1. Bell Ringer 11/14/16
A) A-A-U B) G-G-T C) T-T-C D) U-U-A

2. DNA Replication

3. Chromosomes Chromosomes Genes
Strands of DNA that contain all of the genes an organism needs to survive and reproduce
The E. Coli genome includes approximately 4,000 genes
Genes
Segments of DNA that specify how to build a protein
Chromosome maps are used to show the locus (location) of genes on a chromosome

4. Chromosomes Genetic Variation
Phenotypic variation among organisms is due to genotypic variation (differences in the sequence of their DNA bases)
Differences exist between species and within a species
Different genes (genomes)
Different versions of the same gene (alleles)

5. DNA Replication Cell Division (mitosis)
Cells must copy their chromosomes (DNA synthesis) before they divide so that each daughter cell will have a copy
A region of the chromosome remains uncopied (centromere) in order to hold the sister chromatids together
Keeps chromatids organized to help make sure each daughter cell gets exactly one copy
Nondisjunction is when sister chromatids do not assort correctly and one cell ends up with both copies while the other cell ends up with none

6. DNA Replication DNA Synthesis
The DNA bases on each strand act as a template to synthesize a complementary strand
Recall that Adenine (A) pairs with thymine (T) and guanine (G) pairs with cytosine (C)
The process is semiconservative because each new double-stranded DNA contains one old strand (template) and one newly-synthesized complementary strand A G C T A G C T

7. DNA Replication DNA Polymerase DNA Polymerization
Enzyme that catalyzes the covalent bond between the phosphate of one nucleotide and the deoxyribose (sugar) of the next nucleotide
DNA Polymerization

8. Bell Ringer 11/17 Adenosine Triphosphate B) Ribonucleotides
C) Genes D) Chromosomes

9. DNA Replication 3’ end has a free deoxyribose
5’ end has a free phosphate
DNA polymerase:
can only build the new strand in the 5’ to 3’ direction
Thus scans the template strand in 3’ to 5’ direction

10. DNA Replication Initiation
Primase (a type of RNA polymerase) builds an RNA primer (5-10 ribonucleotides long)
DNA polymerase attaches onto the 3’ end of the RNA primer
DNA polymerase

11. DNA Replication Elongation
DNA polymerase uses each strand as a template in the 3’ to 5’ direction to build a complementary strand in the 5’ to 3’ direction
DNA polymerase

12. DNA Replication Elongation
DNA polymerase uses each strand as a template in the 3’ to 5’ direction to build a complementary strand in the 5’ to 3’ direction
results in a leading strand and a lagging strand

13. DNA Replication Leading Strand
Topisomerase unwinds DNA and then Helicase breaks H-bonds
DNA primase creates a single RNA primer to start the replication
DNA polymerase slides along the leading strand in the 3’ to 5’ direction synthesizing the matching strand in the 5’ to 3’ direction
The RNA primer is degraded by RNase H and replaced with DNA nucleotides by DNA polymerase, and then DNA ligase connects the fragment at the start of the new strand to the end of the new strand (in circular chromosomes)

14. DNA Replication Lagging Strand
Topisomerase unwinds DNA and then Helicase breaks H-bonds
DNA primase creates RNA primers in spaced intervals
DNA polymerase slides along the leading strand in the 3’ to 5’ direction synthesizing the matching Okazaki fragments in the 5’ to 3’ direction
The RNA primers are degraded by RNase H and replaced with DNA nucleotides by DNA polymerase
DNA ligase connects the Okazaki fragments to one another (covalently bonds the phosphate in one nucleotide to the deoxyribose of the adjacent nucleotide)

15. DNA Replication Topoisomerase - unwinds DNA
Helicase – enzyme that breaks H-bonds
DNA Polymerase – enzyme that catalyzes connection of nucleotides to form complementary DNA strand in 5’ to 3’ direction (reads template in 3’ to 5’ direction)
Leading Strand – transcribed continuously in 5’ to 3’ direction
Lagging Strand – transcribed in segments in 5’ to 3’ direction (Okazaki fragments)
DNA Primase – enzyme that catalyzes formation of RNA starting segment (RNA primer)
DNA Ligase – enzyme that catalyzes connection of two Okazaki fragments

16. Bell Ringer 11/29+11/30
Gabby Williams is 9 years old, but she is as small as a newborn baby. She is 11lbs and has not aged since she was a 2 years old. The doctors say that a protein malfunction may be the cause. What enzymes may be at fault for no growth and lack of healing in Gabby? Why?

