1. CHAPTER 12 DNA Technology and the Human Genome
Modules 12.7 – 12.14

2. 12.7 Reverse transcriptase helps make genes for cloning
OTHER TOOLS OF DNA TECHNOLOGY
12.7 Reverse transcriptase helps make genes for cloning
Reverse transcriptase can be used to make smaller cDNA libraries
These contain only the genes that are transcribed by a particular type of cell

3. RNA splicing (removes introns)
CELL NUCLEUS
Exon
Intron
Exon
Intron
Exon
DNA of eukaryotic gene 1
Transcription
RNA
transcript 2
RNA splicing (removes introns)
mRNA 3
Isolation of mRNA from cell and addition of reverse transcriptase; synthesis of DNA strand
TEST TUBE
Reverse transcriptase 4
Breakdown of RNA
cDNA strand 5
Synthesis of second DNA strand
cDNA of gene (no introns)
Figure 12.7

4. 12.8 Nucleic acid probes identify clones carrying specific genes
A nucleic acid probe can tag a desired gene in a library
Radioactive probe (DNA)
Mix with single- stranded DNA from various bacterial (or phage) clones
Single-stranded DNA
Base pairing indicates the gene of interest
Figure 12.8A

5. DNA probes can identify a bacterial clone carrying a specific gene
Bacterial colonies containing cloned segments of foreign DNA
Radioactive DNA 1
Transfer cells to filter
Solution containing probe
Filter paper 2
Treat cells on filter to separate DNA strands 3
Add probe to filter
Probe DNA
Gene of interest
Single-stranded DNA from cell
Hydrogen-bonding 4
Autoradiography
Colonies of living cells containing gene of interest
Developed film 5
Compare autoradiograph with master plate
Figure 12.8B
Master plate

6. This technique may revolutionize the diagnosis and treatment of cancer
12.9 Connection: DNA microarrays test for the expression of many genes at once
A labeled probe can reveal patterns of gene expression in different kinds of cells
This technique may revolutionize the diagnosis and treatment of cancer
cDNA
DNA of gene
DNA microarray, actual size (6,400 genes)
Figure 12.9

7. 12.10 Gel electrophoresis sorts DNA molecules by size
Restriction fragments of DNA can be sorted by size
Mixture of DNA molecules of different sizes
Longer molecules
Power source
Gel
Shorter molecules
Glass plates
Completed gel
Figure 12.10

8. 12.11 Restriction fragment analysis is a powerful method that detects differences in DNA sequences
Scientists can compare DNA sequences of different individuals based on the size of the fragments
Allele 1
Allele 2 w
Cut z x
Cut
Cut y y
Figure 12.11A
DNA from chromosomes

9. 1 2
Longer fragments
Shorter fragments
Figure 12.11B

10. Radioactive probes are also used to make comparisons1
Restriction fragment preparation
Restriction fragments 2
Gel electrophoresis
Filter paper 3
Blotting 4
Radioactive probe
Radioactive, single- stranded DNA (probe)
Probe 5
Detection of radioactivity (autoradiography)
Film
Figure 12.11C

11. 12.12 The PCR method is used to amplify DNA sequences
The polymerase chain reaction (PCR) can quickly clone a small sample of DNA in a test tube
Initial DNA segment 1 2 4 8
Number of DNA molecules
Figure 12.12

12. 12.13 Most of the human genome does not consist of genes
THE CHALLENGE OF THE HUMAN GENOME
Most of the human genome does not consist of genes
The 23 chromosomes in the haploid human genome contain about 3 billion nucleotide pairs
This DNA is believed to include about 35,000 genes and a huge amount of noncoding DNA

13. NUCLEOTIDE SEQUENCE OF A HUMAN TELOMERE
Much of the noncoding DNA consists of repetitive nucleotide sequences
One example includes telomeres at the end of the chromosomes
Repeated unit
End of DNA molecule
NUCLEOTIDE SEQUENCE OF A HUMAN TELOMERE
Figure 12.13A

14. Barbara McClintock discovered that segments of DNA called transposons can move about within a cell’s genome
Figure 12.13B, C

15. The Human Genome Project involves:
Connection: The Human Genome Project is unlocking the secrets of our genes
The Human Genome Project involves:
genetic and physical mapping of chromosomes
DNA sequencing
comparison of human genes with those of other species
Figure 12.14