DNA STRUCTURE AND FUNCTION

DNA Structure DNA is composed of a chain of nucleotides.

DNA Structure

There are 4 different DNA nucleotides

DNA Replication

Replication = identical new strand Occurs for cell division –mitosis or meiosis. Replication Steps:

1. Helicase Enzyme unzips DNA molecule

2. Free nucleotides combine with complementary base pairs

3. Backbone forms by nucleotides bonding

Protein Synthesis

Protein Synthesis has 2 steps:1. In nucleus:

○ TRANSCRIPTION = forming RNA strands

2. In a ribosome: ○ TRANSLATION = coding for amino acid

chains or proteins

Transcription

3 Types of RNA:Ribosomal RNA – rRNA: makes up the ribosomesTransfer RNA – tRNA: bring Amino Acids to

ribosomeMessenger RNA – mRNA: transfers gene code

from DNA in nucleus to ribosome○ Carries the correct amino acid sequence to make

proteins

Transcription

How RNA is different from DNA:

1. RNA is a single stranded

2. RNA has ribose sugar instead of Deoxyribose sugar

3. RNA contains Uracil instead of Thymine

4. RNA can leave the nucleus

Transcription

Process of making mRNA which is the replicating of a gene

Each mRNA is made from a series of DNA nucleotides which code for one Gene (trait).Only one side of the DNA is coded

The mRNA can then leave the nucleus to make proteins

Transcription Process Steps

1. Enzyme unzips DNA at the gene location

2. Free RNA nucleotides match up to their complementary bases on DNA

DNA: RNA:

A U

T A

C G

G C

3. RNA breaks off and leaves nucleus and the DNA strands Hydrogen bonds reconnect

Translation

mRNA attaches to a Ribosome in the cytoplasm.

The code is read by the ribosome in a series of 3 nucleotides (aka triplicate) – called a codon.

Translation – mRNA code

Translation

Each codon codes for one amino acid3 RNA nucleotides = 1 amino acid1 codon = 1 amino acid

9 nucleotides =_?_Codons = _?_ Amino acids tRNA matches up to the codons using anticodons Each tRNA brings 1 amino acid to the mRNA Amino Acids connect together to form proteins via

polypeptide bonds

How Our Bodies Use Proteins

Proteins control cell functions:StructureEnzyme actionHormones