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BIO 101 > CHAPTER 10 > Flashcards

CHAPTER 10 Flashcards

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1
Q

STRUCTURE OF GENETIC MATERIAL

A
  • DNA = genetic material
  • Transforming factor, 1928, Fredrick Griffith
  • Hershey-Chase experiments, 1952, determined heredity material was DNA not protein
  • *Studied the simple bacteriophage T2
  • *Showed that the virus injects its DNA into host cells and reprograms them to produce more viruses
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2
Q

DNA & RNA

A

*DNA & RNA = polymers of nucleotides
*Nucleic acids = polynucleotides made of long chains of nucleotide monomers
*Nitrogenous Bases:
1 Single-ring pyramids: T thymine, C cytosine
2 Double-ring purines: A adenine, G guanine
*Sugar-phosphate = backbone

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3
Q

DNA & RNA

A 
*DNA & RNA IDENTICAL EXCEPT FOR 2 THINGS
1 Nitrogenous Bases:
**DNA: A, G, C, T
**RNA: A, G, C, U
2 Sugars:
**DNA: Deoxyribose
**RNA: Ribose
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4
Q

DNA

A
  • DNA = Double-stranded helix
  • James Watson and Francis Crick worked out the 3-dimensional structure of DNA, based on X-ray crystallography by Rosalind Franklin
  • DNA consists of 2 polynucleotide strands wrapped around each other in a double helix
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5
Q

DNA

A
  • In DNA, each base pairs with a complementary partner
  • A with T (apple tree)
  • G with C (chewing gum)
  • Hydrogen bonds between the bases hold the strands together
  • Watson-Crick model of DNA suggested a molecular explanation for genetic inheritance
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6
Q

DNA REPLICATION

A
  • DNA Replication depends on a specific pairing
  • Watson-Crick model of DNA structure suggested a mechanism for its replication
  • DNA strands separate
  • Enzymes use each strand as a template to assemble nucleotides into complementary strands
  • Each new double helix consists of one old and one new strand
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7
Q

DNA REPLICATION

A
  • DNA Replication begins at specific sites (origins of replication) on the double helix
  • Proteins attach and separate the strands
  • Replication proceeds in both directions, creating replication bubbles
  • *Parent strands open, daughter strands elongate
  • Replication occurs simultaneously at many sites
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8
Q

DNA

A
  • DNA’s sugar-phosphate backbones are oriented in opposite directions
  • The enzyme DNA polymerase adds nucleotides at only the 3 ends
  • *One daughter strand is synthesized as a continuous piece
  • *The other strand is synthesized as a series of short pieces
  • *The 2 strands are connected by the enzyme DNA ligase
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9
Q

DNA TO RNA TO PROTEIN

A
  • The DNA genotype is expressed as proteins which provide the molecular basis for phenotypic traits
  • *The info constituting an organism’s genotype is carried in its sequence of DNA bases
  • *A particular gene - a linear sequence of many nucleotides - specifies a particular polypeptide
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10
Q

GENETIC INFO

A

*Flow of Genetic Info
1 Transcription of the genetic info in DNA into RNA
2 Translation of RNA into polypeptide
*Beadle-Tatum one gene - one enzyme hypothesis
1 Studies of inherited metabolic disorders in mold suggested that phenotype is expressed through proteins
2 A gene dictates productions of a specific enzyme
3 The hypothesis has been restated to one gene - one polypeptide

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11
Q

GENETIC INFO

A
  • Genetic info written in codons, is translated into amino acid sequences
  • Genetic info flows from DNA to RNA to Protein
  • Nucleotide monomers represent letters in an alphabet that can form words in a language
  • *Triplet Code:
  • **3-letter word (codons)
  • **Each word codes for one amino acid in a polypeptide
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12
Q

GENETIC CODE

A
  • The genetic code specifies the correspondence between RNA codons and amino acids in proteins
  • *Includes start and stop codons
  • *Redundant but not ambiguous
  • Nearly all organisms use exactly the same genetic code
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13
Q

TRANSCRIPTION

A
  • Transcription produces genetic messages in the form of RNA
  • *One DNA strand serves as a template for the new RNA strand
  • *RNA polymerase constructs the RNA strand in a multistep process
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14
Q

RNA

A

*RNA strand constructed in a multistep process
*Initiation:
1 RNA polymerase attaches to the promoter
2 Synthesis starts
*Elongation:
1 RNA synthesis continues
2 RNA strand peels away from DNA template
3 DNA strands come back together in transcribed region
*Termination:
1 RNA polymerase reaches a terminator sequence at the end of the gene
2 Polymerase detaches

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15
Q

RNA

A
  • Eukaryotic RNA is processed before leaving the nucleus
  • RNA that encodes an amino acid sequence is messenger RNA (mRNA)
  • In prokaryotes, transcription and translation both occur in the cytoplasm
  • In eukaryotes, RNA transcribed in the nucleus is processed before moving to the cytoplasm for translation
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16
Q

RNA SPLICING

A
  • Non-coding segments called introns are cut out
  • Remaining axons are joined to form a continuous coding sequence
  • A cap and a tail are added to the ends
17
Q

RNA

A
  • Transfer RNA molecules serve as interpreters during translation
  • Transfer RNA (tRNA) molecules match the right amino acid to the correct codon
  • tRNA = a twisted and folded single strand of RNA
  • *Anticodon loop at one end recognizes a particular mRNA codon by base pairing
  • *Amino acid attachment site is at the other end
  • Each amino acid is joined to the correct tRNA by a specific enzyme
18
Q

