Genetics Answers

2.6) Albino mice lack pigment in their fur and eyes, Hybrids between pure coloured and pure albino mice are coloured (heterozygotes). If coloured and albino are alternatives for the gene locus, then:

• Is the albino or coloured allele dominant?

• What frequency of albino progeny (offspring) is expected from the crosses between heterozygous coloured mice?

• What types of progeny are expected if albino mice are mated?

• Why can’t you make an exact prediction of the types of progeny if coloured mice are mated?

2.6) What chromosomal phenomenon lessens the co-migration of loci located on the same chromosome and what is the significance of this phenomenon?

2.6) The location of two genes on the same chromosome would appear to violate Mendel’s rule of Independent Assortment. What term is used to describe this situation?

2.6) During which division of meiosis do Mendel’s rules of Segregation and Independent assortment apply?

2.6) 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 females and in males? What is it due to?

Answer the following questions with either True or False. Provide a justification for your choice.

1. Alleles occupy different loci on homologous chromosomes.
2. Although alleles govern the same kinds of characteristics, they do not necessarily contain identical information.
3. A hybrid cross involves individuals that have different alleles of one locus.

2.5) The common housefly has a haploid number of 6 consisting of 3 long chromosomes (one metacentric, one acrocentric, and one telocentric); 3 short chromosomes (one metacentric, one acrocentric, and one telocentric). Draw and label a typical housefly primary spermatocyte in Metaphase I and spermatozoa at Telophase II

At Metaphase I of human gametogenesis, each oocyte contains:

An aside: (1° Oocyte (2n) → 2° Oocyte (n) 1^st meiotic division → mature ovum (n) and other three gametes become polar bodies at end of meiosis after 2^nd division

1. How many chromosomes?
2. How many tetrads (bivalents)?
3. How many chromatids?
4. How many centromeres?

1. How many chromosomes are present in a diploid cell of a human?
2. How many of these chromosomes are autosomes and how many are sex chromosomes?
3. How many autosomes and sex chromosomes would a sperm have in its nucleus?

2.5) Why does the arrangement of chromosomes differ in the metaphase stage of mitosis and meiosis?