2.7/7.1 (DNA Unit) Flashcards

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1
Q

Describe the meaning of “semi-conservative” in relation to DNA replication.

A

Semi-conservative means the products of DNA replication each contain one of the original DNA strands and one new strand.

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2
Q

Explain the role of complementary base pairing in DNA replication.​

A

Complementary base pairing (A-T, C-G) ensures that the DNA sequence remains consistent after DNA replication. This ensures that the genetic code remains intact between generations.

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3
Q

State why DNA strands must be separated prior to replication.

A

The two strands of the parent DNA molecule must separate so that each can serve as a template for the new DNA strands that are being built.

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4
Q

Outline two functions of helicase.

A

Helicase is an enzyme that attaches to the DNA and moves along the molecule separating unwinding the helix and separating the two strands by breaking hydrogen bonds.

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5
Q

State the role of the origin of replication in DNA replication.

A

The origin of replication is the sequence of DNA nucleotides at which replication is initiated.

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6
Q

Contrast the number of origins in prokaryotic cells to the number in eukaryotic cells.​

A
  • Prokaryotic cells have 1 origin of replication (therefor one replication bubble with two replication forks)
  • Eukaryotic cells have many origins of replication (therefor multiple replication bubbles that eventually fuse)
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7
Q

Describe the movement of DNA polymerase along the DNA template strand.

A
  • DNA polymerase moves along the parent DNA strand from the 3’ end to the 5’ end of the parent strand. The parent/template is read from 3’ to 5’.
  • DNA polymerase builds a complementary strand of DNA from the parent/template strand. The daughter strand is built from 5’ to 3’.
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8
Q

Describe the action of DNA polymerase III in pairing nucleotides during DNA replication.

A
  • DNA polymerase “reads” a parent/template DNA strand and adds complementary nucleotides to build a new strand of DNA.
  • DNA polymerase can only add new nucleotides to the 3’ end of the growing daughter strand.
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9
Q

Outline the features of DNA structure that suggested a mechanism for DNA replication.

A
  • Complementary base pairing
    • A to T, C to G ensure that genetic message conserved when each strand replicate
  • Covalently bonded sugar-phosphate backbone
    • relatively strong bonds keep nucleotides in backbone connected in correct sequence
  • Hydrogen bonds between complementary strands
    • allow complementary strands separate easily for replication
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10
Q

Compare replication on the leading strand and the lagging strand of DNA.

A
  • On leading strand, DNA polymerase III move in same direction as helicase, adding complimentary nucleotides to growing daughter strand
  • On lagging strand, DNA polymerase III move opposite as helicase
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11
Q

Explain why replication is different on the leading and lagging strands of DNA.

A

Because DNA polymerase III only add new nucleotides to 3’ of growing strand, replication run opposite on leading & lagging strands

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12
Q

Outline the formation of Okazaki fragments on the lagging strand.

A

Because DNA polymerase III moving away from replication fork on lagging strand, must build DNA in short sections called Okazaki fragments

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13
Q

Outline the role of the following proteins in DNA replications: helicase, topoisomerase (AKA gyrase), single stranded binding proteins, primase, DNA polymerase III, DNA polymerase I, and DNA ligase.

A
  1. Helicase open DNA helix by breaking hydrogen bonds between nitrogenous bases
  2. Topoisomerase (gyrase): hep relieve tension stress on DNA when unwinding
  3. Single stranded binding proteins: bind to single stranded DNA, preventing parent strands from reconnecting
  4. Primase: synthesize RNA primers needed to start replication
  5. DNA polymerase III: main enzyme that build complementary DNA strand by adding nucleotides in 5’ to 3’ direction
  6. DNA polymerase I remove RNA primer & replace with DNA nucleotides
  7. Ligase covalently bond sugar-phosphate backbone between adjacent okazaki fragments on lagging strand
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14
Q

Explain the need for RNA primers in DNA replication.

A
  • Primer is short strand of RNA (=10 bases) tht act as starting point for DNA replication
  • Needed because DNA polymerase III can only add nucleotides to existing strand
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15
Q

Explain what is meant by DNA replication occurring in a 5’ to 3’ direction.

A
  • 5’ to 3’ has 2 meanings
    • new DNA strand built from its 5’ end towards 3’ end
    • new incoming nucleotide triphosphate added from its 5’ end to 3’ end of previously placed nucleotide
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16
Q

Define “coding sequences” and “repetitive sequences” of DNA.

A
  • Coding Sequences are the sequences that code for a certain protein that is expressed in the organism.
  • Repetitive Sequences (non-protein coding) are the sequences which does not code for a protein but is repeated over and over in the genome, they’re also known as “tandem repeats.”
17
Q

Outline five functions of non-coding DNA sequences found in genomes, one of which must be the telomere.

A
  • satellite DNA: tandemly repeating sequences of DNA; structural component of heterochromatin and centromeres; commonly used for DNA profiling
  • telomeres: regions of repetitive DNA at the end of a chromosome; protects against chromosomal deterioration during replication
  • introns: non-coding sequences within genes; are removed by RNA splicing prior to the formation of mRNA
  • non-coding RNA genes: codes for RNA molecules that are not translated into protein; examples include genes for tRNA
  • gene regulatory sequences: sequences that are involved in the process of transcription; includes promoters, enhancers, and silencers
18
Q

Define VNTR.

A

Variable Number Tandem Repeat (sequences of repeating DNA nucleotides)

19
Q

Explain why VNTR are used in DNA profiling

A

Each person has a different VNTR, which can be differentiated by the size of the fragments after they are cut by restriction enzymes.

20
Q

Outline the process of DNA sequencing, including the role of chain terminator nucleotides, fluorescence, and electrophoresis.

A
  • Copies of DNA sequences are placed with polymerase, nucleotides, and primers
  • Polymerase replicates the sequences and stops when adding dideoxynuceotide
  • Strands of new replications of various lengths end with fluorescent nucleotides
  • DNA is separated by size in electrophoresis