30 Questions
What is the significance of having two copies of each gene in an organism?
This allows for the possibility of having different alleles of the same gene, one inherited from each parent.
What do ideograms represent in a cell nucleus?
They represent the long coiled DNA molecule in one chromosome.
What is the difference between a homozygous and heterozygous individual in terms of gene alleles?
A homozygous individual has two identical alleles of a gene, while a heterozygous individual has two different alleles of a gene.
During which stage of the cell cycle can chromosomes be seen?
During cell division, specifically during mitosis.
What is the relationship between the two chromatids in a chromosome during mitosis?
They are exact replicas of each other, containing the same alleles.
What is the difference between chromatin and a chromosome?
Chromatin is the DNA-histone complex present during interphase, while a chromosome is the compact, X-shaped form of chromatin visible during mitosis.
What is the cell cycle, and what are the three main stages involved in this process?
The cell cycle is a regulated process in which cells divide into two identical daughter cells, and it consists of three main stages: interphase, mitosis, and cytokinesis.
What is the significance of mitosis in terms of growth, repair, and reproduction?
Mitosis contributes to growth, repair, and asexual reproduction.
What is the result of the process of meiosis, and what is the significance of this outcome?
The result of meiosis is haploid gametes.
What is polysomy, and what is an example of a condition that results from this phenomenon?
Polysomy is a condition where there are three or more sets of chromosomes, and an example of a condition that results from this is Down's syndrome.
What is monosomy, and what is an example of a condition that results from this phenomenon?
Monosomy is a condition where there is a single set of chromosomes, and an example of a condition that results from this is Turner's syndrome.
What is the role of the cell cycle in the development of an organism, and what would happen if it were not regulated?
The cell cycle plays a crucial role in the development of an organism by allowing for growth, repair, and reproduction. If it were not regulated, it could lead to uncontrolled cell growth and potentially cancer.
What is the primary purpose of meiosis and sex in terms of genetic variation?
To introduce genetic variation, which allows species to adapt to their environment and evolve.
What is the minimum number of chiasmata found in a bivalent?
One
What is the result of crossing over in terms of allele combination?
Maternal and paternal alleles can be combined despite being on physically different chromosomes.
What is the role of chiasmata in meiosis?
They hold the bivalent together
What is the significance of genetic variation in a population?
It allows species to adapt to their environment and evolve.
During which stage of meiosis does crossing over occur?
Prophase I
What is the primary cause of nondisjunction during meiosis?
A fault in anaphase, where the chromatids or chromosomes fail to separate and move to opposite poles.
What is the outcome of polysomy in a chromosome?
The resulting zygote will have the wrong number of chromosomes.
What is trisomy, and how does it occur?
Trisomy is the presence of three copies of a chromosome instead of two, occurring when a gamete with an extra chromosome is fertilized by a normal gamete.
What is the exception to the general rule that trisomy is fatal?
Trisomy 21, which causes Down syndrome, is the exception.
What is the result of trisomy 21?
Down syndrome, which has severe consequences on the individual's phenotype.
At which stage of meiosis can nondisjunction occur?
Anaphase I or anaphase II.
What is the term for the presence of a single copy of a chromosome in a cell, and what is the exception to its fatal effects?
Monosomy; the exception is the X chromosome, as seen in Turner syndrome.
What is the genetic composition of a gamete with nondisjunction, and what is the resulting zygote's ploidy?
Diploid; triploid.
What is the frequency of Turner syndrome in births, and how do X0 individuals appear?
About 1 in 5000; they appear female.
What is the difference between the genetic makeup of X0 individuals and normal females?
X0 individuals have one copy of the X chromosome, while normal females have two copies.
What is an example of a triploid organism in nature, and how common is polyploidy in plants?
Apples; very common.
What is the effect of polyploidy on the phenotype, and how does it compare to the effects of monosomy?
Little adverse effect; monosomy is usually fatal, whereas polyploidy has a minimal impact on the phenotype.
Test your knowledge of Cell Cycle, Mitosis, Meiosis, Chromosome Mutations, and Sexual Reproduction in Humans and Plants with this quiz from Heckmondwike Grammar School Biology Department. This quiz covers the contents of Edexcel A-Level Biology B Unit 3.
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