cell gentics Flashcards
Interphase/ Mitotic phase
Cell grows and carries on
its usual activities
mitotic phase: Cell divides into two
three subphases
G1 (gap 1): vigorous growth and metabolism
S (synthetic): DNA replication occurs
G2 (gap 2): preparation for division
DNA replication
the cell makes a copy of
DNA
Double-stranded DNA helices unwind and
unzip
Replication fork: point where strands
separate
Replication bubble: active area of
replication
Each strand acts as a template for a new
complementary strand
RNA starts replication by laying down short
strand that acts as a primer
DNA polymerase
attaches to primer and
begins adding nucleotides to form new strand
DNA polymerase synthesizes both new
strands at one time
End result
two identical “daughters”
DNA molecules are formed from the
original
Mitosis
Prophase
Metaphase
Anaphase
Telophase
Interphase
Dung interphase, nuclear material is in uncondensed chromatic state
Semi conservative replication
Each new double- stranded DNA is composed of one old strand and one New strand
Semi conservative replication
Each new double- stranded DNA is composed of one old strand and one New strand
Early prophase
Chromatin condenses, forming visible chromosomes
•Each chromosome and its duplicate (called sister chromatids) are held together by a centromere
•Centrosome and its duplicate begin synthesizing microtubules that push each centrosome to opposite poles of cell
Late prophase
Nuclear envelope breaks up
•Special microtubules attach to specific area on centromeres called kinetochore and serve to pull chromosomes to center of cell
•Remaining nonkinetochore microtubules push against each other, causing poles of cell to move farther apart
Metaphase
Centromeres of chromosomes are precisely aligned at cell’s equator
Anaphase
‘Centromeres of chromosomes split simultaneously—each sister chromatid now becomes a separate chromosome
Telophase
chromosome movement stops
•Each set of chromosomes (at opposite ends of cell) uncoils to form chromatin
•New nuclear membranes form
Cytokinesis final phase
Begins during late anaphase and continues through mitosis Two daughter cells are pinched apart
Protein Synthesis
DNA is master blueprint that holds the code for protein synthesis
Transcription
‘DNA information coded in mRNA
Translation
mRNA decoded to assemble polypeptides
Translation
mRNA decoded to assemble polypeptides
Transcription factors
protein complex) activate transcription ‘
Loosening histones from DNA in area to be transcribed so DNA segment can be exposed
•Binding to special sequence of gene to be transcribed, called promoter (starting point)
‘
•Mediating binding of RNA polymerase, enzyme that synthesizes mRNA, to promoter region
Initiation
RNA polymerase separates DNA strands
Elongation
RNA polymerase adds complementary nucleotides to growing mRNA matching sequence of based on DNA template strand
Termination
Transcription stops when RNA polymerase reaches special termination signal code
-Anticodon
. at other end (head) is triplet code that determines which amino acid will be bound at stem
Translation. Initiation
Small ribosomal subunit binds to a special initiator tRNA (methionine) and then to the mRNA to be decoded
Translation
Elongation
►Codon recognition: tRNA binds complementary codon in A site of ribosome
►Peptide bond formation: Ribosomal enzymes transfer and attach growing polypeptide chain from tRNA in P site over to amino acid of tRNA in A site
Translation
Termination
When one of three stop codons (UGA, UAA, UAG) on mRNA enters A site, translation ends’Final polypeptide product will be further processed by other cell structures into functional 3-D protein
