Chromosomes Flashcards
What is chromatin?
DNA and its associated protiens.
What is the structure of a chromosome?
- 2 sister chromatids
- joined by centromere
- short arm at top and long arm at bottom
What is a homologous pair of chromosomes?
A pair of homologous chromosomes contains chromosomes of similar length, gene position, and centromere location. One from each parent.
What are telomeres, what are they used for?
Highly repetitive sequences at the end of each sister chromatid that act as protective caps. They allow for erosion to occur during replication, without damaging the coding part of DNA.
What is a chiasma?
The point at which cross over occurs.
What is ploidy?
The number of sets of chromosomes in a cell.
Notation: ānā
What are the names for:
n, 2n, 3n, >2n
n = haploid 2n = diploid 3n = triploid >2n = polyploid
What ca ploidy vary between.
Within an organism, e.g. gametes
Between individuals in a species.
What is a haplodiploid species?
Where one sex has haploid cells and the other has diploid cells. The haploid sex develops from unfertilized eggs and the diploid from fertilized.
e.g. bees
What does a higher ploidy result in?
- bigger organisms with bigger cells
- smaller seeds
e. g. banana
Why is odd ploidy usually described as an evolutionary dead end?
Organisms are generally infertile, kept alive by vegetative cloning.
What is an autopolyploid?
Appears when an individual has more than two sets of chromosomes, both of which from the same parental species.
(Accidental doubling of the ploidy.)
What is allopolyploidy?
Allopolyploidy, on the other hand, occurs when the individual has more than two copies but these copies, come from different species.
(hybridization)
