S1-L9: Nucleic Acids

Question 1

Explain what nucleic acids are

Answer 1

• organism store protein structure information in macromolecules known as nucleic acids
• ->this info passed onto daughter cells during cell division
• nucleic acids serve as storage units for our unique hereditary info

Question 2

What does DNA stand for and describe it

Answer 2

• DNA is deoxyribonucleic acid
• basic hereditary material in nucleus
• contains info necessary to make proteins

Question 3

Similarly, what does RNA stand for and describe it

Answer 3

• RNA is ribonucleic acid
• exists in several forms
• translates info found in DNA
• directs protein production in cytoplasm

Question 4

State what is common between DNA & RNA

Answer 4

-both polymers of nucleotides also known as polynucleotides or nucleic acids

Question 5

What is the basic structure of nucleotides?

Answer 5

• nucleotides made up of 3 building blocks
• ->sugar (ribose OR 2-deoxy ribose)
• ->nitrogenous base
• ->phosphate group(s)

Question 6

What is each of the following composed of and outline some key features:

1-Nucleobase
2-Nucleoside
3-Nucleotide

Answer 6

1-is nitrogenous base 
2-nucleobase + sugar 
3-nucleoside + phosphate 
-normally named after nucleobase 
-additional phosphate may be present- nucleotide diphosphate/ nucleotide triphosphate 
-nucleotide can be cyclic

Question 7

Describe a nucleobase (refer to figure 2)

Answer 7

• attach to sugar with B-N-glyosidic link to form nucleoside
• adenosine formed from nucleobases adenine + sugar ribose
• nucleobases can be either pyrimidines OR purines

Question 8

What are pyrimidine nucleobases? (figure 3)

Answer 8

-heterocyclic organic compounds consisting of pyrimidine ring

Question 9

Define a purine (figure 4)

Answer 9

-heterocyclic organic compound consisting of pyrimidine ring infused to an imidazole ring

Question 10

State the common nucleotides which contain ribose

Answer 10

• multiphosphorylated nucleotides (figure 5)
• DNA (in deoxy form) figure 6
• ->other forms exist too (figure 7)
• NAD+ (figure 8)
• cAMP (figure 9)

Question 11

Describe NAD+

Answer 11

1-NAD+: co-enzyme in cellular reactions

• NADP+ is phosphorylated form
• act as e- acceptor (oxidising agent)
• involved in cellular respiration

Question 12

Similarly describe cAMP

Answer 12

• Cyclic AMP can be produced by adenylate cyclase

- cAMP important in cell signalling molecule

Question 13

How may adenosine triphosphate be changed to release energy? (figure 10)

Answer 13

• adensoine triphosphate (ATP) can be dephosphorylated to release energy:
• ATP ADP + P
• ADP AMP + P
• ATP

Question 14

What is Guanosine triphosphate (GTP)?

Answer 14

• it similar to ATP

- important in protein synthesis AND cell signalling

Question 15

Structure of common nucleotides

Answer 15

• purines
• ->adenine/ guanine
• pyrimidines
• ->cytosine/ uracil/ thymine
• nucleoside–>nucleoside monophosphate etc
• figure 11 shows all of the common nucleotides

Question 16

Outline and describe the structure of of a single strand of DNA (figure 12 gives a visual representation)

Answer 16

• DNA polymer made of nucleotides
• phosphate on one nucleotide covalently links (phosphodiester bond) t o2-deoxy ribose sugar on next nucleotide
• ->forms strand (sugar phosphate backbone)
• nitrogenous bases protrude from each sugar unit

Question 17

Explain what DNA is and how it forms (figure 13)

Answer 17

• 2 strands twist around each other- to form double helix
• 2 single DNA strands complementary to each other in terms of orientation AND their nitrogenous base
• structure discovered by Watson & Crick 1953

Question 18

What is the interaction between anti-parallel strands in DNA?

Answer 18

• DNA strands are anti-parallel–> read 5’ to 3’ (figure 14)
• complementary strands have asymmetric ends
• H bonds form between bases which follow base pair rulings (figure 15):
• ->A-T (2 H bonds)
• ->G-C (3 H bonds)

Question 19

Explain what genes are and their function

Answer 19

• portions of DNA

- genes carry instructions for making proteins

Question 20

What does the order of bases determine?

Answer 20

-determines order of amino acids in protein (genetic code)

Question 21

What do proteins determine?

Answer 21

-determine cell structure/function AND identity

Question 22

How may genetic info be passed on?

Answer 22

-DNA able to replicate genetic code to pass genetic info on to daughter cells

Question 23

Outline the way DNA is organised in a cell

Answer 23

-cell–>nucleus–>contains 46 chromosomes–>tightly packed DNA (associated with histone proteins)–>DNA organised in double helix–>DNA determined by sequence of DNA

Question 24

Define the term Karyotype (figure 17)

Answer 24

• number and appearance of chromosomes in nucleus of eukaryotic cell
• Karyotype: (22+X OR Y)=23

Question 25

Describe RNA (refer to 4 diagrams in figure 18)

Answer 25

- RNA similar to DNA except: - ->ribose sugar replaces deoxyribose - ->ribose single-stranded - ->uracil (U) replaces thymine (T)

Question 26

What is the function of RNA?

Answer 26

- RNA serves as template for polynucleotide RNA synthesis | - information contained in DNA preserved in the RNA

Question 27

Outline each of the following types of RNA: 1-Messenger RNA (mRNA) (figure 19) 2-Transfer RNA (tRNA) (figure 20) 3-Ribosomal RNA (rRNA)

Answer 27

1-converts genetic info in DNA into template which used to construct a protein molecule 2-helps transport amino acids which build polypeptide chain of proteins 3-with ribosomal proteins, rRNA makes up ribosomes-the organelles which translate the mRNA

Question 28

How does it all fit together?

Answer 28

- transcription and translation occurs involving all the different features discussed before (involving): - tRNA/mRNA/rRNA - figure 21 shows a visual representation

Question 29

What did Lewin state about the Central Dogma? (figure 22)

Answer 29

- central dogma states that info in nucleic acid can continue indefinitely OR be transferred - ->but transfer of information into protein is irreversible

Question 30

Similarly what did Crick say about the Central Dogma? (figure 22)

Answer 30

-once sequential information has been passed into protein it cannot get out again

Question 31

What is the use of DNA in forensic biology? (figure 23)

Answer 31

- DNA testing for forensic use | - ->forensic DNA "fingerprint analysis"

Question 32

How is DNA used in medicine? (figure 24)

Answer 32

-for medical use-->DNA sequencing AND somatic gene therapy

Question 33

Outline the use of DNA in genetic engineering (figure 25)

Answer 33

- DNA used in genetic engineering to make OR change proteins | - ->like insulin

Question 34

What is gene editing using CRISPR (family of DNA sequences found in genomes of prokaryotic organisms like bacteria/ archaea) ?

Answer 34

- changing single nucleotide genome - ->deletion in certain places and then insertion of DNA - ->good as very specific - reach targeted genome editing - figure 26 gives a visual representation of the process