Biology Chapter 5: Chromosomes and Reproduction

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Questions and Answers

What is the number of chromosomes in diploid cells for Human body cells?

46 (correct)

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

G1 phase

Mitosis

S phase (correct)

G2 phase

What is the number of homologous chromosome pairs in a Leopard Frog?

26 pairs

13 pairs (correct)

12 pairs

14 pairs

Which process is the division of somatic (body) cells?

Mitosis Signup and view all the answers

What is the haploid number of chromosomes for a Housefly?

6 Signup and view all the answers

What type of eggs do queen bees lay that develop into drones?

Unfertilized eggs Signup and view all the answers

Which reproductive process results in the production of haploid spores in the sporophyte?

Meiosis Signup and view all the answers

In the life cycle of conifers, which phase do they spend most of their lives in?

Diploid generation Signup and view all the answers

What do gametophytes produce during their life cycle?

Haploid gametes Signup and view all the answers

Which of the following statements about spore formation is incorrect?

Spores are always produced asexually. Signup and view all the answers

What is the primary characteristic of a zygote in terms of stem cell potential?

It is totipotent. Signup and view all the answers

What happens to telomeres every time a cell divides?

They shorten. Signup and view all the answers

What does a significant shortening of telomeres indicate?

Potential for cancerous growth. Signup and view all the answers

By the end of metaphase in human cells, how many chromosomes are present?

46 Signup and view all the answers

What serves as a molecular clock for cellular aging?

Telomere length. Signup and view all the answers

How many chromatids are present in one human cell by the end of interphase?

92 Signup and view all the answers

What is the consequence of telomeres becoming too short?

The cell undergoes apoptosis. Signup and view all the answers

What is one ethical concern regarding stem cell research from a zygote?

Extracting stem cells from zygotes can destroy a potential human life. Signup and view all the answers

What type of tumor consists of abnormal cells that do not spread to other parts of the body?

Benign tumor Signup and view all the answers

Which of the following is NOT a method of cancer treatment mentioned?

Antibiotic Therapy Signup and view all the answers

What is the primary purpose of chemotherapy in cancer treatment?

To kill fast-growing cells Signup and view all the answers

What does metastasis refer to in the context of cancer?

The spread of cancer cells to other body parts Signup and view all the answers

Which type of twins are produced when a single fertilized egg splits into two?

Monozygotic twins Signup and view all the answers

Which of the following is considered a carcinogen?

X-rays Signup and view all the answers

What is a common characteristic of malignant tumors?

They can spread to other parts of the body Signup and view all the answers

What is a key developmental stage that stem cells undergo in the context of cloning?

Specialization into tissues Signup and view all the answers

What is the primary difference in cytokinesis between animal and plant cells?

Animal cells form a cleavage furrow, while plant cells form a cell plate. Signup and view all the answers

During which phase do daughter cells enter after cytokinesis?

G1 phase Signup and view all the answers

What structure is formed in plant cells to separate daughter nuclei?

Cell plate Signup and view all the answers

What role do proteins play in the cell cycle?

They control how often a cell goes through mitosis via checkpoints. Signup and view all the answers

Why do most cells in a healthy tissue sample appear to be in interphase or early prophase?

The majority of the cell cycle is spent in interphase. Signup and view all the answers

What are mutagens that specifically cause cancer called?

Carcinogens Signup and view all the answers

Which of the following is NOT a characteristic of plant cell mitosis?

Presence of centrioles. Signup and view all the answers

What might happen if cells were to divide uncontrollably?

Cancers may develop. Signup and view all the answers

What do homologous chromosomes consist of?

A pair of chromosomes with the same traits, one from each parent Signup and view all the answers

What is a karyotype?

A display of an individual's chromosomes ordered by size and length Signup and view all the answers

Which of the following correctly describes human chromosomes?

Humans possess 46 chromosomes, including 22 pairs of autosomes. Signup and view all the answers

Which of the following statements is true regarding the number of chromosomes and complexity?

Chromosome number is irrelevant to an organism's intelligence. Signup and view all the answers

What is the diploid number of chromosomes in human somatic cells?

46 Signup and view all the answers

What distinguishes sister chromatids from homologous chromosomes?

Sister chromatids are identical, whereas homologous chromosomes can have different alleles. Signup and view all the answers

Which statement about gametes is accurate?

Human gametes contain 23 chromosomes and are considered haploid. Signup and view all the answers

Which organisms are classified as polyploid?

