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Questions and Answers

What is the primary function of chromatin?

Facilitating DNA replication

Controlling gene expression

Protecting DNA from damage (correct)

Storing genetic information

What is the key structural unit within eukaryotic chromatin?

Nucleosome (correct)

Nucleotide pair

Chromosome

Histone

Why is eukaryotic DNA organized into chromosomes?

To increase nucleotide stability

To enhance DNA replication

To prevent chromosome breakage (correct)

To promote histone synthesis

What is the significance of nucleosomes in chromatin structure?

They help in DNA coiling around histones Signup and view all the answers

Which proteins are primarily involved in the formation of chromatin?

Histone proteins Signup and view all the answers

In eukaryotic cells, where is the genetic information stored?

Nucleus Signup and view all the answers

What did Watson and Crick suggest about the replication of the double helix?

Each strand acts as a template for a new strand Signup and view all the answers

What is the complex combination made up of DNA and proteins in the nucleus called?

Chromatin Signup and view all the answers

Why does the DNA need to be highly organized or condensed in a cell?

To fit billions of nucleotides inside the limited nuclear space Signup and view all the answers

What is a thread-like coiled structure suspended in nucleoplasm known as?

Chromatin Signup and view all the answers

What is the primary function of histones in eukaryotic cells?

To package and organize DNA into chromosomes Signup and view all the answers

What is the significance of the centromere in eukaryotic chromosomes?

It facilitates the separation of sister chromatids during cell division Signup and view all the answers

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

S phase Signup and view all the answers

What is the primary function of the replication fork during DNA replication?

To unwind the double-stranded DNA molecule Signup and view all the answers

Which of the following statements about the cell cycle is correct?

The G1 checkpoint determines if the cell will divide or undergo apoptosis Signup and view all the answers

What is the primary function of telomeres in eukaryotic chromosomes?

To protect the ends of chromosomes from degradation Signup and view all the answers

What is the significance of replication bubbles during DNA replication?

They allow DNA replication to occur at multiple sites simultaneously, speeding up the process Signup and view all the answers

Which of the following statements about somatic cells is correct?

Somatic cells do not divide regularly Signup and view all the answers

What is the primary function of the G2 checkpoint in the cell cycle?

To ensure that DNA replication has occurred properly before mitosis Signup and view all the answers

What is the primary function of the mitotic phase in the cell cycle?

To separate the replicated genetic material and cytoplasmic contents into two daughter cells Signup and view all the answers

Study Notes

Chromatin Structure

Chromatin is composed of double-stranded DNA wrapped around an octamer of histone proteins.
160 bp of DNA wraps twice around a nucleosome core.
40 bp of linker DNA connects nucleosomes.

Histones

Histones are the main structural proteins found in eukaryotic cells.
They are low molecular weight, basic proteins with a high proportion of positively charged amino acids.
Histones bind to DNA along most of its length, playing a crucial role in packing long DNA molecules.

Chromosomes

Chromosomes are organized structures of DNA and protein found in the nucleus.
They are composed of repeating 200 bp units called nucleosomes.
Chromosomes are the carriers of genes or units of hereditary.
They are condensed and visible during cell division.

Chromosome Structure

Chromosomes have telomeres at the ends to protect them.
They have a centromere that mediates migration during mitosis and meiosis.
Humans have 23 pairs of chromosomes, consisting of 22 pairs of autosomes and 1 pair of sex chromosomes.
Each gene is located at a specific gene locus on the chromosome.

DNA Replication

DNA replication occurs in the nucleus during the S phase of the cell cycle.
It is a semiconservative process that results in two new double-stranded molecules.
Each original single strand is paired with one newly made single strand.

Replication Fork and Bubble

A replication fork is a structure that forms within the nucleus during DNA replication.
It is created by helicases, which break the hydrogen bonds holding the two DNA strands together.
Replication bubbles allow DNA replication to speed up.

Cell Cycle

The cell cycle consists of two major phases: interphase and the mitotic phase.
During interphase, the cell grows and DNA is replicated.
During the mitotic phase, the replicated DNA and cytoplasmic contents are separated and the cell divides.

Phases of Cell Cycle

Interphase is divided into three stages: G1, S, and G2.
G1 is the primary growth stage, lasting 11 hours.
S is the genome replication stage, lasting 8 hours.
G2 is the secondary growth stage, lasting 4 hours.
M is the mitosis stage, lasting 1 hour.
C is the cytokinesis stage.

Checkpoints

G1 checkpoint is the main cell cycle checkpoint.
If DNA is damaged, apoptosis will occur.
Otherwise, the cell is committed to divide when growth signals are present and nutrients are available.
G2 checkpoint is the mitosis checkpoint.
Mitosis will occur if DNA has replicated properly.

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Description

Learn about how a cell's genetic information in the form of DNA is stored and organized in the nucleus. Explore the structure of eukaryotic DNA, its linear nature, and compaction into chromosomes by histones. Understand the importance of organization for the billions of nucleotides that make up DNA.