Chapter 12- Molecular Biology Of The Cell Flashcards Preview

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Flashcards in Chapter 12- Molecular Biology Of The Cell Deck (50):

What must be stored characteristics of genetic material to maintain control?

Development of cells
Structure of cells
Metabolic activity of cells


What characteristics of genetic material must be stable?

Replicate accurately during cell division
Be transmitted for generations


Griffiths experiment:

Injected mice with pneumococcus
-encapsulated strain (S)
-shiny colonies
-non encapsulated
-non capsule
-dull colonies
-non virulent
Tries to determine if capsule alone causes virulence S strain.
R strain bacteria were transformed
Transforming substance must have passed from S to R strain


Avery's Experiment:

Identified DNA as the genetic material
-DNA from the S strain causes the r strain to be transformed and become virulent
-DNA is the genetic material and could transform the biosynthetic properties of a cell.


What nucleotide that makes up DNA?

2 ring: adenine and Guanine
1 ring: thymine and cytosine


Which nucleotides are purines and pyrimidine?

Purines: adenine and guanine
Pyrimidine: thymine and cytosine


What composes a nucleotide ?

Building blocks of nucleic acid. Composed of a nitrogenous base, five carbon sugar and one phosphate group.


What are chargaffs rules?

Amount of A,T,G and C are different in different species.


Describe the structure of DNA, by Watson and Crick.

The DNA strands of the helix are anti parallel. Meaning the sugar phosphate groups are chained together to make each strand oriented in other directions.


Describe steps of DNA,

Helicase unwinds the DNA molecule.
Creates two replication forks that move away from each other.
Single stranded binding protiens attach to prevent the unstable single strands from forming a helix.
Each strand becomes a template and can be replicated.


Describe steps of DNA,
Complementary base pairing:

Free nucleotides must be present in nucleus.
RNA polymerase forms and RNA primer on the strand to be replicated.
DNA polymerase attaches to the primer and joins DNA nucleotides together.
DNA can only be synthesized in the 5' to 3' direction.


Describe steps of DNA,

DNA polymerase serves a proofreading function
-recognizes errors and RNA primers
-cuts out the sequence and replaces it with complementary nucleotides.


What enzymes are involved in DNA replication?

Helicase, Polymerase, Ligase, Single stranded binding protiens


Which direction do the leading and lagging strand run?

Lagging strand: 3' to 5'
Leading strand: 3' to 5'


Describe Introns and Exons:

Introns: non protein coding regions.
Exons: Protein coding regions.


What did Rosalind Franklin discover?

She produced an xray diffraction photographs of DNA.
A concentrated vicious solution of DNA can be separated into fibers.
DNA is a helix.


Where is RNA produced?

RNA is found in the cytoplasm. It is made by DNA transcription. A process catalyzed by a class of the enzyme of RNA polymerase.


Where are okazaki fragments formed?

They are formed on the lagging strand of DNA.



An enzyme used to break down weak hydrogen bonds between paired bases. Unwinding DNA.


(DNA) Ligase:

An enzyme that joins together DNA fragments and strands, creating a seamless DNA molecule


Single Strand binding proteins:

They attach to prevent the unstable single strands from reforming the helix. (DNA replication)


Eukaryotic Replication:

-They begin at numerous origins of replication on the length of the linear chromosome.
-Form a replication bubble with a fork on each end.
-Slower DNA replication.
-500 to 5,000 base pairs per minute.
-Replicate diploid amount of DNA in humans in a matter of hours.


Prokaryotic Replication:

-Bacteria have a single circular loop chromosome.
- Must replicate before the cell divides.
-Replication may move around the DNA molecule in only one direction or in two directions.
-Replicate complete chromosome in 20-40 minutes. They can begin before a previous one is complete.


What is the one gene-one enzyme hypothesis? and who stated this?

George Beadle and Edward Tatum stated this hypothesis. They said; one gene specifies the synthesis of one enzyme.


What did Garrod mean by "Inborn error of metabolism"?

-Inherited defects could be caused by the lack of a particular enzyme.
-Knew the enzymes were proteins.
-Suggested link between genes and proteins.


State the one gene-one polypeptide hypothesis. Who stated this Hypothesis?

Vernon Ingram stated this hypothesis. He stated; each gene specifies one polypeptide of a protein.



Chain of amino acids.


Where are DNA & RNA found in the cell?

DNA is found in the nucleus and RNA is found in the nucleus or cytoplasm.


