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Page 1: + B.8 Nucleic Acids. + B8.1 - Describe the structure of nucleotides and their condensation polymers (nucleic acids or polynucleotides). Nucleic Acid –

+

B.8 Nucleic Acids

Page 2: + B.8 Nucleic Acids. + B8.1 - Describe the structure of nucleotides and their condensation polymers (nucleic acids or polynucleotides). Nucleic Acid –

+ B8.1 - Describe the structure of nucleotidesand their condensation polymers(nucleic acids or polynucleotides).

Nucleic Acid – class of biopolymer, carries genetic information, also known as polynucleotides

Nucleotide – monomers of nucleic acids, combine to form polynucleotides

Page 3: + B.8 Nucleic Acids. + B8.1 - Describe the structure of nucleotides and their condensation polymers (nucleic acids or polynucleotides). Nucleic Acid –

+Composition of a nucleotide

Phosphate group

Pentose sugar

Organic nitrogenous base

Page 4: + B.8 Nucleic Acids. + B8.1 - Describe the structure of nucleotides and their condensation polymers (nucleic acids or polynucleotides). Nucleic Acid –

+Nucleotide Composition (con’t)

Phosphate – allows more nucleotides to be added to the chain, forming long strands; ionized, partially responsible for solubility of nucleic acids in water

Pentose Sugar – deoxyribose in DNA, ribose in RNA

Base – Continually synthesized within the cell

Page 5: + B.8 Nucleic Acids. + B8.1 - Describe the structure of nucleotides and their condensation polymers (nucleic acids or polynucleotides). Nucleic Acid –

+Bonding within nucleotides

Phosphate group is bonded covalently with the 5’ carbon of the pentose sugar

Nitrogenous base is bonded covalently with the 1’ carbon of the pentose sugar

Page 6: + B.8 Nucleic Acids. + B8.1 - Describe the structure of nucleotides and their condensation polymers (nucleic acids or polynucleotides). Nucleic Acid –

+Full nucleotide

H atom H atom

Page 7: + B.8 Nucleic Acids. + B8.1 - Describe the structure of nucleotides and their condensation polymers (nucleic acids or polynucleotides). Nucleic Acid –

+Formation of polynucleotides Condensation reaction occurs between the

hydroxyl group on the 3’ carbon of one sugar and the phosphate group on the 5’ carbon of the other sugar releases water and forms a covalent bond (known as

phosphodiester bond)

Page 8: + B.8 Nucleic Acids. + B8.1 - Describe the structure of nucleotides and their condensation polymers (nucleic acids or polynucleotides). Nucleic Acid –

+Intermolecular forces

Hydrogen bonding occurs between the bases 3 bonds occur between guanine and cytosine 2 occur between adenine and thymine/uracil

Page 9: + B.8 Nucleic Acids. + B8.1 - Describe the structure of nucleotides and their condensation polymers (nucleic acids or polynucleotides). Nucleic Acid –

+

B.8.2 Distinguish between the structures of DNA and RNA.

Page 10: + B.8 Nucleic Acids. + B8.1 - Describe the structure of nucleotides and their condensation polymers (nucleic acids or polynucleotides). Nucleic Acid –

+

Cytosine : Guanine bases

Molecules are polynucleotides

Sugar is linked to a phosphate and

nitrogenous base

Deoxyribose sugar (lacks oxygen atom on C2)

Adenine : Thymine bases

Double helix: two polynucleotide chains

held together by hydrogen bonds

Stable towards enzymes and chemicals

Millions of nucleotides per strand (long)

Ribose (pentose) sugar

Adenine : Uracil bases

Typically single-stranded (but can be

double in some cases)

Less stable towards enzymes or chemicals

100-1,000 nucleotides per strand (short)

Page 11: + B.8 Nucleic Acids. + B8.1 - Describe the structure of nucleotides and their condensation polymers (nucleic acids or polynucleotides). Nucleic Acid –

+DNA and RNA* nucleotide structure

*RNA has ribose sugar rather than deoxyribose

Page 12: + B.8 Nucleic Acids. + B8.1 - Describe the structure of nucleotides and their condensation polymers (nucleic acids or polynucleotides). Nucleic Acid –

+Nucleotide Bases

Purines are double-ringed structures Include adenine and

guaninePyrimidines are single-ringed Include cytosine,

thymine (in DNA), and uracil (in RNA)

Purines and pyrimidines bond with one another using hydrogen bonds.