RIBOSOMES

A
  • Ribosomes build polypeptides
  • A ribosome consists of 2 subunits
  • *Each is made up of proteins and ribosomal RNA (rRNA)
  • The subunits of a ribosome
  • *Hold the tRNA and mRNA close together in binding sites during translation
  • *Allow amino acids to be connected into a polypeptide chain
19
Q

INITIATION CODON

A
  • An initiation code marks the start of an mRNA message
  • Initiation phase of translation
  • *Brings together mRNA, a specific tRNA, and the 2 subunits of a ribosome
  • *Establishes exactly where translation will begin
  • *Ensures that mRNA codes are translated in the correct sequence
20
Q

INITIATION

A
  • Initiation is a 2 step process
  • Step 1:
  • *mRNA binds to a small ribosomal subunit
  • *Initiator tRNA, carrying the amino acid Met, binds to the start codon
  • Step 2:
  • *A large ribosomal subunit binds to the small one, forming a functional ribosome
  • *Initiator tRNA fits into one binding site, the other is vacant for the next tRNA
21
Q

ELONGATION

A

*Elongation adds amino acids to the polypeptide chain until a stop codon terminates translation
*Once initiation is complete, amino acids are added one by one in a 3-step elongation process
1 Codon Recognition
2 Peptide Bond Formation
3 Translocation
*Elongation continues until a stop codon reaches the ribosome’s A site, terminating translation

22
Q

REVIEW

A

*The flow of genetic info in the cell is DNA -> RNA -> Protein
*Sequence of codons in DNA via the sequence of codons in RNA, spells out the primary structure of a polypeptide
1 Transcription of mRNA from a DNA template
2 Attachment of amino acid to tRNA
3 Initiation of polypeptide synthesis
4 Elongation
5 Termination

23
Q

MUTATIONS

A
  • Mutation can change the meaning of genes
  • Mutation = any change in the nucleotide sequence of DNA
  • *Caused by errors in DNA replication or recombination, or by mutagens
  • *Can involve large regions of a chromosome or a single base pair
  • *Can cause many genetic disease, such as sickle-cell disease
24
Q

GENETIC MUTATIONS

A
  • 2 General categories of genetic mutations
  • Base substitutions replace one base with another
  • *Most are harmful but many occasionally have no effect or be beneficial
  • Base insertions or deletions alter the reading frame
  • *Result is most likely a non-functioning polypeptide
  • Mutagenesis caused by spontaneous error or a physical or chemical mutagen
25
Q

TYPES OF MUTATIONS (SILENT)

A
  • Silent Mutation
  • *If mutation causes an mRNA codon to change from GAA to GAG, there would be no effect
  • *Both GAA and GAG code for same amino acid
26
Q

TYPES OF MUTATIONS (MISSENSE)

A
  • Missense Mutation
  • *If mutation changes one amino acid to another
  • *If changes from GGC (gly) to AGC (ser), it would change from gly (GGC) to ser (AGC)
27
Q

TYPES OF MUTATIONS (NONSENSE)

A
  • Nonsense Mutation
  • *If mutation changes an amino acid codon into a stop codon
  • *If changes from AGA (arg) to UGA (stop), it would prematurely terminate the protein
28
Q

MICROBIAL GENETICS

A
  • Viral DNA may become part of the host chromosome
  • *Viruses are infectious particles consisting of nucleic acid enclosed in a protein capsid
  • *Virus depend on their host cells for the replication, transcription, and translation of their nucleic acid
  • DNA enters host bacterium, circularizes, and enters one of two pathways
29
Q

LYTIC CYCLE

A
  • Host provides more viruses

* Host cell lyses (breaks opes) to release new viruses

30
Q

LYSOGENIC CYCLE

A
  • Phage DNA inserted by recombination into the host chromosome, it is now a prophage
  • Prophages replicated each time host cell divides, passed on to generations of daughter cells
  • Doesn’t destroy host
  • Environmental signal may trigger switch from lysogenic to lytic cycle
31
Q

AIDS

A
  • The AIDS virus makes DNA on an RNA template
  • HIV, the AIDS virus is a retrovirus
  • Flow of genetic info is RNA to DNA
  • Inside a cell, HIV uses its RNA as a template for making DNA
  • The enzyme reverse transcriptase catalyzes reverse transcription
32
Q

BACTERIA

A
  • Bacteria can transfer DNA in 3 ways
  • Bacteria can transfer genes from cell to cell by one of 3 processes
  • Transformation: the uptake of foreign DNA from surrounding environment
  • Transduction: transfer of bacterial genes by a phage
  • Conjugation: union of 2 bacterial cells and the transfer of DNA between them (sex)
33
Q

DNA

A
  • Once new DNA is in a bacterial cell, part of it may integrate into the recipients chromosome
  • Occurs by crossing over between the 2 molecules
  • Leaves the recipient with a recombinant chromosome
34
Q

BACTERIAL PLASMID

A
  • Bacterial plasmids can serve as carriers for gene transfer
  • The F factor is a piece of bacterial DNA
  • Carries genes for things needed for conjugation
  • Contains an origin of replication
  • *Can transfer chromosomal DNA by integrating into the door bacterium chromosome or entering the cell as a plasmid
35
Q

PLASMIDS

A
  • Small circular DNA molecules separate from the bacterial chromosome
  • Can serve as carriers for the transfer of genes

BIO 101 (4 decks)

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