DNA, RNA, & Protein Synthesis

Mrs. Morgan

Biology

Discovering DNA 1928 – F. Griffith discovers that a factor in heat-killed, disease-causing

bacteria can “transform” harmless bacteria into ones that can cause disease. (pg 287)

1944 – O. Avery and his team determine that genes are composed of DNA. (pg 289)

1950 – E. Chargaff observed that in any sample of DNA the number of adenine molecules was equal to the number of thymine molecules. The same was true for the number of cytosine and guanine molecules.

1951 – L. Pauling & R. Corey determine that the structure of a class of protein is a helix.

1952 – R. Franklin studies the DNA molecule using a technique called X-ray diffraction. (pg 292)

1953 – J. Watson & F. Crick develop the double-helix model of the structure of DNA. (pg 293)

Source: Biology, Prentice-Hall, Miller-Levine, pg. 292-293

Part IDNA

DNA

“DNA is the nucleic acid that stores and transmits the genetic information from one generation of an organism to the next.”

Basically, “DNA carries the genetic code.”

Source: Biology, Miller-Levine, Prentice Hall, page 139

Components & Structure of DNA DNA (DeoxyriboNucleic

Acid) is a polymer made up of units called nucleotides.

Nucleotides are made up of three basic parts: 5-carbon sugar (deoxyribose), a phosphate group, and a nitrogenous base.

Nucleotides

Source: www.msu.edu.

Nitrogenous Bases There are four kinds of

nitrogenous bases in DNA.

Adenine & Guanine belong to the group of compounds known as purines.

Cytosine & Thymine belong to the group pyrimidines.

Source: home.comcast.net

Nitrogenous Bases Adenine will ALWAYS pair with Thymine in

DNA Thymine will ALWAYS pair with Adenine in

DNA Cytosine will ALWAYS pair with Guanine Guanine will ALWAYS pair with Cytosine HYDROGEN BONDS hold the bases

together

Nucleotide Chain Individual nucleotides are

joined together to form a long chain. Note that the sugars and phosphate groups form the backbone of the chain, and the nitrogenous bases stick out from the chain.

Source: www.nicksnowden.net

Double Helix

Double Helix in Review1. What are the 3 parts of a nucleotide?

2. Name the 4 nitrogenous bases.

3. What is the name of the sugar in DNA?

4. What base pairs with adenine?

5. What base pairs with cytosine?

6. What is the structure of DNA called?

7. What holds the base pairs together?

8. What makes up the “backbone” of the DNA structure?

9. How do they know that adenine always pairs with thymine?

10. What does the shape of DNA look like?

DNA Replication “Before a cell divides, it duplicates its DNA in a

copying process called replication. This process ensures that each resulting cell will have a complete set of DNA molecules. During DNA replication, the DNA molecule separates into 2 strands following the rules of base pairing. Each strand of the double helix of DNA serves as a template or model for the new strand.”

Source: Biology, Miller-Levine, Prentice Hall, page 299

Source: science.howstuffworks.com

Source: http://3.bp.blogspot.com

Source: personal.psu.edu

DNA Replication Helicase – enzyme that is

capable of unwinding DNA double helix. Causes DNA to “unzip” which is when the hydrogen bonds are broken.

DNA Polymerase – joins individual nucleotides to produce a DNA molecule.

Primase – synthesize short RNA sequences.

DNA Replication Review

1. What causes the strand of DNA to “unzip”?

2. What is the goal of DNA replication?

3. What is holding the strand of DNA together that eventually breaks?

Part IIRNA

RNA RNA (RiboNucleic Acid) The structure of RNA is similar to DNA, it

consists of a long chain of nucleotides. RNA is the nucleic acid that acts as a

messenger between DNA and the ribosomes and carries out the process in which proteins are made from amino acids.

There are 3 main differences between RNA & DNA.

DNA RNA Sugar is deoxyribose

Thymine

Double stranded

Sugar is ribose

Uracil (replaces thymine)

Single stranded

Source:http://images1.clinicaltools.com

Types of RNA

There are 3 main types of RNA that are

involved in the synthesis of proteins. The

assembly of amino acids into proteins is

controlled by RNA. Messenger RNA (mRNA) Ribosomal RNA (rRNA) Transfer RNA (tRNA)

Transcription: RNA synthesis Transcription is the process of transferring

information from DNA to RNA. Due to the fact that DNA is found in the nucleus

and never leaves the nucleus and ribosomes are found in the cytoplasm,a messenger must bring the genetic information from the DNA in the nucleus out to the ribosomes in the cytoplasm.

Messenger RNA (mRNA) performs this function.

RNA Review

1. Name the 3 differences between DNA and RNA.

2. Name the 3 types of RNA

3. What is the goal of transcription?

4. What type of RNA is responsible for transcription?

5. Why is transcription necessary?

Part IIIProtein Synthesis

Protein Synthesis The information that DNA transfers to mRNA is in the form of a code.

This code is determined by the way in which the four nitrogenous bases are arranged in DNA.

The nitrogenous bases in DNA contain info that directs protein synthesis. Proteins play an important role in biological systems. Proteins control biochemical pathways within the cell, they direct the synthesis of lipids, carbohydrates, and nucleotides, and they are also responsible for cell structure and cell movement.

Like a manager of a factory, DNA does not work on the assembly line but it can control what the cell factory makes by issuing orders to the organelles (workers). Together, DNA and its assistant, RNA, are directly responsible for making proteins. DNA & RNA are like nucleic acid executives who run the entire cell factory. Source: Biology, Miller-Levine, Prentice Hall, page 148

Protein Synthesis Each combination of 3 nucleotides on

messenger RNA is called a codon (a 3 letter code word).

Each codon specifies a particular amino acid that is to be placed in the polypeptide chain (protein chain).

Protein Synthesis How does messenger RNA actually produce a protein chain? The

decoding of a messenger RNA message into a protein chain is known as TRANSLATION. The message is being translated from the language of nulceic acids into a protein chain. The messenger RNA does not produce a protein chain itself, instead it uses transfer RNA, ribosomal RNA, and ribosomes.

During translation, messenger RNA binds to the ribosomes on which ribosomal RNA (rRNA) is found. Amino acids in the cytoplasm are picked up by transfer RNA (tRNA) and are carried to messenger RNA (mRNA). The anticodons in transfer RNA attach to the proper codons in messenger RNA. Thus messenger RNA acts as the pattern for protein synthesis. In this way, amino acids are brought together in the correct sequence to form a protein molecule.

Source: Biology, Miller-Levine, Prentice Hall, pg 150, 155

Amino Acid Chart

Source: http://biosphemera.com

Amino Acid Chart

Source: www2.visalia.k12.ca.us

Source: stemcells.nih.gov

Mutations Original – A B C * D E F

Deletion – A C * D E F (loss of all or part of chromosome) Duplication – A B B C * D E F (produce extra copies) Inversion – A E D * C B F (reverse the direction of parts of

a chromosomes) Translocation – A B C * J K L

- G H * I D E F (part of one chromosome breaks off & attaches to another)