1 - Structure of RNA and DNA

What is a nucleotide made up of?

* Pentose sugar (5C, ribose/deoxyribose)
* Phosphate group
* Nitrogenous organic base

What are the five bases in nucleotides?

* Cytosine
* Thymine
* Uracil
* Adenine
* Guanine

What does adenine pair with in DNA?

Thymine

What does adenine pair with in RNA?

Uracil

How are the parts of a nucleotide joined to make a nucleotide and nucleotides joined?

Condensation reactions

What is formed when two mononucleotides are joined by a condensation reaction?

Dinucleotide

What is formed when many mononucleotides are joined by condensation reactions?

Polynucleotides

How are mononucleotides bonded together?

Strong covalent phosphodiester bond between pentose sugar and phosphate group in adjacent nucleotides, catalysed by DNA polymerase

How is RNA structured?

Single-stranded, relatively short polynucleotide

What is the pentose sugar in RNA?\`

Ribose

What are the bases in RNA?

* Adenine
* Uracil
* Cytosine
* Guanine

What are the types of RNA?

* mRNA
* rRNA
* tRNA

What is the function of mRNA?

Transfer genetic information from DNA to ribosomes

What is the structure of mRNA?

Single-stranded

Where is mRNA found?

Cytoplasm & nucleus

What is the function of rRNA?

Makes up ribosomes with proteins

What is the structure of rRNA?

Single stranded

Where is rRNA found?

Ribosomes

What is the function of tRNA?

Carries amino acids for photosynthesis

What is the structure of tRNA?

Folded clover leaf with H bonds

Anti-codon specific to codons

Where is tRNA found?

Cytoplasm

When and how was DNA discovered and who by?

1953

Watson, Crick & Franklin

X-ray diffraction patterns

Where is DNA found?

Nucleus

What is the pentose sugar in DNA?

Deoxyribose

What are the bases in DNA?

* Adenine
* Thymine
* Cytosine
* Guanine

What is the structure of DNA?

2 long polynucleotide strands joined by H bonds between bases

What bonds hold together bases?

Hydrogen bonds

How many bonds are there between adenine and thymine?

2 H bonds

How many bonds are there between cytosine and guanine?

3 H bonds

How are A and T or C and G described in relation to each other?

Complementary

How does the ratio of AT and CG change between species?

Varies

What is the double helix in DNA?

Phosphate and deoxyribose uprights wind around each other, form structural backbone

How does the phosphodiester backbone of DNA provide stability?

Protects more reactive bases inside the double helix

How do the hydrogen bonds in DNA provide stability?

Form bridges between phosphodiester uprights

Higher proportion of CG = more H bonds = more stable

How do the interactive forces between base pairs in DNA provide stability?

Hold molecules together = base stacking

What is the function of DNA?

Hereditary material responsible for passing genetic material

How many possible sequences of bases in DNA are there?

Almost infinite variety

What is the effect of the variety in DNA base sequences?

Provides genetic variety

What are the adaptations of DNA?

* Stable structure
* 2 strands joined by H bonds
* Large
* Backbone
* Base pairing
* Weak H bonds

How does having a stable structure help DNA?

Rarely mutates

How does having 2 strands joined by H bonds help DNA?

Separate during DNA replication & protein synthesis

How does being large help DNA?

Lots of genetic information

How does having backbone help DNA?

Protects genetic information somewhat from corruption by outside chemical & physical forces

How does having base pairing help DNA?

DNA can replicate & transfer information as mRNA

How does having weak H bonds help DNA?

Easy unzipping of two strands during replication