Genetics Answers

An XXX individual may be result of an abnormal complement of chromosomes in the egg or sperm. At what point of meiosis does this abnormality arise in female and in males? What is it due to? Make use of diagrams to explain your answers.

Primary spermatocyte with genotype AaBbee.

A & B loci are linked in cis configuration on long arm of an acrocentric chromosome.

E locus is on metacentric chromosome.

1. Show chromosomes containing genes at Metaphase I, Telophase I & II using diagrams.      
2. Show resulting Telophase I & II diagrams after crossover between A & B locus has occurred at Pachytene of Meiosis I.                                                                                                     

A primary spermatocyte has the genotype DdEe. These genes assort independently at Meiosis I. Show the chromosomes containing these genes at Metaphase I, Telophase I and Telophase II using diagrams. Diagrams must be clearly labelled and show metacentric chromosomes undergoing meiosis.                                                                                                         (8 x ½ = 4)

A sexually reproducing organism has a haploid number of 4, consisting of two metacentric chromosomes and 2 telocentric chromosomes. Diagrammatically show the primary meiocyte in metaphase I, and the results of meiosis I and meiosis II.    

An important function of meiosis is to reduce the chromosome number to exactly half.

How is this done? What makes such a process necessary?     

If half the chromosomes of a human primary oocyte segregate into the first polar body, which degenerates, why aren’t some of the different kinds of chromosomes of the diploid chromosome complement absent from the egg? 

The weaknesses/strengths and comment on potential future uses, with respect to reliability, validity and other factors on DNA extraction, Gel electrophoresis and cell transformation.

apply and use Mendel’s laws of independent assortment and segregation to analyse the results of the genetic crosses, and explicitly state conclusions.

• Apply Mendel’s laws of independent assortment and segregation to analyse the results of the genetic crosses. You should make clear conclusions based on the results. 

You must use correct scientific terminology throughout your work including the following terms:

• allele, genotype, phenotype, heterozygous, homozygous, carrier, affected/sufferer, non-affected/non-sufferer