A1.2 - Nucleic Acid - IB Bio Flashcards
What do nucleic acids contain?
-They contain carbon, hydrogen, oxygen, nitrogen and phosphorus.
-Chains of sub-units called nucleotides (Adenine, Guanine, Thymine, Cytosine and Uracil)
-They consist of base, sugar, and phosphate groups that are covalently bonded together.
- If the sugar is ribose then the nucleic acid RNA is formed. If the sugar is deoxyribose than the nucleic acid DNA is formed.
What are the two different types of nucleic acid?
DNA - Deoxyribonucleic acidRNA - Ribonucleic acid
What is important about DNA?
DNA is the genetic material for all living organisms
What do viruses contain?
Viruses can contain either RNA or DNA, but not both as their genetic material. Either way, viruses are not considered to be living. Some examples of viruses that include DNA are poxyvirus and papillomavirus. Some examples of viruses that include RNA are Ebola and hepatitis. The difference between RNA and DNA viruses has several important implications for how they function and replicate.For example: Genetic material: RNA viruses have RNA as their genetic material, which can be single-stranded (ssRNA) or double-stranded (dsRNA).DNA viruses have DNA as their genetic material, which can be single-stranded (ssDNA) or double-stranded (dsDNA).Replication: RNA viruses typically replicate in the host cell cytoplasm and use an RNA-dependent RNA polymerase to replicate their RNA genomes. This process can be error-prone, leading to a high mutation rate and the potential for rapid evolution.DNA viruses generally replicate in the host cell nucleus and use DNA-dependent DNA polymerases to replicate their DNA genomes. DNA replication is generally more accurate than RNA replication.Reverse transcription: Some RNA viruses, like retroviruses (e.g., HIV), have a reverse transcription step where their RNA genome is converted into DNA using the enzyme reverse transcriptase. This DNA is then integrated into the host genome.DNA viruses do not require a reverse transcription step as they already have DNA genomes.
What do a human, a rose and a bacterium all have in common?
All these things, as well as every other organism on Earth, contain the molecular instructions for life, called deoxyribonucleic acid (DNA). DNA carries the genetic code. Across the DNA molecule are important sequences of bases known as genes. Each gene contains the coded description for making a specific protein.
What is the backbone of a molecule made of?
Sugar - phosphate bonding makes a continuous chain of covalently bonded atoms in each stand of DNA or RNA nucleotides, which forms a strong ‘backbone’ in the molecule.
What does each nucleotide consist of?
- Nitrogen compounds called bases. In DNA it’s ACTG and in RNA its AUCG. - 5 carbon sugar. Deoxyribose sugar in DNA and ribose sugar in RNA. Phosphate group.
What bond is used in RNA and where?
- The backbone is strong between nucleotides because it’s formed by a phosphodiester bond, which is a type of covalent bond. - A N-glycosidic bond is used to hold the ribose and nucleic bases together.
What bond is used in DNA and where?
- The three bonds between the nucleic bases is a hydrogen bond. - The bond between the deoxyribose and phosphate group is a phosphodiester bond, which is a type of covalent bond.- The bond between the deoxyribose and nucleic base is an N-glycosidic bond.
What happens during a condensation reaction?
The phosphate group off the 5th carbon forms a covalent bond with the hydroxyl - OH off of the 3rd carbon of the sugar with another nucleotide. condensation involves the combining of two molecules into one with loss of a water molecule. The ends of the backbone are identified as 5’ and 3’, but this is dependent on which carbon is at the top.
Why is the 5’ to 3’ linkage in the sugar-phosphate backbone important for replication?
Because it determines the direction in which new nucleotides can be added to the growing strand. DNA and RNA polymerases can only add nucleotides to the 3’ end of an existing strand, utilizing the free 3’ hydroxyl (-OH) group as a site for attachment.This directional specificity ensures that the genetic information is copied in the correct order during replication and allows for accurate transcription.
Why is the 5’ to 3’ linkage in the sugar-phosphate backbone important for transcription?
The 5’ to 3’ directionality ensures that the RNA transcript is synthesized in the same direction as the DNA template is read.
Why is the 5’ to 3’ linkage in the sugar-phosphate backbone important for translation?
The genetic code, which specifies the sequence of amino acids in a protein, is read in triplets of nucleotides called codons. Each codon on the mRNA corresponds to a specific amino acid or a start or stop signal. The ribosome reads the mRNA in a 5’ to 3’ direction, moving along the mRNA and matching each codon with the appropriate amino acid. The correct reading frame and order of codons are essential for synthesizing a functional protein. The 5’ to 3’ orientation ensures that codons are read in the proper sequence.
State two reasons why the directionality if the DNA and RNA molecule are important
- DNA replication- Protein synthesis- Enzymes can only bind to the RNA, DNA and synthesize new molecules in a specific direction.
