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Transcript of Nucleic Acids and Protein Synthesis I love the color selection from MS PowerPoint.
Nucleic Acids and Protein Synthesis
I love the color selection from MS PowerPoint
DNA: Structure
• Double Helix: Twisted ladder shape of DNA
DNA: Structure
• Monomer: _____________– 5 Carbon Sugar (_________________)– Phosphate– Nitrogenous Base (2 kinds)
Types of Nitrogenous Bases
• Purines:– Adenine (A)– Guanine (G)
• Pyrimidines– Thymine (T)– Cytosine (C)– Uracil (U) – Not in DNA
Nucleotide Structure
DNA Structure
• Double stranded molecule (Ladder)
• Rungs: Nitrogenous bases• Uprights: Alternating Sugar and Phosphates
DNA Structure
• Antiparallel: The 2 strands run in opposite directions
Antiparallel
DNA Structure
• The bases connect the two strands of DNA– Each base ONLY bonds to a corresponding
base• A – T• G – C• NO EXCEPTIONS = Mutations
• Practice: AAGTACTAGATTACCG
Double Helix
• Why does the DNA ladder twist into a double helix?– ANSWER: Hydrophobic vs Hydrophilic
interactions
A DNA Review
• What are the three components of a nucleotide?
• DNA ladder: rungs and uprights
• Antiparallel
• Hydrogen bonding between bases
• Double helix and Hydrophobicity
Famous Scientists
• Chargaff’s Rules (%A = %T, %G = %C)
• Rosalind Franklin (X-Ray Crystallography)– DNA = 2 strands that coil around one another
Famous Scientists Take 2
• Watson and Crick (1953)– 3D molecule of DNA (Double Helix)– Hydrogen bonds between purines and
pyrimidines
DNA and Chromosomes• Prokaryotic Cells (No True nucleus)
– DNA arranged in a large circle
OR- DNA found in small circles (plasmids)
Eukaryotic Cells (True Nucleus)
• DNA is on several linear chromosomes in the nucleus
• Each species has its own unique number of chromosomes– Humans – 46– Fruit fly – 8– Giant Sequoia Tree – 22
DNA is huge . . . How can it fit in the nucleus?
• DNA winds around protein complex (Histones)
How it fits continued…
• DNA and Histone complex coil to form a Nucleosome
• Nucleosomes coil tighter (Supercoil) to form a chromomome
Histones and Evolution
• Histones are very conserved throughout among different species– Conserved – similar structure and amino acid
sequence due to evolution
• WHY???
DNA Replication
• When does it occur?
• Why does it occur?
• How does it occur (5 steps)?– Uncoil– Unzip– Add parts– Recoil– Proof-read
DNA Replication Take 2
• The process is controlled by many enzymes• Steps in detail:
1. Uncoil
2. Unzip– DNA helicase unzips the 2 DNA molecules by
breaking the Hydrogen bonds between the bases– Typically begins at a site rich in A’s and T’s. WHY?
DNA Bases
Result: Replication Fork
DNA Replication3. Add parts
– Each strand serves as a template for the construction of a seconds strand of DNA
– Problem: The 2 strands are anti-parallel– Solution:
• One strand copied continually – Leading strand• One strand copied in segments – Lagging strand
DNA Replication
• Leading strand = 3’ 5’• Lagging strand = 3’ 5’ but leaves gaps
– Gaps = Okasaki Fragments
DNA Replication
3. Add Parts– DNA Polymerase begins adding
corresponding nucleotides to the template strands
EX) ATTATACG
TAATATGC– When finished, DNA Polymerase comes
back and fills in the gaps (Okasaki fragments)
DNA Replication
4. DNA Recoiled
5. DNA is proof-read– DNA Polymerase proof-reads the 2 strands of
DNA for any mistakes
Result: 2 strands of DNA
Semi-conservative: Definition?
Sex Determination and Sex Linkage
• Sex is determined by the 23rd chromosomes
XX =
XY =
Chances of Having Male vs Female Child
• Hypothetical Sex ratio:
• Birth Ratio:
• Population Ratio:
• Kutztown Ratio:
X-Linked Traits
• The x chromosome is bigger than the y and therefore holds more genes
Examples:
- Hemophilia
- Red/Green Color-blindness
- Baldness
Sex Linked crosses
• These are all recessive traits (For our purposes)• Females must have two bad copies in order to
be infected– XX– XXC
– XCXC
• Males only need one bad copy– XY– XCY
Morale of this story
• Who is responsible for a son being bald?Cross One: Cross a bald man with a
homozygous normal woman
Cross Two: Cross a normal man with a woman carrying the bald gene.
RNA and Protein Synthesis
• RNA (Ribonucleic Acid
• Type of Nucleic Acid (3 parts)
RNA VS DNA
• RNA is single stranded
• RNA’s sugar is Ribose, not Deoxyribose
• RNA uses Uracil (U) as a base rather than Thymine (T)– Uracil connects to Adenine (A)
Types of RNA
• Messenger RNA (mRNA)
• Ribosomal RNA (rRNA)
• Transfer RNA (tRNA)
What is the job of RNA
Ribosome