3.8 - Nucleic Acids
How are the two strands that make up DNA held together?
By hydrogen bonds
How are phosphodiester bonds broken?
By hydrolysis
How do DNA nucleotides form polymers?
By the formation of phosphodiester bonds in condensation reactions
How do RNA nucleotides form polymers?
By the formation of phosphodiester bonds in condensation reactions
What elements are found in nucleic acids?
Carbon, hydrogen, oxygen, nitrogen and phosphorous
How does complementary base pairing affect the amount of nitrogenous bases in DNA?
Complementary base pairing means that DNA always has equal amounts of adenine and thymine, and equal amounts of cytosine and guanine. This is because in DNA the only base that can bind to adenine is thymine, so there will be equal amounts. The only base that can bind to cytosine in DNA is guanine, so there will be equal amounts.
Nucleotides are linked together by ______ reactions to form a polymer called a _______
Condensation Polynucleotide
What type of reaction combines DNA nucleotides to form polynucleotides?
Condensation reaction
What type of reaction combines RNA nucleotides to form polynucleotides?
Condensation reaction
What type of bond are phosphodiester bonds?
Covalent
What is the name of the base, represented by the letter C?
Cytosine
Name the pyrimidines
Cytosine, Thymine and Uracil
Name all of the types of nucleic acid
DNA and RNA
Describe the differences between DNA and RNA nucleotides
DNA nucleotides have deoxyribose sugars, whereas RNA nucleotides have ribose sugars. DNA contains the bases adenine, cytosine, guanine and thymine. However RNA does not contain the base thymine, and instead has the base uracil.
Explain the relationship between DNA and RNA in protein synthesis
DNA stores all of the genetic information needed by an organism, however the DNA of each eukaryotic chromosome is a very long molecule, and is unable to leave the nucleus in order to supply the information directly to the sites of protein synthesis. The short section of the long DNA molecule corresponding to a single gene is transcribed into a similarly short messenger RNA molecule (mRNA).
What does DNA stand for?
Deoxyribonucleic acid
What components make up the backbone of a DNA molecule?
Deoxyribose sugars and phosphate groups
Explain how the structure of DNA is ideally suited to it's role
It is a polymer so contains a lot of information. The sequence of bases is used to code for proteins. The molecule is double stranded, and therefore stable. The molecule is double stranded and so replication is accurate.
Why is RNA important?
It plays a very important role in the transfer of genetic information from DNA to the proteins that make up the enzymes and tissues of the body
What is mRNA?
Messenger RNA
What is mtDNA?
Mitochondrial DNA
If you were to do a DNA extraction from plant material, using ethanol, salt, protease, detergent etc. what would form/ would the DNA look like?
The DNA will be seen as white strands forming between the layer of sample and layer of alcohol
What happens to the RNA molecules after protein synthesis has occurred?
The RNA molecules are degraded in the cytoplasm- the phosphodiester bonds are hydrolysed and the RNA nucleotides are released and reused
DNA is a double helix composed of two 'backbones', and connected by 'rungs'. What are the 'backbones' and 'rungs' referring to?
The backbones are composed of deoxyribose-phosphate molecules (they are polynucleotides) and the 'rungs' are the pairs of bases (complementary bases connected by hydrogen bonds)
Imagine a vertical strand of DNA. How long would a length of DNA containing 10 base pairs ('rungs') be? And how wide would the base of the strand be?
The length of 10 base pairs would be 3.4 nm, while the width of the strand would be 2 nm
What is the 3 prime end (3' end)?
The part of the pentose with the OH exposed
What is the 5 prime end (5' end)?
The part of the pentose with the phosphate exposed
Where on the pentose sugar is the phosphate group?
The phosphate group is on the fifth carbon (a pentose sugar is a pentagon shape. First carbon is the carbon at the right, fifth carbon is the carbon coming off the ring)
What is complementary base pairing?
The standard arrangement of bases in nucleotides in relation to their opposite pairing, such as thymine being paired with adenine and cytosine paired with guanine.
How does an RNA nucleotide differ from a DNA nucleotide in terms of structure?
The sugar in DNA is deoxyribose, whereas RNA has ribose. Also thymine is not found in RNA, and instead the complementary base of adenine in RNA is uracil.
Describe the structure of DNA
There are two strands of polynucleotides coiled into a double helix. These strands are antiparallel (they run in opposite directions), and the two strands are held together by hydrogen bonds.
What is the name of the base, represented by the letter T?
Thymine
Like ______, uracil is a _______ that forms ______ hydrogen bonds with it's complementary base _______
Thymine Pyrimidine Two Adenine
In DNA, which bases are complementary?