State the purines
Adenine and guanine because they’re double ringed
State the pyrimidines
Thymine, cytosine, and uracil because they’re all single ringed
What nucleic acids bond together
A and T always bond together (2 hydrogen bonds)C and G always bond together (3 hydrogen bonds)A purine always has to bond with a pyrimidine
Why does a purine have to bond with a pyrimidine
Because it adds stability to the DNA molecule and the rungs are all the same width.
Describe the structure of DNA
DNA is a double helix made of two antiparallel strands of nucleotides with two strands linked by a hydrogen between complementary base pairing.
What is the role of complementary base pairing?
It allows genetic information to be replicated and expressed
When does DNA replication happen?
It happens before the cells divide
What is DNA replication
Semi-conservativeDuring DNA replication, each new DNA molecule consists of one strand that is conserved (the original or “parental” strand) and one newly synthesized strand (the “daughter” strand). This is mainly to maintain genetic information.
Does DNA have a large capacity?
DNA has an enormous capacity for storing data with great economy.
Why is there a limitless amounts of DNA base sequences?
The nucleic bases (A,C,T,G) can be:- arranged in any order - DNA can vary in lengthso an endless amount different sequences
Do all organisms use the genetic code?
Yes all organisms use DNA and RNA as genetic material and the genetic code by which proteins are synthesised (the creation of something often two things joining together to create one) is universal.
How many bases are grouped together in a sequence?
All living organisms use the sequences of bases in groups of 3 to code for a particular amino acid. No matter the organism the sequence on DNA (codon) code for the same amino acid.
Over the course of millions of years, mutations will accumulate within an given segment of DNA, what are they?
- The number of differences between comparable base sequences demonstrates the degree of evolutionary divergence - A greater number of differences between comparable base sequences suggests more time has passed since two species diverged.
Structure of a nucleosome
A DNA molecule is wrapped around a core of 8 histone proteins held together by additional histone proteins attached to a linker DNA.
How is the DNA wounded to the 8 histones?
Through Hydrogen bonds
What are nucleosomes helpful for?
They help supercoil chromosomes and help to regular transcription.Supercoiling condenses DNA molecules by a factor of X 15,000.
What are histones responsible for?
They’re responsible for the packaging of DNA at different levels. The fiber must be less condensed for transcription to occur during the interphase.Condensing controls if the genes are transcribed or not.
What were Hershey and Chase’s two findings?
- Protein is not genetic material- DNA is the genetic material This is because during the 1950s it was still unclear whether genes were made of DNA or proteins.
How did Hershey and Chase’s experiment work?
They did a series of experiments with viruses to determine what genes were made of. That used a virus that infects cells of bacteria. Bacteriophages are viruses that infect bacteria and are made of DNA surrounded by a protein coat. Phosphorus radioactivity was detected in the bacteria pellet and there was no radioactive sulfur. This showed that the virus had transferred DNA into the bacteria because DNA contains phosphorus. The virus had not transferred the protein
What did Chargaff’s data show?
The amount of A in a sample of DNA is always the same as the amount of T, as well as T always presents the same amount as G. The amount of thymine and adenine should be equal and cytosine and guanine should be equal in all strands of the DNA.
What does DNA stand for?
Deoxyribose nucleic acid
What does DNA carry?
DNA carries the genetic code in all living organisms
Where is DNA found in eukaryotes?
DNA is mainly found in the nucleus where it forms chromosomes.However, in eukaryotes, DNA can also be found in the mitochondria and chromosomes.
What does RNA stand for?
Ribonucleic acid
What is RNA?
RNA is another type of nucleic acid.
What is one thing that RNA is important for?
RNA is the main component of ribosomes, which play an important part in protein synthesis.
Where is RNA found?
The two places that RNA is found in the cell are the nucleus and the cytoplasm.
Can viruses contain RNA instead of DNA?
Yes. Certain viruses contain such as SARS-CoV-2 contain RNA as their genetic material instead of DNA. These viruses cause a variety of different diseases, such as COVID19, Ebola, mumps and influenza.
Are viruses considered living?
No, they aren’t considered to be a living organism.
State 2 reasons why viruses are considered living
Because they are unable to replicate by themselves. They’re dependent on living cells for replication and survival. Viruses also lack a cellular structure.
What is something that RNA and DNA have in common?
Both RNA and DNA are polymers that are made up of many repeating units called nucleotides.
List what a nucleotide includes
- a pentose sugar (a sugar with 5 carbon atoms) - a nitrogenous base, with either 1 or 2 rings of atoms) - a phosphate group, which is acidic and negatively charged
What bond holds the base and phosphate group to the sugar
The base and phosphate group are covalently bonded to the sugar.
