Flashcards in Chromosomes and Cell Division Deck (23):
What is the end replication problem?
through multiple generations, strands will get shorter
What is the solution to the end replication problem?
What are centromeres?
-Protein complexes that bind to microtubules and are required during cell division
-They are the constricted region joining sister chromatids
-site of kinetochores
-repetitive SNA sequences- satellite DNA
Hererochromatin vs Euchromatin
-Heterochromatins has a condensed structure and silenced genes
-Euchromatin has an open structure and active genes
Describe the structure of chromatin.
-formed of DNA packaged histones
-histones have a positive charge, DNA negative
-146 bp DNA wrapped around core of 8 histones= nucleosome
-further wrapping of nucleosomes
-form solenoid structure
By what factor is DNA condensed by at metaphase?
What is the purpose of packaging DNA?
-negatively charged DNA neutralised by positive charged histone proteins
-DNA takes up less space
-Inactive DNA can be folded into inaccessible locations until required
What is colchine?
-a microtubule inhibitor
-it enriches the population of cells that are visible
p length= q length
p length< q length
p length <<< q length
What does FISH stand for?
Fluorescent in situ hybridisation
What types of FISH probes are there?
-unique sequence probes
-centromeric probes (useful for determining chromosome number)
-telomeric probes (detecting subtelomeric rearrangements, often present in children wit unexplained mental retardation)
-whole chromosome probes (cocktail of probes, used with different dyes, spectral karyotype, detecting translocation and rearrangements)
What is meiosis?
-cell division in germ cells
-diploid cells (in ovaries and testes) divide to form haploid cells)
-chromosomes are passed on as re-arranged (recombinant) copies which creates genetic diversity
What is a defining event in sexual reproduction?
recombination between homologues
What are the 2 forms of gametogenesis?
-oogenesis= process of egg formation
-spermatogenesis= process of sperm formation
Why is there a greater chance of mutation in sperm than in eggs?
they go through more cell divisions
How many sperm and eggs are produced in each cycle of gametogenesis?
-1 egg + 3 polar bodies
-two haploid cells form 1 diploid cell which develops into an embryo
-whether sperm contains an X or Y chromosome determines if the embryo is female or male
-embryo contains an assortment of genes from each original parent- more genetic diversity
What is maternal inheritance?
mitochondria (and their DNA) come only from the mother via the egg
When does X inactivation occur?
-In the zygote both X chromosomes are active
-In the early embryo random inactivation of one X occurs
What are 2 tandemly repeated DNA extragenic sequences?