Thymine bonds with Adenine Cytosine bonds with Guanine
What base is different in RNA?
Thymine is changed to Uracil
RNA molecules are small enough to leave the nucleus. Where do they go?
To the ribosomes- the site of protein synthesis
True or false? Both deoxyribose and ribose are pentose sugars
True
True or false? Nucleic acids are large molecules
True
True or false? Nucleic acids are polymers
True
True or false? Nucleotides are monomers
True
True or false? Phosphodiester bonds are covalent
True
True or false? Purine bases are larger, while pyrimidine bases are smaller
True
True or false? The phosphate group found in nucleotides are acidic
True
True or false? Uracil is a pyrimidine
True
How many carbon rings do purines have?
Two
How many carbon rings does Adenine have?
Two
How many types of nucleic acid are there?
Two
The four bases found in DNA can be divided into how many groups?
Two
What is the sugar in DNA?
deoxyribose
How does deoxyribose differ from ribose?
deoxyribose has one less oxygen atoms/ ribose has one more oxygen atoms than deoxyribose
A phosphodiester bond forms between the phosphate group attached to the fifth carbon and the ______ group attached to the _____ carbon of an adjacent nucleotide
hydroxyl group attached to the third carbon
What is the anagram for messenger RNA?
mRNA
In terms of nucleic acids, the monomer is called a _______ and the polymer a ________
monomer = a nucleotide polymer = polynucleotide
What is the anagram for mitochondrial DNA?
mtDNA
Define heredity
the passing on of physical or mental characteristics genetically from one generation to another.
Explain the base pairing rule
-A pyrimidine base always pairs with a purine base, and vice versa -Adenine and thymine/uracil always hydrogen bond together -Cytosine and guanine always hydrogen bond together
A sample of DNA was tested and 17% of the total bases present were found to be adenine. Calculate the percentages of each of the other three bases present in this sample.
17% = thymine 33% = cytosine 33% = guanine
How many carbon rings does Guanine have?
2
How many hydrogen bonds does uracil form with it's complementary base?
2
What type of bond forms between thymine and adenine, and how many?
2 hydrogen bonds
Which of the following represents the genetic material that DNA is transcribed into, for transport to the site of protein synthesis? 1) mDNA 2) mRNA 3) mtDNA 4) mtRNA
2)mRNA
A 6.8 nm long section of DNA contains 11 guanine bases. Determine the remaining number of bases present.
20 base pairs overall (10 base pairs= 3.4 nm, so 20 base pairs= 6.8 nm) 11 cytosine bases 9 thymine bases 9 adenine bases
A 3.4 nm long section of DNA contains 3 cytosine bases and 7 thymine bases. How many guanine bases are there?
3
An individual nucleotide is made up of ___ components
3
What type of bond forms between cytosine and guanine, and how many?
3 hydrogen bonds
Which of the following represents the genetic material in mitochondria? 1) mDNA 2) mRNA 3) mtDNA 4) mtRNA
3) mtDNA
How many carbon atoms are in a pentose monosaccharide?
5
How many carbon atoms does deoxyribose have?
5
How many carbon atoms does ribose have?
5
A 3.4 nm long section of DNA contains 4 cytosine bases and 6 adenine bases. How many thymine bases are there?
6
What is a nitrogenous base?
A complex organic molecule containing one or two carbon rings in its structure as well as nitrogen
What type of sugar is deoxyribose?
A pentose monosaccharide
What type of sugar is ribose?
A pentose monosaccharide
State the components of a nucleotide
A pentose monosaccharide A phosphate group A nitrogenous base
Name the 3 components of a nucleotide
A pentose sugar A phosphate group A nitrogenous base
What is a polynucleotide?
A polymer made up of nucleotide monomers
Explain the base pairing rules in terms of purines and pyrimidines
A small pyrimidine base always binds to a larger purine base
Name all 4 bases in DNA by their letters
A, C, G, T
Nucleic acids are slightly ______
Acidic
What is the name of the base, represented by the letter A?
Adenine
Which is larger: Adenine or Cytosine?
Adenine
Name the purines
Adenine and Guanine
Classify the following bases as pyrimidines and purines: Adenine, Cytosine, Guanine, Thymine
Adenine and Guanine = Purines Cytosine and Thymine = Pyrimidines
Name the bases that are found in DNA
Adenine, cytosine , guanine and thymine
What are the bases found in RNA?
Adenine, cytosine, guanine and uracil
What groups are involved in a phosphodiester bond?
An OH group and phosphate group
Why are the two coiled polynucleotide chains parallel to one another?
Because of the arrangement of the bases- a small pyrimidine base always binds to a larger purine base
Why is there a constant distance between the DNA 'backbones'?
