Chromosomes and Cell Division 2/2 - First Lecture Flashcards
What are the stages of the cell cycle?
Interphase and mitosis
What are the different stages of interphase?
G1, S and G2
What happens during the G1 stage of interphase?
Protein and RNA synthesis
Growth and maturation of cell
DNA checking and subsequent repair during pause between G1 and S
What happens during the S phase of interphase?
DNA synthesis
What happens during the G2 phase of interphase?
Further synthesis of RNA and proteins
Further growth of organelles
Proof reading and subsequent repair of newly synthesised DNA
What are the stages of Mitosis?
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis
What happens during Prophase?
Chromosomes condense
Nuclear membrane disappears
Spindle fibres form from centriole
What happens during metaphase?
Chromosomes align at equator of cell
Attached by fibre to each centriole
Maximum condensation of chromosome
What happens during anaphase?
Sister chromatids separate at centromere
Move to opposite ends of cell
What happens during telophase?
Nuclear membranes form
What happens during cytokinesis?
Cytoplasm separates
What is the structure of the centromere?
Repetitive DNA sequences (satellite DNA)
Site of kinetochore - protein complex that binds to microtubules
What is the difference between Heterochromatin and Euchromatin?
Heterochromatin - condensed structure, Silenced genes
Euchromatin - Open structure, Active genes
Where can you find satellite DNA and what is it?
Centromeres
Telomere
Tandemly repeated DNA sequences
How is chromatin formed?
DNA packed within histone proteins
What is the charge of histone?
Positively charged
What is a nucleosome?
Unit of eukaryotic chromosome
Length of DNA wrapped around core of 8 histones
How is a solenoid structure formed?
Further wrapping of nucleosomes
What are the different levels of structural elements of chromatin?
Nucleosome
Chromatin fibre
Fibre-scaffold complex
Chromosome
What is the purpose of packaging DNA?
Charge neutralised
Takes up less space
Inactive DNA can be folded into inaccessible locations until required
What is the purpose of FISH (fluorescent In Situ Hybridisation)
Mark or tag a specific DNA sequence out of the whole genome
What is the process of FISH?
Denature DNA into single strands
Hybridise DNA with fluorescent tag (tag complimentary to desired DNA sequence)
Excess tags washed away
Tags either fluorescent themselves or can attach to fluorescent molecule
Chromosome viewed under fluorescence microscope, revealing physical location of desired gene
What are the different types of FISH probes?
Unique sequence probes
Centromeric probes
Telomeric probes
Whole chromosome probes
What are the stages of meiosis?
DNA replication
Homologous chromosomes pair up
Recombination
Homologous chromosomes separated by spindle fibres
Cell division 1
Meiotic division 2 takes place
What is the purpose of meiosis?
Germ Cell division to form haploid gametes from diploid cells in ovaries and testes
What are the different names given to egg formation and sperm formation?
oogenesis spermatogenesis
When does gametogenesis begin in males and females?
Males - Puberty
Females - Early embryonic life
What determines the sex of the zygote?
If sperm has Y chromosome
Where does mitochondrial DNA come from?
Only mother via egg
What happens to the X chromosome in females?
One is randomly inactivated
