Ap Biology 027 – Dna & Rna (Part 2) Video Review Sheet Answers

Indelible Understanding
IST-1
Heritable information provides for continuity of life.

LEARNING OBJECTIVE
IST-1.K
Describe the structures involved in passing hereditary information from ane generation to the next.
IST-1.L
Describe the characteristics of DNA that permit it to be used as the hereditary fabric.

ESSENTIAL Cognition
IST-1.Grand.1
Deoxyribonucleic acid, and in some cases RNA, is the principal source of heritable data.

IST-1.K.ii
Genetic information is transmitted from ane generation to the adjacent through DNA or RNA–

1. Genetic data is stored in and passed to subsequent generations through Dna molecules and, in some cases, RNA molecules.
2. Prokaryotic organisms typically have round chromosomes, while eukaryotic organisms typically accept multiple linear chromosomes.

IST-1.K.3
Prokaryotes and eukaryotes tin contain plasmids, which are minor actress-chromosomal, double-stranded, round Dna molecules.

IST-1.L.1
DNA, and sometimes RNA, exhibits specific nucleotide base pairing that is conserved through evolution: adenine pairs with thymine or uracil (A-T or A-U) and cytosine pairs with guanine (C-Chiliad)–

1. Purines (Thou and A) accept a double band structure.
2. Pyrimidines (C, T, and U) accept a single ring structure.

6.one Dna and RNA Structure Overview

All life on World, from the single-celled bacterial cells that populate every inch of the globe, to the multicellular fungi that serve as food recyclers in various ecosystems, to plants big and pocket-size, to animals of all sizes, use the same basic Deoxyribonucleic acid and RNA molecules to store and transmit genetic information.

The differences between Deoxyribonucleic acid and RNA are minute, but agreement their structure is an of import foundation to agreement the molecular basis of genetics. While prokaryotes and eukaryotes use essentially the same molecules to store genes, there are important structural differences and methods that these organisms utilize to transmit genetic information. This data volition definitely be on the AP Test. So, follow along every bit nosotros cover everything you lot need to know virtually Deoxyribonucleic acid and RNA construction!

Before we swoop into the specific structures of DNA and RNA, let's take a look at the full general purposes of these structures and the reasons they exist. This volition be an extremely short review since we covered about of these topics in detail in our video on section 1.6.

Deoxyribonucleic acid exists as a double-helix, with two strands held together by hydrogen bonds between nitrogenous bases. Past dissimilarity, RNA exists equally a unmarried strand. There are several functional reasons for this difference. Dna stores genetic information for long periods of time and a double-stranded structure can help it protect the information from damage. The double-stranded structure also helps it notice when harm has taken identify since the base pairing between strands volition become disrupted.

Deoxyribonucleic acid and RNA have several important structural differences

RNA, on the other hand, exists but for a curt period of fourth dimension in virtually organisms and is not typically the chief source of heritable data. RNA is simply transcribed from the DNA and tin can easily get out the nucleus every bit a single strand to exist translated into a protein. Some viruses break this rule, using RNA as a primary storage molecule for their genetic code.

Between DNA and RNA, there are only a few structural differences at the molecular level. As their names imply, ribonucleic acid uses ribose in the carbohydrate-phosphate backbone, while deoxyribonucleic acid uses deoxyribose. While the only difference betwixt these two sugar molecules is the presence of a unmarried oxygen atom, this makes a structural and functional deviation. The oxygen in ribose makes this section of the saccharide much larger and makes this section more electronegative. This tends to brand RNA more reactive than Dna, part of the reason it is shorter-lived. This not only changes the specific structure of the saccharide-phosphate backbone but also makes information technology harder for RNA to course a double-helix structure unless the perfect base pairs are created (such as in tRNA molecules).

The only other departure between DNA and RNA is the exact nucleotide monomers they apply to create a strand. While these are mostly the same, Dna uses thymine while RNA uses uracil. This deviation helps the jail cell recognize the difference between DNA and RNA, and uracil is slightly less energetically expensive to produce, saving the prison cell some energy.

Earlier we have a closer look at DNA and RNA structure, let's take a look at how these molecules actually shop genetic information. Data is stored in DNA and RNA in the sequence of nucleotides inside each molecule. This sequence is copied during RNA transcription, creating an RNA molecule that carries the same information. This RNA molecule leaves the nucleus, and it is translated into a protein by a ribosome. Within the ribosome, sets of 3 nucleotides called codons are matched to anticodons on tRNA molecules.

Each tRNA has a specialized anticodon and carries a specific amino acid. One reason we assume that all life on Earth comes from a common antecedent is that all organisms utilise the aforementioned basic lawmaking to tell ribosomes how to construct proteins. This codon is "read" in sequence from the 1st nucleotide, to the second, to the third, to determine what amino acid is added to the growing polypeptide chain. For case, a codon of GAA signals to the ribosome that it should add together glutamic acid to the growing polypeptide concatenation – in all organisms!

The "code" used to specify certain amino acids is the same in all living organisms.

Similar proteins, Deoxyribonucleic acid and RNA take a master, secondary, tertiary, and even quaternary structure. Master structure is made from the specific sequence of nucleotides. Secondary structure is formed mostly by base-pairing, making a helix betwixt two strands or a stem-loop when ane strand folds back on itself. The tertiary construction of both Deoxyribonucleic acid and RNA is formed both by base pairing and the unique interactions between different nucleotides and the saccharide-phosphate courage. Quaternary structure is formed when Deoxyribonucleic acid or RNA molecules form larger complexes with other nucleic acids or proteins.

