Scanning probe microscope observation of plastic DNA. Progressive images from atomic force microscopy show the compaction of DNA in yeast

Left: A digitally-colorized scanning electron micrograph shows the RNA virus Ebola virus particles (blue) budding from a chronically-infected VERO E6 cell (yellow-green).

Right: Simple extraction of strawberry DNA.

1.6 Nucleic acid

Objectives

• Importance of nucleic acid

• Types of nucleic acid

• Differences of DNA and RNA

Importance of nucleic acid 核酸• Include DNA (deoxyribonucleic

acid) in nucleus, mitochondria and chloroplast, and RNA (ribonucleic acid) in chloroplast.

• Form molecules that codes the genetic information in the cell (DNA, or RNA in some virus).

• Basis for genetic variation.

• Protein synthesis: translating the genetic codes into protein (RNA).

• Regulate gene expression (RNA).The Central Dogma 分子生物學的中心法则: DNA Encodes RNA, RNA Encodes Protein. The central dogma of molecular biology describes the flow of genetic information in cells from DNA to messenger RNA (mRNA) to protein.

Quiz

• The information for protein synthesis is stored in:

a. amino acids

b. fats

c. glucose

d. nucleic acids

Chemical composition• Nucleic acids is made up

with chemical elements carbon, hydrogen, oxygen, nitrogen, and phosphorus.

• Nucleic acids is enormous and complex.

• The monomers of nucleic acid are nucleotides 核苷酸.

• A nucleotide is formed by a nitrogenous base, a pentose sugar (or five-carbon sugar), and a phosphate group.

Quiz

• Which are the compositions of DNA?

a. Deoxyribose, Nucleic acid, Phosphate group

b. Deoxyribose, Nitrogenous base, Phosphate group

c. Ribose, Nitrogenous base, Phosphate group

d. Ribose, Cytosine, Adenine, Phosphate group

Types of nucleotides

• Five types of nitrogenous base: adenine (A), guanine (G), cytosine (C), thymine (T) and Uracil (U).

Naming convention

• Nucleotides are generally refers by their nitrogenous bases, i.e. adenine (A), guanine (G), cytosine (C), thymine (T) and Uracil (U).

“adenine” “thymine”

Quiz

• How many nucleotide bases occur in a nucleic acid:

a. five

b. four

c. infinite

d. six

Quiz

• What nucleotide base does RNA contain that DNA does not:

a. adenine (A)

b. cytosine (C)

c. thymine (T)

d. uracil (U)

• The double helix is condensed into chromatin and chromosome (during replication 复制)

Structure of DNA

• The double helix form of DNA is more stable.

染色体

染色质

(for replication)

Quiz

• The sugar that is in the backbone of DNA is called:

a. deltaglucose

b. deoxyribose

c. fructose

d. ribose

Conclusion

• Nucleic acid is a polymer of nucleotides, which include DNA and RNA.

• Nucleotides store genetic information that is heritable and codes for protein synthesis.

• Nucleic acids is consists of carbon, hydrogen, oxygen, nitrogen, and phosphorus.

• A nucleotide is formed by a nitrogenous base, a pentose sugar (or five-carbon sugar), and a phosphate group.

• There are five nitrogenous bases, adenine (A), guanine (G), cytosine (C), thymine (T) (only in DNA) and Uracil (U) (only in RNA).

Short-answer question

• Below is the table about monosaccharide and nucleic acid. Mark “✓” (correct) or “✘” (wrong) for statements regarding monosaccharide and nucleic acid.

Explanations Monosaccharide Nucleic acids

Generally contains C, H, O

Can form long chain of molecules

Obtained by hydrolysis of starch

Basic unit of genetic materials

Can be broken down tp produce energy

Explanations Monosaccharide Nucleic acids

Generally contains C, H, O ✓ ✓

Can form long chain of molecules ✓ ✘

Obtained by hydrolysis of starch ✓ ✘

Basic unit of genetic materials ✘ ✓

Can be broken down tp produce energy ✓ ✘