DNA and Chromosomes

This set of flashcards summarizes key concepts from a lecture on DNA and chromosomes, covering genetics, cell biology, and molecular mechanisms.

What is the basic unit of heredity in living organisms?

Gene

What structure contains the genetic material in eukaryotic cells?

Nucleus

What is the main component of chromosomes?

DNA and protein

Who proposed the Chromosomal Theory of Inheritance?

No specific person, the theory emerged in the early 1900s.

What significant role did Griffith's experiment in the 1920s demonstrate?

Transformation in bacteria and the notion of genetic material.

What did Watson and Crick propose in 1953?

The structure of DNA as a double helix.

What is the term for the molecule that carries the heritable 'transforming principle'?

DNA.

What is the composition of a nucleotide?

Phosphate, sugar, and a nitrogenous base.

What type of bond links nucleotides in a DNA strand?

Phosphodiester bond.

Which bases pair together in DNA?

Adenine pairs with Thymine, and Guanine pairs with Cytosine.

What is the structure of DNA described as?

A double helix.

What happens to DNA during the cell cycle?

It replicates and segregates into daughter cells.

What are the two stages of the cell cycle?

Interphase and M phase (cell division).

Where are nucleosomes located?

On the DNA wrapped around histone proteins.

What do telomeres do?

Protect the ends of chromosomes from degradation.

What is the main function of chromosomes?

To carry genes.

What is euchromatin?

Less condensed chromatin that contains active genes.

What is heterochromatin?

Highly condensed form of chromatin, usually transcriptionally inactive.

What process does the SMC Ring Complex facilitate?

Formation of chromatin loops.

How do histone modifications affect chromosome structure?

They can influence gene expression and chromatin accessibility.

In which phase does chromosome duplication occur?

Interphase.

What are sister chromatids?

Identical copies of a chromosome linked at the centromere.

What is the role of the nucleolus in interphase cells?

Assembly of ribosomal units.

What is the purpose of chromosome 'painting'?

To identify different chromosomes under a microscope.

What do acetylation and methylation of histones commonly regulate?

Gene expression.

What occurs during X-inactivation in female mammals?

Randomly selected X chromosome becomes inactivated.

What is the net result of DNA packaging into chromosomes?

DNA is condensed into a mitotic chromosome 10,000-fold shorter.

What is the result of Griffith's transformation experiment?

Demonstrated that DNA serves as genetic material.

What occurs at the centromere during cell division?

It serves as the attachment point for spindle fibers.

What does the term 'nucleosome' refer to?

A unit of genetic material consisting of DNA wrapped around histone proteins.

How do cohesins contribute to chromosome structure?

By holding sister chromatids together.

What facilitates the condensation of chromatin?

Cohesin and condensin complexes.

What is the main function of the mitotic spindle?

To separate chromosomes during mitosis.

How many base pairs are typically in a nucleosome?

About 200 nucleotide pairs.

What does the term 'chromatin' refer to?

The material that makes up chromosomes, consisting of DNA and proteins.

What experimental evidence established DNA as the genetic material in the early 1940s?

Studies of bacterial transformation and viral infection.

What is the significance of base pairing in DNA?

Ensures accurate replication and transcription.

What is the length of a DNA molecule reduced to when packaged into a chromosome?

10,000-fold shorter than its full length.

What kind of chemicals can modify histones?

Acetyl groups, methyl groups, phosphate groups.

What cellular structures are visualized by chromosome painting techniques?

Individual chromosomes in a karyotype.

What happens to chromatin during cell division?

It condenses into visible chromosomes.

What is the role of ATP in chromatin remodeling complexes?

Provides energy to change the position of DNA around histones.

How does heterochromatin affect gene expression?

It typically represses gene activity.