1.2 Flashcards
What is a protein composed of?
Each protein is composed of amino acids joined together by peptide bonds into a unique sequence. The type and order of amino acids give the protein its characteristics.
In what direction are nucleotides joined together?
5’ to 3’
What is the structure of DNA?
Double helix structure
What are the four bases and their pairings in DNA?
adenine - thymine
guanine - cytosine
How is the order of amino acids determined?
Determined by the DNA of the gene which codes for the protein. Specifically, it is the sequence of the bases in the DNA which stores the genetic information, the genotype and the genome, of the organism.
Is genetic information inherited?
Yes - the base sequence of the DNA forms the gentic code. Copies of the cell’s gentic information are inherited by daughter cells when it divides.
What are chromsomes?
thread-like structures found in the nucleus of the cell; they contain DNA, which is tightly wound around protains called histones.
Requirements for DNA replication
DNA template - provide the intial genetic code.
Supply of free DNA nucleotides - DNA nucleotides will be added together to form the strand.
Supply of energy (ATP) - provide energy to allow this process to take place.
Enzymes (DNA polymerase) - adds DNA nucleotides, using complementary base pairings, to the deoxyribose (3’ end).
Ligase - fragments of DNA are joined together by ligase.
Primers for DNA polymerase - short strand of nucleotides which binds to the 3’ end of the template DNA strand.
What are the three stages of the replication of the leading strand of DNA?
- After the hydrogen bonds break, the DNA strands separate forming two template strands.
- A DNA primer attaches to the start of the 3’ strand piece of DNA being copied.
- DNA polymerase then attaches free nucelotides to the 3’ end of the primer. Formation of the sugar-phosphate backbone is also a result of this enzyme.
This process is continous.
How do you replicate the lagging strand of DNA?
DNA polymerase can only add onto the 3’ end of a primer therefore lagging strand is replicated in fragments. Many primers attach along the strand and are extended by DNA polymerase. These DNA fragments are then oined by the enzyme ligase.
This is a discontinuous process.
What does PCR do?
Amplifies DNA using complementary primers for specific target sequences.
What are primers?
In PCR, primers are short strands of nucleotides which are complementary to specific target sequences at the two ends of the region of DNA to be amplified.
What are the requirements for PCR?
DNA Template, Free DNA nucleotides, Heat-tolerant DNA polymerase and Primers.
What is the process of PCR?
- DNA is heated to between 92 and 98°C to separate the strands.
- It is then cooled to between 50 and 65 °C to allow primers to bind to target sequences.
- It is then heated to between 70 and 80°C for heat-tolerant DNA polymerase to replicate the region of DNA.
What is essential that heat tolerant DNA polymerase is used?
PCR requires high temperatures in order to replicate the DNA. Generally, enzymes denature at high temperatures so for PCR a heat-tolerant enzyme must be used.