Page 13: + B.8 Nucleic Acids. + B8.1 - Describe the structure of nucleotides and their condensation polymers (nucleic acids or polynucleotides). Nucleic Acid –

+Phosphates

Link sugars together to create a strand backbone Phosphate heads have covalent phosphodiester bonds to

create a DNA or RNA strand

Page 14: + B.8 Nucleic Acids. + B8.1 - Describe the structure of nucleotides and their condensation polymers (nucleic acids or polynucleotides). Nucleic Acid –

+DNA is double-stranded

Page 15: + B.8 Nucleic Acids. + B8.1 - Describe the structure of nucleotides and their condensation polymers (nucleic acids or polynucleotides). Nucleic Acid –

+RNA forms

Messenger mRNA

Transfer tRNA

Ribosomal rRNA Only RNA that can contain thymine

tRNA and rRNA can be either single or double stranded. However, double-stranded RNA does not form a helix like DNA.

Page 16: + B.8 Nucleic Acids. + B8.1 - Describe the structure of nucleotides and their condensation polymers (nucleic acids or polynucleotides). Nucleic Acid –

+B.8.3 Explain the double helical structure of DNA.

DNA consists of two linear polynucleotide strands which are wound together in the form of a double helix

Both chains coil around the same axis

Bases are on the inside of the helix

Sugar-phosphate backbone on the outside

Strands are anti-parallel  run in opposite directions 3’  5” and 5’  3’

Page 17: + B.8 Nucleic Acids. + B8.1 - Describe the structure of nucleotides and their condensation polymers (nucleic acids or polynucleotides). Nucleic Acid –

+B.8.3 Explain the double helical structure of DNA. Two chains held to together by hydrogen bonds between

the bases

Double helical structure is largely due to hydrogen bonding between base pairs.

Four bases Each have an exposed hydrogen, nitrogen, or oxygen These can bond to other exposed hydrogen, nitrogen, or

oxygen

Hydrogen bond Special type of dipole-dipole interaction involving an

attraction between an H atom bonded to an O, N, or F and an O, N, or F atom in another molecule.

Page 18: + B.8 Nucleic Acids. + B8.1 - Describe the structure of nucleotides and their condensation polymers (nucleic acids or polynucleotides). Nucleic Acid –

+

Guanine Cytosine

Adenine Thymine

Page 19: + B.8 Nucleic Acids. + B8.1 - Describe the structure of nucleotides and their condensation polymers (nucleic acids or polynucleotides). Nucleic Acid –

+B.8.3 Explain the double helical structure of DNA.

Hydrogen bonds are weak attractions between a hydrogen atom on one side and an oxygen or nitrogen atom on the other.

Hydrogen atoms of bases serve as the hydrogen bond donors

The carbonyl oxygens and ring nitrogens serve as hydrogen bond acceptors

The specific location of hydrogen bond donor and acceptor groups gives the bases their specificity for hydrogen bonding in unique pairs.

Page 20: + B.8 Nucleic Acids. + B8.1 - Describe the structure of nucleotides and their condensation polymers (nucleic acids or polynucleotides). Nucleic Acid –

+B.8.3 Explain the double helical structure of DNA.

Complementary base pairing Adenine to Thymine Cytosine to Guanine A to T 2 hydrogen

bonds C to G 3 hydrogen

bonds

One purine is paired with one pyrimidine

Page 21: + B.8 Nucleic Acids. + B8.1 - Describe the structure of nucleotides and their condensation polymers (nucleic acids or polynucleotides). Nucleic Acid –

+B.8.3 Explain the double helical structure of DNA.

