14.3 Studying the Human Genome

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Oct 23, 2013 (3 years and 5 months ago)

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DNA TECHNOLOGY STUDY GUIDE (14.3 + CH 15)


14.3
Studying the Human Genome

Lesson Summary

Manipulating DNA
Since the 1970s, techniques have been developed that allow
scientists to cut, separate, and r
eplicate DNA base
-
by
-
base. Using these tools, scientists can
read the base sequences in DNA from any cell.

Restriction enzymes

cut DNA into smaller pieces, called restriction fragments, which are
several hundred bases in length. Each restriction enzyme cu
ts DNA at

a different sequence
of bases.

Gel electrophoresis

separates different
-
sized DNA fragments by placing them at one end
of a porous gel, then applying an electrical voltage. The e
lectrical charge moves the DNA.

Using dye
-
labeled nucleotides, scie
ntists can stop replication at any point along a single
DNA strand. The fragments can then be separated by size using gel electrophoresis and
“read,” base
-
by
-
base.


The Human Genome Project

was a 13
-
year international effort to sequence all 3
billion base
pairs in human DNA and identify all human genes. The

project was completed in
2003.

They used “shotgun sequencing,” which uses a comput
er to match DNA base sequences.

The Human Genome Project identified genes associated with many diseases and
disorders.
From the project came the new science of
bioinformatics
, the creation and use
of databases and other computing tools to manage data. Bioinformatics launched
genomics
, the study of whole genomes.

The human genome project pinpointed genes and associated par
ticular sequences in those
genes with numerous diseases and disorders. It also found that the DNA of all humans
matches base
-
for
-
base at most sites, b
ut can vary at 3 million sites.

The 1000 Genomes Project, launched in 2008, will catalogue t
he variation
among 1000
people.


Manipulating DNA

For Questions 1

4, write True if the statement is true. If the statement is false, change
the underlined word to make the statement true.

T



1.

Bacteria produce restriction enzymes that cut the
DNA

molecule into smal
ler


pieces.

Nucleotides

2.

Restriction fragments are always cut at a particular sequence of
proteins

T


3.

The technique that separates differently sized DNA fragments is
gel



electrophoresis
.

Polymerase

4.

The enzyme that copies DNA is DNA
res
trictase
.





5.

Complete the graphic organizer to summarize the steps used to determine the sequences
of bases in DNA.


Purpose

Tool or Technique Used

Outcome

Cutting DNA

Restriction enzymes

Large molecule of DNA is cut into
smaller fragments

Separatin
g DNA

Gel Electrophoresis

Smaller DNA fragments move
faster on the gel, so fragments are
separated by size

Reading DNA

Dye
-
Labeled nucleotides
and gel electrophoresis

Labeled nucleotides stop the
synthesis of a new strand at
different lengths. Gel
electro
phoresis then separates
them so they can be read


For Questions 6

10, complete each statement by writing in the correct word or words.

6.

By using tools that cut, separate, and then replicate DNA, scientists can now read the

base

sequence in DNA from any

cell.

7.

Restriction enzymes cut pieces of DNA sometimes called restriction
fragments
.

8.

Each restriction enzyme cuts DNA at a different sequence of
nucleotides
.

9.

The smaller the DNA, the
faster

and farther it moves during gel electrophoresis.

10.

After chemically dyed bases have been incorporated into a DNA strand, the order of
colored
bands

on the gel reveals the
exact sequence of bases in DNA.


The Human Genome Project


11
.

What were the goa
ls of the Human Genome Project?


To sequence the base pa
irs of DNA to identify all human genes























15.1

Selective Breeding

Lesson Summary

Selective Breeding

Through
selective breeding
, humans choose organisms with
wanted characteristics
to produce the next generation.

This takes advantage of
natural variation among organisms and pas
ses wanted traits to
offspring.

The numerous breeds of dogs and varieties of crop plants and domestic animals are
examples of selective breeding.

Hybridization

crosses dissimilar individuals to bring together the b
est of both parents in the
offspring.
Inbreeding

is the continued breeding of individuals with selected characteristics. It
ensures that wanted traits are preserved, but can also res
ult in defects being passed on.


Increasing Variation
Mutations are the so
urce of biological diversity. Breeders
introduce mutations into populations to increase genetic variation.
Biotechnology

is the
application of a technological process, invention, or method to living organisms. Selective
breeding i
s one example of biotechno
logy.

Radiation and chemicals can increase the mutation rate. Diverse bacterial strains hav
e
been bred from mutated lines.

