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Mutations

Mutations

Mutations are changes in the sequence of DNA. These changes can occur spontaneously or they can be induced by exposure to environmental factors. Mutations can be characterized in a number of different ways: whether and how they alter the amino acid sequence of the protein, whether they occur over a small or large area of DNA, and whether they occur in somatic cells or germline cells.
Chromosomal Alterations Are Large-Scale Mutations
While point mutations are changes in a single nucleotide in...

Nucleotide Excision Repair

Nucleotide Excision Repair

DNA Distortion and Damage
Cells are regularly exposed to mutagens—factors in the environment that can damage DNA and generate mutations. UV radiation is one of the most common mutagens and is estimated to introduce a significant number of changes in DNA. These include bends or kinks in the structure, which can block DNA replication or transcription. If these errors are not fixed, the damage can cause mutations, which in turn can result in cancer or disease depending on which sequences are...

Meiosis I

Meiosis I

Meiosis is the division of a diploid cell into haploid cells forming sperm and eggs in animals through differentiation. Meiosis I is the first stage of meiosis, where the genetic recombination of homologous chromosomes and the reduction of the ploidy level by half occurs.
Prophase I is the most extended and complex step of meiosis I characterized by synapsis, chromosome pairing, and recombination of the homologous chromosomes. This process is facilitated by a proteinaceous structure called the...

Meiosis vs. Mitosis

Meiosis vs. Mitosis

Cell division is necessary for growth and reproduction in organisms. Mitosis aids cell growth and development by dividing somatic cells. In contrast, meiosis causes the division of germ cells and plays an essential role in sexual reproduction. Due to their unique functional requirements, mitosis and meiosis differ from each other in multiple aspects.
Before the start of mitosis and meiosis I, the cell synthesizes DNA, resulting in two homologous copies of each chromosome. DNA synthesis is...

X and Y Chromosomes

X and Y Chromosomes

Among mammals, the gender of an organism is determined by the sex chromosomes. Humans have two sex chromosomes, X and Y. Every human diploid cell has 22 pairs of autosomes and one pair of sex chromosomes. A human female has two X chromosomes, while a male has one X chromosome and one Y chromosome.
The germline cells such as egg and sperm cells carry only half the number of chromosomes, i.e., 22 autosomes and one sex chromosome. All eggs have an X chromosome, while sperm cells can carry an X or...

Lampbrush Chromosomes

Lampbrush Chromosomes

In 1882, Flemming observed lampbrush chromosomes (LBC) in salamander eggs. Later in 1892, Rückert observed LBCs in shark egg cells and coined the term "lampbrush chromosomes" because they looked like brushes used to clean kerosene lamps.
LBCs are made up of two pairs of conjugating homologous chromatids. Each chromatid consists of alternatively positioned regions of condensed-inactive chromatin and loosely placed-active side loops, which can be contracted and extended. The loops resemble the...

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Related Experiment Video

Updated: Jun 19, 2026

The Lambda Select cII Mutation Detection System

The Lambda Select cII Mutation Detection System

Published on: April 26, 2018

DIFFERENTIAL SENSITIVITY OF PROPHASE POLLEN TUBE CHROMOSOMES TO X-RAYS AND ULTRAVIOLET RADIATION.

¹Agricultural Experiment Station, East Lansing, Michigan.

The Journal of General Physiology

|October 30, 2009

Summary

This study used the pollen tube technique to examine Tradescantia chromosome sensitivity to x-rays and ultraviolet light during prophase. Sensitivity varied with germination time, influenced by nuclear changes and radiation type.

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Published on: July 3, 2015

Area of Science:

Plant genetics
Radiation biology
Cell biology

Background:

Understanding chromosome sensitivity to mutagens is crucial for radiobiology.
The generative nucleus in Tradescantia pollen undergoes significant changes during germination.

Purpose of the Study:

To investigate the sensitivity of Tradescantia prophase chromosomes to x-rays and ultraviolet radiation.
To correlate chromosome sensitivity with dynamic changes in the generative nucleus.

Main Methods:

Utilized the pollen tube technique for observing Tradescantia microspore development.
Exposed pollen to controlled doses of x-rays and ultraviolet radiation at various germination stages.
Quantified chromosome breaks as a measure of sensitivity.

Main Results:

Ultraviolet sensitivity decreased over time, with no breaks observed after 11 hours.
X-ray sensitivity peaked at 4 hours and declined, with no breaks after 10 hours.
Chromosome breakage correlated with nuclear water uptake and spiralization events.

Conclusions:

Chromosome sensitivity to radiation is temporally regulated during germination.
Nuclear events like hydration and spiralization are key determinants of x-ray sensitivity.
Further research is needed to elucidate the factors influencing ultraviolet sensitivity, potentially involving the nucleic acid cycle or chromosome structure.