What role does each different RNA play?
Messenger RNA (mRNA):

Takes message from DNA in the nucleus to ribosomes in the cytoplasm.


What role does each different RNA play?
Transfer RNA (tRNA):

Transfers a particular amino acid to a ribosome.


What role does each different RNA play?
Ribosomal RNA (rRNA):

Together with ribosomal proteins make up ribosomes where polypeptides are synthesized.


What is a codon? What does it code for?

A triplet code is a codon. Codes for amino acids, or it starts or stops a translation. Identifies each of the 20 different types of amino acids found in proteins.


Name four characteristics of the genetic code.
Degenerate (has redundancy):

Most amino acids have more than one codon. Protects against potentially harmful effects of mutations.
CCC, CCU, CCA, CCG = proline.


Name four characteristics of the genetic code.

Each triplet codon has only one meaning.
CUG- leucine
CAG- Glutamine


Name four characteristics of the genetic code.
Start and stop signals do not code for an amino acids:

One start (AUG) signal.
Three stop signals (UAA, UGA, UAG)


Name four characteristics of the genetic code.

Strong evidence that all living things share a common evolutionary heritage.
Same genetic code is used by all living things-genes can be transferred between organisms.


Where does Transcription occur? Define Transcription.

It produces mRNA, tRNA, and rRNA.
-It takes place in the nucleus.
-It is the first step required for gene expression-making of a gene product.
-Based on complementary base pairing.


What is a promoter?

DNA region that defines:
-start of a gene.
-direction of transcription.
-which strand is to be copied.


What is a terminator?

DNA region that:
-stops transcriptions of DNA.
-causes the release of the mRNA molecule, now called the mRNA transcript..


Where does Translation occur?

Takes place in the cytoplasm.


Define Translation.

The second step needed to express a gene into a protein.
Requires the conversion of info from a nucleic acid language into an amino acid language.


What must be present for Translation to occur?

mRNA: carries the polypeptide "blueprint" into the cytoplasm.
rRNA: packaged with ribosomal proteins to form two sub units that join together to make a ribosome.
tRNA: carries amino acids to the ribosome for polypeptide assemblu.
Amino Acids: bond together to make a polypeptide.


Name the three steps involved in translation.
Chain Initiation:

-All components are brought together by proteins called initiation factors.
-Small ribosomal subunit attaches to mRNA at the start codon.
-Initiator tRNA pairs with AUG codon.
-Large ribosomal sub unit joins small subunit.
-3 binding sites for tRNA are on a ribosome.
-P site binds with initiator tRNA.
-A site binds the tRNA carrying the next amino acid
-E site discharges tRNA.


Describe the appearance of tRNA structure.

-Single srtanded 5' to 3'
-Double back on itself to create regions where complementarty bases are H bonded to one another.
-3' end binds to amino acid specified by the anticodon region.


Name the three steps involved in translation.
Chain Elongation:

-Polypeptide increases in length, one amino acid at a time.
-Requires elongation factors to facilitate the binding tRNA anticodons to mRNA codons within a ribosome.
-tRNA with an attached peptide is at the P site.
-The next tRNA carrying an amino acid attaches to the A site.
-Growing peptide is transferred to the tRNA at the A site.


Name the three steps involved in translation.
Chain Termination:

-Termination of polypeptide synthesis occurs at a stop codon that does not code for an amino acid.
-requires a release factor that binds to the last stop codon and cleaves the polypeptide from the last tRNA.
-Polypeptide is set free and begins to fold and take on a 3 dimensional form.
-Ribosome dissociates into its two sub units and returns to the cytoplasmic pool.


Where does the amino acid bind to tRNA?

-occurs in the cytoplasm
-A tRNA with it amino acid attached is called "charged tRNA"
-Requires energy in the form of ATP.
-tRNA Synthase: amino acid charging enzymes with a recognition site for a particular amino acid to be joined to a specific tRNA.


What is an anticodon?

Three bases that are complementary and antiparallel to an mRNA codon.


Describe the binding sites found on a ribosome.

-A binding site for mRNA.
-3 binding sites for tRNA.
-Large sub unit has enzyme activity that creates the peptide bond between adjacent amino acids, which forms a polypeptide chain.


What is the role of ribosome during translation?

-Produced from the DNA template in the nucleolus of a nucleus.
-Packages with proteins into two sub units, one small one large.
-Sub units move separately through nuclear pores into the cytoplasm.
-join at the start of translation.
-Can remain in the cytoplasm or attach to the rough endoplastic reticulum.