Chapter 3 (I) Flashcards
what is the life time of a single cell called?
cell cycle
the cell spends most of its time in the ______ part of the cell cycle.
interphase
what are the 3 stages in interphase?
G1, S, and G2
what stage of interphase is involved in growth, is metabolically active, synthesizes proteins rapidly, and begins centriole replication?
G1
what stage of interphase is involved in growth and DNA synthesis, and forms new histones to assemble into chromatin?
S
what stage of interphase is involved in growth and synthesis of enzymes/proteins, moves them to their proper sites, completes centriole replication, and is ready to divide?
G2
DNA synthesis begins simultaneously on several ______ and at several _______ of replication, which _______ speed of the reaction.
begins simultaneously on several chromatin threads
and at several origins of replication
which increases speed of reaction.
what are the 4 steps of DNA replication?
- uncoiling (enzyme unwinds DNA, form replication bubble)
- separation (DNA strands separate as H bonds between base pairs are broken)
- assembly (old strands act as template & DNA polymerase add nucleotides to template strand)
- restoration (ligase enzymes splice short segments of DNA together to restore double helix structure)
what happens if DNA is damaged?
stops at the the G2/M checkpoint until DNA repair mechanism fixes problem
what do histones do during replication?
associate with DNA to form chromatin strands
cell division
body growth and tissue repair
mitosis divides the ______ while cytokinesis divides the ______.
mitosis divides nucleus
cytokinesis divides cytoplasm
4 phases of mitosis?
prophase, metaphase, anaphase, telophase
what draws plasma inward to form cleavage furrow?
contractile ring
what is the contractile ring made of?
actin filaments
ratio of cell surface area to cell volume,
chemical signals (growth factors/hormones),
availability of space,
G1 and G2/M checkpoints,
and repressor genes control what?
controls cell division
what is the purpose of cyclins and CDKs?
cyclins are regulatory proteins made in G1 to power synthesis and division
CDKs bind to cyclins to be activated- tag enzymes with protein to start enzyme cascade to prepare for division
what is the function of G1 checkpoint and G2/M checkpoint?
G1- tell to go to S phase
G2/M- tell to go to M phase
what are p53 and retinoblastoma (Rb) genes?
repressor genes that suppress tumors/prevent cancer
what is a segment of DNA molecule that carries instructions for creating one polypeptide chain?
gene
what is the ratio of DNA bases in a gene to amino acids in a polypeptide?
3:1
what region codes for amino acids and what region is non-coding?
coding- exons
noncoding- introns
what is the purpose of introns?
omit/include certain exons
allow exons to be swapped between genes
allow novel combinations
what is the role of RNA
DNA decoding mechanism and messenger
what RNA does this describe:
a single strand with introns spliced out
carry coded info to cytoplasm where protein synthesis occurs
carry instructions for building polypeptides
from gene in DNA to ribosomes in cytoplasm
mRNA
what RNA does this describe:
forms ribosomes (2 subunits)
sites for protein synthesis
makes proteins based on mRNA message
rRNA
what RNA does this describe:
ferry amino acids to ribosomes
decode mRNA’s message
bind amino acids and pair with bases of codons
tRNA
transcription
DNA’s info encoded in mRNA (DNA to mRNA)
translation
info carried by mRNA decoded
used to assemble polypeptides
(mRNA to protein)
transcription cannot begin until ______ stimulate histones to loosen.
transcription factors
where does the transcription factor bind?
promoter
what is the region of DNA that serves as the start point and specifies template?
promoter
what oversees synthesis of mRNA and initiates transcription?
RNA polymerase
what are the 3 phases of transcription?
- initiation: RNA polymerase bind to promoter, pull apart DNA strands, begin mRNA synthesis
- elongation: RNA polymerase moves along template to join RNA nucleotides complementary to DNA
- termination: reach termination signal, mRNA transcript released
how is mRNA processed?
remove introns by spliceosomes
why are some amino acids represented by more than 1 codon?
protect against errors
what RNA bonds to amino acids and mRNA codon? and what is the attachment process controlled by?
tRNA binds to amino acids and mRNA codon
aminoacyl-tRNA synthetase enzyme activated by ATP controls the attachment process
once an amino acid is loaded, tRNA diffuse to _______ where amino acid is positioned.
ribosome
what site receives incoming aminoacyl-tRNA?
A site
what site involved tRNA holding growing polypeptide chain?
P site
what site is made for outgoing RNA?
E site
where does translation occur and what does it require?
occur in cytosol
requires ATP, protein factors, and enzyme
what are the 3 steps in translation?
- initiation (4 components combine at P site)
- elongation (amino acids add 1 at a time to growing peptide chain)
- termination (stop codon -UGA, UAA, UAG- arrives at A site and elongation stops)
what directs the mRNA-ribosome complex to the rough ER?
signal recognition particle
what is the role of rough ER in protein synthesis?
enclose protein in vesicle for transport to golgi apparatus
