0210 - Chromosomes, DNA replication, Cell Cycle - RM

Question 1

What is a chromatin and a chromosome?

Answer 1

Chromatin – A strand of DNA coiled around a HISTONE protein. If tightly packed it is heterochromatin (AT rich), if loosely packed it is euchromatin (GC rich, lots of genes).Chromosome - A tightly compacted, linear structure of DNA that is present in the cell nucleus during cell division. Consists of pairs of short and long arms (sister chromatids), connected by a centromere. The end points are telomeres.

Question 2

What is Mitosis

Answer 2

Reproduction of somatic cells to produce two cells that are identical to the parent cell. Consists of prophase, prometaphase, metaphase, anaphase, and cytokinesis.

Question 3

What is Meiosis

Answer 3

Reproduction of germ cells to produce four cells that each contain half of the genetic material of the parent cell. Consists of Meiosis I and II, each of which has a prophase, metaphase, anaphase and telophase.

Question 4

What is the cell cycle?

Answer 4

The cycle of cell reproduction – All stages except M occur in INTERPHASE. G0 – Cell has left the cycle/stopped dividing (e.g. neuronal tissue) G1 – RNA is synthesised. S – DNA is replicated G2 – Chromatin condenses into chromosomes M – Cell division.

Question 5

Briefly outline the process of DNA replication

Answer 5

DNA polymerase attaches to the DNA, moves along each strand, producing new DNA in a 5’-3’ direction, drawing in nucleotides to produce a complimentary strand.5’-3’ strand is LEADING strand, fairly simple (everything goes in this direction)3’-5’ strand is LAGGING strand – more complex (need to stop-start).DNA primase allows the DNA strand to form on RNA primers. It creates OKAZAKI fragments on the lagging strand, which are joined by DNA ligase.

Question 6

What is Gene expression?

Answer 6

Very complex process by which different portions of the genome are ‘activated’ to use in synthesis of a functional product (e.g. protein, cell differentiation). It is regulated by RNA, and is constantly changing in response to just about everything (DNA mutation, environment, infection, food etc).Errors in gene expression can lead to many diseases, along the full spectrum of benign to fatal.