Ch. 10 Molecular Biology of the Gene Flashcards Preview

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Flashcards in Ch. 10 Molecular Biology of the Gene Deck (73):
1

Bacteriophage (Phage)

A virus that infects bacteria

2

Molecular Biology

The study of the molecular basis of genes and gene expression; molecular genetics.

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Nucleotide

An organic monomer consisting of a 5-carbon sugar covalently bonded to a nitrogenous base and a phosphate group; building blocks of nucleic acid

4

Polynucleotide

A polymer made up of many nucleotides covalently bonded together

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Sugar-phosphate backbone

Repeating pattern of sugar phosphate

6

What are pyrimidines?

Single ring of nitrogen and carbon
- Thymine and Cytosine

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What are purines?

Large double ring
- Adenine and Guanine

8

What does RNA have that DNA doesn't?

Uracil

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Double Helix

2 DNA strands with 2 nm diameter

10

What are 3 major things learned?

1) How DNA is hereditary material of life
2) DNA stores information and replicates self
3) DNA controls cells by directing DNA synthesis

11

Virus

Infective substance, packaged genes
- 1000x smaller than bacterium
- DNA or RNA

12

What are the lifelike aspects of a virus?

1) Highly organized
2) Contain nucleic acids (RNA or DNA)
3) Experiences reproduction

13

What are non lifelike aspects of a virus?

1) Not cellular (not made of cells)
2) Cannot reproduce on its own (Inert)

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Nucleic Acids

Polymer/monomers of DNA and RNA
- made of nucleotides

15

What are the 3 parts of a nucleotide?

1) Phosphate group
2) 5 Carbon Sugar (Deoxyribose or ribose)
3) Nitrogen Base

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What is a nitrogen base?

Rings of nitrogen and carbons with various functional groups attached

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What is encoded in the nucleotide sequence?

Genetic information in chromosomes
- how to make proteins
- makes each organism unique
- understand/explains life's process

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DNA Replication

Process in which genetic instructions are copied before the cell divides

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What are the 3 steps of DNA Replication?

1) Two parent strands separate to serve as a template for complimentary strand
2) Free nucleotides line along template and connect to corresponding nucleotide according to base pairing
3) Enzymes link nucleotides together to form new DNA strand

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Why is DNA replication biochemically complicated?

1) DNA must unravel and copy simultaneously
2) Speed! Occurs very rapidly!!

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Origin of Replication

Site where proteins attach to DNA molecule and separate strands

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Replication Bubble

Areas where origin of replication are; several exist to reduce time; eventually combine for daughter strands

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DNA Polymerase

Enzyme that links DNA nucleotides to growing strand (proper location)
- only adding on 3' (5' -> 3')
- Adds nucleotides in continuous pieces for one and in discontinuous pieces for another
- proofreads the sequence and fixes it (repairs DNA damage)

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DNA Ligase

Enzyme that ties all the pieces intro one strand
- 12 altogether

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What does DNA replication ensure?

Ensures all somatic cells have same genetic instructions for continuity between generations

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What is the 3' end of a DNA strand?

3' with -OH

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What is the 5' end of DNA strand?

5' with phosphate group

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What is the connection between genotype and proteins of phenotype?

DNA specifies the synthesis of proteins.

DNA -> RNA -> Proteins

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Transcription

Transfer of info from DNA to RNA
- occurs in nucleus
- uses only 1 DNA strand and hydrogen bonds

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Translation

Transfer of info from RNA into protein synthesis
- nucleotide -> amino acid (converts language)
- occurs in cytoplasm/ribosome

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What did Archibald Garrod hypothesize?

Genes dictate phenotypes thru enzymes, the proteins that catalyze chemical processes in the cell

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What did Beadle and Tatum hypothesize?

"One-Gene One-Polypeptide"
- each polypeptide is specified to its own genre

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Triplet Code

Set of rules giving the correspondence between nucleotide triplets (codons) in mRNA and amino acid in protein

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Codons

A 3 nucleotide sequence in mRNA that specifies a particular amino acid or polypeptide termination sequence; basic unit of the genetic code

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What is the code for the start of a polypeptide chain?

AUG

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What is the stop/end code for a polypeptide chain?

UAA, UAG, UGA

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RNA Polymerase

An enzyme that links together the growing chains of RNA nucleotides during transcription, using a DNA strand as a template

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Promoter

A specific nucleotide sequence in DNA, located at the start of a gene, that is the binding site for RNA Polymerase and the place where transcription begins

39

What are the 3 steps for transcription?