Organisms that have more than two homologous chromosome sets in each cell Signup and view all the answers

Study Notes

Biology 30 - Cell Division

Cell division is the process by which a cell divides and creates new daughter cells.
Two types of cell division:
- Mitosis: Division of somatic (body) cells.
- Meiosis: Division of gametes (sex) cells.

Topic 1: Mitosis

Somatic cells vs. sex cells
Autosomes vs. sex chromosomes
Chromosomes vs. chromatin
Homologous chromosomes vs. sister chromatids
Haploid (n) vs. diploid (2n)
Stages of interphase: G1, S, G2
Stages of mitosis: prophase, metaphase, anaphase, telophase
Cancer, cloning, and stem cells
Telomeres & aging
Textbook pages: 556-571

Why do cells divide?

Replace damaged cells.
Growth of an organism.
Reproduction.

From the moment of fertilization...

Cells are continuously growing, dying, and being replaced.

Two Types of Cell Division

Mitosis:
- Somatic cells (body cells)
- Produces two identical daughter cells
Meiosis:
- Sex cells (gametes)
- Sperm and egg
- Produces four haploid (half the number of chromosomes) daughter cells.

Asexual Reproduction (Mitosis)

One parent passes copies of its genes to offspring without the fusion of gametes.
The daughter cell is a clone of the parent.
Genetic differences sometimes arise from mutations.

Sexual Reproduction (Meiosis)

Two parents produce offspring with unique combinations of genes inherited from both parents.
Meiosis creates variations, not exact replicas.
Crossing-over is the shuffling of genes in meiosis when gametes cells are created.
Higher genetic diversity means higher chances of survival when environmental conditions change.

Chromosomes

Structure: Condensed DNA organized structure.
Chromatid: Arm of the chromosome.
Centromere: Region in the middle of chromosome where sister chromatids attach.
Chromatin: DNA + proteins (histones)
Telomeres
Sister chromatids: Two identical chromatids after replication, attached at the centromere.

Karyotype

A display of chromosome pairs ordered by size and length.
In actual karyotypes, it can be difficult to see sister chromatids in each pair.
A picture of an individual's chromosomes.
Chromosomes are isolated, stained, and examined under a microscope, often using white blood cells.
The chromosomes in a karyotype differ in size, location of their centromere, and staining properties.

Chromosome Number

Chromosome numbers vary from species to species.
Human cells have 46 chromosomes (23 pairs)
- 22 pairs of autosomes
- 1 pair of sex chromosomes (either XX or XY)
More chromosomes do not necessarily correspond to higher intelligence or complexity.

The Cell Cycle

The process by which a cell divides and creates new daughter cells.
Has two main phases:
- Interphase: Normal cellular functions & DNA replication, growth stage
- Mitosis (M phase): DNA is divided and cytoplasm is divided to form two new daughter cells. This has multiple phases:
  - Prophase
  - Metaphase
  - Anaphase
  - Telophase
  - Cytokinesis (division of cytoplasm)

Preparing for Cell Division

Chromatin becomes highly compact as chromosomes become visible under a light microscope.
Chromosomes duplicate to form two identical sister chromatids.
Sister chromatids are joined at the centromere, a narrow region.

Haploid vs. Diploid

Haploid (n): one set of chromosomes. In humans, gametes (sperm and ova) are haploid.
Diploid (2n): two sets of chromosomes. In humans, all body cells (other than gametes) are diploid.

Division Stage (M-Stage)

Mitosis: Division of the nucleus
Cytokinesis: Division of the cytoplasm.

Mitosis stages (summary)

Prophase: Chromosomes condense, nuclear membrane breaks down.
Metaphase: Chromosomes line up at the cell's equator.
Anaphase: Sister chromatids separate and move to opposite poles.
Telophase: Chromosomes decondense, nuclear membrane reforms.

Mitosis (Amoeba Sisters)

A video about mitosis.

Mitosis (Summary, Purposes)

Mitosis: performed by all autosomes
It is a form of cell division that produces daughter cells.
Purposes: Growth, Maintenance, and Repair.

Mitosis and Growth

Example demonstrating how mitosis relates to growth.

Cancer and the Cell Cycle

Uncontrolled cell division may be caused by mutagens or agents that change an organism's genetic material. These include physical, chemical or biological origins. Mutagens can be classified as carcinogens.

Carcinogens

Cancer-causing substances that can lead to mutations in DNA.

Examples of carcinogens (summary)

UV radiation
X-rays
Chemicals in cigarettes
Unhealthy Drinking/Eating (alcoholic beverages, processed foods, etc.)
Environmental exposure (car exhaust, fumes, work chemicals)

Types of Tumors

Benign tumor: Cells remain at the tumor site and are unable to spread elsewhere in the body.
Malignant tumor: Cells lose their anchorage dependency and can leave the tumor site.

