test 2: lecture 8 - cell division & dna replication Flashcards
somatic cells go through which process? mitosis or meiosis?
mitosis (ex: skin cells) - more common
sexual cells go through which process? mitosis or meiosis?
meiosis (ex: eggs, sperm)
who discovered DNA?
waston, crick and franklin
what is always the first step of mitosis or meiosis?
DNA replication
DNA replication
- DNA unzips and gets copied
- happens in nucleus
- result: 2 identical copies of DNA
- replication is semiconservative: 1 parent strand + 1 new strand
semiconservative model
two strands of the parental molecule seperate and each functions as a template for synthesis of a new, complementary strand
base pairing in DNA
adenine - thymine
guanine - cytosine
what does DNA copying start with?
RNA primer
in which direction does replication occur?
5’ to 3’ (nucleotides added onto 3’ end)
what enzyme helps DNA replication?
DNA polymerase
what is the mechanism that checks for & corrects mistakes?
mismatch repair
what are the 4 noncoding DNA sequences?
- transcription/translation regulators
- origins of DNA replication
- centromeres
- telomeres
what are telomeres?
special noncoding sequences added onto the end of eukaryotic chromosomes to protect them from being eroded
true or false? when eukaryotic cells divide, chromosomes get shorter
true - ends of chromosomes do not get fully replicated
facts about telomeres
- do not contain genes
- provide protective function by postponing erosion of genes located near ends of DNA molecules
- shrink every time cell divides
- proposed that shortening telomeres is connected to the aging process
what is the name of the special enzyme germ cells have and what does it do?
telomerase - catalyzes the lengthening of telomeres in eukaryotic germ cells
cell cycle
G1, S, G2, mitosis
what is interphase?
G1, S, G2
what is the shortest phase of the cell cycle?
mitosis
what happens during G1 and G2?
cells grows and makes proteins, organelles
what happens during S phase?
only DNA replication going on
G1 phase:
- beginning of cell’s life
- centrioles divide
- cytokinesis
- cell grows to full size
- transcription and translation occur
- DNA in single strands
what causes the area around centrioles to be thicker than rest of cytoplasm? what is this called?
it’s called the centrosome - the helper proteins used by centrioles to help make spindle fibers cause this area to be thicker
S phase:
- DNA replicates - 2 double stranded DNA molecules
- diploid and haploid
- no more RNA (leftovers used for repairs)
- centrosomes, centrioles still replicating
- WITHOUT THIS PHASE CELLS CANT DIVIDE
G2 phase:
- well defined nucleus with membrane
- centrosomes present, centriole copying complete
- DNA has duplicated, but it in chromatin form
- RNA transcribed to make proteins (spindle fibers)
- leftover RNA used for repairs
which is the most important permission point of the cell cycle?
G1 checkpoint
centrosome
area for production and organization of microtubules
true or false? plant has centrioles
FALSE - plant has centrosome, but no centrioles
explain how centrioles and centrosome act in animal cells
centrioles replicate
centrosome divides
— result: two centrosomes (each with a pair of centrioles), move to opposite ends of nucleus, microtubules grow into spindle from each centrosome
what are spindle fibers responsible for?
seperating the dividing cell and contents into new cell
nerve and muscles cells are always in which phase?
G0
liver cells are in which phase?
G0, but can be activated to come out of it
true or false? cancerous cells obey checkpoint control
false
what are check points controlled by?
regulatory protein - p53
what is p53?
most important regulatory protein, classified as a tumor suppressor protein
how does p53 fight cancer?
1- pause cell cycle and initiate DNA repair
2- if DNA cannot be repaired, it will induce apoptosis
apoptosis
programmed cell death
how can cells lead to cancer?
if a damaged cell does not undergo apoptosis and divides
