1. Lecture 21 Nucleic Acids
Nucleic acids are
molecules that store information for cellular
growth and reproduction;
deoxyribonucleic acid (DNA) and ribonucleic
acid (RNA) are large molecules consisting of
long chains of monomers called nucleotides

2. The bases in DNA and RNA are
pyrimidines C, T, and U
and purines A and G
In DNA, the bases are A: T
G: C
In RNA, U replaces T
The sugars are :

3. A nucleotide is formed when a sugar combines with a base and phosphate

4. Adding phosphate groups to AMP forms the diphosphate ADP and the triphosphate ATP.

5. The primary structure of RNA and DNA is the sequence of the four nucleotides A-T-G-C in DNA and A-U-G-C in RNA
The nucleotides are combined in the sequence:
phosphate-sugar-phosphate sugar attached at the 3’ and 5’ locations of the sugar

6. An example of a partial structure of RNA

7. In DNA, the amount of A always equals the amount of T; G equals the amount of C

8. The DNA structure is a double helix
that consists of two strands of
nucleotides that form a double helix
structure like a spiral stair case;
DNA has hydrogen bonds between
the bases A–T and G–C;
DNA has bases along one strand that complement the bases along the other

9. When DNA unravels into a single strand, a duplicate copy of the departed strand can be reproduced

10. In RNA uracil replaces thymine

11. The sequence in DNA is transmitted to messenger RNA
RNA has several types:
Messenger RNA (mRNA) carries genetic information from DNA to the ribosomes.
Transfer RNA (tRNA) brings amino acids to the ribosome to make the protein.
Ribosomal RNA (rRNA) makes up 2/3 of ribosomes where protein synthesis takes place.

12. aminoacid attached here
Each tRNA
has a triplet called an anticodon that complements a codon on mRNA;
bonds to a specific amino acid at the acceptor stem;
there is a transfer tRNA for every amino acid
tRNA binds to -A-A-A on mRNA here which was TTT in DNA

13. Where you see UUU, the DNA must have read AAA; UUC was AAG

14. The activation of tRNA
occurs when a synthetase uses energy from ATP hydrolysis to attach an amino acid to a specific tRNA
each tRNA uses a triplet called an anticodon to complement a codon on mRNA
For the initiation of protein synthesis,
an mRNA attaches to a ribosome
the start codon (AUG) binds to a tRNA with methionine
the second codon attaches to a tRNA with the next amino acid
a peptide bond forms between the adjacent amino acids at the first and second codons

15. How is it known that for example, UUU or UUC only codes for phenylalanine
If a synthetic mRNA with only the UUU is used, the protein that is synthesized is polyphenylalanine even though all other tRNA’s are present

17. A mutation
alters the nucleotide sequence in DNA
results from mutagens such as radiation and chemicals
produces one or more incorrect codons in the corresponding mRNA
produces a protein that incorporates one or more incorrect amino acids
causes genetic diseases that produce defective proteins and enzymes
Phenyketonuria results when phenylalanine cannot be converted to tyrosine due to the lack of the enzyme phenylalanine hydroxylase
large amounts of phenylalanine and phenylpyruvate lead to mental retardation

18. Hemoglobin is made up of 2  and 2 chains
Hemoglobin is made up of 2  and 2 chains. Each carries a heme which contains the Fe+
gene DNA code
... ATG-GTG-CAC-CTG-ACT-CCT-GAG-GAG-AAG-TCT-GCC
normal chain:Val- His- Leu- Thr - Pro – Glu -Glu - Lys - Ser - Ala
... ATG-GTG-CAC-CTG-ACT-CCT-GTG-GAG-AAG-TCT-GCC
missense Val- His- Leu- Thr - Pro - Val -Glu - Lys - Ser - Ala
mutation: the sickle cell mutation
... ATG-GTG-CAC-CTG-ACT-CCT-GAG-GAG-TAG-TCT-GCC
Val- His- Leu- Thr - Pro – Glu -Glu - STOP
nonsense mutation resulting in  thalassemia
... ATG-GTG-CAC-CTG-ACC-CTG-AGG-AGA-AGT-CTG-CC...
Val- His- Leu- Thr - Leu– Arg -Arg - Ser - Leu ...
frameshift mutation also resulting in  thalassemia

19. Genetic diseases result from a mutation which results in a defective enzyme.