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?