, while STRs undergo reassortment during meiosis at
every generation. So, in a large family extending across several generations, all
members who share the same maternal ancestry will have identical mtDNA, but
they will differ in many of their STRs.
e
One person could have 10 different alleles at one STR locus.
False: While many different alleles are possible at each STR locus, a person can
have at most only two alleles at each STR locus, one on each homologous
chromosome pair.
16
List two differences between the techniques of DNA fingerprinting and DNA
profiling.
DNA fingerprinting uses:
 minisatellites
 repeated sequences from 9 to 80 bases
 regions with tens to hundreds of repeats
 sites located at chromosome ends
DNA profiling uses:




short tandem repeats (STRs, also known as microsatellites)
repeated sequences from 2 to 5 bases
regions with commonly 5 to 20 repeats
sites located at loci within chromosomes
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Chapter 12: QUICK-CHECK answers
17
Who invented the technique of DNA fingerprinting?
Alex Jeffreys (now Professor Sir Alex Jeffreys) developed the technique of DNA
fingerprinting in 1985.
18
Identify the following statements as true or false.
a
The gender marker used in DNA profiling is an STR.
False: The gender marker is not an STR. The gender marker used is the Amel
gene, and, unusually, this gene has a locus on both the X and the Y
chromosomes. The size of the gene differs on each sex chromosome. As a result,
a male with both an X and a Y chromosome shows two DNA bands for the gender
marker, while a female with two X chromosomes shows just one marker.
b
The national DNA databank in the United States is known as CODIS.
True: The national DNA databank set up by the FBI in the United States is known
as CODIS (Combined DNA Index System).
c
DNA profiling in Australia uses nine different STR loci.
True
19
What is the name of the national DNA database in Australia?
The national DNA data base in Australia is called CrimTrac.
20
A DNA profile shows two peaks for the gender marker. What is the gender of the
person concerned?
If a profile shows two peaks for the Amel gender marker, this indicates the presence of
both an X chromosome and a Y chromosome and so identifies the gender of the
person concerned as male.
21
Give one example of the use of DNA profiling in assisting in a criminal
conviction.
Examples include the conviction of Bradley Murdoch for the murder of Peter Falconio
in Australia (see page 446) and the conviction of Francisco Montes for the murder of
Caroline Dickinson in France (see page 447).
(Note: More recent high profile cases includee the conviction in 2007 of Glenn McNeill
for the murder in March 2002 of Janelle Patton on Norfolk Island.)
22
List two non-human species for which DNA profiling has been done and, in each
case, identify one reason why it was done.
Examples include:
 DNA profiling of a cat was critical evidence in one case in Canada (see page 451).
Cat hairs were found on a bloodstained jacket found near a crime scene and the
blood matched that of the victim. The estranged husband of the victim was a
suspect and so the cat hairs on this jacket were tested to see if there was a link to
him. The DNA profile from the roots of the cat hairs identified the cat as one that the
man had had contact with. This finding linked the bloodstained jacket to him and
was part of the evidence that led to his conviction for murder.
 In the USA, DNA profiling of human bloodstains and dog bloodstains on clothing
worn by the accused matched that of the victims of a murder and their dog that was
killed at the same time. This finding became part of the evidence that led to the
conviction of the accused for murder.
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Chapter 12: QUICK-CHECK answers
23
Refer to figure 12.44 and identify the approximate size:
a
of the gender marker for cats
The marker used as to identify gender in the DNA profiling of cats is the SRY
marker on chromosome Y. This gender marker is just under 100 base pairs in
length.
b
range for the FCA740 marker in the cat population.
The FCA740 marker used in the DNA profiling of cats can range from about 310 to
about 345 base pairs in length.
24
Identify one means by which tissue is obtained from dogs for DNA profiling.
Tissue for DNA profiling may, for example, be obtained from:
 a buccal swab that contains epidermal cells (see figure 12.47)
 a sample of hair (with roots)
 a blood sample.
(Note: A DNA sample for profiling can be obtained from any biological material in
which living cells are present. So, for example, a sample of dog saliva taken from the
bitten area of skin of a person attacked by a dog could be used to implicate or
exonerate a particular dog from the attack.)
25
Identify the following as true or false:
a
Alleles at each STR locus behave in a Mendelian fashion.
True: The alleles at each STR locus are inherited in a manner identical to that of
the alleles of any other autosomal gene.
b
Boys inherit all their STR alleles from their fathers.
False: For every STR gene, each child, whether boy or girl, inherits one STR allele
from the mother and one allele from the father.
c
DNA testing can be used to exclude a man as the biological father of a child.
True: In a case of disputed paternity, DNA testing has the power to exclude a man
as being the father of a particular child on the basis of his DNA profile as
compared with that of the child in question.
26
A mother with alleles 10 and 15 and a man with alleles 12 and 14 at the D8 STR
locus could have a child with the alleles 14 and 15 at the same locus.
True: For the D8 STR marker, a child could inherit allele 15 from the mother and allele
14 from the father.
(Note: Other possible combinations are 10/12, 10/14 and 15/14.)
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