defining the genome I - chromosomes Flashcards
what is cytogenetics?
a fiel where microscopic analysis of cellularr structures, specifically nuclear chromosomes is used to investigate inheritance
what is mitosis?
process where a single cell divides into 2 identical daughter cells
what are the 5 phases of mitosis?
interphase prophase metaphase anaphase telophase+cytokinesis
what is meiosis?
process where a single cell divides twice to produce 4 cells containing half the original genetic info
how many parts does meiosis have? what are the different phases in each part?
2 parts part 1: interphase prophase I metaphase I anaphase I telophase+cytokinesis I
Part 2: prophase II metaphase II anaphase II telophase+cytokinesis II
what is a karyotype?
number and appearance of a complete set of chromosomes
what is G-banding?
common method for determining the karyotype of a cell using a dye called giesma
what is the pattern that creates giesma when staining the chromosomes? what does this pattern depend on?
the pattern is light and dark staining depending on the level of condensation of the chromatin
what are euploid and aneuploid cells?
euploid: cells with a normal chromosome number
aneuploid: cells with an abnormal chromosome number
what is chromatin?
chromosomes are made of chromatin
is chromatin condensed during metaphase? during interphase?
during metaphase: chromatin –> condensed
during interphase: chromatin –> diffuse
what are the different types of chromatin during interphase? what nucleotides are more prominent in each type
heterochromatin –> darkly stained ==> highly condensed
AT-rich
euchromatin –> lightly stained ==> lightly condensed
GC-rich
what regions are heterochromatic all the time? what is then this form called?
what does the heterochromatin that can vary depending on the cell type form?
centromere and tolemere
==> form constitutive heterochromatin
it is a facultative form of heterochromatin
are housekeeping genes euchromatic or heterochromatic?
euchromatic
what are nucleosomes?
DNA wrapped around histone octamers
DNA can be condensed up to 10000-fold
what are the post-translational modifications that can control chromatin condensation? and what are their effects on condensation?
acetylation and phosphorylation –> chromatin decondensation
methylation –> chromatin condensation
what does cohesin do? what forms cohesin?
role in the cohesion of sister chromatids, It ensures that sister chromatids remain attached during mitosis UNTIL anaphase
cohesin is a complex of 5 proteins:
2 structural maintenance of chromosome (Smc) proteins Smc1 ans Smc3
3 non Smc proteins
what does Condensin do? what is it made of?
plays a key role in chromosome condensation
ring-like structure made of 5 proteins:
2 Smc proteins: Smc2 and Smc4
3 non Smc proteins
how many types of Condensin are there? what differs between them?
2 types of Condensin: Condensin I and II
they change depending on which non-Smc protein forms them
large proportion of the eukaryotic genome is transcribed intoned-coding RNA (ncRNA) transcripts. what can they do?
they can regulate gene expression by degrading mRNAs
what long non-coding RNA inactivates randomly one of the X chromosomes ? how do we call the X chromosome that transcribes it and becomes inactive? how does the lncRNA inactivate the X chromosome?
Xist
Xi
inactivates Xi by binding to proteins that promote methylation and deacetylation of histones
what features does mitochondria share with bacteria? why do they have shared features?
double membrane
circular chromosome
because mitochondria are thought to have evolved from free-living bacteria that invaded a host cell
