L4 Chromosome Structure Flashcards
What do diploid eukaryotic cells contain
two copies of each chromosome
What can individual chromosomes be easily distinguished
metaphase of mitosis
Karotype
organised representation of all chromosomes at metaphase
Describe the organisation of individual chromosomes in interphase
occupy distinct subnuclear terriotories
Chromosome
highly coiled fibre of chromatin
Types of chromatin
euchromatin, heterochromatin
Nucleosome
building material of chromosomes
Types of histone
4 distinct types
Core histones
protein subunit of nucleosome
Function of histone tails
interact with proteins, facilitate regulation of chromatin
H1
linker histone
Function of H1
straps DNA onto histone octamers - limits DNA movement
What does H1 facilitate
establishment of transcriptionally silent heterochromatin
Interphase chromatin
set of dynamic fractal globules
Nuclear periphery in interphase cells composition
transcriptionally inactive DNA
Heterochromatin
transcriptionally silent
Inner part of the nucleus in interphase cells
RNA transcripts, transcriptionally active genes
Telomere
DNA sequences at ends of linear chromosome
Telomere function
maintain chromosomal integrity
Replication origin
DNA sequence, initiation of DNA replication
Centromere
DNA sequences, kinetochore assembly
Centromere function
Mediate chromosome segregation
Kinetochore
protein complex
Kinetochore function
binds microtubules in mitotic spindle
Telomerase
DNA polymerase that replicates telomeres
True or False - telomeres are double stranded
false
Two forms of kinetochore
inner and outer plate
Inner kinetochore plate function
binds to chromatin containing alpha satellite DNA
Kinetochore outer plate function
binds to protein components of mitotic spindle
What do centromeres contain
alpha satellite DNA repeats
Alpha satellite DNA repeats function
form condensed heterochromatin with histone octamers
CENP-A
specialised histone in centromeric chromatin
CENP-A function
connects inner kinetochore plate to methylated histones
H3-K4me
methylated histone
H3-K4me function
hold sister chromatids together
Kinetochore in yeast
Hollow cylinder / basket
Kinetochore in yeast function
links single nucleosome of centromeric chromatin to single microtubule
Relationship between complex organisms and protein coding genes
More complex organisms, more protein coding genes, more non protein coding DNA
Transposons
mobile repeated DNA sequences
Types of transposons
DNA transposons, Retroviral retrotransposons, Non-retroviral polyA retrotransposons
DNA transposon movement
cut and paste mechanism, without self duplication
Requirements of DNA transposon movement
transposase
DNA transposon discovery
Maize by Barbara McClintock
Retroviral transposons function
replicate via RNA intermediates, produce new DNA copies - integrate at new genomic locations
Retroviral transposon requirement
self encoded reverse transcriptase
non-retroviral retrotransposons
replicate via RNA intermediate, copy and paste
non-retroviral retrotransposon requirement
retrotransposon encoded reverse transcriptase
TRUE or FALSE - most transposons are defective
true
Large numbers of transposable elements are found in…
genomes of more complex organisms
How much of the human genome is made up of transposons
around 50%