Topic 1B- More Biological Molecules (DNA and RNA) Flashcards
What are nucleic acids?
What is an individual unit of a nucleic acid called?
What is DNA a type of and what is it’s full name?
What are the three components of DNA?
What are the two types of bases in DNA and describer the structure of each?
What are the four bases of DNA and state which base each of them join to?
What is the base and sugar joined with in DNA?
What is the phosphate and sugar joined with in DNA?
What do both of these bonds require to occur?
What happens twice in the formation of a nucleotide?
Polymers
A mononucleotide
A type of nucleic acid called deoxyribonucleic acid
- Pentose sugar (deoxyribose in DNA)
- Phosphoric acid
- Organic base (always contains nitrogen)
- Purines (double ringed structure)
- Pyrimidine’s (single ringed structure)
Purines: Adenine (A) and Guanine (G)
Pyrimidine’s: Thymine (T) and Cytosine (C)
Glycosidic bond
Ester bond
Both require a condensation reaction
Two condensation reactions occur.
What is the structure of DNA described as?
What does this mean that a DNA molecule is formed and what does this then form?
What are the strands of DNA?
What is the result of DNA molecules being really long and coiled up very tightly?
What three things is a DNA nucleotide made from?
What always pairs with what in DNA?
What are the two polynucleotide strands in DNA?
What do these strands do and what does this form?
What is formed from many nucleotides joined together?
DNA has a double helix structure
A DNA molecule is formed from two separate molecules which wind around each other to form a spiral
Polynucleotides
A lot of genetic information can fit into a small space in the cell nucleus
- A phosphate group
- The pentose sugar deoxyribose
- A nitrogen-containing organic base
Purines always pair with pyrimidine’s
Antiparallel- meaning they run in opposite directions
The two antiparallel strands twist to form a DNA double helix
Polynucleotide strands (or chains).
How do the nucleotides join up (full description)?
What does this then form?
What does this consist of?
What is the chain of phosphates and sugars known as?
What does RNA stand for?
What does RNA have that similar to DNA?
What is the sugar in DNA called?
What is the sugar in RNA called?
What type of sugar is RNA?
What type of stranded molecule is DNA?
What type of stranded molecules is RNA always?
What replaces thymine as a base in RNA and describe this base?
What does this base always pair with in RNA?
What is the complementary base pairing in RNA?
What are RNA strands compared to DNA strands?
Join up via a condensation reaction between the phosphate group of one nucleotide and the sugar of another
This then forms a phosphodiester bond
The phosphate group and two ester bonds
The sugar-phosphate backbone
Ribonucleic acid
RNA has a very similar structure to DNA
Deoxyribose
Ribose
Still a pentose sugar, like DNA
Double-stranded molecule
Always a single-stranded molecule
Uracil (U, a pyrimidine) replaces thymine as a base
Uracil always pairs with Adenine in RNA
C pairs with G ; but A pairs with U
RNA strands are much shorter than most DNA polynucleotides.
What does the phosphodiester backbone in DNA protect?
What’s formed between the bases C and G and what does this make the nucleic acid more of?
What does DNA make up?
What are these in DNA?
What are these instructions for?
What are these made of and what determines them?
What order of bases determines what in a gene?
What is each amino acid coded for by and what is this called?
What do different triplets code for?
What does the sequence of triplets in a section of DNA act as?
Protects the more chemically reactive bases inside the helix
Hydrogen bonds link in pairs and triplets between the bases (C (3) G) and the more triple bonded CG combos there are the more stable the nucleic acid
DNA makes up genes
Genes are sections on DNA found on chromosomes
Genes are instructions for proteins
Proteins are made of amino acids, and it is the order of amino acids that determines the protein
In a gene, it is the order of bases in the DNA that determines which amino acid is made
A sequence of 3 bases- called a triplet or a codon
Code for different amino acids
Acts as a template for the production of a protein.
What is one end of DNA called?
What is the other end of DNA called?
What happens during DNA replication concerning DNA polymerase?
What does this mean the enzyme can only do?
What does this mean that the new DNA strand is made of?
How does this mean that the DNA polymerase moves?
What are the strands in the double helix?
What does this result in the DNA polymerase doing (full description)?