Since many of these structures are formed by the procedure of base-pairing, allow'south accept a closer expect at how this works. If you remember how hydrogen bonds work from Unit 1, you remember that hydrogen bonds are formed between the positive and negative charges held on ii polar molecules. The purines (with a double-ring structure) course hydrogen bonds with a specific pyrimidine (with a unmarried-ring structure). Since each nucleotide base has a specific charge, it can only bind with its complementary nucleotide base. And so, G always binds with C, while A ever binds with T (or Uracil in the example of RNA). If the bases approach each other in any other combination, similar charges repel each other. Therefore, correct base pairing is necessary for the normal double-helix construction of Deoxyribonucleic acid and the several unlike forms of folded RNA (such as tRNA and rRNA).

Base pairing only occurs between complementary nucleotides.

This base pairing is an important mechanism that controls several aspects of DNA and RNA structure. In a Deoxyribonucleic acid molecule, base of operations pairing is the main method that DNA replication takes place. Each new nucleotide base pairs with the nucleotide in front of DNA polymerase, which fuses information technology to the growing sugar-phosphate backbone. This procedure creates ii double helices out of i.

Though RNA molecules are created in a like mode, the ribose sugar backbone and the uracil nucleotides use create slightly less stable hydrogen bonding between base pairs. This allows the RNA molecule to leave the nucleus as a single strand. All the same, sure sequences, such as those that accept evolved to exist tRNA molecules, accept a specific sequence of nucleotides that can base of operations-pair with each other if folded into the correct shape. RNAs with tertiary shapes such equally this serve a number of roles inside cells.

Let'southward turn our attention to the structure of Dna and RNA on a higher level – chromosomes. Chromosomes are made upward of many genes, and each gene contains a large number of nucleotide base of operations pairs (somewhere between a few m and a few million, depending on the gene). Each gene is made up of exons (the coding regions that carry genetic data) and introns (not-coding regions that divide exons). The purpose of introns is non well established, simply many genes take a far greater number of nucleotides inside introns than exons. Every bit these genes are transcribed into RNA and processed into mRNA, the introns will be removed – a process covered in our video on section 6.iii.

These genes are all continued together into a long sequence. Considering that the man genome contains around 20,000 genes made upward of 3.2 billion base pairs, this is an extremely long strand of Dna. Stretched out end-to-end, these genes would be virtually 6 anxiety long.

Withal, Dna is wrapped around protein complexes called histones to create nucleosomes. Much like wrapping up a ball of yarn, this greatly reduces the length of each chromosome.

Further, these nucleosomes pack tightly together into a complex structure that farther condenses the Dna into a structure called a chromatin fiber. Chromatin can be packed together into a very dense construction, which is how we can see the individual chromosomes during mitosis and meiosis. During interphase of the jail cell cycle, the chromosomes relax into a loose structure, and then that the Dna can be transcribed into RNA and replicated in grooming for the next cell division.

Chromosomes condense during cell division so they tin be easily sorted and separated.

Chromosomes like this that use histones to compact themselves are known as linear chromosomes and are seen mostly in eukaryotic organisms. By contrast, near prokaryotes apply a much smaller circular chromosome. While nosotros frequently depict them together, in reality, a linear chromosome is many times larger than a circular chromosome and typically carries many more genes. We also typically depict chromosomes in an X-shape, just this is not always accurate. First off, the 10-shape represents a duplicated chromosome – 2 sister chromosomes leap at the centromere. Furthermore, the centromere of linear chromosomes is not always located in the middle of the chromosome – information technology can be at the top or closer to one end than the other.

Finally, allow's accept a quick look at prokaryote genomes. While nearly prokaryotes reproduce asexually and have just a unmarried circular chromosome (which limits genetic variation), most prokaryotic organisms can as well exchange small, circular units of Dna known as plasmids.

A plasmid is a chunk of DNA that can contain as little every bit one gene, making it much smaller than the main circular chromosome of a prokaryote. These plasmids may conduct genes that help a bacteria survive. Since many bacterial cells benefit when they alive in colonies that tin can create biofilms and other defensive mechanisms, bacterial cells gain a measure of fettle when they can assistance other bacteria survive. Bacterial cells tin can share the genes carried in plasmids through the parasexual reproduction method of bacterial conjugation.

During bacterial conjugation, one bacterium can pass plasmids to another bacterium.

During this procedure, the plasmid is replicated. And so, it is passed through a channel between the 2 bacterial cells. Plasmids are known to acquit many important genes – such as those that confer antibiotic resistance or an enzyme necessary to procedure a detail food source. Past passing these genes to another bacterial cell, the bacterium tin can greatly increase how quickly a colony is formed, protecting itself in the process.

Nevertheless, scientists can likewise utilize plasmids to place certain genes within bacterial cells. Past modifying a plasmid to incorporate pieces of foreign DNA (called recombinant DNA because it is from different species), scientists can put most any gene they want into a bacterial colony. The plasmids are created, bacteria heated up and cooled downwardly to help the plasmid slip through the cell membrane, and some of the leaner take upwards and successfully express the genes contained in the plasmid. When they reproduce, they can carry this new cistron with them.

In a simple example, scientists were able to take normal Due east. coli bacteria, and introduce a gene that causes fluorescence in jellyfish. When this plasmid is successfully incorporated into a colony, the whole colony glows light-green. But, this tin besides exist used for more of import reasons than just getting bacteria to glow – human insulin (an important poly peptide hormone used as medicine past people with diabetes) is produced by bacteria that accept been transformed with recombinant Deoxyribonucleic acid!

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Source: https://biologydictionary.net/ap-biology/6-1-dna-and-rna-structure/