Download Genes

This presentation was originally prepared by
C. William Birky, Jr.
Department of Ecology and Evolutionary Biology
The University of Arizona
It may be used with or without modification for
educational purposes but not commercially or for profit.
The author does not guarantee accuracy and will not
update the lectures, which were written when the course
was given during the Spring 2007 semester.
A Brief Review of Genes and DNA
Genes are DNA
Flourescence micrograph of
alga Olisthodiscus. Chlorophyll
autofluoresces red. DNA stained
with DAPI fluoresces white.
•Chloroplasts and cpDNA
•Mitochondria and mtDNA
•Nucleus and nuDNA
Genes and Chromosomes in Eukaryotes
Human DNA in one genome is
≈ 1 meter long.
It is divided into 23 chromosomes.
Somatic cells have two sets of 23
23 chromosomes.
Genes and Chromosomes in Bacteria
cell
gene 1
gene 2
gene 3
Some Definitions
• The phenotype of a cell or organism is determined
jointly by the organism’s genotype and environment.
• The genotype consists of the genes that control the trait
of interest.
• A gene is a segment of a DNA molecule (or RNA in
some viruses).
• The genome of an organism is (i) the sum of all of the
DNA in one set of chromosomes (broad sense); (ii) the
sum of all of the genes in one set of chromosomes
(narrow sense).
Electron micrograph
Very small circular DNA
(this one is knotted!)
Original and Space-filling Models
Jim Watson, Francis
Crick, and their original
hand-made model
Computer-built space-filling models of side
view (left) and end view (right)
Structural Models of DNA
Copyrighted figure removed.
major
groove
minor
groove
Some viruses have a single-stranded DNA genome.
Structural Models of Nucleotides
Copyrighted figure removed.
Remember:
• A and G are purines, C and T are pyrimidines
• Purines have short name & long base (2 rings); pyrimidines vice versa
You will not be asked to draw these, but should be able to recognize and name them.
Structural Models of Polynucleotides
Copyrighted figure removed.
Note 5’ to
3’
polarity
Simplifying a Structural Model
Copyrighted figure removed.
Base Pairs
Copyrighted figure removed.
DNA Structure: The Final Simplification
A gene is a sequence of bases in one strand of DNA.
3' OH – dR – P – dR – P – dR – P – dR – P 5'
|
|
|
|
T
C
G
A
..
...
...
..
A
G
C
T
|
|
|
|
5' P – dR – P – dR – P – dR – P – dR – OH 3’
3’ T C G A
5’ A G C T
5’ A G C T
AGCT
Learn these models and practice drawing them.
DNA Structure: The Final Simplification
AGCT
DNA sequences are written for the strand that has the
same sequence as the RNA transcript (“sense strand”).
Sequences are written 5’ to 3’.
Human b-globin Gene Determines Amino
Acid Sequence of b -globin
1
10
20
30
40
50
60
70
80
90
100
AcatttgcttctgacacaactgtgttcactagcaactcaaacagacaccATGGTGCACCTGACTCCTGAGGAGAAGTCTGCCGTTACTGCCCTGTGGGGC
101
AAGGTGAACGTGGATGAAGTTGGTGGTGAGGCCCTGGGCAGgttggtatcaaggttacaagacaggtttaaggagaccaatagaaactgggcatgtggag
201
acagagaagactcttgggtttctgataggcactgactctctctgcctattggtctattttcccacccttagGCTGCTGGTGGTCTACCCTTGGACCCAGA
301
GGTTCTTTGAGTCCTTTGGGGATCTGTCCACTCCTGATGCTGTTATGGGCAACCCTAAGGTGAAGGCTCATGGCAAGAAAGTGCTCGGTGCCTTTAGTGA
401
TGGCCTGGCTCACCTGGACAACCTCAAGGGCACCTTTGCCACACTGAGTGAGCTGCACTGTGACAAGCTGCACGTGGATCCTGAGAACTTCAGGgtgagt
501
ctatgggacccttgatgttttctttccccttcttttctatggttaagttcatgtcataggaaggggagaagtaacagggtacagtttagaatgggaaaca
601
gacgaatgattgcatcagtgtggaagtctcaggatcgttttagtttcttttatttgctgttcataacaattgttttcttttgtttaattcttgctttctt
701
tttttttcttctccgcaatttttactattatacttaatgccttaacattgtgtataacaaaagcaaatatctctgagatacattaagtaacttaaaaaaa
801
aactttacacagtctgcctagtacattactatttggaatatatgtgtgcttatttgcatattcataatctccctactttattttcttttatttttaattg
901
atacataatcattatacatatttatgggttaaagtgtaatgttttaaaattttgcatttgtaattttaaaaaatgctttcttcttttaatatactttttt
1001
gtttatcttatttctaatactttccctaatctctttctttcagggcaataatgatacaatgtatcatgcctctttgcaccattctaaagaataacagtga
1101
taatttctgggttaaggcaatagcaatatttctgcatataaatatttctgcatataaattgtaactgatgtaagaggtttcatattgctaatagcagcta
1201
caatccagctaccattctgcttttattttatggttgggataaggctggattattctgagtccaagctaggcccttttgctaatcatgttcatacctctta
1301
tcttcctcccacagCTCCTGGGCAACGTGCTGGTCTGTGTGCTGGCCCATCACTTTGGCAAAGAATTCACCCCACCAGTGCAGGCTGCCTATCAGAAAGT
1401
GGTGGCTGGTGTGGCTAATGCCCTGGCCCACAAGTATCACTAAgctcgctttcttgctgtccaatttctattaaaggttcctttgttccctaagtccaac
1501
tactaaactgggggatattatgaagggccttgagcatctggattctgcctaataaaaaacatttA
Two Alleles of Human b-globin Gene
One change in position 20 of b-globin gene results in sickle-cell
anemia
Normal HbA allele
glutamate in b-globin
ATGGTGCACCTGACTCCTGAGGAGAAGTCTGCCGTTACTGCCCTGTGGGGC
Mutant HbS allele
valine in b-globin
ATGGTGCACCTGACTCCTGTGGAGAAGTCTGCCGTTACTGCCCTGTGGGGC
Next we will review how genes replicate, then how we use enzymes
to manipulate genes, then how genes determine the sequence of
amino acids in proteins.