Mitosis, meiosis, chromosomes and genetics Flashcards
where is the telomere on a chromosome and what does it do
found at one end of the chromosome and stops them unraveling
what does telomerase do
rebuilds the telomere as they become smaller with each cell division
what does Bp mean
base pairs
which arm is shorter and which is longer on a chromosome, p or q
p is the shorter arm, p stands for petit
what dye stains G banding on chromosomes
Giemsa
what dye stains Q banding on chromosomes
Quinacrine
what happens in G0 of the cell cycle
the cell is mitotically inactive
what happens in S phase of the cell cycle
DNA and centrosome replication
what happens in G1 of the cell cycle
the cell grows and many intracellular components are replicated. the cell also undertakes cell monitoring to make sure that it can undergo the process of mitosis
what happens in G2 of the cell cycle
the cell grows more and also replicates it organelles, makes proteins and organises itself to undergo mitosis
what does a high number of mitoses indicate
a possible malignant tumour, only malignant tumors are graded, benign are not
how do many anti-cancer drugs work ?
they are more like anti-mitosis drugs e.g. Colchicine which prevents anaphase or taxol/vinca alkaloids which target the mitotic spindle
what does crossing over do and when does it occur
it makes the daughter cells genetically different from its parents and it only happens in prophase 1
what is spermatogonia
they are primordial/undifferentiated sperm cells
what are Oogonia
they are immature/primordial egg cells
what is gonadal mosaicism
In the gametes there is meant to be one population of identical spermatogonia/oogonia but in this case there are 2 or more due to a genetic mutation. This mutation is not present in the somatic cells and so the parent is healthy but the child can be affected. Most common on autosomal (non-sex) genes and X linked. e.g. Osteoporosis imperfecta
Prophase
- Chromatin condenses in chromosomes
- Centrosomes nucleate microtubules and move to opposite poles of the nucleus
Prometaphase
- Nuclear membrane breaks down
- Microtubules from centrosomes invade the nuclear space
- Chromatids attach to microtubules
Metaphase
chromosomes line up along the equatorial plane (metaphase plate)
Anaphase
- sister chromatids separate
- they are then pulled to opposite poles of the cell
Telophase
- Nuclear membranes reform
- Chromosomes unfold into chromatin
- Cytokinesis begins
Sperm production
- Primordial germ cells -> lots of mitoses -> spermatogonia
- mitotic divisions begin at puberty,
- the cytoplasm divides evenly and after meiosis II there are 4 equal gametes,
- they are continuously produced and the process takes 60-65 days
egg production
- primordial germ cell -> 30 mitoses -> oogonia
- Oogonia enter prophase 1 by the 8th month of intra-uterine life
- cells then enter ovulation 10-50 years later
- the cytoplasm is divided unequally so there is one huge egg cell and 3 smaller polar bodies that apoptose
- Meiosis 1 is completed at ovulation
- Meiosis 2 is only completed if fertilisation occurs
what is non-disjunction
failure of chromosome pairs to separate in meiosis 1 or if sister chromatids fail to separate in meiosis 2
what is a disease allele
the allele that carries the pathogenic variant
what is polymorphism
frequent hereditary variations at a locus
what does congenital
present from birth
Karyotype
an individuals complete set of chromosomes
what does the body tolerate better, duplications or deletions
duplications
