dna stucture and replication Flashcards
How are the Okazaki fragments in the lagging strand joined together?
joined together by DNA ligase to create a continuous strand.
What is DNA replication
DNA replication is the process by which a cell makes an identical copy of its DNA. It occurs during the S phase of the cell cycle before cell division, ensuring that each daughter cell receives a complete set of genetic instructions. DNA replication is semi-conservative, meaning each new DNA molecule consists of one original strand and one newly synthesized strand.
What is semi conserative replication
each newly synthesized DNA molecule consists of one original (parental) DNA strand and one newly synthesized (daughter) DNA strand.
What is a template strand?
The original DNA strand that serves as a guide for the synthesis of a complementary DNA strand during replication.
Why is DNA replication semi conserative?
- each new DNA molecule contains one original DNA strand and one new DNA strand.
- This conserves genetic information and reduces the likelihood of errors.
What is the function of helicase in DNA replication?
Helicase unwinds the double helix by breaking hydrogen bonds and separating complementary DNA strands, creating a replication fork.
What is the role of ligase in DNA replication?
Ligase glues the gaps between Okazaki fragments on the lagging strand, forming a continuous DNA strand. It also seals the final gaps between new strands, ensuring the double-stranded helix is complete.
Why is DNA replication crucial for the continuity of species?
DNA replication ensures genetic continuity from parent cells to daughter cells. Genetic variation, due to mutations and genetic recombination, influences natural selection and evolution, driving species adaptation over generations.
What is the role of DNA polymerase III in replication?
DNA polymerase III binds to separated DNA strands and adds complementary nucleotides, creating new strands. It follows the antiparallel structure of DNA and works continuously on the leading strand, adding nucleotides in the 5’3’ direction towards replication fork and in fragments (Okazaki fragments) on the lagging strand.
What is the structure of DNA?
DNA (deoxyribonucleic acid) is a double-helix structure composed of nucleotides. Each nucleotide consists of a phosphate group, a sugar molecule (deoxyribose), and one of four nitrogenous bases: adenine (A), guanine (G), cytosine (C), or thymine (T).
Sugar and phosphate forms a sugar-phosphate backbone with one of the nitrogenous bases attached
two DNA strands are held together by hydrogen bonds
How are the two DNA strands held together?
The two DNA strands are held together by hydrogen bonds between complementary base pairs: adenine (A) pairs with thymine (T) and guanine (G) pairs with cytosine (C). This pairing is known as complementary base pairing.
function of DNA
DNA contains the genetic instructions necessary for the growth, development, functioning, and reproduction of all living organisms. It carries the hereditary information that is passed from parents to offspring.
What is the directionality of the DNA strands?
The two DNA strands have opposite directions. They are antiparallel, meaning one strand runs in the 5’ to 3’ direction, while the complementary strand runs in the 3’ to 5’ direction.
