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IB Biology Topic 2 > 2.7 DNA Replication, Transcription And Translation > Flashcards

2.7 DNA Replication, Transcription And Translation Flashcards

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1
Q

What is the function of helicase?

A

Unwinds and separates the DNA double helix. Breaks h bonds.

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2
Q

What are SSBs?

A

Single stranded binding proteins stabilize the newly single stranded regions

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3
Q

What is the function of DNA Gyrase?

A

Used to stop the double stranded areas outside the replication fork from supercoiling.

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4
Q

What is the function of RNA primase?

A

Adds a short length of RNA primer to the template strand of DNA to allow DNA polymerase to bind and begin replication

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5
Q

What is DNA polymerase III?

A

Adds nucleotides in a 5’ to 3’ direction.

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6
Q

What is a leading strand?

A

Polymerase III can add continuously in a 5’ to 3’ direction (same direction as replication fork)

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7
Q

What is a lagging strand?

A

Polymerase III must move away from the fork and replicate DNA in small chunks (Okazaki fragments)

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8
Q

What is the function of DNA polymerase I?

A

Removes RNA primers and replaces them with DNA. Corrects error in DNA bases.

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9
Q

What is the function of DNA ligase?

A

Seals up the bases to make new strands (connects Okazaki fragments).

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10
Q

How does DNA replication differ in euk and prok cells?

A

Initiated at many points in euk cells. In prok starts at one end and continues until finished.

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11
Q

What is protein synthesis?

A

The making of proteins. Occurs in 2 stages: transcription and translation.

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12
Q

What is transcription?

A

Copying of a portion of DNA containing the information for making the needed protein into RNA. RNA copy carries DNA message to ribosome where protein will be built.

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13
Q

What is translation?

A

Reading of RNA message and translation from nucleotide language to amino acid language at the ribosome

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14
Q

What is the purpose of RNA polymerase?

A

Binds to a site on the DNA at start of a gene. Moves along gene to separate DNA

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15
Q

What is the antisense strand?

A

Strand of DNA used in transcription. Only this strand is copied.

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16
Q

What is the RNA called that is copied from the DNA?

A

Messenger RNA (mRNA)

17
Q

What is a promoter region?

A

Region of DNA located “upstream” of a gene that allows RNA polymerase to recognize the gene that needs to be transcribed. Tends to be repetitive ATAT

18
Q

What is a terminator?

A

Region of DNA that tells RNA polymerase to stop transcription. When terminator is reached, mRNA peels off of DNA template and DNA reforms h bonds.

19
Q

What is a codon?

A

Sequences of mRNA nucleotides grouped into triplets.

20
Q

What are the functions of non-coding DNA?

A

Regulators of gene expression (operator in lac operon), introns (chopped out of mRNA), telomeres (ends of chromosomes), and genes for tRNA. Some DNA sequences produce polypeptides, tRNA, rRNA, and regulate gene expression (lac operon).

21
Q

What happens when euk cells modify mRNA?

A

Introns are removed from mRNA and are not translated. Exons are kept and spliced together to form mature mRNA

22
Q

How does the environment of a cell impact gene expression?

A

Some proteins required at all times and are expressed continuously. Others only need to be produced at certain times in certain amounts so production is regulated (lac operon for lactose in prok cells)

23
Q

How does the lac operon in E.coli work to express the genes responsible for the absorption of lactose when required?

A

In the presence of lactose, a repressor gene is deactivated and does not bind to the operator. In absence of lactose, repressor protein is activated and binds to the operator to save energy instead of creating enzymes to process lactose.

24
Q

What is needed for translation?

A

mRNA, ribosome, and tRNA

25
Q

What is a ribosome?

A

Ribosomes are made of proteins and rRNA. They have a large and small subunit. 3 binding sites for tRNA mocs, 2 at any time fit. E, P, and A sites. Binding site for mRNA.

26
Q

What are the two types of ribosome?

A

Free ribosomes: in cytoplasm, synthesize proteins for use in cell.
Bound ribosomes: attached to ER, synthesize proteins for secretion from cell or for lysosomes

27
Q

What are the features of tRNA?

A

Sections that become double stranded by base pairing (loops), triplet of bases called anticodon

28
Q

How are tRNA molecules activated?

A

Recognized by tRNA activating enzyme that attaches specific amino acid to tRNA. Each enzyme is specific to one of the 20aas and the correct tRNA moc. Active site of the enzyme specific to correct aa and correct tRNA

29
Q

What are the steps in translation?

A
  1. Initiation
  2. Elongation and translocation
  3. Termination
30
Q

What is initiation?

A

mRNA moc binds to small subunit of ribosome at binding site. Initiator tRNA (methionine), binds to start codon (AUG). Large subunit of ribosome binds to small one. Initiator tRNA is in P site. Next codon signals another tRNA to bind at A site. Peptide bond formed between aas.

31
Q

What is elongation and translocation?

A

The continuation of the aa building process and movement of the mRNA through the ribosome. Ribosome translocates 3 bases along mRNA, moving tRNA to E site and allowing new tRNA to bond w mRNA in A site.

32
Q

What is termination?

A

The ribosome reaches a stop codon (no tRNA has anticodon), polypeptide is released, ribosome mRNA and tRNA fall apart, polypeptide chain folds into a shape based on the aa’s it has.

33
Q

What is a group of ribosomes moving along the same mRNA?

A

Polysome

34
Q

What is PCR?

A

Polymerase chain reaction

35
Q

How does PCR work?

A

Heat used to separate DNA. Cooling to attach DNA primers. Taq polymerase (does not denature at high temperatures) used to build new DNA (5’ to 3’). Heat separates strands and cycle begins again.

36
Q

What is satellite DNA?

A

Repetitive sequences of non coding DNA. (Telomeres)

37
Q

How did human insulin become commercially available?

A

Genetically modified E.coli. Gene from healthy human pancreas cell transferred to host cell DNA. Gene transcribed and translated into insulin that is harvested in large quantities. Works because DNA has universal genetic code.

38
Q

What did Meselson and Stahl prove?

A

The replication of DNA is semiconservative

IB Biology Topic 2 (7 decks)

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