transcription
translation
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
Fig. 9.17 Processing eukaryotic mRNA
Protect from
degradation
and facilitate
translation
Different combinations of exons can generate different
polypeptides via alternative splicing
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
6. The polypeptide chain
grows until the protetin is
completed.
Amino
acid
Completed
polypeptide
tRNA
5’
Ribosome moves
toward 3’ end
Cytoplasm
Fig. 9.18 How
protein synthesis
works in
eukaryotes
Ribosome
5. tRNAs bring their amino
acids in at the A site of the
ribosome. Peptide bonds
form between amino acids at
the P site, and tRNAs exit the
ribosome from the E site.
4. tRNA molecules
become attached to
specific amino acids
with the help of
activating enzymes.
Amino acids are
brought to the
ribosome in the order
dictated by the mRNA.
DNA
Nuclear
membrane
3’
3’
RNA
polymerase
1. In the cell nucleus, RNA
polymerase transcribes
RNA from DNA
3’
Poly-A
tail
5’
5’
5’
3’
Primary
RNA transcript
Exons
Cap
Small
ribosomal
subunit
Nuclear
pore
5’
Cap
Large
ribosomal
subunit
mRNA
Poly-A
tail
Introns
mRNA
3’
2. Introns are excised from the RNA
transcript, and the remaining exons are
spliced together, producing mRNA
3. mRNA is transported out of the
nucleus. In the cytoplasm, ribosomal
subunits bind to the mRNA
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
Fig. 9.23
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
9.9 Mutation
Mutation and recombination provide the raw
material for evolution
Evolution can be viewed as the selection of
particular combinations of alleles from a pool
of alternatives
Mutations in germ-line tissues can be inherited
Mutations in somatic tissues are not inherited
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
Mutation, Smoking and Lung Cancer
Agents that cause cancer are called
carcinogens
These are typically mutagens
Many investigations have determined that
chemicals can cause cancer in both animals
and humans
For example, tars and other chemicals in
cigarette smoke can cause cancer of the lung
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
10.1 A scientific Revolution
Genetic engineering is the process of moving
genes from one organism to another
A major impact on agriculture & medicine
Fig. 10.1
Producing insulin
Curing disease
Increasing yields
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
Making “Magic Bullets”
In diabetes, the body is unable to control levels of
sugar in the blood because of lack of insulin
Diabetes can be cured if the body is supplied
with insulin
The gene
encoding insulin
has been
introduced into
bacteria
Fig. 10.1
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
10.7 Genetic Engineering
of Crop Plants
ƒ Pest resistance
ƒ Leads to a reduction
in the use of
pesticides
Herbicide resistance
Crop plants have
been created that
are resistant to
Fig. 10.14
glyphosate
Glyphosateresistant plants
Glyphosatesensitive plants
Herbicide resistance offers two main advantages
1. Lowers the cost of producing crops
2. Reduces plowing and conserves the top soil
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
Petunias
10.7 Genetic Engineering
of Crop Plants
More Nutritious Crops
Worldwide, two major deficiencies are iron and
vitamin A
Deficiencies are especially severe in developing
countries where the major staple food is rice
Ingo Potrykus, a Swiss
bioengineer, developed
transgenic “golden” rice
to solve this problem
Fig. 10.15
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
Potential Risks of Genetically Modified (GM) Crops
The promise of genetic engineering is very much in
evidence
However, it has generated considerable
controversy and protest
Two sets of risks need to be considered
1. Are GM foods safe to eat?
2. Are GM foods safe for the environment?
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
11.1 Genomics
The full complement of genetic information
of an organism is its genome
Genomics is a new field of biology
concerned with the sequencing and study
of genomes
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
11.3 The Human Genome
The sequence of the entire human genome was reported
on June 26, 2000
It consists of 3.2 billion base pairs
The number of genes in humans is only about 25,00030,000
However, there are about 4 times more mRNA molecules
The genes are divided into exons and introns
Thus alternative mRNA splicing can generate much more
mRNA than there are genes
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
Noncoding DNA
Only 1-1.5% of the human genome is coding DNA
There are four major types of noncoding DNA
1. Noncoding DNA within genes
Together introns make up about 24% of the
human genome
2. Structural DNA
~ 20% of the genome is constitutive
heterochromatin
Located near centromeres and telomeres
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
Noncoding DNA
Only 1-1.5% of the human genome is coding DNA
There are four major types of noncoding DNA
3. Repeated sequences
Simple sequence repeats (SSRs)
Two- or three-nucleotide sequences repeated
thousands of times
Constitute ~3% of the human genome
Duplicated Sequences
Repeated sequences, other than SSRs
Constitute ~7% of the human genome
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
11.4 Gene Microarrays
A gene microarray is a
glass square smaller than a
postage stamp, covered
with millions of DNA
strands
Microarray chips, or
biochips, can be used to
delve into a person’s genes
The DNA is denatured then
washed over the microarray
Bound complementary
sequences are detected by
a computer
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
11.4 Gene Microarrays
Microarrays are also used
to detect the level of gene
expression
Complementary
binding results in a dotpatterned microarray
Similarly, two different
sources of DNA can be
compared
For example, the
genetic similarity
between two different
organisms/individuals
can be determined
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
11.4 Gene Microarrays
Single nucleotide polymorphisms (SNPs)
Spot differences between “reference sequences”
and the DNA of a particular individual
Some SNPs are associated with cancers and
other genetic disorders
Others may give red hair or high cholesterol
Each of us differs from the standard “type
sequence” in some 25,000 nucleotide SNPs
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
Fig. 11.6
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
11.4 Gene Microarrays
Researchers have identified over a million different
SNPs, all of which can reside on a few biochips
So, the SNP, and thus DNA, profile of an individual
can be easily obtained
This raises critical issues of personal privacy
Protecting medical information, for example
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display