A1.2 Nucleic Acids

Question 1

State thetwo primary functions of nucleic acids.

Answer 1

Nucleic acids have 2 functions :

1.Pass information between generations

2.Code for protein production

Question 2

State the two types of nucleic acids used in cells.

Answer 2

1.RNA - ribonucleic acid

2.DNA - deoxyribonucleic acid

Question 3

Outline the meaning and implication of DNA being the genetic material of all living organisms.

Answer 3

DNA being the genetic material for all living things implies that all living things contain DNA and all living things come from a common ancestor. The more similar the genes, the more similar the organisms.

Question 4

State why RNA viruses do not falsify the claim that all living things use DNA as the genetic material.

Answer 4

RNA viruses do not falsify the claim that all living things use DNA because viruses aren’t composed of cells therefore they are non-living.

Question 5

List three components of a nucleotide

Answer 5

Nitrogenous base, phosphate group , and pentose sugar

Question 6

Identify and label the carbons of a pentose sugar.

Answer 6

The carbons of a pentose sugar are numbered clockwise, starting with an oxygen at the top and a phosphate group at the left

Question 7

Define “backbone” as related to nucleic acid structure.

Answer 7

The back bone is the chain of sugar phosphate bonds that are found in a polymer of a nucleic acids.

Question 8

Explain how nucleotides connect to form a nucleic acid polymer.

Answer 8

The 5’ phosphate group forms a covalent bond with the 3’ carbon of another nucleotide through condensation, water is a biproduct of this reaction.

Question 9

State the names of the nitrogenous bases found in DNA and RNA.

Answer 9

Thymine, Uracil, Guanine, Adenine and Cytosine

Question 10

State a similarity and a difference between the nitrogenous bases.

Answer 10

All nitrogenous bases have different structures, however they all contain nitrogen

Question 11

Outline how the sequence of bases in a nucleic acid serves as a ‘code.’

Answer 11

The sequences of bases serves as a a code for storing genetic information for all living organism. Code meaning a symbol that signifies the meaning of another symbol. For example in genetic code three nitrogenous bases signifies an amino acid

Question 12

Define gene.

Answer 12

A specific sequence of nitrogenous bases in DNA that codes for the making of a protein

Question 13

Describe the condensation reaction that forms a polymer of RNA from RNA nucleotides.

Answer 13

The condensation reaction that forms a polymer of RNA is the linking of the phosphate group at 5’ and the sugar at 3’ this link creates water as a bi-product

Question 14

Identify the monomer and polymer of an RNA molecule.

Answer 14

The monomer is a single nucleotide whereas the polymer is the chain of nucleotides

Question 15

Describe the structure of a DNA double helix.

Answer 15

Two antiparallel strands of nucleotides each with a sugar phosphate backbone are linked through their nitrogenous bases through complementary base pairing. A and T; C and G so when the 2 strands wind around each other it forms a helix

Question 16

Outline the complementary base pairing rule, including the type and number of bonds between bases.

Answer 16

Complementary base pairing always links the bases cytosine with guanine (3 H-bonds) and adenine with thymine 2(H-Bonds).

Question 17

Define antiparallel in relation to DNA structure.

Answer 17

An antiparallel structure means that one DNA strand runs 5’ to 3’ and the other runs 3’ to 5’

Question 18

Compare and contrast the structures of DNA and RNA.

Answer 18

DNA and RNA are both made up of nucleotides linked in a chain and they both have the nitrogenous bases A, C and G. However DNA is made up of 2 chains of nucleotides that run antiparallel to each other, and DNA has the bases A, C, G, and T whereas RNA has the bases A, C, G, and U

Question 19

Compare and contrast the functionsof DNA and RNA.

Answer 19

DNA is used to store all genetic information, and pass hereditary information between generations of cells. Codes for making RNA during transcription

RNA codes for making proteins during translation.

Question 20

Compare and contrast the location ofDNA and RNA in prokaryotic and eukaryotic cells.

Answer 20

In a eukaryotic cell DNA and RNA are both found in the nucleus whereas in a prokaryotic cell DNA and RNA are found in the cytoplasm, and the DNA is clumped in a region called the nucleoid.

Question 21

Outline the role of complementary base pairing in maintaining the DNA sequence during DNA replication.

Answer 21

When duplicating a DNA sequence the DNA splits in half, and each strand is used as a template for the creation of the new strand. The new strand can only have a specific code as complementary base pairing suggests that there is only one possible base that can match with each base. So when both strands are finished you now have two identical DNA sequences.

Question 22

Outline the role of complementary base pairing in transmitting the genetic code in transcription and translation.

Answer 22

During transcription one of the two DNA strands is used as a template for the creation of an RNA strand. Because of the base pairing rule the DNA strand will always code for the complementary base sequence of RNA nucleotides (A to U, C to G). The complementary base pairing will maintain the sequence of the gene as mRNA is translate into protein.

