Session 2 - Lecture 2 Flashcards
2 - Some Notes
- Replication (and transcription and translation) is very quick
- DNA polymerase acts at about 100 NTs per second
- S phase of cell cycle = synthesis (DNA replication)
- M phase = mitosis or meiosis
3 - Chromosome structure
When chromosomes are replicated they become one chromosome with two sister chromatids (See Review Lecture)
Chromosomes visible in cell division (classical X shape) have been replicated – contains two identical DNA molecules
P arm is small (petite), Q arm is long (arbitrary nomenclature by scientists, P and Q can also be the same length)
Centromere in middle of 2 arms, telomere ends of 2 arms
Each sister chromatid is an identical DNA molecule to each other, each one having a p arm, q arm, telomeres either end and a single centromere joining the 4 arms.
4 - Telomere
In eukaryotes, telomeres are repeated sequences (TTAGGG) at each end of chromosome (single)/chromatid (replicated) - telomere repeats
5 - Centromeres
Centromere is a complex of proteins
Centromeres binds to specific regions within the chromosome, or of the DNA molecule – often repetitive sequences
Humans have meta-, submeta- and acrocentric chromosomes
6 - chromosomes and centromeres
Can be represented in either format
RHS – make more simple so shows only one line rather than X shape
However – remember, if the chromosome is visible then it most likely has been replicated
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