Tutorial #17- DNA Replication

describe Xeroderma pigmentosum (XP)

- a recessive autosomal genetic condition that occurs as a mutation of a DNA polymerase that repairs UV-damaged DNA

what are the components of nucleotides?

-5 carbon sugar phosphate functional group nitrogenous base

define mismatch repair:

-DNA polymerase and other proofreading enzymes remove incorrectly paired nucleotides

describe the lagging stand of DNA replication

-it has a discontinuous mode of replication because DNA polymerase can only work by starting from the replication fork and progressing outward (until it runs into a previously synthesized fragment)

https://media.ed.science.psu.edu/sites/media/ed/files/h5p/content/4877/images/file-59df766bc5fe2.jpg In the diagram above, A and B refer to which ends respectively? A = 5' and B = 5'. A = 5' and B = 3'. A = 3' and B = 5'. A= 3' and B = 3'

A = 3' and B = 5'

describe elongation

-DNA polymerase copies the template segment of DNA.

how is the lagging strand started?

-Primase has the ability to synthesize a short primer made of a few nucleotides of RNA. -DNA polymerase can then add DNA nucleotides to the end of this primer sequence and synthesize relatively short stretches of DNA (ozaki fragments)

example of a neutral mutation:

-an organism's DNA sequence changes but this change has no effect on the organism's phenotype

what are the symptoms of XP?

-damage is cumulative and irreversible -stay away from sunlight -"children of the dark" -skin cancers in early childhood -decreased life expectancy

what is the third basic step of PCR?

-elongation

what is an important limitation of DNA polymerase?

-it can only add nucleotides to the 3' end of the newly synthesized strand of DNA

What is polymerase chain reaction?

-it uses the basic steps and materials of DNA replication to create a large number of copies of a small piece of DNA in a short period of time

describe interphase of mitosis

-longest stage in cell cycle -cell prepares for division -chromosomes are replicated during S-phase

describe thymine dimers

-occurs due to DNA exposure to sunlight -2 thymines are next to each other in a strand and they covalently bond to each other, and not hydrogen bond to the adenine on the complementary strand

Considering DNA replication along the 5' to 3' template strand, what event takes place first? DNA polymerase begins adding DNA nucleotides. DNA polymerase begins adding RNA nucleotides. primase removes the 5' phosphate. primase adds an RNA primer

-primase adds an RNA primer

what is the fourth basic step of PCR?

-repeat the process (repeated until the desired amount of DNA is obtained)

what are ozaki fragments?

-short sequences of DNA nucleotides which are synthesized discontinuously and later linked together by the enzyme DNA ligase to create the lagging strand during DNA replication

what are nucleic acids responsible for?

-storing genetic information -protein synthesis

describe denaturation

-the DNA is heated to separate the two complimentary strands -(note that in a cell helicase would play this role).

describe annealing

-the temperature is lowered and the DNA primers attach (or anneal) to the regions around the segment of DNA to be copied.

Describe the strands of DNA

-they are anti-parallel complementary strands -they have opposite chemical polarities

when can PCR be used?

-when you find a single drop of blood at a crime scene and want to see its DNA

what is the effect of a mutation dependent on?

-whether or not the mutation occurred in a gene -if it occurrs in a gene, how much it changes the resulting protein

when and where was tax polymerase found?

1976 and hot springs

Given this DNA template strand, what would be the sequence of nucleotides in the newly synthesized DNA strand? DNA Template 3' ATTGGCATGCCGAGACC 5' 3' CCAGAGCCGTACGGTTA 5'. 3' GGTCTCGGCATGCCAAT 5'. 3' TGCCGATTGCATACGGA 5'. 3' TAACCGTACGGCTCTGG 5'

3' GGTCTCGGCATGCCAAT 5'

If a DNA molecule contains 20% Adenine, approximately what percentage of Guanine is present?

30%

The number of amplified pieces of DNA equals _________ after five cycles of PCR. 5. 32. 10. 25

32

Which strand below would make the sequence 5' AAACGCTT 3' a double stranded DNA molecule? 5' UUUGCGUU 3'. 5' AAGCGTTT 3'. 5' AAGCGUUU 3'. 5' TTTGCGAA 3'

5' AAGCGTTT 3'

DNA Replication proceeds in a ______ to ______ direction.

5' to 3'

who invented PCR

Kerry Mullis

how does DNA replicate?

The double helix unwinds and nitrogenous bases are added to each strand of the parent molecule (but only onto one end of each), resulting in two identical copies of the original parent strands.

who discovered the structure of DNA?

Watson and Crick

what does DNA replication result in?

a chromosome that is comprised of two identical sister chromatids

what does DNA polymerase do?

adds nucleotides to the unwound parent molecule

example of a beneficial mutation:

antibiotic resistance

If a nucleic acid is found to contain 20% A and 20% T, the molecule is probably double-stranded DNA.. single-stranded RNA.. double-stranded RNA.. single-stranded DNA.

double-stranded DNA

describe the "specific pairing" of DNA

hydrogen bonds between adenine and thymine, cytosine and guanine

what is the second basic step of PCR?