During the translation of mRNA to protein. The ribosome builds a polypeptide by reading the mRNA template and binding the coded amino acid to the polypeptide chain.

Question 23

Outline why there is a limitless diversity of DNA base sequences.

Answer 23

There are four nitrogenous bases in DNA. These 4 bases are components of nucleotides that can form a DNA molecule in any order and of any length.

Question 24

Defineuniversalin relation to the genetic code.

Answer 24

Genetic code is universal because the genetic code can be found in all living organisms meaning that genetic code is universal.

Question 25

Outline why conservation of the genetic code across all forms of life is evidence of common ancestry.

Answer 25

The conservation of the genetic code across all life forms is evidence of common ancestry because it means that all life forms inherited this code from a common ancestor.

Question 26

Outline the impact of DNA directionality on DNA replication.

Answer 26

DNA replication can only be done in a 5’ to 3’ direction because you can only attach to the 3’ of a template strand.

Question 27

Compare and contrast the structures of purines and pyrimidines.

Answer 27

Purines are double ringed structures and pyrimidines are single ringed structures and are both nitrogenous bases found in RNA and DNA. Purines are guanine, and adenine whereas pyrimidines are cytosine, thymine and uracil.

Question 28

State that in DNA, a purine forms hydrogen bonds with a pyrimidine.

Answer 28

In DNA a purine always pairs with a pyrimidine using hydrogen bonds. In DNA and RNA, guanine bonds with cytosine with three hydrogen bonds. In DNA, adenine bonds with thymine with two hydrogen bonds and in RNA adenine bonds with uracil with two hydrogen bonds.

Question 29

State two consequences of purine-to-pyrimidine bonding on the structure of DNA.

Answer 29

Two consequences of purine-to-pyrimidine bonding is that

1. Each pair of nitrogenous bases are all the same length
2. The number of hydrogen bonds are consistent

Question 30

Describe the structure of eukaryotic DNA and associated histone proteins during interphase (chromatin).

Answer 30

To compact DNA while regulating gene accessibility for transcription, eukaryotic organisms organize their genomes:

1. DNA double helix
2. DNA wraps around 8 histone proteins, and the two ends are held together by an H1 histone forming 1 nucleosome. The linker DNA is then linked to another nucleosome and it creates a string of nucleosomes. Multiple nucleosomes wrap into a fibre (chromatin). Supercoiling of the chromatin produces a chromosome. Supercoiling refers to repeated twisting and winding of the DNA strand. Supercoiling functions to reduce the space required for DNA packaging.

Question 31

Outline the mechanism of histone-DNA association.

Answer 31

DNA wraps around histones to stay more compact

Question 32

State the experimental question being tested in the Hershey and Chase experiment.

Answer 32

The Hershey and Chase experiment is designed to see if DNA or protein is the hereditary material.

Question 33

Outline the procedure of the Hershey and Chase experiment.

Answer 33

They performed their experiments by incorporating radioactive isotopes of phosphorus. and sulfur into bacteriophages (viruses that infect bacteria). DNA contains phosphorus but not sulfur and protein contains sulfur but not phosphorus. Therefore when H & C marked phages with radioactive isotopes of those elements, they placed separate distinguishable tags on the protein and DNA parts of the phages. They allowed the phages to replicate by infecting bacteria. By tracking the location of the radioactive tags, H & C showed that phages only injected their DNA into host bacteria, and the DNA served as the replicating genetic element of phages. The phages did not inject their protein coats remained outside the bacteria adhered to the bacterial membranes

Question 34

Explain how the results of the Hershey and Chase experiment supported the notion of nucleic acids as the genetic material.

Answer 34

The molecule of heredity must be pasted from generation to generation. When H & C demonstrated that radioactively tagged DNA is present across generations of bacteriophages and that radioactively tagged protein is not. It shows that nucleic acids are the genetic material

Question 35

Outline the use of radioisotopes as research tools.

Answer 35

Radioisotopes were used to determine that DNA is the genetic material because they give off energy while returning to a stable form, the isotopes allow biologists to track molecules.

Question 36

Explain the role of falsifiability in determining the structure and function of DNA.

Answer 36

Falsifying a statement means proving a theory wrong.

Chargaff demonstrated this by finding that the amount of one base in DNA wasn’t equal to the amount of the other three therefore disproving the theory that there is a tetranucleotide structure

Question 37

Describeimplications of Chargaff’s data that showed a 1:1 ratio of purine to pyrimidine in a sample of DNA.

Answer 37

Chargaff’s research revealed the percentage of each base (A, T, C and G) found in different species of DNA. He found that there is an equal number of A and T bases and an equal number of C and G bases, resulting in a 1:1 ratio purine to pyrimidines in DNA