bio ch. 13-14 questions
What are the possible ways that a mutation may affect an organism?
A mutation in an organism causes the wrong protein to be produced or the cycle to be stopped. This can result in a silent mutation, where the letter is changed but the amino acid remains the same, a missense mutation where the amino acid specified is changed, or even worse, a nonsense mutation, where the cycle is stopped when it is not supposed to causing the protein to be unfinished.
What process changes one type of bacteria into another?
A signal in DNA that indicates to an enzyme where to bind to make RNA, transcription.
Which researcher used radioactivity markers in experiments to show that DNA was the genetic material in cells?
Alfred Hershey and Martha Chase
What did the X shaped pattern in the center reveal about the structure of DNA?
An X-shaped pattern was discovered - showed that the strands in DNA are twisted around each other like the coils of a spring. other clues suggested that the nitrogenous bases are near the center of the DNA molecule.
What are the discoveries that led to the modeling of DNA?
Chargaff discovered base pairing rules. Franklin took X-ray photographs that revealed that DNA has a spiral structure. This finding helped Watson and Crick create a model of DNA and discover the double-helix.
Describe the ways mutations can affect DNA and chromosomes.
DNA - substitution: switching a letter in the mRNA sequence - deletion: deleting a letter in the mRNA sequence - insertion: inserting the wrong codon to match the mRNA Chromosomes - Deletion: the loss of one or all of the chromosome - Duplication: produces an extra copy of all or part of a chromosome - Inversion: reverses the direction of parts of the chromosome - Translocation: when part of the chromosome breaks off and attaches to another
What are the key roles of DNA?
DNA is a deoxyribonucleic acid that holds the code on how to make proteins. DNA, or deoxyribonucleic acid, is a long chain molecule that plays a central role in life on earth. The information encoded in strands of DNA controls the genetic makeup of organisms. The DNA molecule has a backbone of sugars and phosphate groups off of which hang simpler units called nucleotide bases. DNA contains only four bases, called A, T, C and G. The sequence of the nucleotides along the backbone encodes genetic information. The four roles DNA plays are replication, encoding information, mutation/recombination and gene expression.
When a DNA molecule is replicated, how do the new molecules compare with the original molecule?
DNA replication begins with the "unzipping" of the parent molecule as the hydrogen bonds between the base pairs are broken. Once exposed, the sequence of bases on each of the separated strands serves as a template to guide the insertion of a complementary set of bases on the strand being synthesized. The two strands are identical
What did Avery conclude caused transformation?
DNA was the transforming factor; meaning it stores and transmits genetic information form one generation to another.
What are the components and structure of a DNA nucleotide?
Each nucleotide has three parts:5-carbon sugar called deoxyribose, a phosphate group, and a nitrogenous base. Explain how Chargaff's rules helped Watson and Crick model DNA. That adenine bonds only to thymine and cytosine bonds only to guanine.
What are the chemical compounds of DNA?
Each strand of a DNA molecule is composed of a long chain of monomer nucleotides. The nucleotides of DNA consist of a deoxyribose sugar molecule to which is attached a phosphate group and one of four nitrogenous bases: two purines (adenine and guanine) and two pyrimidines (cytosine and thymine).
How does crystallography work?
Franklin stretched DNA fibers in a thin glass tube so the strands were parallel. She aimed a powerful X-Ray beam at the concentrated DNA & recorded the scattering pattern of X-Ray's on film. This is a form of diffraction.
Explain Rosalind Franklin's experiment.
Franklin used crystallography to study DNA. She revealed that the X shape of DNA is twisted around each other, which is called a helix. It also shows that the nitrogenous bases are stacked at regular intervals near the center of the molecule.
what type of experiments of Griffith and Avery show about genetic information?
Griffith and Avery studied bacteria and mice. Their S and R experiment revealed that DNA stores and transmits genetic information from one generation of bacteria to another. Chromosomes consist of protein and DNA, but mainly DNA.
What were the steps to Griffiths experiment of transforming bacteria?