Annealing

2. Which of the following statements are true about nuclear DNA replication in a cell that is preparing to divide (select all that apply)? A. DNA replication occurs during the M-phase B. DNA replication occurs during interphase C. DNA replication occurs during prophase D. DNA replication occurs during the S-phase E. DNA replication occurs during metaphase F. DNA replication results in the formation of sister chromatids G. DNA replication results in the formation of homologous chromosomes

B, D, F

. DNA is replicated: A. during mitosis, producing sister chromatids. B. during interphase, producing sister chromatids. C. during interphase, producing homologous chromosomes. D. during mitosis, producing homologous chromosomes.

B. during interphase, producing sister chromatids.

Is it possible to use PCR to produce many copies of all DNA of one chromosome? No, PCR cannot copy DNA, only RNA.. No, PCR copies short sequences of DNA only.. Yes, if the correct primers are available.. Yes, if the telomeres are present

No, PCR copies short sequences of DNA only.

where does the replication of DNA take place?

S-phase of interphase

what do you need to add to a tube for PCR

Template strand (DNA sample) Raw nucleotides DNA Primers Dna polymerse- taq polymerase Stable solution

define the replication fork

The point at which the two strands of DNA are separated to allow replication of each strand.

define mutation

a permanent change in an organism's DNA

Ultraviolet radiation damages DNA by causing an extra ___________________ bond to form between adjacent ______________. hydrogen, guanine. hydrogen, thymines.. covalent, thymines.. covalent, guanine.

covalent, thymines.

what is the first basic step of PCR?

denaturation

why was PCR long and laborious at first?

denaturation would kill DNA polymerase due to the heat

why is DNA termed semiconservative replication?

each newly formed molecule of DNA has one strand conserved from the parent molecule and one newly synthesized strand.

*cell cycle photo*

https://media.ed.science.psu.edu/sites/media/ed/files/styles/image_lightboxed/public/biol110-dna-replication-cell-cycle_0.jpg?itok=WX5IULUW

*photo of DNA structure*

https://media.ed.science.psu.edu/sites/media/ed/files/styles/image_lightboxed/public/biol110-dna-replication-dna-structure_0.jpg?itok=tHm6RvlC

*photo of an overview of DNA replication*

https://media.ed.science.psu.edu/sites/media/ed/files/styles/image_lightboxed/public/biol110-dna-replication-overview_0.jpg?itok=nswm_wVz

*photo of semi conservative DNA replication*

https://media.ed.science.psu.edu/sites/media/ed/files/styles/image_lightboxed/public/biol110-dna-replication-semiconservative-replication_0.jpg?itok=EaNV-v_L

*photo of up close DNA structure*

https://media.ed.science.psu.edu/sites/media/ed/files/styles/image_lightboxed/public/biol110-dna-replication-structure-strands_0.jpg?itok=nmnHCH6H

what does primase do?

initiates DNA replication

define excision repair:

involves the removal of damaged nucleotides from a DNA molecule.

what happens if a DNA mutation occurs in a reproductive cell?

it can be passed to future generations and potentially become established in a population

describe tax polymerase

it is a DNA polymerase that can withstand heat and has made PCR a very fast and less labor intensive process

During DNA replication, Okazaki fragments are produced along the ____________ strand because DNA polymerase can only add nucleotides to the ___________________________________​ leading / 3' end of the new strand of DNA.. leading / 5' end of the new strand of DNA.. lagging / 5' end of the new strand of DNA.. lagging / 3' end of the new strand of DNA.

lagging / 3' end of the new strand of DNA.

what enzyme seals the ozaki fragments into one continuous DNA strand?

ligase

how many copies of a DNA strand can be made from PCR in a few hours?

millions of copies

can PCR copy an entire chromosome?

no!

what are the monomers of nucleic acids?

nucleotides

where does DNA replication take place in a eukaryotic cell?

nucleus

describe how the DNA strands are antiparallel

one strand is designated to the 3'-5' strand one strand is designated to the 5'-3' strand

where does replication begin?

origins of replication

DNA replication is: semiconservative.. dispersive.. conservative.. semidispersive.

semiconservative

examples of harmful mutations:

sickle-cell anemia down syndrome CF

what can occur to someone's phenotype due to thymine dimers?

skin cancer

what is an example of a DNA enzyme that helps defend against mutations?

specific DNA polymerases that fix errors due to exposure of UV radiation (sunlight)

what phosphate group is in a DNA and RNA nucleotide

sugar-phosphate group?

where is DNA polymerase always located?

the 3' prime of the newly synthesized DNA

what DNA strand is responsible for the nucleotide addition process?

the leading strand of DNA replication

H-bonding that occurs between bases is only achieved if...

the strands have opposite polarities

what do single-strand binding proteins do?

they keep the two parental DNA strands apart

defne antiparallel

they run parallel to each other but with opposite alignments

what is an example of damage that can occur in DNA due to UV radiation?

thymine dimers

what is the role of helicase?

unwinds the DNA double helix