Molecular Biology - 2.6 Structure of DNA and RNA

Question 1

Understandings:

Answer 1

The nucleic acids DNA and RNA are polymers of nucleotides

DNA differs from RNA in the number of strands present, the base composition and the type of pentose

(structure) DNA is a double helix molecule made of two antiparallel strands of nucleotides linked by hydrogen bonding between complementary base pairs

Question 2

Nucleic acids:

Answer 2

group of chemicals in cells concerned with the transmission of inherited information

The two types:
1. Deoxyribose Nucleic Acid (DNA)
2. Ribose Nucleic Acid (RNA)

They are also POLYMERS OF NUCLEOTIDES

Question 3

Polymers of nucleotides

Answer 3

a large molecule made up of repeated nucleotide units

Question 4

What is a nucleotide made up of?

Answer 4

• a 5-carbon sugar (ribose or deoxyribose)
• A phosphate group
• Nitrogen base (guanine, adenine, thymine, cytosine, uracil)

= bonds within the nucleotide are COVALENT bonds

Question 5

more about nucleotide BASE COMPONENTS:

Answer 5

Purines (double ringed molecules):
- Adenine
- Guanine

Pyrimidines (single ringed molecules):
- Cytosine
- Thymine
- Uracil

Question 6

Complementary base pairing:

Answer 6

(occours by way of WEAK HYDROGEN BONDS between the completementart bases)

(Shapes of the molecules determine what they bind to):

DNA = A <-> T (2 hydrogen bonds)
RNA = A <-> U

DNA & RNA = C <-> G (3 hydrogen bonds)

Question 7

DNA (Deoxyribonucleic Acid) - INFORMATION

Answer 7

“DNA carries the genetic message for the functioning of the organism”

Can be found in:
= Chromsomes in the nucleus of eukaryotes and in the plastids of prokaryotes”
= Mitochondria
= Chloroplasts

2 strands

Question 8

What is a gene?

Answer 8

A gene is a length of DNA that codes for a polypeptide which forms a protein (ie DNA codes for the synthesis of Proteins

Question 9

DNA structure

Answer 9

Understanding:
DNA is a double helix molecule made of two antiparallel (opposite directions) strands of nucleotides linked by hydrogen bonding between complementary base pairs - the 5 carbon sugars are known as DEOXYRIBOSE (the pointy end is 5’ and the flat end is 3’) - one side of the ladder has the sugers going up and the other has the sugars going down

Nucleic acids are composed of nucleotide monomers which are linked into a single strand via condensation reactions

The phosphate group of one nucleotide attaches to the sugar of another nucleotide (at the 3’– hydroxyl (-OH) group)
This results in a phosphodiester bond forming between the two nucleotides (and water is produced as a by-product)
Successive condensation reactions result in the formation of long polynucleotide strands

As the antiparallel chains lengthen, the atoms will organise themselves into the most stable energy configuration

The two strands of DNA are described as being antiparallel

Two polynucleotide chains of DNA are held together via hydrogen bonding between complementary nitrogenous bases

Adenine (A) pairs with Thymine (T) via two hydrogen bonds
Guanine (G) pairs with Cytosine (C) via three hydrogen bonds

Question 10

Extra information for DNA - need to know

Answer 10

• one turn of the helix (structure) contains 10 nucleotide
• 3 DNA bases (= a triplet) code for ONE amino acid
• Sizes of molecules (some of the thing = equivalent to roughly how many molecules):
  Virsus = 5-200 kb (kilo base pairs)
  Bacteria = 500-5000kb
  Yeast = 13,500kb
  Fruit Fly = 165,000kb
  Human = 2,900,000kb

Question 11

DNA history (part 1) - CRICK AND WATSON

Answer 11

1953 - They took paper shapes and found that A&T and G&C would match and that A&T needed 2 bonds and G&C needed 3 bonds to fit in the double helix shape - used the shape that was discovered by FRANKLIN

https://ib.bioninja.com.au/standard-level/topic-2-molecular-biology/26-structure-of-dna-and-rna/watson–crick.html

Question 12

DNA history (part 2) - ROSALIND FRANKLIN (AND WILKINS)

Answer 12

Crick and Watson treated her and her legacy like she was below them ->

She used an X-ray defraction technique to show the double helix model in crustallised DNA (photos were taken (“photograph 51” was the photo that proved it)) - Watson and Crick took these photos/ideas and based their research off it

https://ib.bioninja.com.au/standard-level/topic-2-molecular-biology/26-structure-of-dna-and-rna/watson–crick.html

Question 13

RNA =

Answer 13

Ribose Nucleic Acid

RNA (ribonucleic acid) is a more versatile single stranded form that transfers the genetic information for decoding

Pentose sugar = ribose (instead of deoxyribose)
(U (Uracil) instead of T (thymine))

one strand

Question 14

how RNA differs from DNA

Answer 14

1. sugar = ribose (instead of deoxyribose)
2. Base Uracil (instead of thymine)
3. Sting strand (instead of double helix)
4. less stable than DNA
5. Small (DNA is 1000 - 1,000,000x larger)

Question 15

The three types of RNA

Answer 15

1. messenger RNA (mRNA)
2. transfer RNA (tRNA)
3. Ribosomal RNA (rRNA)

Many VIRUSES only contain RNA rather than DNA

Question 16

Messenger RNA (mRNA)

Answer 16

carries the genetic information from the nucleus to the ribosome. It is a long string with nucleotides arranged in groups (3 base = CODON)

Question 17

Codon =

Answer 17

3 based in mRNA = each code for a specific amino acid

complimentary to ANTICODON (tRNA)

Question 18

Transfer RNA (tRNA)

Answer 18

‘clover leaf’ shaped molecule

3-base code = ANTICODON (complementary to the condom on mRNA), at the other end it has the appropriate amino acid

Question 19

Ribosomal RNA (rRNA)

Answer 19

makes up part of the structure of the ribosomes = the site of protein synthesis