The Structure & Function of DNA
Week 11 Bell Work What is the basic unit of a DNA molecule?
DNA Structure: DNA is a double helix structure made up of two strands of nucleotides, held together by hydrogen bonds. DNA Replication: The process of DNA replication is the process by which a cell makes an identical copy of its DNA before it divides. Genetic Code: The genetic code is the set of instructions that tells the cell how to make proteins from the information contained in DNA.
DNA is composed of two strands of nucleotides that twist around each other to form a double helix. Replication is the process of DNA making an exact copy of itself before a cell divides. The two daughter strands contain one original strand and one newly synthesized strand.
DNA Structure and Replication
Week 11 Bell Work What is the full name of DNA?
- Deoxyribonucleic acid
- Ribonucleic acid
- Deoxyribose nucleotide
DNA or deoxyribonucleic acid is the molecule that stores the genetic information for all organisms DNA is heritable, this means that it can be passed from parent to offspring The information from DNA is used to build another nucleic acid called RNA, or ribonucleic acid, and which then builds proteins Each protein has a unique structure and function in the cell, so proper coding is critical for building each protein
Codes for Proteins
The subunit, or monomer, that makes up DNA is called a nucleotide One molecule of human DNA contains billions of nucleotides The nucleotides that make up DNA differ only in their bases The four different bases are cytosine, guanine, thymine, and adenine We abbreviate these bases using C, G, T, and A
Which nucleotide most resembles Thymine?
Nucleotides are held together in a string by covalent bonds The DNA is composed of two of these nucleotide strings spun in what is known as a double helix The DNA double helix is held together by hydrogen bonds between the bases in the middle The nucleotide bases only bond in a particular matter A bonds with T C bonds with G
Current DNA Model
Fill in the other half of the DNA based on the bonding rules
Week 12 Bell Work Should DNA tests be required for all 10th grade students to determine their ancestral heritage and risk of certain diseases?
The process by which DNA is copied during the cell cycle is called replication The two strands will separate and become templates for the new strand Replication ensures that every cell has a complete set of identical information
If the original strands nucleotides are: AGC-TAA-GCG What is the new strands nucleotides?
DNA is not responsible for copying itself Enzymes and proteins do the work of replication
DNA Process for Replication
An enzyme called helicase binds to the DNA molecule and unzips the strands in both directions This will occur at many points The bonds between the nucleotides will be broken Stabilizing proteins bind to help keep the strands separated at the replication fork
An enzyme called primase makes an RNA primer, this is a short beginning strand so DNA polymerase can work properly DNA polymerase goes down the strand matching nucleotides to the template strand based on the base pairing rules Once both template strands have been paired, and enzyme called DNA Polymerase III will replace the RNA primer Then an enzyme called ligase will come through and make sure everything is bonded or glued together
Week 12 Bell Work What enzyme is responsible for unzipping the DNA molecule?
Bell Work What is a gene?
When replication is complete, there are two identical molecules of DNA Each molecule contains one strand of DNA from the original molecule and one new strand This is called semiconservative replication
A gene is a piece of DNA that provides instructions for a cell Genes are the most basic unit of heredity Genes determine the traits of an organism Some proteins give cells structure, while others catalyze reactions or act as chemical messengers
Genes Code for Proteins
Proteins are the connection between DNA and traits DNA can not leave the nucleus of the cell, therefore the process by which genes are turned into proteins requires two parts One part to get the information out of the nucleus, and the second part to create the protein
How do you think DNA information gets out of the nucleus?
Bell Work Semiconservative refers to?
The process of creating proteins consists of two stages: transcription and translation Transcription is the process of copying a sequence of DNA into a messenger RNA molecule mRNA is like a disposable copy of the DNA message During translation they translate this mRNA into a functional protein
Ribonucleic Acid A molecule of RNA is similar to DNA, but it has some distinct differences RNA has a base called Uracil instead of having Thymine, U instead of T A pairs with U for RNA RNA is also single stranded, and this allows it to sometimes take on a 3D shape and act similarly to enzymes
Comparing DNA to RNA
TAC-GCG-AAT This is the DNA molecule, what would the mRNA molecule bases be?
In transcription, a gene will be transcribed not the entire DNA molecule RNA polymerase will bind to the promoter region of the DNA sequence RNA polymerase will separate the two strands to provide a single stranded template
Steps of Transcription: Initiation
One strand of DNA acts as the template RNA polymerase does down the DNA molecule building the RNA using complimentary base pairs RNA polymerase will use Uracil (U) instead of Thymine (T)
Steps of Transcription: Elongation
A sequence on the DNA called a terminator signal that RNA transcription is complete This causes the newly formed RNA molecule to be released from the RNA Polymerase
Steps of Transcription: Termination
Bell Work What is the difference between DNA and RNA?
Translation is the process that decodes the mRNA to produce a protein This is exactly what you did in your work sheet yesterday RNA will leave the nucleus and bind to a ribosome Ribosomes are the site where proteins will be made
Steps of Translation
The RNA strand will be sandwiched by the ribosomes large and small subunit The RNA will have the instructions needed to make a protein An initiator tRNA carrying the first amino acid will come in and bind to the start codon This amino acid will always be Methionine or Met
Steps of Translation: Initiation
A codon is.....
- A group of two nucleotides
- A group of three nucleotides
- It is a long segment of DNA
This is where the chain of amino acids continues to grow tRNA molecules will continue to enter the ribosomal unit bringing in amino acids that match the RNA molecule As each new amino acid is brought in the RNA shifts
Steps of Translation: Elongation
Termination takes place when a stop codon is reached This signals for the RNA molecule to be released from the tRNA The ribosome will then separate from the RNA and the ribosome can then be reused The amino acid chain will then fold into a distinct 3D structure before it is ready to do work in the cell
Steps of Translation: Termination
What processes are involved in DNA replication?
DNA replication happens in both directions - 5' to 3' and 3' to 5'. A single replication of the double helix produces two identical molecules. DNA can be found in a variety of shapes. In addition to the classic double helix, it can also take on a quadruple helix or even a single-stranded form. DNA strands can be broken apart and reassembled in any order, allowing them to be used in a wide variety of applications, such as genetic engineering and DNA sequencing.
Did you know?
What are the components that make up the structure of a DNA molecule?
How do the components of a DNA molecule interact?
How are the processes of DNA replication related to the passing of genetic traits?
Brain break: Draw a bird with human legs wearing elegant high heels
Question: What are the three main components of DNA structure and replication? Clues: • DNA is made up of repeating units called nucleotides. • DNA replication is a process in which a single strand is copied to create two identical strands. • The DNA double helix is formed by two strands held together by hydrogen bonds. In pairs: Select and solve one of the tasks: A. In pairs, draw a diagram to illustrate the components of DNA structure and replication. B. Explain in writing how DNA replicates and how the components are involved in the process.
What are the building blocks of DNA called?
- Amino acids
What are the four nitrogenous bases found in DNA?
- Adenine, Guanine, Cytosine, Thymine
- Adenine, Uracil, Cytosine, Thymine
- Adenine, Guanine, Cytosine, Uracil
Which nitrogenous bases pair together in DNA?
- Adenine-Thymine and Guanine-Cytosine
- Thymidine-Adenosin and Cytidine-Guanosin
- Uridin-Thymin and Adenosin-Guanin
How does DNA replicate?
- Semi-conservative replication
- Conservative replication
- Dispersive replication
Work together in pairs: What are the three main components of DNA and what role do they each play in DNA replication?