biology: cellular reproduction Flashcards
what is in the nucleus
deoxyribonucleic acid
chromatin
chromosome
histones
why do cells divide?
need for large surface-volume ratio
limited capacity of nucleus
deoxyribonucleic acid function
DNA
provided information for determining characteristics
majority in nucleus
what is chromatin and where is it found
threadlike form of DNA
exists when cell is not dividing
at is a chromosome and where is it found in cell cycle?
condensed form of DNA
during cell division
allows movement without tangling or breaking
what is a histone and what do they do?
protein DNA wraps around
provide stability/ organization and compaction to fit in cell
creates a nucleosome
what about prokaryotes that do not have a nucleus?
single, circular DNA
“naked”- no histones to wrap around
no nucleus, DNA attaches to plasma membrane
chromatid
duplicated half of a chromosome
collectively identical halves called “sister chromosomes”
centromere
protein dish that attaches sister chromatids together
Sex chromosomes
chromosomes that determine sex
in humans 2 X= female
1 Y and 1 X= male
autosomes
all chromosomes except sex chromosomes
all sexually reproducing organisms have two copies of each
one from each parent
homologous chromosomes
two copies of each autosome
same size, shape, and genetic information
karyotype
picture of chromosome in dividing state
diploids
cells that have two homologies of each chromosome
represented as 2n
in humans found in every single cell except sperm or egg
haploid
cell that has one set of chromosomes, half of diploid
represented as n or 1n
in humans only in sperm or egg (23 chromosomes)
how do prokaryotes divide?
easy because theirs no nucleus
asexual
binary fission
division of one cell into two identical cells
what happens during binary fission? 5 steps
- DNA replicates
- New cell membrane grows between DNA
- Cell grows to twice its size
- Cell wall grows around new membrane
- Cell divides into two identical cells
how do eukaryotes divide?
more complicated due to nucleus
mitosis and meiosis and then cytokinesis
what is mitosis
division of one nucleus (2n) into two identical nuclei (2n)
used for all cells except sperm and egg
what is meiosis
division of one nucleus (2n) into two haploid nuclei (1n)
used for sperm and egg
what is cytokinesis
division of cytoplasm
wht is the cell cycle?
repeating set of events in the life of a cell
includes interphase, mitosis, and cytokinesis
what is interphase?
time when cell is not dividing
most time spent in this phase
DNA in chromatin form
three phases
G1 phase
first phase
longest phase
cell volume grows as it produces cell components
S phase
second phase
DNA replication occur
92 chromatids- two per chromosome
G2 phase
third and final phase
cell gets ready for mitosis/ cytokinesis
G0 phase
non-dividing state, most human cells
some cells never divide like muscle and nerve fiber
what triggers a cell to leave interphase and begin to divide?
regulated by proteins and feedback signal
cell growth (G1) checkpoint
cell healthy and suitable size- go to S phase
unfavorable conditions- stop and rest or go to G0
DNA synthesis G2 checkpoint
accurate DNA synthesis/ replication- go to M phase
Mitosis checkpoint
chromosomes lined up correctly- finish mitosis
what is cell senescence
limited number of times a cell divides
what happens if cell loses control?
mutations in DNA can cause: checkpoints not to work properly unresponsiveness to crowding unlimited number of cell dividion CANCER
benign tumor
growing mass of cells that pose no threat to life
malignant tumor
growing mass of cells that may invade or destroy healthy tissue (cancer)
metastasis tumor
malignant cells that travel beyond original cite of growth
Carcinogen tumor
any substance that causes cancer
carcinomas
cancer of the skin and tissue that line the organs of the body
lymphomas tumor
cancer of the lymphatic tissue
leukemia tumor
cancer of white blood cells
how does mitosis work? what are the stages?
divides nucleus so both daughter cells are genetically identical
- prophase
- metaphase
- anaphase
- telophase
prophase
- nuclear envelope and nucleoli disappear
- chromatin condenses into chromosomes
- centrioles (in chromosomes) separate to opposite sides
- mitotic spindles radiate from centrosome
metaphase
- chromosomes connected to spindle fibers at centromere
2. chromosomes arranged across center of cell
anaphase
- sister chromatids pulled apart into individual chromosomes
telophase
- Nuclear envelope forms around each set of chromosomes to form two nuclei
- chromosomes turn back into chromatin
- Nucleoli reappear
how does the rest of the cell divide?
cytokinesis
cytokinesis
divides cytoplasm into two cells during telophase
cytokinesis in animal cells
cleavage furrow forms
ring of microfilaments contracts and pinches cell into two cells
cytokinesis in plant cells
vesicles from golgi bodies join at a midline and form cell plate
cell plate becomes cell wall and divides cell into two cells
how are haploid gametes form?
meiosis
what is meiosis
reduction division, if it doesn’t happen zygote won’t form
produces daughter cells with half genetic information of parents
sperm and egg each have 23 chromosomes (1n)
sperm (1n) + egg (1n) = zygote with 46 chromosomes
meiosis 1
homologous chromosomes seperate and from haploid cell
meiosis 2
sister chromatids seperate
meiosis 1- prophase 1
tetrad forms- homologous chromosomes pair together
crossing over occurs
DNA exchanged between chromatids of homologous pairs
source of genetic variation in species
centrosomes move to opposite poles
spindle fiber forms
meiosis 1- metaphase 1
spindle fibers attach to centromeres
random alignment of tetrads at midline of cell
meiosis 1- anaphase 1
homologous from tetrads randomly separate to opposite poles
independent assortment- source of variation in species
telophase 1 and cytokinesis
chromosomes reach opposite poles
two nuclei now formed with half the chromosomes (1n)
each chromosomes contains two chromatids
cytokinesis occurs
prophase 2
no tetrads no crossing over
metaphase 2
chromosomes align singly on metaphase plate (no tetrads)
anaphase 2
sister chromatids separate now each called a chromosome
chromosomes migrate to opposite poles
telophase 2
each cell contains half the chromosomes (1n)
gametognensis
formation of gametes (sperm or egg)
oogenesis
formation of eggs in ovaries
one large (1n) egg cell and three small (1n) polar body cells
formed by meiosis
due to unequal cytokinesis
spermatogenesis
formation of sperm in testes
four (1n) sperm cells formed by meiosois