Review- Test 4 Flashcards
(66 cards)
What are the steps of DNA replication?
- unwinding of the DNA molecule
- complementary nitrogen base pairing
- joining of the DNA nucleotides
What happens in step one of DNA replication? (unwinding of the DNA molecule)
helicase unwinds the DNA molecule and breaks the hydrogen bonds between nitrogen bases, DNA template strands separate, DNA nitrogen bases are left exposed (unpaired), RNA primase adds a primer to a “promoter” region on DNA template strands to begin replication
What happens in step two of DNA replication? (complementary nitrogen base pairing)
new DNA nucleotides with their nitrogen bases diffuse into the nucleus and the nitrogen bases pair up with their complements on the DNA template strands, new DNA nucleotides with their nitrogen bases pair up with complements in a 5’ to 3’ direction according to the new strand, DNA polymerase acts as a “proof reader” to ensure that the correct nucleotide with its nitrogen base is in the proper place, hydrogen bonds form between complementary nitrogen bases
What happens in step three of DNA replication? (joining of the DNA nucleotides)
DNA polymerase catalyzes the formation of covalent bonds between adjacent nucleotides, ligase joins Okazaki fragments together (and seals “nicks”) between phosphate groups and pentose sugars
What is the purpose of DNA polymerase in DNA replication?
It catalyzes (speeds up) the formation of covalent bonds between adjacent nucleotides.
Where does DNA replication occur within the cell?
the nucleus
each new DNA molecule is composed of one original (template) DNA strand and one new strand
semi-conservative replication
properties of mitosis: location
animals: skin, liver, muscles, hair (in the dermis), stomach, etc.
plants: meristem
properties of mitosis: chromosome number
stays the same from cell to cell (46 chromosomes in humans, 104 in goldfish, etc.)
properties of mitosis: genetics
produces genetically identical cells
basic structure of a duplicated (double-stranded) chromosome
2 sister chromatids (genetically identical) and 1 centromere (holds them together)
Name the components of the cell cycle.
interphase, mitosis, cytokinesis
What are the main structures seen in a cell when it is in its Interphase state?
intact nuclear membrane, nucleolus is present, chromatin (unwound DNA + protein) present
In which part of Interphase does DNA replication occur?
S phase
Name the stages of mitosis (in order).
Prophase,
Metaphase,
Anaphase,
Telophase
What happens in prophase?
chromatin condenses into visible chromosomes, nuclear membrane begins to break down and eventually disappears, nucleolus disappears, pairs of centrioles migrate to opposite poles of the cell, spindle fibers appear, asters appear;
(centrioles and asters are only found in animal cells)
What happens in metaphase?
distinct and short-lived; centromeres of the chromosomes align themselves at the equator, spindle fiber formation is complete and the spindle fibers attach to the centromere of the duplicated chromosomes
What happens in anaphase?
centromeres of the duplicated chromosomes will split, chromatids separate and move away from one another, chromatids are now called chromosomes, chromosomes migrate to opposite poles of the cell
What happens in telophase?
chromosomes reach their poles and uncoil back into chromatin, nuclear membrane reforms around the chromatin, a new nucleolus reappears, spindle fibers disassemble and dissappear, asters disappear, cytokinesis begins
Is interphase a stage of mitosis?
no
the process by which one mother cell divides into two genetically identical daughter cells
mitosis
the division of the cytoplasm and associated cell parts (both plants and animals), occurs in very late mitosis (late anaphase/early telophase)
cytokinesis
What structure forms in plant cells during cytokinesis?
cell plate
What structure forms in animal cells during cytokinesis?
cleavage furrow
