Cytogenetics of Nuclear Chromosomes Flashcards
Recall the changes in number, position, and condensation state of nuclear chromosomes during mitotic and meiotic cell cycles Explain the relationship between Mendelian inheritance and the behaviour of meiotic chromosomes and gametes Understand and interpret basic pedigree analyses and karyotypes
Define cytogenetics
Using microscopic analysis of cellular structures (especially nuclear chromosomes) to investigate inheritance
Compare and contrast mitosis and meiosis.
Mitosis produces somatic cells, meiosis gametes. In Anaphase 1 in meiosis, the homologous chromosomes are pulled apart not the sister chromatids like mitosis. Recombination occurs in mieosis. Mitosis produces 2 diploid cells, meiosis produces 4 haploid cells. Scientists discovered that chromosomes carry the genetic material by movements in mitosis and meiosis
At which stage in mitosis/meiosis are chromosomes examined via cytogenetics? How is this done?
Metaphase. It is only possible it metaphase because this is where the chromosomes are condensed and distinguishable. The cells are halted in metaphase and chromosomes are counted and stained. This is called a metaphase spread.
Describe a metaphase spread in relation to karyotype and G banding.
The karyotype is the number and appearance of a complete set of chromosomes. The chromosomes are distinguished by their banding patterns - Giesma banding.
Explain FISH and how it can be used to help identify chromosomal abnormalities
Fluorescent in situ hybridisation involves labelling a region of interest with complementary fluorescent molecules. It is used to visualise regions of interest in the chromosome.
Summarise the Chromosomal theory of Mendelian Inheritance.
Walther Fleming & von Waldemeyer see & name chromosomes in mid 19th Century.
Weismann proposes that genetic material is nuclear and carried on chromosomes, and inheritance is through cells distinct from somatic cells - germ cells.
Sutton & Boveri rediscover Mendel’s work and connect chromosomes with inheritance.
Boveri discovered gametes are haploid, and through fertilisation zygotes become diploid.
Sutton noticed that pairs of homologous chromosomes separated into daughter cells which leads to haploid gametes with 1 set of chromosomes.
In 1905, Nettie Stevens and Edmund Wilson both independtly showed that gender is determined by sex chromosomes and the XY relationship in males and females.
In 1910, Morgan used genetic crosses to show that eye colour allele is on X.
Highlight the similarities between Mendel’s “units of inheritance” and chromosomes
Mendel’s Chromosomes
pair of alleles Somatic cells contain homologous pair
allele separates in gamete formation chromosomes do too
Alleles paired again at fertilisation Chromosomes too