List the nitrogenous bases in DNA
Adenine (A) Guanine (G) Thymine (T) Cytosine (C)
List the nitrogenous bases in RNA
Adenine (A) Guanine (G) Cytosine (C) Uracil (U)
Why do nucleotides join together?
Nucleotides join together in chains to form strands of DNA or RNA
Explain how nucleotides join together
The phosphate group of one nucleotide forms a covalent bond to the pentose sugar of the next nucleotide.This carries on to form a large polymer. These polymers form nucleic acids, which are also known as polynucleotides.
Where are hydrogen bonds found in DNA?
Hydrogen bonds occur between the two strands. These hydrogen bonds are individually weak but collectively quite strong.
Where are covalent bonds found in DNA?
Covalent bonds occur within the nucleotide. Covalent bonds are what hold the phosphate group, nitrogenous base, and pentose sugar together. Covalent bonds are quite strong.
When is a water molecule released?
A water molecule is released during the formation of each covalent bond.
What does a condensation reaction link?
When a phosphate group of one nucleotide is linked to the pentose sugar of the next one by condensation reactions.
What is a sugar-phosphate backbone made up of?
Each strand has a backbone made of alternating sugar (deoxyribose) and phosphate groups. Attached to each sugar is one of four bases–adenine (A), cytosine (C), guanine (G), or thymine (T).
What is the sugar-phosphate backbone linked to?
A sugar-phosphate backbone with a base linked to each sugar.
How is a sugar-phosphate backbone made?
The phosphate group of one nucleotide is linked to the pentose sugar of the next one by a condensation reaction. This forms a sugar-phosphate backbone with a base linked to each sugar.
What is a strand?
A strand is a polymer of nucleotides.
Is DNA single-stranded or double-stranded?
Double-stranded
Is RNA single-stranded or double-stranded?
Single-stranded
How many separate bases are there?
There are four separate bases, and they can be joined in any sequence and combination.
True or false: There are 4 separate bases that can be joined in any combination and sequences because the sugar and phosphate are the same in every nucleotide.
True
What’s the bond between two nucleotides?
A phosphodiester bond, which is a type of covalent bond
How can two nucleotides be bonded together in the same strand?
The phosphate from one nucleotide bonds to the 3 carbon atom of the adjacent pentose sugar.
How is the nitrogenous base and the pentose sugar held together?
N-glycosidic bond
What are the bonds between nitrogenous bases?
Between adenine and thymine, there are 2 hydrogen bonds.
Between cytosine and guanine, there are 3 hydrogen bonds.
What is the pentose sugar in DNA?
Deoxyribose sugar
What is the pentose sugar in RNA?
Ribose sugar
Is RNA longer or shorter than DNA?
Compared to DNA, RNA molecules are relatively short with lengths of a hundred to a few thousand nucleotides.
What does RNA typically form?
RNA usually forms a single-stranded polynucleotide with ribose as the pentose sugar in each nucleotide.
How are the carbon atoms in RNA nucleotides numbered?
The carbon atoms in nucleotides are numbered from the right in a clockwise direction.
Why are the carbon atoms numbered?
- Makes it easier to identify the bonds in the sugar-phosphate backbone of polynucleotides.
- It also indicates the orientation of the polynucleotide.
Draw an RNA nucleotide
3 different types of RNA found in the cells of living organisms
- messenger RNA (mRNA). This is formed in the nucleus and transported to the ribosomes in the cytoplasm.
- transfer RNA (tRNA). This is responsible for transporting amino acids to ribosomes during protein synthesis.
- ribosomal RNA (rRNA). This forms part of ribosomes.
How are adjacent RNA polynucleotides linked?
Adjacent RNA polynucleotides are linked together by condensation reactions, during which a molecule of water is released.
Where is a phosphodiester bond in RNA?
A phosphodiester bond is between the pentose sugar of one nucleotide and the phosphate group of the next nucleotide.
How will a phosphodiester bond be formed?
Linking RNA molecules together by condensations will result in the formation of phosphodiester bonds.
Describe the structure of DNA
DNA is a double helix made of two antiparallel strands of nucleotides linked by hydrogen bonding between complementary base pairs.
What are DNA molecules made up of?
DNA molecules are made up of two polynucleotide strands lying side by side, running in opposite directions. The strands are antiparallel.
What is each DNA polynucleotide strand made up of?
Alternating deoxyribose sugars and phosphate groups bonded together to form the sugar-phosphate backbone.
Where does the nitrogenous base project out from?
The nitrogenous bases of each nucleotide project out from the backbone towards the interior of the double-stranded DNA molecule.
How are the two antiparellel strands held together?
The two antiparallel DNA polynucleotide strands that make up the DNA molecule are held together by hydrogen bonds between nitrogenous bases.
How many hydrogen bonds between adenine and thymine?
Two hydrogen bonds
How many hydrogen bonds between cytosine and guanine?
Three hydrogen bonds
