DNA Replication

heterochromatin vs. euchromatin

-during replication, DNA must be uncondensed -heterochromatin is what remains compacted and is transcriptionally silent with highly repetitive sequences -euchromatin is dispersed, therefore genetically active DNA that gets copied during replication

If a DNA molecule is found to be composed of 40% thymine, what percentage of guanine would be expected?

10%

When one DNA molecule is copied to make two DNA molecules, the new DNA contains

100% of the parent DNA

DNA replication results in

2 DNA molecules that each contain a strand of the original

DNA replication results in:

2 DNA molecules that each contain a strand of the original

If the DNA of a certain organism has guanine as 30% of its bases, then what percentage of its bases are adenine?

20%

If 32% of the bases in a DNA molecule are adenine, which of the following describes the adbundances of the other bases?

32% thymine, 18% cytosine, 18% guanine.

Nucleoid

In the cytoplasm

DNA polymerase can make mistakes while adding nucleotides. How does this gets fixed?

It edits the DNA by proofreading every newly added base as the polymerization continues.

Nucleo excision repair is important particularly in __________.

thymine dimers: caused by ultraviolet light.

Supercoiling

twisting in the opposite direction to the turns of the double helix during the first stage of mitosis.

DNA replication

uses each strand of a DNA molecule as a template for the creation of a new strand

DNA polymerase

An enzyme that catalyzes the formation of the DNA molecule.

If one strand of DNA is CGGTAC, the corresponding strand would be

GCCATG

In the ladder analogy of the DNA molecule, the "rungs" of the ladder are:

sugars, phosphate, pair nitrogenous bases

The replication of DNA occurs during the __________________ of the cell cycle, before the cell enters mitosis or meiosis.

synthesis phase, or S phase before mitosis and meoisis.

Primase

synthesizes RNA primer

The copying mechanism of DNA is most like

taking a picture of yourself and of your reflection in a mirror.

During DNA replication, each strand serves as a ____________ for the new ____________ strand.

template, complementary

Prymidines

thymine and cytosine

The process of proofreading involves

removing incorrect bases during replication

Which of the following occurs in the nucleus?

replication of genetic material

Which of the following statements about these strands is true?

the leading strand of DNA is synthesized continously

Chargaff showed that

the numbers of Adenine and Thymine are the same in DNA from an organism.

One dangerous mutation that can occur due to the sunlight exposure (ultaviolet light) is called

thmine dimer

The "rule" forumlated by Chargaff states that

A = T and G =C

An example of base complementation in DNA replication is

A and T

phosphate group

A chemical group consisting of a phosphorus atom bonded to four oxygen atoms; important in energy transfer.

lagging strand

A discontinuously synthesized DNA strand that elongates by means of Okazaki fragments, each synthesized in a 5' to 3' direction away from the replication fork.

Deoxyribose

A five-carbon sugar that is a component of DNA nucleotides

DNA ligase

A linking enzyme essential for DNA replication; catalyzes the covalent bonding of the 3' end of a new DNA fragment to the 5' end of a growing chain.

Purines

Adenine (A) and Guanine (G)

Telomerase

An enzyme that catalyzes the lengthening of telomeres. The enzyme includes a molecule of RNA that serves as a template for new telomere segments.

nitrogenous base

An organic base that contains nitrogen, such as a purine or pyrimidine; a subunit of a nucleotide in DNA and RNA

nucleotide excision repair

Another type of repair when the DNA double strands are unzipped and separated - the incorrect bases are removed along with a few bases on the 5' and 3' end, and replace by copying the template with DNA polymerase.

Telomeres

DNA at the tips of chromosomes

Nucleosomes

DNA coiled around histones (proteins that help organize and pack DNA)

Which statement regarding DNA is false? - DNA contains the sugar deoxyribose. x - DNA contains the nitrogenous base uracil. - One DNA molecule can include four different nucleotides in its structure. - DNA molecules have a sugar-phosphate backbone.

DNA contains the nitrogenouse base uracil.

One difference between the structure of DNA in eukaryotes and prokaryotes is

DNA in eukaryotes is linear and DNA in prokaryotes is circular.

The enzume that joins together the sugar-phosphate backbones of DNA segments is called

DNA ligase

Which enzyme catalyzes the elongation of a DNA strand in the 5' to 3' direction?

DNA polymerase

Which of the following enzymes catalyzes the elongation of a new DNA strand?

