Unit 4 Nucleic Acids

Monomer of DNA

Nucleotide

Three components of nucleotides

Phosphate

Deoxyribose

Nitrogenous base

Four nitrogen bases

Adenine

Guanine

Cytosine

Thymine

Purines

Double ring molecules

Pyrimidnies

Single ring molecules

Messenger RNA

Linear

Carries code from DNA to cytoplasm

Ribosomal RNA

Globular

Is the ribosomes

Transfer RNA

T-shape

Carries amino acids to ribosomes to make proteins

Structure of RNA

Single stranded

Ribose sugar

Uracil

When does DNA replication occur?

Interphase

Makes identical copies of chromosomes

DNA replication step 1

DNA helicase attaches itself to the DNA molecule, unwinds and cuts apart the hydrogen bonds

DNA replication step 2

DNA polymerase adds nucleotides and attaches them to each separated DNA strand. It also proof reads for errors

DNA replication step 3

Ligase enzymes bond the new nucleotides to the old nucleotides on the original strands

Why is DNA replication a semi-conservative process

It consists of one original strand and one new strand

Transcription

The process of making RNA from DNA

Occurs in the nucleus during interphase

Transcription step 1

RNA polymerase breaks apart the hydrogen bonds of a DNA at the beginning of the section of the DNA molecule that codes for RNA molecules

Transcription step 2

Free-floating nucleotides form bonds with the leading DNA strand with the assistance of RNA polymerase

Transcription step 3

More enzymes remove unnecessary parts of the RNA molecules before they move out of the nucleus to the cytoplasm

Translation

The process of RNA molecules making proteins

Occurs in the cytoplasm during interphase

Translation step 1

mRNA travels from the nucleus to a ribosome in the cytoplasm or attached to a rough ER

Translation step 2

mRNA is read three nitrogenous bases at a time. These are called codons

Translation step 3

tRNA molecules with an anticodon match with a codon and then are released to match with another amino acid

Translation step 4

Enzymes help form peptide bonds between the amino acids to form protein molecules. (Polypeptide)

Translation step 5

tRNA molecules continue to deliver amino acids to the ribosome until a stop codon is reached on the mRNA strand