DNA structure and replication Flashcards
what is DNA made out of
DNA is made of smaller molecules called nucleotides
what are the main parts of nucleotides
Nucleotide molecules have three main parts:
A Phosphate group
A Deoxyribose sugar
A Nitrogenous base
how are nucleotides arranged
nucleotides are arranged in a spiral, ladder like structure, called a double helix
what makes up the sides of the ladder
Alternating sugar and phosphate make up the sides of the ladder
what makes up the steps of the ladder (double helix)
The nitrogenous bases make up the steps of the ladder
what are the four nitrogenous bases
Adenine (A)
Thymine (T)
Guanine (G)
Cytosine (C)
what are complementary base pairs
Each nitrogenous base will only bond with one other specific base.
Adenine (A)&Thymine (T)
Cytosine (C) &Guanine (G)
which cells have a nucleus containing DNA
All the cells in your body, except red blood cells, have a nucleus that contains DNA.
how do we know it’s possible copy DNA molecules perfectly
The DNA is identical in each cell, which means that it must be possible to copy DNA molecules perfectly.
what is DNA replication and when does it occur
DNA replication is the process by which DNA makes a copy of itself.
This occurs just before the cell divides into two new cells.
what are the three stages of DNA replication
straightening and separation
constructing copies
checking for mistakes
what happens during step one of DNA replication
The double helix untwists.
An enzyme separates the individual strands of the double helix (like unzipping a zipper)
This exposes the nitrogenous bases.
what happens during step two of DNA replication
Within the nucleus, there are free nucleotides which are not part of a DNA chain.
The free nucleotides connect to the exposed nitrogenous bases following complementary base pairing rules (A with T and C with G).
This forms two strands of DNA which are both identical to the original.
what happens during step three of DNA replication
The replication process is now complete, with two identical double helixes being formed.
The two new DNA strands are “proofread” by enzymes.
Any errors in base sequencing are corrected
what happens during step three of DNA replication
The replication process is now complete, with two identical double helixes being formed.
The two new DNA strands are “proofread” by enzymes.
Any errors in base sequencing are corrected
