Cells and Replication Flashcards
what is cell theory?
the cell is an organism’s basic unit of structure and function
- all organisms are made of cells
- all cells come from pre-existing cells
what are the three domain classifications of organisms?
bacteria, archaea, eukarya
archaea look like ______ on the outside and ______ on the inside
bacteria, eukarya
almost all bacteria/prokaryotes are ____-celled
single
almost all eukarya are ____-celled
multi
basic features of all cells
- enclosed by a dynamic [plasma membrane] that regulates the passage of materials between the cell and its surroundings
- contain a semifluid substance called [cytosol]
- use [DNA] as their genetic info
- have [ribosomes] that make proteins
eukaryotic cell vs. prokaryotic cell
eukaryotic cell (animals, plants, fungi, and protists): membrane-enclosed organelles, nucleus, larger, more complex
prokaryotic cell (bacteria, archaea): no membrane-enclosed organelles, no nucleus, smaller, less complex
what is the organelle in plant cells called?
chloroplast (converts sunlight into sugar)
do both plant and animal cells have mitochondria?
yes
why is plant tissue stronger than animal tissue?
because of their surrounding cell wall
dynamic biological membrane
- dual bilayer of phospholipids
- proteins formed in pores
- turn on or off certain genes based on environmental stimuli
- barrier and start of signaling cascade
where are genes turned on and off?
in nucleus
nucleus
contains chromosomes, made of chromatin (DNA and proteins)
- contains nucleoli where ribosomal subunits are made
- pores regulate entry and exit of materials
ribosomes
protein synthesis
endoplasmic reticulum
smooth ER: synthesis of lipids, metabolism of carbohydrates, Ca2+ storage, detoxification of drugs and poisons
rough ER: aids in synthesis of secretory proteins from bound ribosomes; adds carbohydrates to proteins; produces new membrane
Golgi apparatus
modification of proteins, carbohydrates on proteins, and phospholipids; synthesis of polysaccharides; sorting of Golgi products, which are then released in vesicles
lysosome
breakdown of ingested substances, cell macromolecules, and damaged organelles for recycling
vacuole
(mostly in plants) digestion, storage, waste disposal, water balance, cell growth, and protection
mitochondrion function
cellular respiration
chloroplasts function
(in plants) photosynthesis
peroxisome
oxidative organelles which breaks down toxic molecules
nucleus contains ___________
most of cell’s DNA
additional genes, not in nucleus, are in _________ in and __________
mitochondria, chloroplasts
most of the cell’s tRNAs are produced in the __________
mitochondrion
genome
the complete set of genes or genetic material [DNA in an organism’s nucleus and mitochondria (and chloroplasts)] present in a cell or organism
genomics
the large scale study of sets of genes within and between species
chromatin
complex of DNA and proteins
genes found on
chromosomes
in eukaryotes, during cell division, chromatin condenses to form discrete ____________
chromosomes
human genome is diploid or haploid
diploid (contains two complete sets of chromosomes, one from each parent, 23 from each parent)
normal human karyotype
23 from each parent, 22 same pairs, last pair is either XX (female) or XY (male)
gene is unit of ___________
inheritance
what is a gene
a sequence of nucleotides on DNA that provide cells with with the info needed to a produce a specific protein (or for functional RNA molecules)
how many genes are on each chromosome?
hundreds - thousands of genes
one of copy of the human genome consists of _____________
approximately 3 billion base pairs of DNA, distributed across 23 pairs of chromosomes
how many nucleotides in genes?
about 1000-4000 nucleotides per gene
traits
organisms inherited (so in genes) physical appearance; phenotypic traits
some traits are controlled by ______ gene(s), but some by ______ gene(s)
a single gene, multiple genes
different environmental stimuli lead to ____________________
expression of different genes
DNA replication
the ability of cells to divide is the basis of all reproduction, growth, and repair of multicellular organisms
before a cell divides, it must ________ its DNA
replicate
in reproduction, cells go from ______ to ________
haploid, diploid
isolation of pure DNA (DNA was genetic material) was done by
Oswald Avery (1940)
the double-helical model for the structure of DNA was proposed by
James Watson and Francis Crick (1953)
how did the double helix model of DNA show how the molecule can carry info?
- to serve as template for duplication
- for synthesis of proteins
pyrimidine bases
cytosine, uracil (in RNA), thymine (in DNA)
purine bases
adenine and guanine
3 main chemical groups in each nucleotide
phosphate group, pentose sugar group (pyrimidine or purine), and nitrogenous base
nucleotide
building blocks (monomers) of DNA
nucleotide base pairs
A-T
G-C
A-U (in RNA)
phosphodiester bond
holds phosphate group to sugar group in DNA backbone
what are the ends of DNA?
