Chromosomes & The Cell Cycle Flashcards
Prokaryote vs. eukaryote chromosomes
Prokaryote: short and circular
Eukaryote: long and linear
What is a chromosome?
A strand of DNA that carries genetic info in a cell
Prokaryote basics
no nucleus
Single celled
Always haploid
Eukaryote basics
Have a nucleus
Some single celled, some multicellular
Both haploid and diploid
Every cell has it’s own ____ and can be ___ or ___
Genes, haploid, diploid
Haploid definition
1 copy of every gene
Diploid
2 copies of every gene
1 from mom and 1 from dad
Mitosis definition
Cell division that makes 2 daughter cells identical to the mother cell–whether haploid or diploid
Meiosis definition
Cell division that splits diploid cells into haploid cells
Cell division in prokaryotes
Very simple–circular haploid chromosome of DNA duplicates, then cell splits in two
Result: 2 identical haploid daughter cells
Human diploid cell chromosome #
23 pairs, or 46 chromosomes
After DNA duplication, Human diploid cell chromosome #
23 pairs, or 46 chromosomes
BUT each chromosome has a sister chromatid = 92 chromatids in the cell
When the cell is about to divide it first…
Duplicates chromosomes
After duplication of chromosomes…
Each chromosome consists of 2 sister chromatids
Human haploid and diploid #s
Haploid (N) = 23
Diploid (2N) = 46
spindle fiber
long protein molecule (microtubule) that tows chromosomes during division
centromere
area of a chromosome where spindle fibers attach during division
kinetochore
protein structure on a centromere where spindle fibers attach
centrosome
the structure (centriole + aster) where microtubules pull the chromosomes
aka. microtubule organizing center (MTOC)
centriole
strange little cylinder made of short microtubules
located at the center of a centrosome
aster
cluster of spindle fiber
converge at centrosome
bands on chromosomes
numbered in both directions starting at centromere
only visible when chromosomes are stained with a special technique
the earlier in ___ the longer the chromosomes are, and more bands are ____
prophase, visible
karyotype
visual of a person’s 23 chromosome pairs
during the mitotic cell cycle a human cell has how many chromosomes?
46 (23 pairs)
during the mitotic cell cycle is a human cell always diploid?
yes
interphase
happens between cell divisions
chromosomes are decondensed and invisible
3 stages (G1, S, G2)
G1
each chromosome consists of 1 chromatid
S
DNA is duplicated
G2
each chromosome consists of 2 chromatids
G0
some cells exist in this state of non-division
may be permanent (nervous cells) or reversible (immune cells)
at what stage can you see a karyotype?
at the end of G2 in interphase
cytokinesis
dividing the cytoplasm and membrane
at mitosis the cell splits each _____ into _____
2-chromatid chromosome, single-chromatid chromosomes
higher plants don’t have…
centrioles
the haploid number of chromosomes is called __ and the diploid number is called ___
N, 2N
in simple eukaryotes the ___ stage of life is dominant
haploid
fungi spend most of their lives as ____
haploids, growing as little invisible threads called mycelia
more complex plants spend most of their lives as ___
diploids
animals spend their whole lives as ____ except for the _____ stage
diploids, gamete
the diploid stage of any eukaryote begins with ____
syngamy: when two haploid gametes combine to form a diploid cell
meiosis can only occur in the ___ stage because…
diploid
it requires a cell with pairs of homologs
what are the two types of cells in animals in the diploid stage?
somatic and germline
somatic cells
everything other than germline
only go through mitosis
germline cells
exist only in the gonads (testes & ovaries)
go through either mitosis OR meiosis
what is the important function of meiotic recombination?
to shuffle the genes, making new chromosomes with new combinations of parental alleles
