Biology 9 Lesson 24 : Chromosome number mutations (cont’d)
1. Theoretical Summary
– Polyploidy is an organism in which the whole set of chromosomes in a somatic cell increases by multiples of the haploid set n (greater than 2n).
– In polyploid cells, the chromosome set is doubled, so the amount of DNA also increases accordingly, so the synthesis of organic substances is stronger, making the polyploid body grow faster, organs large vegetative and great resistance.
- This ability in polyploid plants is widely used in the field of horticulture.
– Polyploidy is quite common in plants and has been applied in plant breeding:
- Increase crop size to increase wood yield.
- Increase the size of stem, leaves and tubers to increase the yield of agricultural products.
- Breeding high yielding varieties to increase tolerance to adverse environmental conditions.
– Polyploidy is only performed in some animals and not found in humans.
b. Mechanism of polyploidy
– There are many factors that lead to polyploid formation, divided into two main types:
External environmental factors:
- Physical agents: radiation, temperature…
- Chemical agents: Consixin, pesticides…
+ Internal environmental factors: Intracellular disorders…
There are two mechanisms of polyploid formation:
- The duplication of chromosomes in the zygote without segregation results in a polyploid (a).
- Non-mitigation gametophyte formation and their fusion during fertilization (b).
c. Meaning of polyploidy
– Creating high-yielding plant varieties that bring economic efficiency to meet the increasing needs of people.
– Contribute to the formation of new species.
2. Illustrated exercise
The radish species has 2n=18. Determine the number of chromosomes in the haploid form of the species, the number of chromosomes in the vegetative cells of the triploid and the tetraploid of the species?
- The number of chromosomes in the haploid form of the species is: n=9.
- The number of chromosomes in the vegetative cell of a triploid species is: 3n=27.
- The number of chromosomes in the vegetative cells of the tetraploid of the species is: 4n=36.
3.1. Essay exercises
Question 1: How is polyploid formation by mitosis and meiosis unusual?
Verse 2: Can polyploids be recognized by the naked eye or by what signs? How can their characteristics be used in plant breeding?
Question 3: Compare polyploid and heterozygous formation
3.2. Multiple choice exercises
Question 1: What is a polyploid mutation?
A. Chromosomes are changed in structure
B. Chromosomes have a few extra or missing chromosomes
C. Chromosomes increase in multiples of n and greater than 2n
D. Chromosomes increase and decrease in multiples of n
Verse 2: Polyploidy is actually found in which group of organisms?
Question 3: An aneuploidy is a change in the number of autosomes –
A. a pair of chromosomes.
B. several pairs of chromosomes.
C. one or more pairs of chromosomes.
D. all pairs of chromosomes.
Question 4: Which of the following is true about polyploidy and polyploidy?
a) Polyploidy is the phenomenon of number mutation in all pairs of chromosomes, with the set of chromosomes in somatic cells being multiples of n (3n, 4n, 5n…).
b) Organisms with cells whose chromosome sets are multiples of n are called polyploidy.
c) Polyploidy only occurs in nature, not in livestock and plants.
d) Polyploidy has the ability to increase assimilation, change the size and increase the organism’s resistance to adverse conditions.
After completing this lesson, you should:
- Describe the concept and characteristics of polyploidy.
- List some practical applications of polyploidy.
- Analyze the mechanism of polyploid formation.