Topic 2:4 DNA replication Flashcards
(27 cards)
replication of DNA allows for…
genetic information to be inherited and passed on to offspring.
describe the structure of DNA
In terms of strands…
The DNA has a double stranded helical structure, where one strand acts as the template to synthesise a complementary opposite strand.
describe base pairing in DNA
Base pairing is complementary, where the nucleotide bases form hydrogen bonds only with the correct base
A will base pair to T
G will base pair to C
describe the process of DNA replication
the two strands of DNA unzip or separate. then new nucleotides bond to the two separate strands, A to T and C to G to synthesis a new complementary strand. This results in two new identical DNA molecules.
explain why DNA replication is described as semi-conservative?
DNA replication is described as semi-conservative because each new molecule has one template strand from the original DNA molecule and one new synthesised strand. This means the whole original DNA molecule is conserved.
Explain what causes the sequences of bases in each new synthesised strand
Free floating nucleotides are attracted to their exposed complementary bases. Therefore, the sequence of bases in each new strand is complementary to the sequence of bases on the template or ‘old’ strand. This will result in the new synthesised strand being identical to the other template strand that used to be in its place.
state why the two strands of DNA need to be separated
The two strands of DNA in a DNA molecule need to be separated by helicase during replication to allow the semi-conservative process to occur. This process exposes bases so each strand can be used as a template for the synthesis of a new polynucleotide strand.
define complementary base pairing and explain its importance
In complementary base pairing the nucleotide bases on one DNA strand form hydrogen bonds only with the correct base on the complementary strand: A with T and G with C. This is important as it ensures the genetic information is completely and correctly transferred to the next generation.
State the role of helicase and DNA polymerase in DNA replication
Helicase separates the two strands of DNA by breaking the relatively weak hydrogen bonds between the complementary base pairs. DNA polymerase joins the positioned nucleotides, forming new sugar-phosphate backbones with the sugar and phosphate groups covalently connected to form the new strands.
State the name of the enzyme needed to synthesise the new molecules of DNA.
DNA polymerase
State the location of DNA replication in a eukaryotic cell
the nucleus
the first step of DNA replication is…
The two strands separate due to the action of an enzyme (helicase) which breaks the relatively weak hydrogen bonds between complementary base pairs.
the second step of DNA replication is…
Free nucleotides are then attracted to their complementary base pair, A to T, T to A, C to G and G to C, which begins the formation of a new strand.
the third step of DNA replication is…
The nucleotides are rejoined through the sugar-phosphate by another enzyme, DNA polymerase to covalently connect the nucleotides together to form the new strand.
What do the three steps of DNA replication result in?
Two new DNA molecules are formed, each with one newly synthesized strand and one old (template) strand. These DNA molecules then reform the helical structure.
explain the direction of DNA
DNA has an ‘antiparallel’ nature, meaning the two parallel strands run in opposite directions.
DNA is synthesized in the 5’ (five-prime) to 3’ (three-prime) direction.
This means the strand is elongated from the 3’ end.
vocab: DNA
Deoxyribonucleic acid. A double helical molecule made up of nucleotides containing four bases A T G and C. Stores and transmits the genetic information of all organisms.
Vocab: macromolecule
large organic molecules in cells. They include such molecules as nucleic acids, proteins, polysaccharides and lipids.
Vocab: monomer
simple building block molecules that when linked together form a polymer.
Vocab: nucleic acid
a macromolecule made up of a sequence of nucleotides joined together. Examples include DNA,
mRNA and ERNA.
Vocab: nucleotide
the building blocks of nucleic acids. Made up of a sugar, a base and a phosphate.
Vocab: polymer
a large macromolecule made up of repeating monomer units.
Vocab: base
a nitrogen containing chemical that is a component of DNA. The bases constitute the coding sequence for all genetic information. The four bases are represented by the letters A, T, G and C.
Vocab: deoxyribose sugar
The 5 carbon sugar that is a component of the nucleotide building blocks of DNA. Along with phosphate molecules, they make up the backbone of the DNA molecule.
