DNA - Structure and Replication

Overview

• DNA makes up chromosomes and it consists of a double-helix with a protein (histone)

Structure

• building blocks of a nucleic acids are nucleotides, which has three components

  1. phosphate group (very ends)

  2. 5-carbon sugar (connects phosphate and nitrogenous base)

  3. nitrogenous base - adenine and guanine, thymine and cytosine (pairs in the middle)

• two strands of DNA complement one another with the nitrogenous base pairings

Semi-conservative Replication

Each newly formed DNA molecule contains one original parent strand and one newly synthesized strand.

Steps to replications

1. hydrogen bonding forces between complementary base pairs are broken two strands of DNA double helix are unzipped by an enzyme called helicase

2. Free nucleotides in the nucleus pair with the exposed bases on each original strand, following base-pairing rules, with the help of the enzyme DNA polymerase.

3. Newly paired strands naturally recoil into the double-helix shape when formed

Transcription + Translation

• genes along DNA contain instructions for making specific proteins

• along a gene, sets of three bases called triplets code for specific amino acids

• Amino acids are linked together in a specific sequence to form a different kind of protein

Importance of Proteins

• structural - provides support

• storage proteins - provides amino acids for growth

• contractile proteins - help movement

• transport proteins - transport substances (i.e., protein hemoglobin w/in RBCs transport oxygen

• enzymes - help chemical reactions

Amino Acid Codes

• thymine and adenine

• guanine and cytosine

• ATG = start code

• TAA, TAG, TGA = STOP code