Usefulness of the structure Hydrogen bonds strongest type of the

intermolecular forceStrong enough to maintain structure and

keep strands togetherWeak enough to separate easily

Replication can occur by breaking the hydrogen bonds

Page 22: + B.8 Nucleic Acids. + B8.1 - Describe the structure of nucleotides and their condensation polymers (nucleic acids or polynucleotides). Nucleic Acid –

+B.8.3 Explain the double helical structure of DNA.

Base stacking Rigid bases stack on top

of one another (much like stacking coins) Purine and pyrimidines

have the same width Hydrophobic interactions

and van der Waal’s forces hold the bases together

Page 23: + B.8 Nucleic Acids. + B8.1 - Describe the structure of nucleotides and their condensation polymers (nucleic acids or polynucleotides). Nucleic Acid –

+B.8.3 Explain the double helical structure of DNA. Van der Waal’s forces draw the bases

closer to each other and the DNA twists to accommodate their positions

The middle of the molecule where the bases are is hydrophobic and the polar groups are in the sugar-phosphate backbone which interacts with the aqueous solution. The hydrophobic interactions

between the bases helps to stabilize the DNA molecule.

Page 24: + B.8 Nucleic Acids. + B8.1 - Describe the structure of nucleotides and their condensation polymers (nucleic acids or polynucleotides). Nucleic Acid –

+ 8.4 - Describe the role of DNA as the repository of genetic information, and explain its role in protein synthesis.

DNA consists of genetic information inherited from both parents

DNA is transcribed into mRNA during transcription

mRNA is processed before leaving the nucleus

mRNA is used as a template for protein synthesis during translation

Page 25: + B.8 Nucleic Acids. + B8.1 - Describe the structure of nucleotides and their condensation polymers (nucleic acids or polynucleotides). Nucleic Acid –

+Transcription

DNA is transcribed into messenger RNA (mRNA)

RNA polymerase binds to the promoter Unwinds the dsDNA to form an open promoter complex and

initiate a transcription bubble

RNA polymerase adds nucleoside triphosphates from a 3’ to 5’ direction on the DNA (antisense) template strand 5’ end of RNA comes out first Nucleoside Triphosphates are being added 5’ to 3’

Page 26: + B.8 Nucleic Acids. + B8.1 - Describe the structure of nucleotides and their condensation polymers (nucleic acids or polynucleotides). Nucleic Acid –

+Transcription (con’t)

The transcription bubble moves from the DNA promoter region towards the terminator

The terminator is a sequence of nucleotides that, when transcribed, causes the RNA polymerase to detach from the DNA

The transcript carries the code of the DNA and is referred to as messenger RNA (mRNA)

Page 27: + B.8 Nucleic Acids. + B8.1 - Describe the structure of nucleotides and their condensation polymers (nucleic acids or polynucleotides). Nucleic Acid –

+Translation

Basic Information mRNA is read in triplets by the tRNA Triplets of mRNA are called codons tRNA molecules have 3 bases which make anticodons

Respond to a specific amino acid that they carry The complimentary tRNA link with mRNA and the

amino acids start to line up in the right order and form peptide bonds to make a polypeptide strand

Page 28: + B.8 Nucleic Acids. + B8.1 - Describe the structure of nucleotides and their condensation polymers (nucleic acids or polynucleotides). Nucleic Acid –

+Translation

The genetic code A triplet code

Same in all organisms - universal Sequence of bases in DNA dictates the sequence of amino

acids in all proteins via RNA This area of biology is called the central dogma

Page 29: + B.8 Nucleic Acids. + B8.1 - Describe the structure of nucleotides and their condensation polymers (nucleic acids or polynucleotides). Nucleic Acid –

+

Page 30: + B.8 Nucleic Acids. + B8.1 - Describe the structure of nucleotides and their condensation polymers (nucleic acids or polynucleotides). Nucleic Acid –