Griffith studied bacteria that can cause long cancer. 1. He had S bacteria which was deadly and smooth edged. Then he had R bacteria which was harmless and rough edged. 2. He made the S bacteria harmless by heating it up. 3. He then mixed the harmless heat killed S bacteria with the harmless R bacteria. 4. The mixed bacteria killed the mouse even though it was "harmless." This revealed that genetic information from the S was transferred to the R bacteria. This happened because of transformation, the harmless was changed into harmful through the inherited gene from the offspring. Information from the S to R changed the harmless bacteria to deadly.
How did the results of the Hershey-Chase experiment strengthen Avery's conclusions?
Hershey and Chase studied bacteriophages which are viruses that attack bacteria. In their experiment Hershey and Chase labeled the bacteriophages with radioactive isotopes to see where the virus attacks. They use phosphorus 32 and sulfur 35 because proteins contain almost no phosphors and DNA contains almost no sulfur. Nearly all of the radioactivity was found in phosphorus, meaning DNA holds genetic information, not protein.
Why did Hershey and Chase label the viral DNA with radioactive phosphorus and not radioactive sulfur?
Hershey and Chase studied bacteriophages which are viruses that attack bacteria. They labeled the bacteriophage with radioactive isotopes to see where it goes when a virus attacks. They used phosphorus-32 and sulfur-35 because proteins contain no phosphorus (only found in protein) and DNA contains no sulfur (only found in DNA.) They discovered that nearly all the radioactivity was found in phosphorus, confirming that DNA contains genetic material, not protein.
Where is DNA found in prokaryotes and eukaryotes?
Prokaryotes: cytoplasm Eukaryotes: nucleus
What is the function of RNA polymerase in the process of transcription?
RNA polymerase are enzymes which transcribes DNA into RNA
How are RNA and DNA similar and different?
RNA: single strand, sugar phosphate backbone of Ribose, a-u c-g, three types of RNA DNA: double stranded, sugar phosphate backbone with deoxyribose, a-t c-g
What is the role of DNA polymerase in the process of DNA replication?
The main function of DNA polymerase is to make DNA from nucleotides, the building blocks of DNA. There are several forms of DNA polymerase that play a role in DNA replication and they usually work in pairs to copy one molecule of double-stranded DNA into two new double stranded DNA molecules.
Why is it significant that the two strands of DNA are antiparallel?
This means that the two strands describe Chargaff's rule. The 2 strands of DNA run on opposite sides of each other, making the nitrogenous bases on both strands come to contact near the center.
What facts about DNA does the Watson-Crick model explain?
Watson and Crick made models to try and understand DNA shapes. They realized that nitrogen bases complemented/attracted each other and that the two strands are anti parallel, making the nitrogenous bases on both strands come to contact near the center. Each strand carries a sequence of nucleotides arranged like a latter. They discovered that hydrogen bonds form between nitrogenous bases proving enough forces to hold the stands together.
What did Watson and Crick discover about the double helix?
Watson and Crick made models to try and understand DNA's shape. To help them construct their model they used Franklins "photo 51" along with her analysis. They realized that the nitrogenous bases complemented/attracted each other. The strands are antiparallel meaning the 2 strands of DNA run on opposite sides of each other making the nitrogenous bases on both strands come to contact near the center. Each strand carries a sequence of nucleotides arranged like a ladder. Hydrogen bonds are what keep the nitrogenous bases together.
What are bacteriophages?
a virus that parasitizes a bacterium by infecting it and reproducing inside it.
What does nucleotide not contain?
an amino acid
How is base pairing involved in DNA replication?
base pairs are involved with hydrogen bonds forming between only certain pairs
Before DNA could definitely be shown to be the genetic material in cells, what did scientists had to show that it could do?
carry and make copies of information
What is the appearance of DNA in a typical prokaryotic cell?
Prokaryotes are unicellular organisms that lack organelles or other internal membrane-bound structures. Therefore, they do not have a nucleus, but, instead, generally have a single chromosome: a piece of circular, double-stranded DNA located in an area of the cell called the nucleoid.