Drugs can prevent the separation of chromosomes during mitosis, leading to polyploidy in
plants. Such plants may be larger or stron
ge
r than their diploid relatives.


Selective Breeding

For Questions 1

5, write True if the statement is true. If the statement is false,
change the underlined word or words to make the statement true.

True



1.

Selective

breeding

works because of the natu
ral genetic variation in a

population.

dissimilar


2.

Hybridization crosses
similar

individuals to bring together the best of both.

hybrids

3
.

The individuals produced by crossing dissimilar parents are
purebreeds
.

inbreeding

4
.

The continued cros
sing of individuals with similar characteristics is
hybridization
.

True

5
.

Inbreeding
increases

the risk of genetic defects.


6.

Complete the table describing the types of selective breeding.


Selective Breeding

Type

Description

Examples

Hybridization

Crossing dissimilar individuals
to bring together the best of
both organisms

Burbank potatoes that
are disease resistant

Inbreeding

The continued breeding of
individuals with similar
characteristics

Elberta peaches




15.2
Recombinant DNA

Lesson Summary

Copying DNA
Genetic engineers can transfer a gene from one organism to another to
achieve a goal, but first, individual genes must be identified and separated from DNA. The
original method (used by Douglas P
rasher) involved several steps:


Determine the
amino acid sequence in a

protein.


Predict t
he mRNA code for that sequence.


Use a complementary base sequence

to attract the predicted mRNA.


Find the DNA f
ragment that binds to the mRNA.

Once scientists find a gene, they can use a technique called the

polymerase chain reaction

to
make many copies.


Heat sepa
rates the DNA into two strands.


As the DNA cools, primers are added t
o opposite ends of the strands.


DNA polymerase adds nucleotides between the primers, producing two complementary

strands. T
he process can be re
peated as many times as needed.


Changing DNA
Recombinant DNA

molecules contain DNA from two different sources.
Recombinant
-
DNA technology can change the genetic c
omposition of living organisms.


Plasmids

are circular DNA molecules fou
nd in bacteria and yeasts; they are widely used

by scientists studying recombinant DNA, because DNA joined
to a plasmid can be

replicated.


A
genetic marker

is a gene that is used to differentiate a cell that carries a recombinant

plasmid from those th
at do not.


Transgenic Organisms
Transgenic

organisms contain genes from other species. They
result from the insertion of recombinant DNA into the genome of the host organism. A
clone

is a member of a population
of genetically identical cells.


Copying DNA

For Questions 1

5, complete each statement by writing in the correct word or words.

1.

Genetic engineers can transfer
genes

from one organism to another.

2.

As a first step toward finding a gene, Douglas Prasher studied the
amino acid

sequence
of part of
a protein.

3.

Prasher next found the
mRNA

base seque
nce that coded for the protein.

4.

Using the technique of
gel electrophoresis
, Prasher matched the mRNA to a DNA
fragment that contained the gene for GFP.

5.

Southern blot analysis uses
radioactive

probes

to bind to fragments with complementary
base sequences.





6.




Make a sketch to show the steps in the polymerase chain reaction
(PCR) method of copying genes.
Label each part of your sketch.





THINK VISUALLY























Changing DNA

For Questions 7

10, write the letter of the correct answer on the line at the left.

B


7.


Why is DNA ligase so important in recombinant DNA technology?

A.

It causes DNA to make
multiple copies of itself.

B.

It joins two DNA fragments together.

C.

It shapes bacterial DNA into a circular plasmid.

D.

It cuts
DNA into restriction fragments.

D


8.


A recombinant plasmid can be used to

A.

pre
vent nondisjunction at meiosis.

B.

double
the number of chromosomes in a plant cell.

C.

cut DNA into restriction fragments.

D.

transform a bacterium.


C


9.

What do genetic engineers use to create the “sticky ends” needed to splice two
fragments of DNA together?

A.

an amino acid sequence

B.

DNA

ligase

C.

restriction enzymes

D.

mRNA



10
.

Give a reason why a plas
mid is useful for DNA transfer.


It has a DNA sequence that helps promote plasmid replication, helping to ensure
that the foreign DNA will be replicated





















Transgenic Org
anisms

11
.

Complete the flowchart about how a transgenic plant is produced, using
Agrobacterium

as
an example.



Agrobacterium

can cause tumors in plants. The part of the DNA that
causes tumors is deactiv
ated and replaced with
recombinant

DNA.

The
transformed

bacteria are placed in a dish with plant cells. The
bacteria infect the plant cells.

Inside a plant cell,
Agrobacterium

inserts part of its DNA into the host cell
chromosome
.

A
complete or new plan
t

is generated from the transformed cell.

