Unit 5 DNA, Protein Synthesis
In this unit we will look more closely at the structure of the fourth type of organic molecule - nucleic acids! The most important nucleic acid is DNA - the recipe for all life on earth. We will learn how DNA replicates so that each new cell formed from other cells contains the information it needs to survive. Next, we will compare DNA with RNA and examine how they are both important in using the information encoded in DNA to make proteins - the molecules our bodies are mostly made of (minus water and fat that is). Lastly, we will look at errors made during replication and protein synthesis to better understand how cells mutate and in turn, how organisms change over time.
Learning Objective #1: Explain the structure of DNA.
Learning objectives in more detail:
□ Describe the structure of DNA in terms of building blocks, arrangement of building blocks, shape, and bonding within the molecule.
□ Define a karyotype and state the # of chromosomes in humans and the significance of the last pair.
□ Describe the structure of a chromosome including histones and sister chromatids.
Describe how cloning occurs - what types of cells do you need? (See amoeba sisters for explanation!)
Learning Objective #2: Explain how & when DNA replicates including the role of enzymes!
o Be sure to include the role of the following vocabulary:
§ helicase
§ DNA polymerase
§ Nucleotides
§ Base-pairing
§ Adenine, cytosine, guanine, thymine
§ Hydrogen bonds
§ Covalent bonds
§ Okazaki fragments
§ Leading strand
§ Lagging strand
BONUS WORDS: RNA primers, primase & ligase
TAKE this practice quiz! https://www.biomanbio.com/Quizzes/LifeChemQuizzes/DNAQuiz_structure_and_replication.html
How do we sequence the human genome? https://www.youtube.com/watch?v=MvuYATh7Y74
The race to sequence the human genome: https://www.youtube.com/watch?v=AhsIF-cmoQQ
LEARNING OBJECTIVE #3 - Explain how DNA is used to make proteins and how proteins are used to make up our bodies!
In this unit you will be learning about the processes of DNA transcription and translation. I imagine those words sounds nearly the same. However, a medical transcriber's job is to take a doctor's notes and type it up (and they often add codes for insurance companies). A scribe, in general, just writes for someone. But a translator takes one language and rewrites it in a new language. This is important to recognize as it will help you remember the difference between these two main processes.
In transcription, the DNA is unzipped and one single strand is copied. Instead of using DNA nucleotides like we did in DNA replication, this time we add RNA nucleotides. The RNA is very similar to DNA only there is no Thymine - instead a similar base, Uracil, is used. The only other major difference is that RNA uses ribose sugar instead of the deoxyribose sugar --so its different by one oxygen atom. Ok...so we make a strand of RNA and because this strand is essentially copying the message from DNA we call this single strand MESSENGER RNA or mRNA. This strand will make its way out of the protected nucleus through holes or pores in the nuclear membrane. That's it. That's transcription. Step one? Check.
From the nucleus, the mRNA travels to a ribosome - either one floating in the cytoplasm or one attached to the rough endoplasmic reticulum organelle. Either way, the ribosome is going to hold on to the mRNA as transcription begins. So now we are ready to move from the language of nucleic acids (DNA and RNA) to the language of proteins ---> amino acids! So how do the amino acids get to the ribosome? Each different amino acid is carried on another molecule of RNA called tRNA - the t stands for TRANSFER as it is literally transferring amino acids around the cell.
At the ribosome, the mRNA is read three bases at a time. We call this a triplet or more importantly, a CODON. This is the code. Each three letter sequence determines what amino acid will be added. The tRNA will only bind to the mRNA if its three exposed bases match the three mRNA nucleotides. Look at an amino acid wheel to determine which amino acids go with each codon. Start by reading from the center of the wheel and move out. There are three layers as you can see. Sometimes the third letter will not matter at all. Sometimes a different second letter gives you the same amino acid - can you find an example? When UGA is read on the mRNA, this is the signal to stop translating. AUG is considered the START codon.
At the ribosome, each amino acid will be covalently bonded to the next amino acid. (Sometimes this gets called a peptide bond because a polypeptide is another name for a chain of amino acids). Once a long chain forms, the amino acids will be folded into very intricate shapes that allow that particular protein to perform its specific job - whether it be an enzyme, a muscle protein, a hair protein, an elastic protein in the skin, or complex hemoglobin protein in a red blood cell. A single error in the base sequence could result in the wrong amino acid - with the wrong amino acid, the protein might not fold correctly or take on the right shape. Without that specific shape it may be doomed. This is protein synthesis in a nutshell...
--> So tonight I looked at my husband's bag of protein powered and noticed many connections to what we are learning in biology. Check it out!
Detailed Learning objectives for protein synthesis:
-State the major differences between DNA and RNA
Name and describe the roles of each of the three types of RNA
Determine the amino acid sequence from a DNA sequence using the codon chart
Observe two or more DNA fragments to determine which type of mutation occurred in one
Describe the complexity of proteins including the 3-dimensional folding of amino acid sequences
Define the following terms and know their role in protein synthesis: codon, anticodon, mRNA, tRNA, rRNA, ribosome, cytoplasm, nucleus, DNA, RNA, amino acid, start codon, stop codon
Describe the different types of mutations and be able to identify each on comparing two DNA sequences
PRACTICE QUIZ FOR PROTEIN SYNTHESIS:
1. https://www.biologycorner.com/quiz/DNA3_qz.html
Take this practice quiz on protein synthesis. There are a couple DNA replication questions mixed in so see if you can pick those out. Also, the other DNA quizzes might have some helpful questions as well! Try those if you have time!
2. Another quiz (although the picture in #9 didn't work for me): http://www.proprofs.com/quiz-school/story.php?title=block3-group3
3. TRY THIS ONE! https://quizizz.com/admin/quiz/57fd86fde575efc325fcc183/dna-rna-protein-synthesis-practice-test
4. NEW QUIZ ADDED 3/25/19: (you have to register for it but the questions are good) https://quizizz.com/admin/quiz/57221ebd0947500b5e621663/protein-synthesis-test-prep
There is an extra coloring page (from Biology Corner) that may be helpful for studying attached below titled "Transcription & Translation Coloring.
LEARNING OBJECTIVE 4: Explain how GEL ELECTROPHORESIS works and how it is used for DNA profiling and paternal testing.
Use this website for the virtual lab: http://learn.genetics.utah.edu/content/labs/gel/
When finished with the lab, read the results of these two criminal cases and answer questions #1-3 at the bottom in your journal.