1) Initiation = attachment of RNA polymerase to promoter and start of synthesis
2) Elongation = RNA strand increases in length, copies DNA sequence
3) Termination = RNA polymerase reaches terminator sequence (Transcription stops, RNA polymerase detaches from RNA molecule & gene, RNA strand is prepared for exportation into cytoplasm)

40

Messenger RNA (mRNA)

Transcribes genetic instructions on DNA in the nucleus to ribosomes
- has codons

41

What are the four things that translation requires?

1) mRNA, tRNA, rRNA
2) Enzymes
4) Chemical energy in ATP

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Transfer RNA (tRNA)

Interpreter of translation
- 3 letter words -> amino acids
- has anticodons

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What are the functions of tRNA?

1) Picking up the appropriate amino acids
2) Recognizing the appropriate codons in the mRNA

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Anticodon

On a tRNA molecule, a specific sequence of 3 nucleotides that is complimentary to a codon triplet on mRNA

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What does a ribosome consist of?

2 subunits, proteins, and rRNA.

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ribosomal RNA (rRNA)

Type of ribonucleic acid that together with proteins make up ribosomes
- most abundant type of RNA

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What are the differences between the two units? Small and large?

Small unit is for binding site of mRNA.
Large unit is for binding site of tRNA.

48

What is the differences between P and A site?

P site holds tRNA carrying the growing polypeptide chain.
A site holds tRNA carrying the next amino acid.

49

What is the role of initiation?

Determined exactly where translation will begin. It brings together mRNA, first amino acid, tRNA, and 2 subunits.

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Start codon

Specific 3 nucleotide sequences AUG to which an initiator tRNA molecule binds, starting translation of genetic info

51

What are the 3 steps of elongation? (Translation)

1) Codon Recognition
- anticodon of incoming tRNA pairs w/ mRNA codon of Site A
2) Polypeptide bond formation
- polypeptide separates from its blinded tRNA and attaches to amino acid carried by tRNA in A site
3) Translocation
- during protein synthesis, the movement of a tRNA molecule carrying a growing polypeptide chain from the A site to P site on ribosome

52

Stop codon

in mRNA, one of 3 triplets (UAG, UAA, UGA) that signal gene translation to stop

53

Mutation

A change in the nucleotide sequence of RNA; the ultimate source of genetic variety
- base substitution and base insertion/deletion

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What base substitution?

Replacement of 1 nucleotide for another.
- no, little, or significant change (usually negative)
- mal alter amino acid w/ little change to function
- improved proteins/capabilities possible

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What is base inception/deletion?

May alter the reading frame (how nucleotides read 3 nucleotides at a time)
- disastrous effects

56

Mutagenesis

Creation of a mutation
- results from errors during DNA replication/recombination
- causes... 1) Spontaneous 2) Mutagen

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Mutagen

A chemical or physical agent that interacts with DNA and causes a mutation
- pH, chemical, radiation, etc

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Lytic cycle

A type of viral replication cycle resulting in the release of new viruses by lysis (breaking open) of the host cell

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Lysogenic cycle

A type of bacteriophage replication cycle in which the viral genome is incorporated into the bacterial host chromosome as a prophage
- new phages are not produced, and the host cell is not killed or lysed unless the viral genome leaves the host chromosome

60

Prophage

Phage DNA that has inserted by genetic recombination into the DNA of a prokaryotic chromosome

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How does the virus's reproductive cycle function?

1) RNA enters cytoplasm
2) Enzymes then remove the protein coat
3) Enzymes of virus enters cell to make complementary strands of RNA
4) New coat proteins assemble around the new viral RNA
5) Viruses leave the cell by cloaking themselves in plasma membrane

62

Retrovirus

An RNA virus that reproduces by means of a DNA molecule. IT reverse transcribes its RNA into DNA, inserts the DNA into a cellular chromosome, and then transcribes more copies of the RNA from the viral DNA

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Reverse Transciptase

An enzyme that catalyzes the synthesis of DNA on an RNA template

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AIDS

Acquired immune deficiency syndrome; the late stages of HIV infection; characterized by a reduced # of T cells; usually results in death caused by other diseases

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HIV

Human immunodeficiency virus, the retrovirus that attacks the human immune system causes AIDS

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What is the flow of genetic info?

DNA -> RNA -> proteins

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What does "In genetic code, there is redundancy, by no ambiguity" means what?

Some codons code for same amino acid but no codon codes for more amino acids

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What are introns?

Genetic garbage that fills gaps
- majority of strand thought to be used for evolution

69

What are extrons?

Sequence that codes for particular protein

70

Primary Transcript

First copy of the template

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What is protein synthesis comprised of?

1) Transcription
2) Translation

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What are the 3 stages of translation?

1) Initiation
- When translation begins, binds to smaller subunit
2) Elongation
- Amino acids added to chain, peptide bonds form
3) Termination
- Stop codon reaches A site

73

Tobacco Mosaic

Rod Shaped plant virus