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.