DNA polymerase

How good is the DNA repair process?

DNA polymerase makes an error once 50K-100K pairs

When a cell divides, it is important that each daughter cell receives an identical copy of the DNA by the process of

DNA replication.

Which of the following statements best explains the mechanism for DNA replication?

DNa replication is semi-conservative, because each DNA strand serves asa template during replication.

What happens during DNA replication?

Each of 2 strands of double helix serves as a template from where new strands are copied.

Which of the following correctly pairs the DNA replication enzyme with its function? - Helicase seals the gaps between DNA fragments - DNA polymerase I open up the DNA at the replication fork - DNA primase extends primers by adding the nucleotides to the 3' end x - Ligase works to seal the gaps between DNA fragments

Ligase works to seal the gaps between DNA fragments.

anti-parallel

Separate strands that run in a different direction. In a DNA molecule, one strand is in the 3' to 5' orientation, and the other is in the 5' to 3'orientation.

Complementation

The DNA polymerase moves to the next nucleotide on the original strand and randomly places nucleotides across from it. If it's not the right nucleotide, it will fall back out. Finally, locks in the right base by the phosphate of this new nucleotide to the sugar of growing new DNA strand.

Which statement regarding a DNA double helix is true?

The amount of adenine is equal to the amount of thymine, and the amount of guanine is equal to the amount of cytosine.

How does the DNA fit into the nucleus of the cell?

The circle of the DNA is crowded and held together in the center by scaffolding proteins. Then the DNA is twisted beyond the double helix (supercoiling). Finally, the DNA condenses to 1/1000th of its original size.

Primer

The initial nucleotide chain that is produced during DNA synthesis is actually a short stretch of RNA

leading strand

The new continuous complementary DNA strand synthesized along the template strand in the mandatory 5' to 3' direction.

What is the role of the phosphate group in DNA?

The phosphate group bonds covalently with the sugar molecule of the next nucleotide, and so on, forming a long polymer of nucleotide monomers.

Helicases

Unzips DNA and separate the template DNA strands at the replication fork.

The Nobel Prize in 1963 was awarded to

Watson, Crick, and Wilkins

Which statement about the discovery of DNA structure by Watson and Crick is false?

X-Ray pictures of DNA were helpful in deducing its structure.

Chargaff's Rule

[A]=[T] and [G]=[C], they pair up across from one another forming two strands also called base pairing.

Mutation

a permanent change in the DNA sequence.

DNA

a polymer of nucleotides consisting of a nitrogenous base, deoxyribose, and a phosphate group.

DNA polymerases require

a primer and a DNA template strand

The shape of a DNA molecule is most like

a twisted rope ladder

The 4 types of nitrogenous bases in DNA are:

adenine (A), thymine (T), guanine (G), or cytosine (C).

mismatch repair

are enzymes in which recognize the wrong incorporated base and excise it from the DNA by replacing the correct base.

Why does a DNA strand grow only in the 5' to 3' direction?

because DNA polymerases can only add nucleotides to the 3' end of the growing molecule.

single strand binding proteins

bind to and stabilize single-stranded DNA

Wilkins and Franklin

both used a technique called x-ray crystallography to produce a picture of the DNA molecule

Mutation may lead to

cancer

Heterochromatin

condensed chromatin

In DNA, guanine from one strand binds to _____________ in the complementary strand.

cytosine

Considering the principle of complementary base pairing, you would expect an equal ratio of which two nitrogenous bases in a DNA molecule?

cytosine and guanine

Histones

the proteins that the DNA uses to wrap around to form nucleosomes.

James Watson and Francis Crick

discovered the structure of DNA

Why is replication called semi-conservative?

each daughter cell gets part of the original DNA & part of the new DNA.

Semiconservative DNA replication means that

each new DNA molecule has half the DNA from the old one

Telomeres tend to

get shorter during each cell division

DNA can be retieved from

hair, blood, or saliva.

The enzymes that break hydrogen bonds and unwind DNA are:

helicases

Condensed chromatin is called

heterochromatin

Base pairing is dependent on

hydrogen bonds

Euchromatin

loosely packed chromatin

If errors are not corrected in DNA, they may result in

mutation.

semiconservation replication

new DNA consists of one old strand and one new strand

Histones are proteins that make up

nucleosomes

Semiconservative replication refers to

one old strand of DNA is used to provide the information for the new strand of DNA.

During replication, which enzyme adds complimentary base?

polymerase