17. Bell Ringer
Create a flow chart that explains the sequence of protein synthesis

18. Protein Synthesis
DNA provides the instructions for how to build proteins
Each gene dictates how to build a single protein in prokaryotes
The sequence of nucleotides (AGCT) in DNA dictate the order of amino acids that make up a protein

19. Protein Synthesis Protein synthesis occurs in two primary steps
mRNA (messenger RNA) copy of a gene is synthesized
Cytoplasm of prokaryotes
Nucleus of eukaryotes 1
mRNA is used by ribosome to build protein
(Ribosomes attach to the mRNA and use its sequence of nucleotides to determine the order of amino acids in the protein)
Cytoplasm of prokaryotes and eukaryotes 2

20. Protein Synthesis Transcription Initiation
RNA polymerase binds to a region on DNA known as the promoter, which signals the start of a gene
Promoters are specific to genes
RNA polymerase does not need a primer

21. Protein Synthesis Transcription Elongation
The gene occurs on only one of the DNA strands; each strand possesses a separate set of genes

22. Protein Synthesis Transcription Termination
1) INITIATION
Transcription Termination
A region on DNA known as the terminator signals the stop of a gene
RNA polymerase disengages the mRNA and the DNA

23. Protein Synthesis Translation
Transcription
Translation
mRNA
tRNA synthesis
Translation
Every three mRNA nucleotides (codon) specify an amino acid

24. Protein Synthesis Translation
tRNA have an anticodon region that specifically binds to its codon

25. Protein Synthesis Translation Each tRNA carries a specific amino acid
Transcription
Translation
mRNA
tRNA synthesis
Translation
Each tRNA carries a specific amino acid

26. Protein Synthesis
Transcription
Translation
mRNA
tRNA synthesis

27. Protein Synthesis Translation Initiation 5’ 3’ AUGGACAUUGAACCG…
Transcription
Translation
mRNA
tRNA synthesis
Protein Synthesis
Translation Initiation
Start codon signals where the gene begins (at 5’ end of mRNA) 5’ 3’
AUGGACAUUGAACCG…
start codon

28. Protein Synthesis Translation Initiation
Start codon signals where the gene begins (at 5’ end of mRNA)

29. Protein Synthesis Translation Scanning
The ribosome moves in 5’ to 3’ direction “reading” the mRNA and assembling amino acids into the correct protein
large ribosome subunit
small ribosome subunit

30. Protein Synthesis Translation Scanning
The ribosome moves in 5’ to 3’ direction “reading” the mRNA and assembling amino acids into the correct protein

31. Protein Synthesis Translation Termination
Ribosome disengages from the mRNA when it encounters a stop codon

32. Protein Synthesis Translation
Multiple RNA polymerases can engage a gene at one time
Multiple ribosomes can engage a single mRNA at one time
Transcription
DNA
mRNAs

33. Protein Synthesis
Eukaryotes: transcription occurs in the nucleus and translation occurs in the cytoplasm
Prokaryotes: Transcription and translation occur simultaneously in the cytoplasm

34. RNA There are four main types of RNA:
mRNA - RNA copy of a gene used as a template for protein synthesis
rRNA - part of structure of ribosomes
tRNA - amino acid carrier that matches to mRNA codon
snRNA - found in nucleus where they have several important jobs

35. Practice Questions Why is DNA synthesis said to be “semiconservative”?
What role do DNA polymerase, helicase, topoisomerase, RNA Primase, and ligase play in DNA replication?
What is the difference between how the leading strand and lagging strand are copied during DNA replication? Why do they have to be synthesized differently in this fashion?
What would happen if insufficient RNA Primase were produced by a cell? What if insufficient ligase were produced by a cell?
What are four key differences between DNA polymerase and RNA polymerase? Compare and contrast codons and anticodons?
Why is it necessary in eukaryotes?
During translation, what amino acid sequence would the following mRNA segment be converted into: AUGGACAUUGAACCG?
How come there are only 20 amino acids when there are 64 different codons?