DNA Flashcards
(14 cards)
What is RNA made up of?
RNA is made up of multiple enzymes.
What must happen for DNA replication and transcription to occur?
The two strands of DNA must separate.
Where and how is DNA stored in eukaryotic cells?
In eukaryotic cells, DNA is bound to proteins (histones).
Where and how is DNA stored in prokaryotic cells?
In prokaryotic cells, DNA is unbound and does not have histones.
What is the purpose of histones in eukaryotic cells?
Histones pack the DNA molecule tightly into a spring.
Compare and contrast DNA and RNA.
- DNA has a deoxy sugar, while RNA has a ribose sugar.
- RNA is single-stranded, while DNA is double-stranded.
- Strands in RNA are shorter.
- DNA and RNA have four bases, however, in RNA, thymine is replaced by uracil.
What does it mean when DNA strands are bi-directional?
One DNA strand goes from 5’ to 3’, while the complementary strand goes from 3’ to 5’.
Which bases are the big nucleotide bases?
Adenine and guanine.
Which bases are the small nucleotide bases?
Thymine and cytosine.
What is the purpose of the bases being small or big nucleotides?
The difference in size is what drives the DNA’s helical structure, as the big and small nucleotides alternate to match their complementary bases.
Describe the structure of DNA.
- Double stranded and consists of two complementary chains of nucleotides joined together by weak hydrogen bonds.
- Sugar units are joined together by phosphate units to form the sugar-phosphate backbone of each strands. The bases are attached to the sugar units.
- The two strands are anti-parallel and every 10 nucleotides forms a double helix.
Describe the process of DNA replication.
- An enzyme called helicase separates the two strands of the DNA by breaking the weak hydrogen bonds between the complementary bases and unwinding the two strands of the DNA into a replication fork.
- An enzyme called DNA polymerase binds to the template strand, making the new strand of DNA by adding bases in one direction (5’ to 3’). The other strand called the lagging strand cannot be made in a similar continuous way, because it runs in the opposite direction. Therefore, the DNA polymerase can only make this strand in a series of small chunks known as Okazaki fragments. Each fragment is started with an RNA primer, then DNA polymerase adds a short row of DNA bases in the 5’ to 3’ direction. This is repeated until the strand is finished.
- The enzyme called exonuclease removes all RNA primers from both strands of DNA. Another DNA polymerase enzyme then fills in the gaps that are left behind with DNA.
- The enzyme called DNA ligase seals up the fragments of DNA in both strands to form a continuous double strand.
Why is DNA replication known as a semi-conservative process?
The process of DNA replication is a semi-conservative replication process meaning each copy has one original strand and one new copied strand.
What direction does DNA replication follow?
5’ to 3’.
