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Biology 101 > Chapter 7: DNA Structure and Gene Function > Flashcards

Chapter 7: DNA Structure and Gene Function Flashcards

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0
Q

Explain how the experiment of Griffith contributed to identifying DNA as the genetic material.

A

Frederick Griffith contributed the first step in identifying DNA as the genetic material. His experiment showed that a molecule in a lethal strain of bacteria, type s, could transform harmless type r bacteria into killers.

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1
Q

Why were proteins initially thought to be the hereditary material?

A

They knew more about proteins than about Nucleic acids. They also thought that protein, with its 20 building blocks, could encode many more traits than DNA, which includes just four types of building blocks.

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2
Q

Explain how the experiments of Avery, MacLeod, and McCarty contributed to identifying DNA as the genetic material.

A

They learned the transforming principle. When the research treated the solution from the type S strain with a protein destroying enzyme, the type R strain still changed into a killer. Therefore the protein was not transmitting the killing trait. But when they treated the solution with a DNA-destroying enzyme, the type remained harmless.

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3
Q

Explain how the experiments of Hershey and chase contributed to identifying DNA.

A

Hershey and chase confirmed the genetic role of DNA. That showed that DNA not protein is the genetic material. Hershey and chase used radioactive isotopes to distinguish the bacteriophage protein coat from the DNA. They showed that the virus transfer DNA not protein to the bacterium, and this viral DNA caused bacterial cells to produce viruses.

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4
Q

Define Bacteriophage.

A

It is a virus that infects only bacteria.

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5
Q

What do the initials DNA represent?

A

Deoxyribonucleic acid

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6
Q

What do the initials RNA represent?

A

Ribonucleic acid

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7
Q

Define Nucleotide.

A

Building blocks of Nucleic acids

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8
Q

Discuss the contribution of biochemists and physicists involved in discovering the structure of DNA

A

Austrian American biochemist Erwin Chargaff showed that DNA contains equal amounts of the base adenine and thymine and equal amounts of the base guanine and cytosine.

English physicist Maurice Wilkins and chemist Rosland Franklin bombarded DNA X-rays, using a technique called X-ray diffraction to determine three dimensional shape of the molecule the X-ray diffraction pattern revealed a regularly repeating structure of building blocks.

Biochemist James Watson and physicist Francis Crick used these clues to build a ball and stick model of the DNA molecule. It included equal amounts of G and C and of A and T.

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9
Q

List the scientist who received the Nobel prize for their work on determining the structure of DNA.

A

Watson, Wilkson, and Crick

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10
Q

Why was Rosalind Franklin not awarded the Prize?

A

franklin had died in 1958, and by the rules of the award, she could not be included.

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11
Q

List the complementary base pairs found in DNA?

A

An A on one strand means a T on the opposite strand. And a G on one strand means a C on the other.

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12
Q

Why does each pair consists of a purine and a pyrimidine?

A

Adenine and guanine are purines, bases with a double ring structure. Cytosine and thymine are pyrimidines, which have a single ring. Each A-T pair are the same width as a C-G pair because each includes a purine and a pyrimidine.

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13
Q

What type of bonds hold the pairs together?

A

Hydrogen Bonds

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14
Q

Why is the double strands of DNA parallel but opposite?

A

The head to tail arrangement is apparent when the carbon atom in deoxyribose are numbered.

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15
Q

What is the three carbon and the five carbon?

A

When the nucleotides joined into a chain, opposite ends of the strand are designated 3 prime and 5 prime. At the same end of the double helix, one chain therefore ends with 3 carbon, while the other chain ends with the 5 carbon.

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16
Q

What are the three components of a nucleotide?

A

Each nucleotide consists of the sugar deoxyribose, one or more phosphate groups, and a nitrogenous base.

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17
Q

Describe the twisted ladder structure of DNA?

A

The twin rails of the ladder, also called the sugar phosphate “backbones” are alternating units of deoxyribose and phosphate joined with covalent bonds, the ladder rungs are A-T and G-C base pair joined by hydrogen bonds.

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18
Q

If you compare the DNA to a ladder, the Sides of the ladder are made of__________ and the steps of the ladder are the __________

A

D

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19
Q

Define genome.

A

It is all of the genetic material In its cell.

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20
Q

Define chromosome.

A

It is a discrete package of DNA and associated proteins.

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21
Q

Define Gene.

A

It is the sequence of DNA nucleotides that codes for a specific protein or RNA molecule.

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22
Q

How does DNA act as the recipe for proteins?

A

DNA stores the information used to make proteins, just as a recipe stores the information needed to make brownies.

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23
Q

Compare DNA and RNA?

A

RNA is a multicellular Nucleic acid that differs from DNA in several ways. First, it’s nucleotides contain the sugar ribose instead of deoxyribose. Second, RNA has the nitrogenous base uracil, which behaves similarly to thymine; that is, uracil binds with adenine in complementary base pairs. Third, unlike DNA, RNA can be single stranded. Finally, RNA can catalyze chemical reactions, a role not known for DNA.

24
Q

Define Gene.

A

It is a sequence of DNA nucleotides that codes for a specific protein or RNA molecule.

25
Q

Define Translation.

A

The information in RNA is used to manufacture a protein by joining a specific sequence of amino acids into a polypeptide chain.

26
Q

Define transcription.

