DNA Replication

DNA Replication

Structure of the DNA in the cell

Must pack between 1and 3 meters into each cell (except RBCs)

Uses a “coiled-coiled strucure” DNA wound around histones Histones cluster into Nucleosomes

Mechanism of Replication

http://www.johnkyrk.com/DNAreplication.html

DNA mRNA

Transcription

RNA vs. DNA

DNA Deoxyribose Double Stranded G, C, A, T bases Durable

RNA Ribose Single Stranded (Usually) G, C, A, U bases Fragile

Types of RNA

Ribosomal RNA (rRNA)

Transfer RNA (tRNA)

Messenger RNA (mRNA)

Transcription

In the nucleus RNA polymerase ONLY ONE SIDE OF

DNA IS USED AS A TEMPLATE

RNA is edited by removing introns

Transcription YouTube

Differences in Prokaryotes and Eukaryotes

Prokaryotes Genome is small and

circular

mRNA is ready for immediate use

Eukaryotes DNA is found in

chromosomes and large Some pieces of DNA

have protein information (exons)

Some pieces are used for regulation or have an unknown use (introns)

mRNA Translation

RNAProtein

RNA Splicing1. mRNA is transcribed as

a whole transcript

2. Introns = DNA or RNA that does not have information for protein

3. Exons = DNA or RNA DNA or RNA containing information for proteins

4. Must splice out introns for RNA to function

mRNA Splicing

mRNA BINDS TO A RIBOSOME mRNA IS READ AND CONVERTED TO

A SPECIFIC AMINO ACID SEQUENCE mRNA CODES FOR AMINO ACID tRNA BRINGS AMINO ACID TO

RIBOSOME ANTICODON PAIRS WITH CODON AND

BINDS WHILE AA ARE BONDED BY ENZYMES--INTO A PROTEIN CHAIN.

RNA to Protein

INFINITE VARIETY OF PROTEINS CAN BE SYNTHESIZED FROM THE 20 AMINO ACIDS. (ANY ORDER & ANY NUMBER OF AA)

THE SEQUENCE OF AA IN A PROTEIN DETERMINES THE CHARACTERISTICS OF THAT PROTEIN.

MUTATION!!!

MUTATION!!!!

Gene Mutations

Point Mutation: change of a single nucleotide

1. substitution

2. insertion

3. deletion

Substitution Example

Frameshifts: Insertions and Deletions

-shift reading of three letter words (codons)

THE CAT ATE THE RAT AND WAS FAT

-Remove the first C of CAT (deletion)

THE ATA TET HER ATA NDW ASF (ignore AT)

-Add and E to THE

THE ECA TAT ETH ERA TAN DWA SFA (ignore T)

Chromosomal Mutations

Overall change in the number or structure of chromosomes

Changes in number of chromosomes

- Aneuploidys : loss or gain of a whole chromosome

e.g. Trisomy 21 Down’s Syndrome 47, X_,+21

Rearrangement of Single Chromosomes