Chromosomes and the Cell Cycle Flashcards
(18 cards)
Identify the Core Histones
H2A, H2B, H3, H4
**Think of linkers H1 and H5; these are the inbetween + 2 H2s because why tf not
Linker Histones
H1, H5
What are histones rich in
Basic amino acids like lysine and arginine
Euchromatin; describe condensation and staining
Genes that are switched on - Less condensed and lightly staining
Heterochromatin; describe condensation and staining
Genes that are switched off - More condensed and densely stained
Locations of heterochromatin and euchromatin
Hetero: Near Nuclear Envelope
Eu: More Central Location
Two types of heterochromatin
Constitutive and Facultative
Constitutive Heterochromatin
Chromatin that is never expressed and highly repetitive - such as telomeres or sequences near centromeres
Facultative Heterochromatin
Genes that are switched on when needed, then switched off when unneccessary
Nucleolus
Responsible for ribosomal formation
Types of Cell Turnover rates
Continuously renewing - Epidermis, Intestinal Epithelium, Blood-forming tissues
Conditionally Renewing - Liver, Kidney, Endocrine Glands
Static/Non-Proliferative - Cardiac, Nerve Cells
Karyokinesis
Nuclear Division (Mitotic Steps)
Cyclins
Proteins that coordinate and regulate the processes of mitosis
How do Cyclins work
Cyclins have no catalytic activity but CDKs do, so when Cyclins bind to CDKs and form a heterodimer, they cause phosphorylation to activate or inactivate target proteins
What can be used as a tumour suppressor
CDK Inhibitors
Stages of Prophase I
Leptotene - Chromatin -> Visible Chromosomes
Zygotene - Bivalents form
Pachytene - Synapsis completed
Diplotene - Chromatids held together by Chiasmata & Centromeres
Diakinesis - Chiasmata move towards chromatid ends (Terminalisation)
Sites of Genetic Variation of Offspring
- Pachytene of Prophase I
- Independent Assortment of Metaphase I
- Fertilisation (Random sperm with random egg)
Aneuploidy
An abnormal number of chromosomes (monosomy or Trisomy)
Synonym of Non-Disjunction