1
2
.

What is a transgenic organism?


An organism that contains genes from other species





13
.

What can happen when DNA is injected into the
n
ucleus of an animal’s egg cell?


Enzymes that are normally responsible for repair and recombination may help insert the foreign
DNA into the chromosomes of the injected cell.





14
.

How is a DNA molecule constructed so that it will eliminate a particula
r gene?


The DNA molecule is constructed with two ends that will sometimes recombine with specific
sequences in the host chromosomes. The host gene between the two sequences may then be lost or
replaced with a new gene.








15
.

What is a clone?


It is
a member of a population of genetically identical cells produced from a single cell





16
.

What kinds of mammals ha
ve been cloned in recent years?


Sheep, cows, pigs, mice, and cats have been cloned






For Questions 17

21
, write True if the statement is

true. If the statement is false, change the
underlined word to make the statement true.

transgenic

17
.

An organism that contains one or more genes from another species is
inbred
.

True


18
.

Transgenic organisms can be made by inserting recombinant DNA
into the
genome

of the host organism.

Gene


19
.

Examining the properties of a transgenic organism allows scientists to discover
the function of the transferred
chromosome
.

True


2
0
.

Plant cells will sometimes take up DNA on their own if their
cell wall
s
are absent.

True


2
1
.

Carefully designed DNA molecules can achieve gene
replacement
.


On the lines below, write
T

next to an example of a transgenic organism, and
C

next to an example
of a clone.

T


22
.

A goat that produces spider’s silk in its milk

T


2
3
.

A plant that is grown from a cell into which
Agrobacterium

has incorporated
recombinant DNA

C


24
.

A lamb that is born with the same DNA as a donor cell

C


25
.

A colony of bacteria that grows from one bacterium

T


26
.

A bacterium

that can pr
oduce human insulin












27
.

Complete the sentences in the diagram below to show the steps in

cloning a
sheep.

























15.3
Applications of Genetic Engineering

Lesson Summary

Agriculture and

Industry

Genetic engineers work to improve the products
we get from plants and
animals.

Genetically modified crops may be more nutritious or higher yielding. They may be resistant to
insects, diseases, or spoil
age. Some can produce plastics.

Genetically

modified animals may produce more milk, have leaner meat, or contain higher levels of
nutritious compounds. Transgenic salmon grow rapidly in captivity. Transgenic goats pro
duce spider
silk in their milk.


Health and Medicine

Recombinant DNA studies are l
eading to advances in the preve
ntion and
treatment of disease.

Examples include vitamin
-
rich rice, human proteins made in animals, animal models of human disease
(for research), and bacte
ria that produce human insulin.

Gene therapy

is the process of chan
ging a gene to treat a disorder. However, gene therapy is still an
experi
mental and high
-
risk technique.

Genetic testing can identify h
undreds of inherited disorders.

Not all genes are active in every cell.
DNA microarray

technology lets scientists study
thousands of genes
at once to
determine their activity level.

THINK VISUALLY

cell

nucleus

divide

embryo


Personal Identification

DNA fingerprinting

analyzes sections of DNA that may have little or
no function but that vary
from one individual to another.

DNA fingerprinting is used in
forensics

th
e scientific study of crime
-
scene evidence


to identify
criminals. It is also used to identify the biological father

when paternity is in question.

Common ancestry can sometimes be determined using mitochondrial DNA (mt
DNA) and Y
-
chromosome analysis.


Agr
iculture and Industry

1.

Give two examples of how genetically modified organisms lead to more environmentally f
riendly
agricultural practices.

a.
Some GM crops do not need pesticide


b.
Some GM pigs have leaner meat



2.

Name two other benefits that may be

gained from gene
tically engineering food crops.

a.
Less expensive food


b.
Crops resistant to insects, disease, or spoilage


3.

Give two examples of how DNA modification has increased the importance of transge
nic animals to
our food supply.

a.
Recombinant

DNA techniques increase milk production in cows


b.
Transgenic salmon grow faster than wild salmon



Personal Identi
fi
cation

4
.

Complete the flowchart about how DNA fingerprints are made.
















Restriction
enzymes


are used to cut the DNA into fragment
s
containing genes and repeats.

The restriction fragments are separated according to size using gel
electrophores
is

.

The DNA fragments containing repeats are then labeled using
radioactive
probes

. This labeling produces a serie
s of
bands

the DNA fingerprint.

5
.

Study the DNA fingerprint below. Which two samp
les may be from a set of id
entical twins? How do
you know?


Samples 1 and 4 may be from identical twins because thy are exactly the same