+8.5 DNA Profiling

Outline the steps involved in DNA profiling and state its use Aim 8: include forensic and paternity tests DNA profiling uses the techniques of genetic engineering to

identify a person from a sample of their DNA Blood, tissue, urine, bodily fluids

Used for criminal cases and paternity tests

Page 31: + B.8 Nucleic Acids. + B8.1 - Describe the structure of nucleotides and their condensation polymers (nucleic acids or polynucleotides). Nucleic Acid –

+DNA

DNA contains coding and non coding DNA

There are large portions of DNA that are identical in everyone. But some fragments of our DNA are unique to each individual They are called the non-coding regions or “satellite DNA” Do not code for anything and are highly repetitive in sequence (5-

300 bases long) Creates the dense and less dense regions of a DNA fingerprint

used to differentiate between individuals

Page 32: + B.8 Nucleic Acids. + B8.1 - Describe the structure of nucleotides and their condensation polymers (nucleic acids or polynucleotides). Nucleic Acid –

+STRs

Thenon-coding regions that repeat are called short-tandem repeats (STRs).

Theseare looked form in multiple locations of the genome to make the tests (DNA profiling tests) more discriminating.

Page 33: + B.8 Nucleic Acids. + B8.1 - Describe the structure of nucleotides and their condensation polymers (nucleic acids or polynucleotides). Nucleic Acid –

+The Steps of DNA Profiling

1. Samples of cells are obtained & DNA is extracted• The sample is usually taken from blood or urine

2. Using restriction enzymes, the DNA is cut into small, double stranded fragments

3. PCR (polymerase chain reaction)is used to copy and amplify the DNA sample to produce a sufficient amount of DNA to analyze

Page 34: + B.8 Nucleic Acids. + B8.1 - Describe the structure of nucleotides and their condensation polymers (nucleic acids or polynucleotides). Nucleic Acid –

+The Steps of DNA Profiling (cont’d)

4. The fragments of DNA are then separated by gel electrophoresis into bands of different lengths

• Remember: DNA fragments are negatively charged due to the phosphate groups

• Place DNA in the negative side because the molecules will be attracted to the positive terminal

• Shorter fragments will move further through the gel.

5. The bands are then analyzed and compared for results

The bands need to be visualized by fluorescent staining and using UV light or by using a radioactive 32P-labelledDNA probe which is exposed using X-ray film

Page 35: + B.8 Nucleic Acids. + B8.1 - Describe the structure of nucleotides and their condensation polymers (nucleic acids or polynucleotides). Nucleic Acid –

+DNA Profiling – Paternity Tests

The chromosomes of the mother and father are cut with the same restriction enzymes

A band present in the child must come from either the mother of the father

Who is the child’s father?

Page 36: + B.8 Nucleic Acids. + B8.1 - Describe the structure of nucleotides and their condensation polymers (nucleic acids or polynucleotides). Nucleic Acid –

+

Example 2 : Who is Eileen’s father?

DNA Profiling – Paternity Tests

Page 37: + B.8 Nucleic Acids. + B8.1 - Describe the structure of nucleotides and their condensation polymers (nucleic acids or polynucleotides). Nucleic Acid –

+DNA Profiling – Forensic Investigations

A sample of DNA is taken from the victim or from the crime scene

DNA samples are then taken from 3 suspects

The bands of the suspects are compared to the sample at the crime scene

The victim’s DNA is also eliminated from the sample at the crime scene

Which suspect committed the crime?

Page 38: + B.8 Nucleic Acids. + B8.1 - Describe the structure of nucleotides and their condensation polymers (nucleic acids or polynucleotides). Nucleic Acid –

+sources

http://brakkeibchem1.wikispaces.com/file/view/TBD08+-+02.02.11+-+B8+Nucleic+Acids.pdf

http://www.usask.ca/education/coursework/mcvittiej/bio30unit1/overheads/1.23.htm

http://ookgm.meb.gov.tr/userfiles/file/programlar/ibo/chem_syllabusguideline(2009).pdf

http://www.microbiologyprocedure.com/genetics/chemical-nature-of-genetic-materials/molecular-structure-of-rna.htm


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