Biology: Chromosomes and DNA Structure

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Questions and Answers

What is the primary purpose of mitosis in eukaryotic cells?

To initiate metabolic processes

To produce gametes for sexual reproduction

To increase the number of chromosomes in daughter cells

To repair damaged tissues and promote growth (correct)

Which phase of the cell cycle is primarily responsible for DNA replication?

G1 phase

G2 phase

S phase (correct)

M phase

During which phase of mitosis do the chromosomes align at the cell's equator?

Prophase

Metaphase (correct)

Anaphase

Telophase

What is cytokinesis?

The division of the cytoplasm during cell division Signup and view all the answers

In which type of cells does mitosis primarily occur?

Somatic (body) cells Signup and view all the answers

What is the primary function of chromosomes?

To store and transmit genetic information Signup and view all the answers

Which of the following best describes the structure of DNA?

A double-helix structure Signup and view all the answers

What is the name of the protein-DNA complex that makes up chromosomes?

Chromatin Signup and view all the answers

How many chromosomes are typically found in a human somatic cell?

46 Signup and view all the answers

Which of the following is NOT a component of a nucleotide in DNA?

Amino acid Signup and view all the answers

What role do histones play in the structure of chromosomes?

They help maintain the shape of chromosomes Signup and view all the answers

What are chromatids?

Identical copies of genetic material Signup and view all the answers

What is the primary characteristic of the centromere in a chromosome?

It is the site where chromatids join Signup and view all the answers

What is the primary function of non-histone proteins?

They control the activity of specific regions of DNA. Signup and view all the answers

How many chromosomes do normal human females have?

46 chromosomes consisting of 22 pairs of autosomes and 2 X chromosomes. Signup and view all the answers

Which of the following statements regarding haploid and diploid cells is true?

Haploid cells have only one set of chromosomes. Signup and view all the answers

During which process do chromosomes number become halved?

Meiosis Signup and view all the answers

If a diploid cell has 24 chromosomes, how many chromosomes will be found in its haploid cells?

12 Signup and view all the answers

What defines the sex chromosomes in humans?

They determine the organism's reproductive system. Signup and view all the answers

What is the total number of chromosomes found in a cat?

32 Signup and view all the answers

Which statement about the number of chromosomes across different organisms is accurate?

Chromosome numbers can vary significantly between species. Signup and view all the answers

Study Notes

Chromosomes

Thread-like structures found in the nucleus of cells.
Composed of DNA and proteins.
Carry genetic information that determines traits and functions.
Humans have 23 pairs of chromosomes (46 total).
Compact packages of genes and other DNA in cells.

DNA

Long thin molecule that stores genetic information.
DNA in a human cell is estimated to consist of six billion pairs of nucleotides.

Structure of Chromosomes

Two main parts:
- Chromatids: identical copies of genetic material
- Centromere: where chromatids join

Importance of Chromosomes

Store and protect genetic material.
Ensure accurate distribution of DNA during cell division.
Determine inheritance of traits.
Essential for proper growth, development, and function of organisms.

Histones & Non-Histones

DNA in eukaryotic cells wraps tightly around proteins called histones.
Histones help maintain the shape of chromosomes and aid in the tight packing of DNA.
Non-histone proteins are generally involved in controlling the activity of specific regions of the DNA.
Chromatids form as the DNA makes a copy of itself before cell division.
When cells divide, each new cell receives one chromatid from each chromosome.

Centromeres

Especially important for the movement of chromosomes during cell division.

Chromosome Numbers

Human and animal chromosomes are categorized as either sex chromosomes or autosomes.
Sex chromosomes determine the sex of an organism and may carry genes for other characteristics in humans.
Sex chromosomes are X or Y.
Normal females have two X chromosomes.
Normal males have an X and a Y chromosome.
Humans have 46 chromosomes = 23 pairs.

Number of Chromosomes in Other Organisms

Cat = 32
Dog = 78
Horse = 64
Fruit fly = 8

Cell Division

Process by which cells produce offspring.
In prokaryotes:
- Binary fission: division of a prokaryotic cell into two offspring cells.
- Binary fission consists of three general stages.

The Cell Cycle

Repeating set of events that make up the life of a cell.
Cell division is one phase of the cell cycle.
The time between cell division is called interphase.
During cell division, the chromosomes and cytoplasm are equally divided between two offspring cells.
Cell division consists of mitosis and cytokinesis.
Mitosis, or M phase, is the division of the nucleus of a cell.
Cytokinesis is the division of the cytoplasm of the cell.

Mitosis

Division of the nucleus, occurring during cell division.
A continuous process divided into four phases:
- Prophase
- Metaphase
- Anaphase
- Telophase

Meiosis

Process of cell division in eukaryotic cells, resulting in the production of four daughter cells, each with half the number of chromosomes as the parent cell.
Crucial for sexual reproduction.
Occurs in germ cells (reproductive cells).
Produces gametes (sperm and egg cells).

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Description

Explore the fundamental concepts of chromosomes and DNA in this quiz. Learn about the structure, function, and importance of these genetic materials in living organisms. Test your knowledge on genetic inheritance, the role of histones, and the mechanics of cell division.