Chromosomes and Cell Division - First Lecture Flashcards
What are the stages of the cell cycle?
Interphase and mitosis then cytokinesis.
A cell spends most of its time in what is called interphase, and during this time it grows, replicates its chromosomes, and prepares for cell division. The cell then leaves interphase, undergoes mitosis, and completes its division.
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 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
S for 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
PMATC
What happens during Prophase?
Chromosomes condense Nuclear membrane disappears Spindle fibres form from the centriole
What happens during metaphase?
Chromosomes allign t the equator of the cell Attached by 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
And 2 diploid cells form (43) (43)
What happens during cytokinesis?
Cytoplasm separates
What is the structure of the centromere?
Repetitive DNA sequences (satellite DNA) Site of the kinetochore which is a protein complex that binds to microtubules
What is the difference between Heterochromatin and Euchromatin?
Heterochromatin; is condensed structure, Silenced genes
Euchromatin; Open structure, Active genes
Where can you find satellite DNA and what is it?
Tandemly repeated DNA sequences at the Centromeres and telomeres of chromosomes
How is chromatin formed?
DNA packed within histone proteins
What is the charge of histone?
Positively charged
What is a nucleosome?
A unit of eukaryotic chromosome 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?
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 the DNA with fluorescent tag (tag complimentary to desired DNA sequence) Excess tags are washed away Tags are either fluorescent themselves or can attach to a fluorescent molecule The chromosome is then viewed under a fluorescence microscope revealing the physical location of the 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 are separated by spindle fibres.
Cell division 1
Meitoic division 2 takes place
What is the purpose of meiosis?
It is the cell division of germ cells to form haploid gamete cells ( egg or sperm) 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?
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
Where are the telomeres of a chromosome?
At the end of the arms.
What is the end replication problem?
Consecutive rounds of DNA replication cause the telomeres to become shorter and shorter.
How do eukaryotes solve the end replication problem?
Telomerase can reverse transcribe its own RNA template to synthesis the additional DNA, increases the 3’ end of the parent strand, allowing the okasaki fragments and polymerase to extend the 5’ end if the other DHA strand.
What is telomerase made up of?
Proteins and RNA
