DNA study guide

Structure of DNA

Rungs are the nitrogenous bases (adenine, thymine, guanine, and cytosine); Backbone is the deoxyribose sugar and the phosphate group

Monomer of DNA

Nucleotides which are made up of 1 deoxyribose, 1 phosphate group, and 1 nitrogenous base

Purines

Adenine and guanine (2 rings)

Pyrimidine

Thymine and cytosine (1 ring)

Semi-Conservative

DNA is semi-conservative because when replicating, one of the two original strands remain in each of the replicated DNA.

DNA Replication

DNA Replication is located in the nucleus of the cell. It involves several different enzymes which have different functions

Helicase

Unzips the double stranded DNA to two single strands

Single Stranded Binding Proteins

Prevents the unzipped DNA from being zipped up

DNA Polymerase

Goes from 5’ to 3’ along the DNA strands, replicating the corresponding side for replication

RNA Primase

Initializes where the polymerase starts making the corresponding side for a DNA strand. Is used mostly in the lagging strand where polymerase needs it to keep making okazaki fragments since the polymerase can’t go from 3’ to 5’.

Ligase

Puts the okazaki fragments in the lagging strand together.

Replication Fork

Prokaryotes have one point of origin for DNA replication, while eukaryotes have multiple points of origin for DNA replication.

Okazaki Fragments

Fragments in the lagging strand which are used to slowly make the replicated DNA. The primase keeps on putting small bits of RNA for the polymerase to make these fragments, and the fragments are then put together with the help of ligase.

Structure of RNA

RNA is single stranded. It contains uracil instead of thymine as a nitrogenous base.

DNA vs RNA

RNA is single stranded, unlike the double stranded DNA.

mRNA

messenger RNA is transcribed from the DNA in the nucleus and sent out to the ribosome in order to be translated for protein synthesis.

tRNA

transport RNA which transports the amino acids to the ribosome for protein synthesis. Has an anticodon to match the codon in the mRNA in order to help the ribosome make the protein.

rRNA

ribosomal RNA is inside the ribosome and helps translate the mRNA to make the protein.

Central Dogma

The process of DNA replication, transcription, and translation

Transcription

DNA in the nucleus is converted to mRNA which is used to go out of the nucleus and get translated for protein synthesis.

Translation

In the cytoplasm, the mRNA goes to the ribosome and works with the tRNA to make the protein. The tRNA’s anticodon matches with the codon of the mRNA and is used to help transport the corresponding amino acids to the ribosome. The rRNA in the ribosome helps translate the mRNA in order to help make the protein.

Codon

A group of three nitrogenous bases, codes for a specific type of amino acid

Anti-codon

The complementary codon on the tRNA

Mutations

Errors in DNA Replication as well as exposure to certain chemicals can result in mutations in the DNA. This can lead to cancer. 

Leading and Lagging Strands & 5’ and 3’

In DNA replication, there are two strands of DNA which are antiparallel, meaning they go in different directions. The DNA polymerase can only go from 5’ to 3’, so one of the strands takes longer to replicate than the other. Therefore, the strand which is from 5’ to 3’ is the lagging strand, and the strand which goes from 3’ to 5’ is the leading strand.

Monomer

Just like DNA, RNA is made up of nucleotides. However, the nucleotides contain a ribose sugar, phosphate group, and nitrogenous base.