1A - DNA replication Flashcards
How do cells store their genetic information?
All cells store their genetic information in the base sequence of DNA.
Describe the structure of a nucleotide.
Nucleotide subunits consist of a deoxyribose sugar, phosphate and a base.
They bond to form a strong sugar-phosphate backbone.
Describe base pairing
Base pairing is specific, with adenine pairing with thymine and cytosine pairing with guanine.
What are Prokaryotes?
Give examples
Prokaryotes are organisms like bacteria which usually no nucleus and have a single circular chromosome and smaller circular plasmids.
What are Eukaryotes?
Give examples
· Eukaryotes are organisms like yeast, plants and animals and all have linear chromosomes in the nucleus. Chromosomal DNA of eukaryotic cells is tightly coiled and packaged with associated proteins (called histones).
Eukaryotes contain organelles such as mitochondria and chloroplasts (in green plants) which contain circular chromosomes. Yeast are unusual because they also have plasmids with circular DNA.
Describe the first stage of DNA replication
-DNA helix is unwound and the hydrogen bonds are denatured this opens up two template strands to be copied
What is the purpose of PCR?
PCR refers to Polymerase Chain Reaction which is a technique used to amplify DNA(make multiple copies) of a specific target sequences.
· It involves repeated cycles of heating and cooling to amplify the target region of DNA.
What are primers in PCR?
· 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.
Why are two different primers needed in polymerase chain reaction?
· Two different primers are needed to locate the two ends of the region to be amplified.
Describe the structure of DNA
DNA is composed of 2 chains of nucleotides (double stranded).
The two nucleotide chains run antiparallel with a deoxyribose sugar at the 3’ end and phosphate group at the 5’ end of each strand respectively.
The nucleic acid bases are paired by hydrogen bondingin the centre to form a double helix
When does DNA replication occur?
· Replication occurs prior to cell division.
What is the first step in the procedure of PCR?
· DNA is heated to between 92 and 98°Cto separate the strands.
What is the base sequence of DNA used for?
- to make proteins
- to control what proteins are made
What are bacteria cells useful in
- genetic engineering
- horizontal gene transfer (to another bacteria cell)
What is the purpose of the DNA found within organelles in eukaryotic cells?
-the DNA (circular chromosomes) codes for some of the proteins used in the organelles
What makes up the strong sugar-phosphate backbone?
- phosphate
- deoxyribose sugar
- covalent bonds
Why is DNA replicated before the cell divides?
-so the new cells have full copies of the genetic information
Explain why primers are necessary for DNA replication.
So DNA polymerase can add nucleotides to the 3′ end of the new strand
To give DNA polymerase a start point for replication
Describe anti parallel structure in DNA
- One strand of nucleotides goes 5’ - 3’
- The other goes the opposite direction, 3’-5’
What is a primer in DNA replication?
· A primer is a short strand of nucleotides which binds to the 3’ end of the template DNAstrand allowing polymerase to add DNA nucleotides.
Describe the second stage of DNA replication
-DNA polymerase needs a complementary primer to start from, the primer binds to the 3’ end of a DNA strand
Describe the third stage of DNA replication
-DNA polymerase adds new nucleotides to the 3’ end of the growing strand (using complementary base pairing so the correct bases match the template)
Describe the fourth stage of DNA replication
-DNA polymerase can only add nucleotides in one direction, thus resulting in one strand being replicated continuously (leading stand) and the other strand is replicated in Okazaki fragments and the fragments are joined together by DNA ligase
What enzyme is DNA replicated by?
DNA is replicated by the enzyme DNA polymerase.
