What is the structure of DNA?

Hw 293-299Q 1-4 p. 299

The Structure of DNA:

Made of units called nucleotides.Nucleotides include:

a. Deoxyribose (a sugar)b. A Phosphate Groupc. One of four possible Nitrogenous Bases…InterActive

http://ny.pbslearningmedia.org/resource/tdc02.sci.life.gen.journeydna/journey-into-dna/

The Four Nucleotides in DNA

1. Adenine (AD-un- neen)

2. Thymine (THY- meen)

3. Guanine (GWAH- neen)

4. Cytosine (SY-to- zeen)

Adenine

Guanine

Cytosine

Thymine

Phosp

hate

gro

up

Deoxyribose

Nucleotide Use

Like letters in the alphabet, many different arrangements can give you an infinite number of words:

The different arrangements of bases to code for and carry genetic information.

2. The Structure of DNA

The Double Helix: A. “A twisted ladder” A=T and G=C in a DNA molecule -This attraction (called Base Pairing) is

caused by hydrogen bonds between the bases.

More on the double helix Two separate

and opposite strands wrap around each other to form a stable twisting molecule

Nucleotide

Sugar-phosphate backbone

Hydrogen bonds

KeyAdenine (A)Thymine (T)Cytosine (C)Guanine (G)

3. Chromosomes

Chromosomes are made of long strands of

DNA nucleotides wrapped around histone proteins.

1. The smallest of the 46 human chromosomes

contains 30 million base pairs.

2. Human Genome Project http://ny.pbslearningmedia.org/resource/tdc02.sci.life.gen.hgp/human-genome-project/

New Strand

Original Strand DNA

Polymerase

Process of DNA Replication:

1. Enzymes “unzip” a molecule of DNA by breaking the hydrogen bonds between base pairs.

2. The two strands unwind and each becomes a template for the other strand.

DNA Replication

3. DNA strands are Complementary (or opposites) if the two strands are separated, they can recreate their own complementary strand.

3. New nucleotides attach to each of the strands, forming two identical sets of DNA!

4. DNA Polymerase- one of the enzymes involved in replication, adds the new bases (nucleotides) and proof-reads each strand so there are very few mistakes.

What is the importance of RNA? The main role of RNA is to aid in Protein

Synthesis

RNA is similar to DNA in that both are made of nucleotides

From DNA to Protein-Video http://ny.pbslearningmedia.org/resource/tdc02.sci.life.gen.proteinsynth/from-dna-to-protein/

How Cells Make Proteins-Interactive http://ny.pbslearningmedia.org/resource/lsps07.sci.life.stru.cellprotein/how-do-cells-make-proteins/

RNA is different than DNA: Sugar backbone in RNA is Ribose (not

Deoxyribose) RNA is single stranded while DNA is

double stranded RNA contains Uracil in place of

Thymine. (U in place of T) DNA always stays in the nucleus, while

RNA can be found in the nucleus and cytoplasm.

Use the following to transcribe DNA to mRNA (codons)

A=U C=G T=AG=C

DNA mRNAACTG

Transcription: DNA is used as a template to make mRNA (messenger)

Types of RNA

Messenger RNA (mRNA) The role of mRNA is to carry instructions

for making proteins from DNA to Ribosomes.

Ribosomal RNA (rRNA) One of the building blocks of RibosomesTransfer RNA (tRNA) Transfers amino acids to ribosomes in the

specific order that mRNA states in order to make a specific protein.

Transcription

Transcription is the process of making mRNA molecules from DNA molecules.

A Look at TranscriptionAdenine (DNA and RNA)Cytosine (DNA and RNA)Guanine(DNA and RNA)

Thymine (DNA only)Uracil (RNA only)

The Genetic Code & Protein Synthesis

1. Proteins are made by joining long chains of amino acids together to form polypeptides. a. There are a total of 20 different

amino acids.b. Different proteins are made by

different combinations and numbers of these amino acids.c. These amino acids are assembled

using the Genetic code.

Translation The process

of a cell using mRNA and ribosomes to make proteins is translation

More on Protein Synthesis

RNA contains 4 different bases A, U, C, and G. The order of these subunits is the Genetic code.

a. The genetic code is read three letters at a time, this is called a “Codon.”

b. Each codon instructs for one amino acid to be built into a chain.

Example: RNA: UCGCACGGU is read as a

series of three codons: UCG-CAC-GGU These different codons represent

three different amino acids. UCG CAC GGUSerine - Histadine - Glycine

The codons for the specific amino acids are listed using this table:

Putting it all together

DNA RNA Proteins TraitsTranscriptio

n Translation

•This simple phrase links all the important genetic components together and is the basis for the science of molecular biology

6. Mutations

Mutations are mistakes cells make when copying DNA.

The most common type of mutation is a Point Mutation, this is when one nucleotide is replaced by another.

These mutations sometimes alter the RNA molecules transcribed and the proteins translated by the ribosomes.

This type of mutation will take place on a piece of DNA that codes for a protein and will be known as a gene mutation

Chromosomal Mutations

Changes in the number or structure of the chromosomes themselves

Types of Chromosomal Mutations

Deletion

Duplication

Inversion

Translocation