Nucleotides
I. nucleotides: sub units „³ DNA
A. Phosphate group
B. 5-carbon sugar molecule (deoxyribose)
C. nitrogen base
1. Adenine
2. Guanine
3. Thymine
4. Cytosine
Chargaff „³ base pairing rule: 1 = 3 and 2 = 4
II. Maurice Wilkins and Rosalind Frankilin „³ X-ray diffraction photos of DNA molecule
- DNA molecules: tightly coiled helix and composed of two or three chains of nucleotides
III. Chargaff builds a model of the double helix: ¡§a spiral staircase¡¨ of 2 strands of nucleotides twisting around a central axis.
A. alternating …
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…I. Genes in Eukaryotes
A. interruped by necleotides that have no coding info.
1. Introns:: noncoding sequences/ intervening
- must be removed
2. Exons :nucleotide segments that code for amino acids
-stitched together once all introns are removed
II. Multigene families: clusters of almost identical sequences; cells exist in multiple copies
A. Some are ¡§silent¡¨ genes: don¡¦t make protein
B. Some are only active during embryonic or fetal development
C. Some encode the two chains of
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