CM1- DNA organization, replication, and repair

* What sugar is present in DNA?

Deoxyribose

* What type of sugar is deoxyribose?

A pentose sugar

* What substance forms the phosphate component of the DNA backbone?

Phosphoric acid

* What bond links nucleotides together in a DNA polynucleotide chain?

A phosphodiester bond

* Between which groups does a phosphodiester bond form in DNA?

Between the 3′-OH of one sugar and the 5′-OH of the next sugar

* What do phosphodiester bonds facilitate in DNA?

Formation of polynucleotides

* What is a nucleoside composed of?

A nitrogenous base attached to a sugar

* What is a nucleotide composed of?

A nucleoside with one or more phosphate groups

* What does NMP stand for in nucleotide terminology?

Nucleoside monophosphate

* What does NDP stand for in nucleotide terminology?

Nucleoside diphosphate

* What does NTP stand for in nucleotide terminology?

Nucleoside triphosphate

* How many polynucleotide chains form one DNA molecule?

Two polynucleotide chains

* What holds the two polynucleotide chains of DNA together?

Hydrogen bonds between complementary bases

* How many hydrogen bonds form between adenine and thymine?

Two hydrogen bonds

* How many hydrogen bonds form between guanine and cytosine?

Three hydrogen bonds

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What is DNA denaturation?

Separation of the two DNA strands caused by destruction of hydrogen bonds

* What conditions listed in the lecture can cause DNA denaturation?

Heat or alkali

* What type of DNA bonds are destroyed during heat- or alkali-induced denaturation?

Hydrogen bonds

* Why do the two DNA strands separate during denaturation while the individual strands remain intact?

Phosphodiester bonds are resistant to the denaturing conditions

* Is DNA dissociation caused by denaturation reversible?

Yes

* What is DNA renaturation?

Reassociation of separated DNA strands when denaturing conditions are reversed

* What is another term for DNA renaturation?

Reannealing

* What is the melting temperature, or Tm, of DNA?

The temperature at which 50% of the DNA is single-stranded

* What major factor affects DNA melting temperature?

Base composition

* According to the denaturation graph, which DNA has a higher melting temperature: high-GC or high-AT DNA?

High-GC DNA

* What is DNA hybridization?

The tendency of single-stranded DNA to bind complementary sequences of DNA or RNA

* What type of sequence is required for single-stranded DNA hybridization?

A complementary sequence

* Can single-stranded DNA hybridize with RNA?

Yes, if the RNA sequence is complementary

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What two locations of DNA are listed in genomic organization?

Mitochondrial DNA and nucleic DNA

* How can genetic information be inherited?

Through replication

* How can genetic information be expressed?

Through transcription and translation

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What is the shape of mitochondrial DNA?

Circular

* Is mitochondrial DNA single-stranded or double-stranded?

Double-stranded

* What theory is associated with the circular, double-stranded nature of mitochondrial DNA in the lecture?

The endosymbiotic theory

* Approximately what percentage of total cellular DNA is mitochondrial DNA?

Approximately 1%

* Does mitochondrial DNA contain histones?

No; it lacks histones

* What is the GC characteristic of mitochondrial DNA?

It is GC rich

* How many genes are present in mitochondrial DNA?

37 genes

* How many mitochondrial genes are involved in energy production?

13 genes

* How many mitochondrial genes are for rRNA and tRNA?

24 genes

* From which parent is mitochondrial DNA derived according to the lecture?

Exclusively from the mother

* Why can mitochondrial DNA be used as a marker for human ancestry?

Because it undergoes no recombination

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Approximately what percentage of nucleic DNA is non-coding?

98%

* Approximately how long is nucleic DNA per cell?

Approximately 6 feet per cell

* Approximately how many genes are encoded by nucleic DNA?

About 22,000 genes

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What is a chromosome centromere?

The constricted region of a chromosome

* What attaches to the chromosome at the centromere?

Spindle microtubules

* Why is the centromere required during cell division?

It is required for correct mitosis

* What are telomeres?

Caps at the ends of chromosomes

* What DNA sequence is repeated in telomeres?

TTAGGG

* Approximately how many times is the TTAGGG sequence repeated in a telomere according to the lecture?

Approximately 1,000 times

* What happens to telomeres with each cell division?

They shorten

* What is the short arm of a chromosome designated?

p

* What is the long arm of a chromosome designated?

q

* What is a metacentric chromosome?

A chromosome with the centromere positioned so that the arms are relatively similar in length

* What is a submetacentric chromosome?

A chromosome with an off-center centromere that produces a shorter p arm and longer q arm

* What is an acrocentric chromosome?

A chromosome with the centromere positioned near one end, producing a very short p arm and a long q arm

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What is chromatin?

A super-compacted DNA-protein complex that forms chromosomes

* How does euchromatin compare with heterochromatin in degree of condensation?

Euchromatin is less condensed, whereas heterochromatin is more condensed

* Where is euchromatin typically located?

On chromosome arms

* Where is heterochromatin typically located?

At centromeres, telomeres, and other specific places

* What type of DNA sequences are characteristic of euchromatin?

Unique sequences

* What type of DNA sequences are characteristic of heterochromatin?

Repeated sequences

* Does euchromatin contain many or few genes?

Many genes

* Does heterochromatin contain many or few genes?

Few genes

* How frequently is euchromatin transcribed?

Often

* How frequently is heterochromatin transcribed?

Infrequently

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At the simplest level, what is chromatin composed of?

Double-stranded helical DNA

* What happens when DNA complexes with histones?

It forms nucleosomes

* What proteins form the nucleosome core?

Eight histone proteins

* According to the packaging diagram, approximately how many times does DNA wrap around the nucleosome histone core?

Approximately 1

* What happens to the 300-nm loops during further chromosome packaging?

They are compressed and folded to produce a 250-nm-wide fiber

* What does tight coiling of the 250-nm fiber produce?

The chromatid of a chromosome

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What is the structural unit of chromatin?

The nucleosome

* What makes up a nucleosome according to the lecture?

A histone octamer core plus double-stranded DNA wrapped around the core

* How many molecules of histone H2B are in a nucleosome core?

\

* According to the text slide, how many times is double-stranded DNA wrapped around a nucleosome core?

Two times

* What connects adjacent nucleosomes?

Linker DNA and histone H1

* What appearance results from nucleosomes connected by linker DNA and histone H1?

A “beads-on-a-string” appearance

* What are supercoiled nucleosomes called?

Chromatin fibers

* What structural forms can chromatin fibers take?

Solenoids or tubular coils

* What results from compaction of chromatin fibers?

Chromosomes

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Why is DNA synthesis required?

For DNA replication and DNA repair

* What is the cell cycle?

Cells replicate their chromosomes and separate into daughter cells

* During which phase of the cell cycle does DNA replication occur?

S phase

* During which phase does the lecture associate DNA repair?

G2 phase

* Approximately how long does genome duplication take in a cell?

Approximately 9 hours

* Where does DNA replication begin?

Origins of replication

* What abbreviation is used for an origin of replication?

ori

* Approximately how many origins of replication are present per chromosome in eukaryotes?

Approximately 100 per chromosome

* How many origins of replication are present in prokaryotes according to the lecture?

One