Topic 13 Chromosomes: Carriers Of Genes Flashcards
What is a kinetochore?
A protein structure surrounding the centromere. Kinetochore forms the attachment point for spindle fibres that are necessary for the orderly movement of chromosomes in cell division.
What is a telomere?
The end of a chromosome that consists of DNA made up of many thousands of repeated sequences of base pairs.
What is a karyotype?
An arrangement of chromosomes by size and centromere position into matching or homologous pairs.
How are karyotypes used?
Karyotypes are used to assist in the analysis of the chromosomes that are present in cells. The chromosome images are organised in a pattern according to international convention.
How is a karyotype produced?
By cutting out and organising pictures of stained chromosomes photographed during metaphase of mitosis. This arrangement enables any abnormalities in either number or structure of the chromosome to be quickly identified.
How are the autosomes matched?
Banding pattern, centromere position, length and presence of satellites.
What does homologous and non-homologous mean in reference to chromosomes?
The members of each matching pair of chromosomes, such as the two number 5 chromosomes are said to be homologous. Non matching chromosomes, such as the number 5 and 14 chromosomes are nonhomologous.
How do changes in total number of chromosomes occur?
This is a condition in which the chromosome number is more or less that the normal diploid or haploid cell. In meiosis, sometimes the normal separation of homologous chromosomes does not occur during meiosis 1 or sister chromatids fail to separate during meiosis 2. Gametes can end up with more or less than the normal number of chromosomes, nondisjunction.
What can nondisjunction of homologous chromosomes result in?
- gametes that lack one member of a homologous pair. If a gamete lacks anautosome and it is involved in fertilisation, the zygote is not viable.
- it can result in gametes that contain 2 chromosomes of the homologous pair. If a gamete with the wrong number of chromosomes is fertilised, the resulting zygote will also have an abnormal number, which has deleterious effects on development, resulting in a syndrome. Most chromosomal abnormalities result in death.
What is deletion in chromosomes?
A break may occur at two points on the chromosome and the middle piece falls out, the two ends then rejoin to form a chromosome deficient in some genes, or the end of a chromosome could break off and become lost.
What is inversion in chromosomes?
The middle piece of the chromosome falls of out and rotates through 180 degrees then rejoins. There is no loss of genetic material, the genes will be in reverse order for this segment of the chromosome.
What is translocation in chromosome?
The movements of a group of genes between different chromosomes, it occurs when a piece of one chromosome breaks off and joins another non homologous chromosome. This causes major problems when the chromosomes are passed to gametes, some will receive extra genes while others will be deficient.
What is duplication in chromosomes?
A segment is lost from one chromosome and is added to its homologue. The chromosome with the segment removed is deficient in genes. Some gametes will receive double the genes while others will have no genes for the affected segment.
What is cri du chat syndrome?
A specific deletion of chromosome number 5; these children have severe mental retardation, a small hand with unusual facial features and a cry that sounds like a distressed cat.
What genetic information is not available from karyotype analysis?
The specific base sequence DNA, point mutations or frame shifts in nucleotide sequence and types of genes.
