BIO Exam #3: CHAPTER 11

BIO CHAPTER 11

Who discovered transformation?

Frederick Griffith.

What is transformation?

The process where genetic material is transferred from one cell to another.

How did Griffith's experiment help identify DNA's role?

It showed a "transforming factor" carried genetic info, later found to be DNA.

Who were Avery, MacLeod, and McCarty?

Scientists who confirmed DNA is the transforming material.

What did Avery, MacLeod, and McCarty's experiments show?

DNA, not protein or RNA, carries genetic information.

What are bacteriophages (phages)?

Viruses that infect bacteria.

Who used phages to show DNA is the genetic material?

Hershey and Chase.

What was the Hershey-Chase experiment's main finding?

DNA, not protein, enters cells and directs viral replication.

What are the five structural levels of DNA organization?

Nucleotides → Single strand → Double helix → Chromatin → Chromosomes.

What is the monomer of DNA and RNA?

Nucleotide.

What are the three components of a DNA nucleotide?

Phosphate group, deoxyribose sugar, nitrogenous base.

What are the four DNA nitrogenous bases?

Adenine, Thymine, Guanine, Cytosine.

What sugar is found in DNA?

Deoxyribose.

What sugar is found in RNA?

Ribose.

What are the three parts of an RNA nucleotide?

Phosphate group, ribose sugar, nitrogenous base.

What are the four RNA nitrogenous bases?

Adenine, Uracil, Guanine, Cytosine.

What replaces thymine in RNA?

Uracil.

What bond connects nucleotides in a strand?

Phosphodiester bond.

Which bases are purines?

Adenine and Guanine.

Which bases are pyrimidines?

Cytosine, Thymine, and Uracil.

How many rings do purines have?

Two.

How many rings do pyrimidines have?

One.

Who was Rosalind Franklin?

Scientist who produced X-ray diffraction images of DNA.

What is Photo 51?

Franklin's X-ray image showing DNA's helical structure.

What did Photo 51 reveal?

DNA is a double helix.

Who was Erwin Chargaff?

Scientist who discovered base-pairing rules (A=T and G=C).

What do Chargaff's rules state?

A=T and G=C; total purines equal total pyrimidines.

Who built the first DNA model?

Watson and Crick.

What helped Watson and Crick discover DNA's structure?

Franklin's Photo 51 and Chargaff's rules.

What does "double helix" mean?

Two intertwined DNA strands forming a spiral.

What holds DNA strands together?

Hydrogen bonds between bases.

What does "antiparallel" mean?

The two strands run in opposite directions (5′→3′ and 3′→5′).

What is complementary base pairing?

A pairs with T, G pairs with C.

If adenine is 20%, what percentage is thymine?

20%.

If adenine is 20%, what percentage are guanine and cytosine?

30% guanine, 30% cytosine.

What are the major and minor grooves in DNA?

Spaces between strands where proteins bind.

Who were Meselson and Stahl?

Scientists who proved DNA replication is semiconservative.

What does "semiconservative replication" mean?

Each new DNA has one old and one new strand.

What is the origin of replication?

The site where DNA replication begins.

What is a replication bubble?

Opened area where DNA strands separate for replication.

What is a replication fork?

Y-shaped area where DNA is unwound and copied.

What does DNA helicase do?

Unwinds the DNA double helix.

What does DNA topoisomerase do?

Relieves twisting tension during unwinding.

What do single-strand binding proteins (SSBs) do?

Prevent separated strands from rejoining.

What is an RNA primer?

Short RNA sequence that starts DNA synthesis.

What does DNA primase do?

Synthesizes RNA primers.

What does DNA polymerase do?

Adds nucleotides to form new DNA strands.

What is the leading strand?

The continuously synthesized strand.

What is the lagging strand?

The strand made in short fragments (Okazaki fragments).

What are Okazaki fragments?

Short DNA segments on the lagging strand.

What does DNA ligase do?

Joins Okazaki fragments together.

In what direction is new DNA synthesized?

5′ to 3′ direction.

What are dNTPs?

Deoxynucleoside triphosphates, building blocks of DNA.

What is the energy source for DNA polymerization?

Breaking of high-energy phosphate bonds in dNTPs.

What ensures DNA replication accuracy?

Base pairing, DNA polymerase fit, and proofreading.

What is DNA proofreading?

Polymerase removes and replaces mismatched bases.

What are telomeres?

Repetitive DNA sequences at chromosome ends.

Where are telomeres found?

In eukaryotic chromosomes.

What happens to DNA after many replications without telomerase?

Chromosomes gradually shorten.

What does telomerase do?

Extends telomeres to prevent shortening.

What is chromatin?

DNA wrapped around histone proteins.

What are histones?

Proteins that package and organize DNA.

What is a nucleosome?

DNA wrapped around a histone core.

How is eukaryotic DNA compacted?

DNA → Nucleosomes → 30-nm fiber → Looped domains → Chromosome.

What is a chromosome?

A highly condensed DNA-protein structure carrying genetic material.