5’ end and 3’ end
polarity in both DNA strands
a free phosphate group (PO4-3) on the 5’ end
a free hydroxyl group (OH) on 3’ end
basically no phosphodiester bond on ends
the DNA strands are _______ to each other
anti-parallel (one strand goes in 5’ to 3’ direction, and the paired strand goes in 3’ to 5’ direction)
paired DNA strands are stabilized by ________ between complimentary bases
H-bonds (A-T, G-C)
more A-T pairs or more G-C pairs
G-C pairs
Hydrogen bonds
form when positively charged H is attracted to negatively charged atoms (S, O, N)
- weak bonds
semi-conservative
DNA replication is semi-conservative
1. parent molecule
2. separation of strand
3. 2 new molecules each consisting of “daughter” strand and original strand
(slide 30 for pics) –> 2 new DNA for each original
DNA replication begins at
origins of replication (ori)
origin of replication (ori)
regions where the two DNA strands are separated, opening up a replication “bubble”
what has one oriC?
bacterial chromosomes (and plasmids)
what has 100s-1000s of oriC?
eukaryotic chromosome
replication fork
Y-shapes; at the end of each replication bubble, where new DNA strands elongate
what direction is replication done?
replication proceeds in both directions from each origin, until entire molecule is copied
enzymes and other proteins in DNA replication
helicases, single-strand binding (SSB) proteins, gyrase (or topoisomerase), DNA polymerase III, RNA primase, DNA polymerase I, DNA ligase
enzymes are
a specific type of protein that performs a specific type of function; catalyst for specific reaction
helicases
enzymes that untwist the double helix at the replication fork
single-strand binding (SSB) proteins
bind and stabilize the unwound DNA until it can be used as a template for DNA replication (makes sure they don’t reconnect)
gyrase (or topoisomerase)
corrects “over winding” ahead of replication forks by breaking, swiveling, and rejoining DNA strands
how many DNA polymerase for each strand in replication?
one DNA polymerase for each strand
DNA polymerase III
complex of proteins that catalyzes the addition nucleotides to generate new polynucleotide strands of DNA
- what is building the daughter strands
can DNA polymerase build a strand on its own?
no, cannot initiate synthesis of polynucleotide from scratch
RNA primase can build nucleotides from
nothing
where does DNA polymerase III add nucleotides to?
the 3’ end of a preexisting strand
what does RNA primase do?
adds priming sequence/RNA nucleotides one at a time at the replication fork, using parental DNA as a template to generate RNA primer (10-12 nucleotides
from that primer DNA polymerase is going to come in and add new nucleoties
how does DNA polymerase synthesize a new strand?
the 3’ end of the RNA primer (10-12 nucleotides) serves as a starting point for DNA polymerase III –> the new strand is synthesized/extended from there
RNA primer is generated by
RNA primase
what happens to the RNA primer after DNA polymerase III synthesizes the new strand?
an enzyme called DNA polymerase I comes in and removes and replaces the RNA primer with DNA nucleotides
what direction does DNA polymerase synthesize a new strand?
the new chain grows in the 5’ to 3’ direction (starts at 3’ of original strand so have to have 5’ on new strand)
draw DNA replication steps
what bond is created by the original strand and new strand with DNA polymerase III?
catalyzes formation of a phosphodiester bond between the free 3’ OH end and a 5’ phosphate group of the incoming nucleotide
what is the problem created due to the anti-parallel structure of double helix?
there is a lagging strand
- *DNA added to lagging strand in discontinuous chunks called okazaki fragments
what direction does DNA polymerase III work for the lagging strand?
works in the direction away from the replication fork (because that is where free 3’ hydroxyl end is located)
how is the lagging strand synthesized?
as a series of short DNA segments called Okazaki fragments
each Okazaki fragment on the lagging strand has its own ___ primer. ________ later removes the ___ primers and replaces them with ____
RNA primer, DNA polymerase, RNA primers and replaces them with DNA
what does DNA ligase do in DNA replication?
joins the sugar-phosphate backbones (restores phosphodiester bonds) of all the Okazaki fragments together into a continuous DNA
telomeres
end regions of chromosomes; multiple repetitive nucleotide sequences (TTAGGG) at the ends of eukaryotic chromosomes; DO NOT encode for anything
telomeres are ______ caps at the ____ of chromosomes
protective, ends
do telomeres contain genes?
no, they protect genes from being eroded through multiple rounds of DNA replication
telomerase
keeps telomeres from being eroded
- every time cell divides, you lose some telomeres (lose as you age)
