Lecture 1: Basics Flashcards
What are sister chromatids?
What do they become after mitosis?
Sister chromatids are the X shaped structures commonly representing chromosomes. It is two identical chromosomes connected by the centromere. Once separated during mitosis they become chromosomes.
What is the difference between the centromere, centriole, and centrosome?
The centrioles are a pair of barrel-shaped organelles found near nucleus that assist in the formation of spindle fibres required for division. Will move to poles of cell during mitosis.
The centromere is the highly compact region of DNA that occurs when sister chromatids are produced and ready to be separated during mitosis. Allow binding of spindle fibres.
The centrosome is the central region of the cell where the cytoskeleton is organised, during mitosis, spindle fibres attach to
What is a kinetochore?
The kinetochores are assembled at the centromere of mitotic chromosomes, and facilitate the binding of spindle fibres formed from centrioles and centrosome.
What names can be given to chromosomes based on the position of the centromere?
They can be metacentric, where the centromere is directly in the middle of the chromosomes.
They can be submetacentric, meaning that the centromere is just above or below the middle.
They can be acrocentric where the centromere is close to the end of the chromosomes.
They can be telocentric, meaning that the centromere is right at the telomere.
What is the basic sequence of genes expression?
RNA polymerase binds to the promoter of the gene, and strands are separated and complementary bases are used to form a template pre-mRNA strand.
The pre-mRNA template is then spliced to take out the introns by the spliceosome.
mRNA then leaves the nucleus and is translated into proteins by 80S ribosomes.
What cell division cycle stages are there?
There is G0, G1, S, G2, and M phase.
What is G0 phase?
This phase is when cells have left the division cycle, and just doing their job. Some cells in G0 can be stimulated to reenter the cell cycle, such as liver cells, but many cannot (myocardial cells, neurons).
What happens in G1 phase?
Cells in this stage will grow bigger and produce many proteins and RNAs, as well as the formation of the centromere (on single chromosome), and duplication of centrosome/centrioles starts.
What happens in S phase?
In S phase, replication of DNA occurs, so by the start of G2 phase, there are sister chromatids for all chromosomes, ready to be separated. Centrosome is replicated fully.
What happens in G2 phase?
The cell will continue to grow and synthesise proteins and RNA, as well as organelles.
DNA repair will be performed (homologous recombination, etc.)
What happens in M phase?
What is the difference between early and late mitosis? (and what stages of M involved)
This indicates the beginning of mitosis in the cell, with this being organised into early stage mitosis and late mitosis with cytokinesis.
Early mitosis involved the formation of spindle fibers, chromatin condensation, nuclear envelope disassembly, centrosome movement to poles, and alignment and fiber attachment of chromosomes. (prophase, prometaphase, metaphase)
Late mitosis involves the separation of sister chromatids to become daughter chromosomes, disassembly of spindle apparatu, formation of nuclear envelope and cytokinesis. (anaphase, telophase, cytokinesis).
What is the order of cell division stages from longest to shortest?
G1, then S, then G2, then M.
What order of stages in cell division cycle?
What does the M cycle consist of?
G1 -> S -> G2 -> M.
M (mitotic) phase consists of prophase, prometaphase, metaphase, anaphase, telophase and cytokinesis.
What is the process of DNA transcription?
DNA transcription involves RNA polymerase creating a complementary pre-mRNA strand from a gene. RNA polymerase recognises part of the promoter called recognition sites.
After the pre-mRNA (no splicing) is produced it is spliced of introns to produce mature mRNA.
What is a karyotype?
The number of and condition of chromosomes in a cell. For instance the karyotype may be different from wild type in the case of trisomy 21 (Down’s syndrome).
