bio 112 dna

What is DNA recognized as in living organisms?

DNA is recognized as the hereditary material.

What is the structure of DNA?

DNA has a double helix structure made up of two strands.

What are the building blocks of DNA?

Deoxyribonucleotides are the building blocks of DNA.

What components make up a deoxyribonucleotide?

Each deoxyribonucleotide consists of a deoxyribose sugar, a phosphate group, and a nitrogenous base.

What type of bond links deoxyribonucleotides in a DNA strand?

Phosphodiester bonds link deoxyribonucleotides in a DNA strand.

What are the two major features of a DNA strand?

A DNA strand has a sugar-phosphate backbone and a series of bases projecting from the backbone.

What directionality do DNA strands have?

DNA strands have a directionality with one end having a 3′ hydroxyl group and the other end having a 5′ phosphate group.

What is the significance of Watson and Crick's model of DNA?

Watson and Crick proposed that DNA strands are antiparallel and twist into a double helix.

What is complementary base pairing in DNA?

Complementary base pairing occurs between adenine (A) and thymine (T), and between guanine (G) and cytosine (C).

What is the first step in DNA replication?

The two strands of a DNA double helix are separated by breaking the hydrogen bonds.

What happens after the strands of DNA are separated during replication?

Free deoxyribonucleotides form hydrogen bonds with complementary bases on each original strand.

What is the conclusion of DNA replication?

Each copy of DNA contains one strand from the original molecule and one new strand.

What experiment demonstrated that DNA is the hereditary material?

The Meselson-Stahl experiment distinguished parental DNA strands from daughter strands using isotopes of nitrogen.

What was used to distinguish between parental and daughter DNA strands in the Meselson-Stahl experiment?

Two different isotopes of nitrogen, 15N and 14N, were used.

What type of reaction forms a phosphodiester bond during DNA synthesis?

A condensation reaction forms a phosphodiester bond.

In what direction does DNA synthesis proceed?

DNA synthesis proceeds from the 5′ end towards the 3′ end.

What is the structure of bacterial DNA?

Bacterial DNA is typically supercoiled and often circular.

How is eukaryotic DNA packed within the cell?

Eukaryotic DNA wraps around histone proteins to form nucleosomes, which further coil to form chromosomes.

What is a nucleosome?

A nucleosome is a complex of DNA wrapped around histone proteins.

What is the role of histones in DNA packing?

Histones are positively charged proteins that adhere to negatively charged DNA, aiding in its compaction.

What is the significance of replication forks in DNA synthesis?

Active DNA synthesis takes place at the replication forks of each replication bubble.

What is the function of enzymes in DNA replication?

Enzymes catalyze the reactions needed for DNA to self-replicate.

What is the result of DNA replication?

The result is two identical daughter DNA molecules.

What is the role of hydrogen bonds in DNA structure?

Hydrogen bonds form between complementary bases, stabilizing the double helix structure.

What is the primary function of DNA?

The primary function of DNA is to store and transmit genetic information.

What are DNA mutations?

DNA mutations are changes in the nucleotide sequence that can affect inheritance.

What mechanisms do bacteria use to exchange genetic material?

Bacteria use mechanisms such as transformation, transduction, and conjugation to exchange genetic material.

What is a replication fork?

A Y-shaped region where the parental DNA double helix is separated into single strands for copying.

What direction does DNA synthesis occur?

DNA synthesis occurs in both directions from a point of origin, making it bidirectional.

What enzyme catalyzes the breaking of hydrogen bonds during DNA replication?

Helicase.

What is the role of single-strand DNA binding proteins (SSBPs)?

They attach to separated strands to prevent them from re-forming the double helix.

What function do topoisomerases serve during DNA replication?

They cut and rejoin DNA downstream of the replication fork to relieve twisting and knots.

In which direction does DNA polymerase III synthesize DNA?

In the 5' to 3' direction.

What is required for DNA polymerase III to start synthesis?

A 3' end and a single-stranded template.

What is a primer in DNA synthesis?

A short stretch of nucleotides bonded to the template that provides a free 3' OH for DNA polymerase.

What are Okazaki fragments?

Short segments of DNA synthesized on the lagging strand during DNA replication.

What is nucleotide excision repair?

A process where defective bases are removed and replaced to repair DNA.

What is Xeroderma pigmentosum (XP)?

A rare genetic disorder that makes individuals extremely sensitive to UV light due to a decreased ability to repair DNA damage.

What causes nucleotide damage?

Chemicals such as hydroxyl groups and aflatoxins, as well as radiation like UV light.

What happens when UV light damages DNA?

It can cause covalent bonds to form between adjacent pyrimidine bases, creating kinks that stall DNA replication.

What is a mutation?

Any permanent change in an organism's DNA that can affect its genotype and phenotype.

What are point mutations?

Mutations that alter one or a few adjacent base pairs, often resulting from mistakes during DNA synthesis or repair.

What is an example of a point mutation?

Sickle-cell anemia, which is caused by a mutation in the gene for hemoglobin.

How can point mutations be induced?

By exposure to chemicals like nitrous acid or UV light.

What are the three mechanisms of gene transfer in bacteria?

Transformation, transduction, and conjugation.

What is the role of primase in DNA replication?

It synthesizes a short stretch of RNA that acts as a primer for DNA polymerase.

Why do gaps appear in the lagging strand during DNA replication?

Because DNA polymerase III moves away from the replication fork, leading to incomplete synthesis.

What happens if DNA damage is not repaired?

The cell may die due to the inability to replicate DNA properly.

What is the significance of DNA polymerase's proofreading ability?

It helps correct errors during DNA synthesis, reducing the frequency of mutations.

What is the function of helicase in DNA replication?

To unwind the DNA double helix by breaking hydrogen bonds between deoxyribonucleotides.

How does UV light specifically damage DNA?

By causing thymine dimers, which create kinks in the DNA structure and stall replication.

What is the consequence of improper DNA repair in individuals with XP?

They experience severe sunburn, skin changes, and an increased risk of skin cancer.

What is the overall process of DNA replication?

It involves several steps and enzymes, including unwinding the DNA, synthesizing new strands, and proofreading for errors.