A

A cell copies a gene’s DNA sequence to complementary RNA molecule.

27
Q

Explain how information flows from DNA to proteins.

A

The relationship between Nucleic acids and proteins as a flow of information they called the central dogma. DNA is copied to RNA (transcription) which is used to assemble proteins (translation).

28
Q

Compare the three types of RNA.

A

mRNA has 500-3000 nucleotides. It’s function is that it encodes amino acid sequence.

rRNA has 100-3000 nucleotides. It’s function is it associates with proteins to form ribosomes, which structurally support and catalyze protein synthesis.

tRNA has 75-80 nucleotides. It’s function is that it binds mRNA codon on one end and an amino acid on the other, linking a gene’s message to the amino acid sequence it encodes.

29
Q

How does DNA serve as a template to create RNA?

A

Transcription uses a DNA template to create RNA.

30
Q

Compare the three steps of transcription?

A

Transcription occurs in three steps initiation, elongation, and termination.

Initiation is the control point that determines which genes are transcribed and when.

RNA nucleotides are added during elongation.

A terminator sequence in the gene signals the end of the transcription.

31
Q

Explain the role of the template strand?

A

It is the strand in the DNA molecule that is actually copied to RNA .

32
Q

Explain the role of RNA polymerase?

A

It is the enzyme that binds an RNA chain.

33
Q

Explain the role of the promoter.

A

It is a DNA sequence sequence that signals the genes start.

34
Q

Explain the role of the terminator?

A

Signals the end of the gene.

35
Q

How is RNA altered in the nucleus?

A

As the RNA molecule is synthesized it curls into a three dimensional shape dictated by complementary base pairing within the molecule. The final shape determines whether the RNA functions as mRNA, tRNA, or rRNA

36
Q

Define introns.

A

Are portions of the mRNA that are removed before translation.

37
Q

What are exons?

A

They are spliced together to form the mature mRNA that leaves the nucleus to be translated.

38
Q

What occurs during translation of the mRNA?

A

In translation, transfer RNA matches mRNA codons with amino acids as specified in the genetic code.

39
Q

Explain the role of mRNA in translation.

A

This product of transcript carries the genetic information that encodes a protein, with each three-base codon specifying one amino acid.

40
Q

Explain the role of tRNA in translation?

A

This molecule binds to an mRNA codon and to an amino acid. The other end of the tRNA molecule forms a covalent bond to the amino acid corresponding to that codon.

41
Q

Explain the role of ribosomes in translation?

A

The ribosomes, built of rRNA and proteins, anchors mRNA during translation. Each ribosome has one small and large subunit that join at the initiation of the protein synthesis.

42
Q

Compare the three stages of translation?

A

Initiation brings together the ribosomal subunits mRNA, and tRNA.

In elongation a tRNA molecule carrying the second amino acid then binds to the second codon. Then the two amino acids and a covalent bond forms between them. With the peptide bond in place, the ribosome releases the first tRNA.

The third tRNA enters, carrying its amino acid. It aligns with the other two and forms a covalent bond to the second amino acid in the growing chain

Termination brings elongation to a stop.

43
Q

Define codon.

A

A Triplett of mRNA bases that specifies a particular amino acid.

44
Q

Define anticodon.

A

Is a three base loop that is complementary to one mRNA codon.

45
Q

Why is the idea that codons are universal so important to understanding biology?

A

Nearly all species us e the same mRNA codons to specify the same amino acids. The most logical explanation is that all life on earth evolved from a common ancestor.

46
Q

Define transcription factor.

A

Bind DNA at specific sequences that regulate transcription.

47
Q

What are the cell reasons to regulate Gene expression?

A

Multicellular organisms consists of many types of specialized cells.

Regulating Gene expression gives cells flexibility to respond to changing conditions.

An intricate set of genetic instructions orchestrates the growth and development of multicellular organisms.

48
Q

Define mutation?

A

A mutation is a change in a cells DNA sequence either in a protein coding Gene or in no coding DNA such as an enhancer.

49
Q

Compare substitution mutation, insertion, and deletion mutations.

A

A substitution mutation is the replacement of one DNA base with another.

Insertions or deletion a of one or two nucleotides dramatically alter a gene’s codons. Adding or deleting three nucleotides restore the reading frame.

50
Q

Define mutagen.

A

Is any external agent that induces mutations.

51
Q

Compare germ line and somatic mutations.

A

Germ lime mutation occurs in cells that give rise to sperm and egg cells.

Somatic mutation occurs in nonsex cells, such as those that make up the skin.

52
Q

Define Allele.

A

Variant genes.

53
Q

Why are mutations important?

A

Mutations are important because they produce genetic variability. Mutations can also be useful in the science and agriculture. Mutations sometimes enhance an organisms reproductive success.
Mutation in a gene sometimes changes the structure of its encoded protien so much that the protien can no longer do its job.

54
Q

Who coined central dogma

A

Crick

55
Q

What are the pyrimidine

A

Cytosine and thymine

56
Q

What are the purines?

A

Adenine and guanine

57
Q

How does restriction enzymes are used by bacteria.

A

The normal function of restriction enzymes is to protect bacteria by cutting up DNA from infecting viruses.

58
Q

How do humans use restriction enzymes?

A

Biologist use them to cut and paste segments of DNA from different sources.

Biology 101 (16 decks)

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