A marine biologist prepared chromosome spreads from the embryonic cells of a marine polychaete worm to construct its karyotype.
During the preparation, the cells (normally maintained in seawater) were incubated in a dilute salt solution with a higher (less negative) water potential than the intracellular fluid of the cells. Explain the mechanism by which this treatment facilitates the separation of chromosomes within the cell without causing cell lysis.
To construct the karyotype, the biologist groups the observed chromosomes into homologous pairs. Define what is meant by a homologous pair of chromosomes.
In the marine environment, many species of bacteria coexist with the polychaete worm. State two structural differences between the arrangement of DNA in a prokaryotic bacterium and the DNA in a eukaryotic chromosome of this worm.
A cytogeneticist prepared a chromosome spread from a mammalian cell culture to analyze its karyotype.
During the preparation of the chromosomes for microscopy, the cells were placed in a solution that had a slightly higher (less negative) water potential than the cell cytoplasm. Suggest two steps in the process of how this procedure moved the chromosomes apart without bursting the cell.
The chromosomes in the karyotype are arranged in homologous pairs. What is a homologous pair of chromosomes?
Give two ways in which the arrangement of prokaryotic DNA is different from the arrangement of eukaryotic DNA in the chromosome spread.
A veterinary research lab is analyzing canine tumor cells to map their chromosomal abnormalities.
During the preparation of a mitotic chromosome spread, the tumor cells were incubated in a dilute salt solution with a higher (less negative) water potential than the cytoplasm of the cells. Explain two steps in the process of how this incubation helps to separate the chromosomes from one another without causing cell lysis.
The resulting chromosomes are aligned and paired up to produce a karyotype. What is meant by a homologous pair of chromosomes?
Contrast the arrangement of eukaryotic DNA in this chromosome spread with the arrangement of DNA in prokaryotic cells by giving two structural differences.
Practise AQA A Level Biology DNA, genes and chromosomes with exam-style questions for A Level Biology. 3 questions, matched to the AQA A Level Biology (7402) specification and written in Paper 1, Paper 2 and Paper 3 style. Every question includes a full worked solution and mark scheme, so you can see where marks are awarded rather than just whether you got the answer right.