Treatment for cancer

Chemotherapy
Surgery
Radiation therapy
Immunotherapy

Cloning

Cloning is a form of asexual reproduction.
Identical offspring can be formed from a single cell or tissue of a parent organ.
Monozygotic twins form from a fertilized egg accidentally undergoing mitosis and splitting into two cells.
Dizygotic twins form from two separate eggs being fertilized by different sperm.

Animal Cloning Technology

Methods to artificially clone animals.

Stem Cell Research

Cloning-based research is focused on cloning individual cells, tissues, and organs.
This research uses cells that have not yet become specialized.

Stem Cell Ethics

Totipotent cells (a zygote) can develop into a complete organism, but usage is usually considered unethical.
Pluripotent stem cells can be easily obtained from adult tissues.

Scientists Create Human Eggs Using Stem Cells

Scientific breakthrough using stem cells to create human eggs.

Mitosis and Aging

Telomeres are caps at chromosome ends.
Every cell division results in telomere shortening.
Short telomeres may trigger cell death.
Telomere length can be a molecular clock for cell aging

Homozygous vs. Non-homozygous chromosomes

Homozygous Chromosomes: Same length and centromere position. Same genes, different alleles (e.g. Brown or blue eyes)
Non-homozygous Chromosomes: Different genes, different alleles

Meiosis overview:

Reduction of chromosome number from diploid (2n) to haploid (n) in sexual reproduction.
Two divisions: Meiosis I and Meiosis II
Results in four haploid cells, genetically distinct from each other.

Stages of Meiosis (Summary)

Important Note: Meiosis I and Meiosis II each have stages very similar to the individual stages of mitosis.
Prophase I: Chromosomes condense, homologous chromosomes pair up. Crossing-over occurs
Metaphase I: Homologous chromosomes line up at the middle of the cell
Anaphase I: Homologous chromosomes separate and move towards opposite ends of the cell
Telophase I: Chromosomes begin to uncoil, and cytoplasm divides; two haploid cells are formed.
Prophase II: Chromosomes condense, nuclear membrane breaks down.
Metaphase II: Chromosomes align at the cell's equator
Anaphase II: Sister chromatids separate and move to opposite poles.
Telophase II: Chromosomes decondense, nuclear membrane reforms, cytoplasm divides.

Alternation of Generations

Life cycle of some plants consists of two generations: Diploid generation (sporophyte) and Haploid generation (gametophyte)
The sporophyte produces haploid spores via Meiosis, which develop into the gametophyte. The gametophyte produces male & female gametes.

Reproductive Strategies

Mitosis is utilized in asexual reproduction
Meiosis is utilized in sexual reproduction
Most organisms' life cycles involve both methods

Spermatogenesis

Meiosis to produce sperm (male gametes).
Results in four viable sperm cells.

Oogenesis

Meiosis to produce eggs(female gametes)
Results in one functional egg and three polar bodies. Cytoplasm is not divided evenly.

Nondisjunction

Failure of chromosomes to separate during meiosis, leading to an incorrect number of chromosomes in gametes. A possible cause of genetic disorders.

Types of Nondisjunction

Nondisjunction during meiosis I yields abnormal gametes.
Nondisjunction during meiosis II yields abnormal gametes.

Monosomy

A condition with one less than the normal number of chromosomes.
example: Turner's Syndrome = 45, XO
Leads to physical and developmental problems.

Trisomy

A condition with one more than the normal number of chromosomes.
example: Down syndrome (Trisomy 21).

Cell Division and Twins

Fraternal twins: Formed from two separate ovum and sperm.
Identical twins: Formed from one ovum and sperm, but the zygote splits in two early in development.

Mitosis vs Meiosis

Mitosis: One division; creates two identical diploid cells.
Meiosis: Two divisions; creates four genetically different haploid cells.

Questions (sample)

How many chromosomes are present in a human cell at the end of interphase? 46
How many chromatids are present in a human cell at the end of metaphase? 92
How many chromosomes are present in a human cell at the end of anaphase? 92
How many chromosomes are present in a human cell at the end of Telophase? 46
How many chromatids are present in a human cell at the end of cytokinesis? 0

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Description

Test your knowledge on chromosomes, cell cycles, and reproduction processes with this engaging quiz. Explore questions related to diploid cells in humans, the life cycles of various organisms, and the specifics of gametophytes and spores. Ideal for students studying cell biology and genetics.