The 3’ (pronounced “three prime”) end
The other is called the 5’ (pronounced “five prime”) end
The active site of DNA polymerase is only complementary to the 3’ end of the newly forming DNA strand
This means the enzyme can only add nucleotides to the new strand at the 3’ end
Made in 5’ to 3’ direction
Moves down the template strand in a 3’ to 5’ direction
Antiparallel
The DNA polymerase working on one of the template strands moves in the opposite directions to the DNA polymerase working on the other template strand.
Describe the following two main stages of cell division:
Nuclear division
Cytokinesis
What must a nucleus do before it divides?
What is this to ensure (full description)?
What is the process of DNA replication called?
What are the four requirements of this replication?
What is the result of this replication in the generations of cells?
What does this basically mean?
The process by which the nucleus divides. Mitosis and meiosis
This follows nuclear division and is the process by which the whole cell divides
It must replicate it’s DNA
To ensure that the daughter cells contain the genetic information required to produce the enzymes and other proteins they need
Semi-conservative replication
- The 4 types of nucleotide, each with their bases of A,T,C and G must be present
- Both strands of the DNA molecule act as a template for the attachment of these nucleotides
- The enzyme DNA polymerase
- A source of chemical energy is required to drive the process
This means that there’s genetic continuity between generations of cells
ie The cells produced by cell division inherit their genes from their parent cells.
Describe the first stage of semi-conservative replication?
Describe the second stage of semi-conservative replication?
Describe the third stage of semi-conservative replication?
Describe the fourth stage of semi-conservative replication?
- The enzyme DNA helicase breaks the hydrogen bonds between bases on the two polynucleotide DNA strands. This makes the helix unwind to form two single strands.
- Each original single strand acts as a template for a new strand. Complementary base pairing means that free-floating DNA nucleotides are attracted to their complementary exposed bases on each original template strand- A with T and C with G.
- Condensation reactions join the nucleotides of the new strand together- catalysed by the enzyme DNA polymerase. Hydrogen bonds form between the bases on the original and new strands.
- Each new DNA molecule contains one strand from the original DNA molecule and one new strand.
How did Meselson and Stahl show that DNA was replicated using the semi-conservative method?
Describe the first stage of Meselson and Stahl’s experiment?
Describe the second stage of Meselson and Stahl’s experiment?
Describe the third stage of Meselson and Stahl’s experiment?
Their experiment used two isotopes of nitrogen (DNA contains nitrogen)- heavy nitrogen (15 N) and light nitrogen (14 N)
- Two samples of bacteria were grown- one in a nutrient broth containing light nitrogen, and one in a broth with heavy nitrogen. As the bacteria reproduced, they took up nitrogen from the broth to help make nucleotides for new DNA. So nitrogen gradually become part of the bacteria’s DNA.
- A sample of DNA was taken from each batch of bacteria, and spun in a centrifuge. The DNA from the heavy nitrogen bacteria settled lower down the centrifuge tube than the DNA from the light nitrogen bacteria- because it’s heavier.
- Then the bacteria grown in the heavy nitrogen broth, were taken out and put in a broth containing only light nitrogen. The bacteria were left for one round of DNA replication, and then another DNA sample was taken out and spun in the centrifuge.
Describe the fourth stage of Meselson and Stahl’s experiment?
Describe the fifth stage of Meselson and Stahl’s experiment?
Describe the sixth stage of Meselson and Stahl’s experiment?
What then happened once Meselson and Stahl confirmed that DNA replication in bacteria was semi-conservative?
- If replication was conservative, the original heavy DNA, which would still be together, would settle at the bottom and the new light DNA would settle at the top.
- If replication was semi-conservative, the new bacterial DNA molecules would contain one strand of the old DNA containing heavy nitrogen and one strand of new DNA containing light nitrogen. So the DNA would settle out between where the light nitrogen DNA settled out and where the heavy nitrogen DNA settled out.
- As it turned out, the DNA settled out in the middle, showing that the DNA molecules contained a mixture of heavy and light nitrogen. The bacterial DNA had replicated semi-conservatively in the light nitrogen.
Other scientists carried out experiments to show that it was the universal method for DNA replication in all living things.
How many hydrogen bonds form between A and T?
How many hydrogen bonds form between C and G?
What two things are equal in DNA?
Two hydrogen bonds form between A and T
Three hydrogen bonds form between C and G
In DNA, there are always equal amounts of Adenine and Thymine; and always equal amounts of Cytosine and Guanine.