Because of the arrangement of the bases- a small pyrimidine base always binds to a larger purine base.
The temperature should be kept low throughout the DNA extraction procedure. Suggest why.
Because the procedure involves the use of a protease. This is an enzyme, and so will denature if the temperature is too high.
Where do phosphodiester bonds form?
Between the phosphate group on the fifth carbon of one pentose sugar, and the hydroxyl (OH) group of the third carbon of an adjacent pentose sugar
How are phosphodiester bonds formed?
By condensation
How are nucleotides linked together?
By condensation reactions
Explain why detergent breaks down cell membranes.
Detergent contains emulsifiers, which have a polar end and non-polar end. These act on the cell membrane, which is made up of phospholipids, which also have regions of polarity and non-polarity.
What phrase is used to describe the shape of DNA?
Double helix
True or false? Nucleic acids are monomers
False
True or false? Nucleic acids are neither polymers nor monomers
False
True or false? Nucleic acids are small molecules
False
True or false? Nucleotides are polymers
False
True or false? Phosphodiester bonds are ionic
False
True or false? Purine bases are usually equal in size to pyrimidine bases
False
True or false? Purines bond with purines and pyrimidines bond with pyrimidines
False
True or false? Pyrimidine bases are larger, while purine bases are smaller
False
True or false? The phosphate group found in nucleotides are alkaline
False
True or false? Uracil is a purine
False
How many different bases are there in DNA?
Four
The nucleotides in DNA each have one of how many bases?
Four
Explain the procedure to extract DNA from plant material. State each step, and explain why this step is necessary
Grind sample with a pestle and mortar- this breaks down the cell walls Mix the sample with detergent- this breaks down the cell membrane, releasing the cell contents into the solution Add salt- this breaks the hydrogen bonds between the DNA and water molecules Add protease enzyme- this will break down the proteins associated with the DNA in the nuclei Add a layer of ethanol on top of the sample- alcohol causes the DNA to precipitate out of solution
What is the name of the base, represented by the letter G?
Guanine
Which is larger: Guanine or Uracil?
Guanine
Nucleic acids are the basis of ______
Heredity
________ bonds are formed between two bases
Hydrogen
Complementary bases bond to one another. What type of bonds are formed between these bases?
Hydrogen bonds
What type of bond holds the two strands of DNA together?
Hydrogen bonds
What reaction breaks down polynucleotides into nucleotides
Hydrolysis
What reaction breaks phosphodiester bonds?
Hydrolysis
Are DNA molecules small enough to leave the nucleus?
No
What is the name of the polymer that is made up of nucleotides?
Nucleic acids
What molecule/s are/is the basis of heredity?
Nucleic acids (DNA and RNA)
What is the name of the monomer that makes up nucleic acids?
Nucleotides
How many bases are attached to each sugar in the sugar-phosphate backbone?
One
How many carbon rings do pyrimidines have?
One
How many carbon rings does Cytosine have?
One
How many carbon rings does Thymine have?
One
A phosphodiester bond forms between the hydroxyl group attached to the third carbon and the ______ group attached to the _____ carbon of an adjacent nucleotide
Phosphate group attached to the fifth carbon
What is the name of the bond that holds RNA nucleotides together in a polymer?
Phosphodiester bonds
What is the name of the bonds that hold nucleotides together in a polynucleotide?
Phosphodiester bonds
What type of bond forms when the backbone of a polynucleotide is synthesised?
Phosphodiester bonds
Condensation of deoxyribose nucleotides forms covalent phosphodiester bonds. What other word could be used instead of 'condensation'?
Polymerisation
What is the name of the larger bases?
Purines
What type of base has a double carbon ring?
Purines
What is the name of the smaller bases?
Pyrimidines
What type of base has a single carbon ring?
Pyrimidines
What are the two types of bases?
Pyrimidines and purines
What are the groups that the four bases found in DNA can be divided into? Which bases are in which groups?
Pyrimidines- Thymine and cytosine Purines- Adenine and guanine
What does RNA stand for?
Ribonucleic acid
What phrase is used to describe the structure of an RNA molecule?
Single Helix
State two roles of DNA
Storage and transfer of genetic information Synthesis of polypeptides
State two roles of RNA
Storage and transfer of genetic information Synthesis of polypeptides
DNA cannot be transported to the site of protein synthesis. Why? How is this problem overcome?
The DNA of each eukaryotic chromosome is a very long molecule, and is unable to leave the nucleus. The short section of the long DNA molecule corresponding to a single gene is transcribed into a similarly short messenger RNA molecule (mRNA).
Are RNA molecules small enough to leave the nucleus?
Yes
