defining the genome I - chromosomes

Question 1

what is cytogenetics?

Answer 1

a fiel where microscopic analysis of cellularr structures, specifically nuclear chromosomes is used to investigate inheritance

Question 2

what is mitosis?

Answer 2

process where a single cell divides into 2 identical daughter cells

Question 3

what are the 5 phases of mitosis?

Answer 3

interphase
prophase
metaphase
anaphase
telophase+cytokinesis

Question 4

what is meiosis?

Answer 4

process where a single cell divides twice to produce 4 cells containing half the original genetic info

Question 5

how many parts does meiosis have? what are the different phases in each part?

Answer 5

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

Question 6

what is a karyotype?

Answer 6

number and appearance of a complete set of chromosomes

Question 7

what is G-banding?

Answer 7

common method for determining the karyotype of a cell using a dye called giesma

Question 8

what is the pattern that creates giesma when staining the chromosomes? what does this pattern depend on?

Answer 8

the pattern is light and dark staining depending on the level of condensation of the chromatin

Question 9

what are euploid and aneuploid cells?

Answer 9

euploid: cells with a normal chromosome number
aneuploid: cells with an abnormal chromosome number

Question 10

what is chromatin?

Answer 10

chromosomes are made of chromatin

Question 11

is chromatin condensed during metaphase? during interphase?

Answer 11

during metaphase: chromatin –> condensed

during interphase: chromatin –> diffuse

Question 12

what are the different types of chromatin during interphase? what nucleotides are more prominent in each type

Answer 12

heterochromatin –> darkly stained ==> highly condensed
AT-rich
euchromatin –> lightly stained ==> lightly condensed
GC-rich

Question 13

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?

Answer 13

centromere and tolemere
==> form constitutive heterochromatin
it is a facultative form of heterochromatin

Question 14

are housekeeping genes euchromatic or heterochromatic?

Answer 14

euchromatic

Question 15

what are nucleosomes?

Answer 15

DNA wrapped around histone octamers

DNA can be condensed up to 10000-fold

Question 16

what are the post-translational modifications that can control chromatin condensation? and what are their effects on condensation?

Answer 16

acetylation and phosphorylation –> chromatin decondensation

methylation –> chromatin condensation

Question 17

what does cohesin do? what forms cohesin?

Answer 17

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

Question 18

what does Condensin do? what is it made of?

Answer 18

plays a key role in chromosome condensation
ring-like structure made of 5 proteins:
2 Smc proteins: Smc2 and Smc4
3 non Smc proteins

Question 19

how many types of Condensin are there? what differs between them?

Answer 19

2 types of Condensin: Condensin I and II

they change depending on which non-Smc protein forms them

Question 20

large proportion of the eukaryotic genome is transcribed intoned-coding RNA (ncRNA) transcripts. what can they do?

Answer 20

they can regulate gene expression by degrading mRNAs

Question 21

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?

Answer 21

Xist
Xi
inactivates Xi by binding to proteins that promote methylation and deacetylation of histones

Question 22

what features does mitochondria share with bacteria? why do they have shared features?

Answer 22

double membrane
circular chromosome
because mitochondria are thought to have evolved from free-living bacteria that invaded a host cell