Gene and Chromosome Dynamics Flashcards
What is a karyotype?
an individual’s full set of chromosomes
What is a chromosome made up of?
2 sister chromatids joined by a centromere
What is a gene loci?
the location for a specific gene on a specific type of chromosome
When does DNA within chromosomes become visible?
when they become compact, sausage-shaped structures in preparation for cell division
What is recombination?
the rearrangement of DNA sequences by the breakage and re-joining of chromosomes or chromosome segments
When does recombination occur?
during the crossing over event in meiosis (prophase I)
What is translocation?
where a chromosome breaks and either the whole thing or a portion of it reattaches to a different chromosome to produce non-homologous chromosomes
What is the detection of chromosomal translocations important for?
the diagnosis of certain genetic diseases and disorders
What is ataxia?
the progressive loss in motor skills that can arise due to translocation
When does chronic myelogenous leukaemia arise?
when the bone marrow produces too many white blood cells caused by a translocation between chromosomes 9 and 22
What do insertion mutations involve?
the addition of one or more nucleotides into a segment of DNA
What are the 2 types of chromosomal insertion?
- interchromosomal - when a segment of one chromosome is translocated and inserted into an interstitial region of another non-homologous chromosome
- intrachromosomal - when a segment of one chromosome is translocated and inserted into an a different region of the same chromosome
Why do deletion mutations shorten chromosomes and what can it lead to?
part of a DNA molecule not being copied during regulation and can lead to genetic diseases e.g. Cri du Chat syndrome
What are duplication mutations?
when one or more copies of a DNA segment is produced
What is chromosome segregation?
the partitioning of genetic material into 2 identical daughter cells driven by the mitotic spindle
What can failure in chromosome segregation lead to?
aneuploidy
What causes Down syndrome?
2 copies of chromosome 21
What is a chiasma?
the point of contact between 2 chromatids of homologous chromosomes
How are sister chromatids in each pair of chromosomes connected?
by cohesin proteins along the entire lengths as well as at their centromeres
What is a bivalent?
the whole unit of 2 chromosomes (4 chromatids)
What holds the 2 duplicated homologs together?
the combination of the chiasma and the tight attachment of the sister chromatids
Do sister chromatids of the same chromosome exchange with each other?
no
What is the smallest human chromosome and how much of the human genome does it make up?
chromosome 22, 1.5%
What does most of the left arm of chromosome 22 consist of?
short repeated sequences of DNA that are packaged in heterochromatin
