DNA Replication Flashcards
DNA Replication
Through the complementary nature of the bases, the genetic material can be copied very easily. This is because one side of the DNA strand has a particular base sequence which acts as a template or pattern to determine the sequence on the other side.
When does DNA replication occur?
DNA replication happens before cell division during interphase of the cell cycle
Process of DNA replication:
The double helix structure unwinds to form a ladder.
The hydrogen bonds break and the DNA strands unzip revealing free nucleotides.
Free-floating nucleotides in the nucleoplasm build a complementary DNA strand onto each of the original DNA strands.
Each strand of the original DNA molecule serves as a template for the production of the complementary strand.
Two identical copies are formed of the original DNA molecule, each with one ‘new’ strand and one original strand.
A number of proteins (enzymes) drive the entire process, e.g. adding complementary nucleotides to the template strand one at a time.
Significance of DNA replication:
DNA replication is required for the cell cycle so that cell division can take place.
This ensures that identical copies of the DNA are available for each daughter cell to form.
Each daughter cell, therefore, contains the same genetic information as the mother cell.
It is the basis for biological inheritance.
DNA Profiling
DNA profiling involves methods of comparing different DNA samples. The pattern of DNA fragments in a DNA profile is caused by specific sequences of the base pairs in the sample. An individual inherits the sequence of base pairs from their parents.
In humans
In humans, each person has their own unique DNA profile. The one exception is for identical twins who have the same DNA profile. Any biological specimens containing human cells can be used to extract and analyse the DNA. For example, skin, blood, saliva, semen and hair are commonly used from crime scenes to obtain DNA profiles as forensic evidence.
Example advantages of DNA profiling:
Useful in solving crimes, missing persons, identifying remains, paternity disputes etc.
Useful for protecting endangered species e.g. poached remains
Useful for identifying species e.g. DNA barcodes
Useful to screen for possible genetic disorders
Example issues with DNA profiling:
The possibility of human error running the analyses or interpreting results
NOTE: DNA profiles will always be legally accepted as reliable evidence if proper protocols were followed.
Possible discrimination against someone with a genetic disorders
Cost may exclude many people from its uses
DNA may be planted at crime scenes
