Download DNA,Rep,RNA,Trans pp

DNA
Deoxyribonucleic acid
DNA structure
1953 – James Watson and Francis Crick,
at Cambridge University, England
Double Helix – (twisted ladder)
- phosphate and sugar alternate on the sides
- Bases are held together by hydrogen bonds
- Complimentary bases:
Adenine - thymine
Cytosine – Guanine
1949 – Chargaff determined:
% A = % T, % C = % G
White Board Practice
1. What is the % of the other bases if A = 10%?
A = 10
C=
T = 10
G=
20
80
2. What is the % of the other bases if C = 37%?
C = 37
A=
G = 37
T=
74
26
White Board Practice
3.What is the % of the other bases if T = 23%?
T = 23
C=
A = 23
G=
46
54
4.What is the % of the other bases if G= 3%?
G=3
A=
C=3
T=
6
94
Open the textbook to page 198
5. Which bases are purines and which bases are
pyrimidines?
Purines: A and G
Pyrimidines: T and C
6. How does their structure differ?
Purines have 2 rings and Pyrimidines have 1 ring
7. How does their structure and base pairing
relate to overall DNA structure?
Correct base pairing is 3 rings long, keeping the
sides of the DNA molecule straight.
DNA Replication – DNA makes an
exact copy of itself
1. During which part of the cell cycle does
replication occur?
During S of interphase
2. Why must the copy be exact?
to prevent mutations
3. What monomers make up the DNA molecule?
nucleotides
4. What are the 3 parts of the DNA nucleotide?
phosphate, deoxyribose sugar, base
5. Draw a DNA nucleotide.
DNA Replication
1. Helicase (an enzyme) separates the DNA by
breaking the hydrogen bonds (DNA unzips)
2. DNA polymerase brings in nucleotides to
bond with their complimentary bases
3. DNA polymerase drops off, 2 DNA molecules
are formed
• Human chromosomes are very long.
• Replication occurs at 50 nucleotides
per second.
• It would take 53 days to replicate 1
chromosome
therefore: replication forks occur at
many sites simultaneously to allow for
rapid replication
RNA – ribonucleic acid
• contains Uracil, not thymine
• contains Ribose, not deoxyribose
3 types:
1. Messenger RNA (mRNA)
- brings messages from the nucleus
into the cytoplasm
- ribbon shape
- contains codons
2. Ribosomal RNA (rRNA)
- makes up the ribosome
3. Transfer RNA (tRNA)
- brings amino acids to the ribosome
- found in the cytoplasm
- t-shaped
- has anticodon
Transcription – making mRNA
1. RNA polymerase (an enzyme) separates the
DNA by breaking the hydrogen bonds (DNA
unzips)
2. RNA polymerase brings in RNA nucleotides
to bond with their complimentary bases
along one side of the DNA molecule
3. RNA polymerase drops off, mRNA moves
away, DNA molecule closes