The nucleos, The cell cycle & meiosis Flashcards
(25 cards)
Most of the cell cycle is spent in ……, while cell division occupies a small part of the cycle
interface, a period of growth and preparation for the division
What are the functions of the nucleus?
- DNA synthesis & repair
- RNA synthesis: transcription of DNA into RNA by three distinct polymerases (each for a different RNA)
- RNA processing: precursor RNA is processed into mature RNA in the nucleus
The nucleus is surrounded by ……, the outer is continuous with ……., and there is a space between the inner and outer called ……
nuclear envelop (double membrane) RER (part of endomemberanous system) perinuclear space
Define nuclear lamins and state their function
An electron dense lining of the inner layer of nuclear envelop. Play a role in structural organization of the nucleus (by connecting the inner membrane to the chromatin, important in mitosis & meiosis)
Define the nuclear pores and their purpose
areas where the inner and outer membrane is fused together to allow communications with the nucleus.
Large molecules need special protein transport, which is included in the pores themselves
The number of pores is usually fixed, but can vary according to cell activity
Chromatin is composed of ….., and is associated with ……
DNA
histones, which are positively charged proteins
The nucleolus is ……..
dense staining region, has large amount of RNA and is the site for ribosome assembly.
* Has 3 zones, outer granular (contains precursors for RNA), and central fibrillar (containing protein fibrils)
The nucleolus is associated with ……. on the chromosome
nuclear organizing region (NOR)
* It contains many copies of genes for ribosomal RNA synthesis
The DNA in the NOR region is …… staining
pale
The cell cycle can divide into ….. & …..
interphase & division phase
Cells perform their differentiated functions while in the …… phase
G1 or G0
G1 phase is …..
period of cell growth, last about 12 hours but may take very long time in nerve and muscle cells (these are called at G0 phase)
S phase is …..
last for 8 hours, includes DNA synthesis and chromosomal replication. RNA synthesis increase. Mitochondria and centrioles divide
Each centrosome is composed of two ….
centrioles
G2 phase is …..
last about 3-4 hours. Resembles G1 in cellular activity except the cell is tetraploid (2 x diploid). Energy is generated for the division in this phase
Define cytokinesis
The division of the cytoplasm resulting in two separate cells
see p. 373 for mitosis details (also copybook)
Meiosis starts before ……. Cells entering meiosis have the same DNA content as ……
maturation of the gametes.
cells entering mitosis (called primary gametocytes)
Meiosis involves two complete ……. resembling ….. . There’s no ….. replication
cell divisions, mitosis
DNA
* DNA replication occurs before the first meiotic division
* Genetic recombination (cross over) occurs in meiosis
Cells entering meiosis II are called ….. and they contain ….. each consisting of …..
secondary gametocytes
23 chromosomes, 2 sister chromatids
Centromeres split during meiosis I. T/F
False
They split during meiosis II
The point of recombination is called …..
chiasma
Recombination changes ……, not ……
allelic linkages, sequences
The centromeres of homologous chromosomes pair. T/F
False
They don’t pair. only the sister chromatids are paired
At the end of telophase I, each cell receives …
23 double stranded chromosome
