L20 - Chromosomes Flashcards
How are chromosomes distinguished?
-The chromosomes are easily distinguished in metaphase because the chromosomes condense
What is a chronometer made up of?
-A chromosome is a highly coiled fibre of chromatin
What does the interphase chromosome resemble?
-Under the electron microscope, the interphase chromatin resembles ‘beads on a string’
-The beads are nucleosomes
What makes up nucleosomes?
Protein subunits that pair as histones
How many core histone subunits is an N terminal made up of?
-N-terminal tails have 8 core histone subunits
What kind of histone is H1?
‘Linker Histone’
What are telomeres?
-These are specialised repetitive DNA sequences at chromosome ends
What are centromeres
-Centromeres are regions of repeated DNA sequences where the chromosomes are connected during mitosis and connected to mitotic spindle and bid to kinetochore which allows stabilisation of the spindle and line up and segregate properly
What do telomeres do?
-Telomeres are on the end of chromosomes and protect them from multiple rounds of replication and genetic information would be lost without them
What are the nucleosomes like in yeast?
-Yeast has a single nucleosome which recognises and binds to sequence specific kinetochore
-Forms a ring like structure for a microtubule to slot into
What % of DNA sequence in eukaryotes encodes information for making cellular proteins?
what % makes up introgenic region?
what % makes up repeated DNA (transposons)?
-1.5%
-20%
-50%
What are the 3 types of repeated DNA transposons? (3)
1) DNA transposons
2) Retroviral retrotransposons
3) Non-retroviral polyA retrotransposons
What enzyme do DNA transposons encode?
Transposase
How do Retroviral retrotransposons replicate?
-Replicating via RNA intermediates, producing new DNA copies that integrate at new genomic locations, using self-encoded Reverse Transcriptase
What are 3 examples of retroviral transposons? (3)
-Ty1-copia
-Ty3-gypsy
-ERV elements
