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 maturation of the cell occurs
DNA checking and subsequent repair occurs during the 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 Organelles such as mitochondria grow and divide.
Followed by 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 from centriole
What happens during metaphase?
Chromosomes align at the equator of the cell
Attached by spindle fibre to each centriole
Maximum condensation of chromosome
What happens during anaphase?
Sister chromatids separate at the centromere
Move to opposite ends of the cell
What happens during telophase?
Nuclear membranes form
What happens during cytokinesis?
Cytoplasm separates
Two new daughter cells
What is the structure of the centromere?
Repetitive DNA sequences (satellite DNA)
Joins sister chromatids
Site of the 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
What is satellite DNA and where can you find it?
Tandemly repeated DNA sequences at the Centromeres and telomeres of chromosomes
what is chromatin
DNA packed within histone proteins
What is the charge of histone?
Positively charged
What is a nucleosome?
A unit of chromatin that makes up eukaryotic chromosomes.
A length of DNA wrapped around a core of histones
How is a solenoid structure formed?
Further wrapping of nucleosomes
What are the different levels of structural elements of chromatin?
lvl1: Nucleosome
lvl2:Chromatin fibre
lvl3:Fibre-scaffold complex
lvl4:Chromosome
What is the purpose of packaging DNA?
+ve histone protein charge neutralises neg. DNA
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 the DNA with fluorescent tag (tag complimentary to desired DNA sequence)
Excess tags are washed away
Tags are fluorescent themselves or can attach to a fluorescent molecule
Chromosome viewed under a 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
Pairing of homologous chromosomes
Recombination takes place
Homologous chromosomes separated by spindle fibres
Cell divides into 2
Further divides to produce 4 haploid gametes
What is the purpose of meiosis?
Cell division of germ cells
Goes from diploid cell to 4 haploid gametes
What is oogenesis?
Process of egg formation
When does gametogenesis begin in males and females?
Males - Puberty Females - Early embryonic life
What determines the sex of the zygote?
Wether or not the sperm contains the y chromosome
Where does mitochondrial DNA come from?
Only from the mother via the egg
What happens to the X chromosome in females?
One of them is randomly inactivated
What are the differences between male and females in gametogenesis
What is spermatogenesis?
Process of sperm formation
What is the purpose of unique sequence probes?
Detecting subtelomeric rearrangements
What is the purpose of whole chromosome probes?
Covering different parts of a chromosome
