Nucleic acids Flashcards
What is DNA?
Deoxyribonucleic acid, the hereditary material in living organisms.
DNA carries coded instructions for development and functioning.
What is the structure of a nucleotide?
A molecule consisting of a five-carbon sugar, a phosphate group, and a nitrogenous base.
Nucleotides are the monomers of nucleic acids.
What are the two phosphorylated nucleotides mentioned?
ADP (adenosine diphosphate) and ATP (adenosine triphosphate).
ATP is used to drive most energy-requiring metabolic processes.
What is a polynucleotide?
A large molecule containing many nucleotides.
Polynucleotides are formed by the linking of nucleotides through phosphodiester bonds.
What is the shape of the DNA molecule?
Double helix, due to coiling of the two sugar-phosphate backbone strands.
The double helix configuration is right-handed.
What is the difference between a nucleotide and a nucleoside?
A nucleotide consists of a pentose sugar, a nitrogenous base, and a phosphate group; a nucleoside consists of only a pentose sugar and a nitrogenous base.
Example: Adenosine is a nucleoside, AMP is a nucleotide.
How do hydrogen bonds contribute to the structure of DNA?
Hydrogen bonds join the two antiparallel DNA strands through complementary base pairing.
Adenine pairs with thymine, and guanine pairs with cytosine.
What are the four nitrogenous bases in DNA?
Adenine, guanine, thymine, and cytosine.
These bases determine the genetic information carried by DNA.
What is the significance of antiparallel strands in DNA?
The two strands run in opposite directions, which is crucial for DNA replication and transcription.
This refers to the orientation of the sugar-phosphate backbones.
Fill in the blank: Adenine always pairs with _______ by means of two hydrogen bonds.
Thymine
Fill in the blank: Guanine always pairs with _______ by means of three hydrogen bonds.
Cytosine
What type of bond is formed between the phosphate group and the sugar in a nucleotide?
Phosphodiester bond.
These bonds are broken during the breakdown of polynucleotides.
True or False: A purine always pairs with a purine in DNA.
False
A purine always pairs with a pyrimidine.
What are the components of coenzyme NADP?
Adenine nucleotides.
NADP is used in photosynthesis.
What is the role of ATP in biochemical pathways?
ATP is an energy-rich end-product used to drive most energy-requiring metabolic processes.
It is formed from ADP and inorganic phosphate.
What is the significance of the sugar-phosphate backbone in DNA?
It forms the upright part of the DNA molecule, resembling a ladder.
The backbone is formed by the covalent bonds between the sugar and phosphate groups.
Fill in the blank: Each DNA nucleotide consists of a phosphate group, a five-carbon sugar called ________, and one of four nitrogenous bases.
Deoxyribose
What are the roles of nucleotides in metabolism?
Regulate metabolic pathways and serve as components of coenzymes.
Examples include ATP, ADP, AMP, NAD, and FAD.
What is the sugar-phosphate backbone in DNA?
A structural framework of DNA consisting of alternating sugar (deoxyribose) and phosphate groups
The sugar-phosphate backbone supports the nucleotide bases that are attached.
In eukaryotic cells, where is the majority of DNA found?
In the nucleus
The DNA is organized into chromosomes.
How is DNA organized in prokaryotic cells?
DNA is in a loop within the cytoplasm and is not enclosed in a nucleus
This DNA is described as naked and does not wind around histone proteins.
What is the role of helicase in DNA replication?
Catalyses the breaking of hydrogen bonds between nitrogenous base pairs
This allows the DNA strands to separate.
Define semi-conservative replication.
A process where each new DNA molecule consists of one old strand and one new strand
This method conserves one original strand in each new molecule.
What is the function of DNA polymerase?
Catalyses the addition of new nucleotide bases to the growing DNA strand
It uses a single strand of DNA as a template.
What is the difference between purines and pyrimidines?
Purines are double-ring structures, while pyrimidines are single-ring structures
Purines include adenine and guanine, whereas pyrimidines include cytosine and thymine.
True or False: DNA in mitochondria and chloroplasts replicates independently of the cell cycle.
True
These organelles replicate their DNA before the cell divides.
What evidence supported the semi-conservative model of DNA replication?
The experiment by Meselson and Stahl showed hybrid DNA after one replication cycle in bacteria
This indicated that each new DNA molecule contained one old strand.
Explain what is meant by ‘complementary base pairing’.
The specific pairing of nitrogenous bases (adenine with thymine, guanine with cytosine) in DNA
This ensures accurate replication and transcription of genetic information.
Fill in the blank: The loops of DNA in prokaryotes replicate _______.
semi-conservatively
List the components of a nucleotide.
- A phosphate group
- A deoxyribose sugar
- A nitrogenous base
The nitrogenous bases can be adenine, thymine, guanine, or cytosine.
What happens during the unwinding phase of DNA replication?
The double helix is untwisted, catalysed by gyrase enzyme
This prepares the DNA for separation into two strands.
How do mutations occur during DNA replication?
Errors may occur when the wrong nucleotide is inserted
This is estimated to happen in 1 in 108 base pairs, potentially altering the genetic code.
What is the direction in which nucleotides are added during DNA replication?
5’ to 3’ direction
What enzyme catalyzes the addition of new DNA nucleotides during replication?
DNA polymerase
What is the term used for different versions of a particular gene?
alleles
True or False: All mutations are harmful.
False
What is a useful mutation that arose in the FOXP2 gene associated with?
human speech
What is the term for the process during which a DNA molecule unwinds and unzips?
DNA replication
Fill in the blank: A _______ is a length of DNA that codes for a polypeptide or RNA.
gene
What is the primary structure of a polypeptide determined by?
the sequence of amino acids
What are the three forms of RNA?
- messenger RNA (mRNA)
- transfer RNA (tRNA)
- ribosomal RNA (rRNA)
What process involves making messenger RNA from a DNA template?
transcription
What is the role of ribosomes in protein synthesis?
formation of proteins by assembling amino acids
How is the genetic code described in terms of universality?
near universal
What does it mean that the genetic code is degenerate?
more than one base triplet codes for most amino acids
What causes a frame shift in the genetic code?
addition or deletion of a base
What percentage of an organism’s dry mass is accounted for by protein?
75%
Where are genes located in a cell?
cell nucleus
What is the term for the assembly of amino acids into a particular sequence at the ribosome?
translation
What is the nitrogenous base that replaces thymine in RNA?
uracil
What is the primary function of DNA helicase during replication?
unwinding the DNA double helix
During DNA replication, what is the name of the structure where the DNA strands separate?
replication fork
What is the difference between a polypeptide and a protein?
A polypeptide is made of many amino acids; a protein is a large polypeptide of 100 or more amino acids.
In which part of the cell are proteins made?
cytoplasm, at ribosomes
True or False: The genetic code is overlapping.
False
