The Cell Cycle Flashcards
The Cell Theory
3 Central Principles:
- All organisms are composed of one or more cells
- The cell is the basic unit of life of structure and function of all organisms
- All cells arise form pre-existing cells
The Cell Cycle
series of events which describes the process by which cells divide.
Interphase
- “resting stage” of the cell ycle
- actively metabolizing and synthesizing materials and components needed for cell division
Stages:
A. Gap 1 (G1) Phase
B. S Phase
C. Gap 2 (G2) Phase
Gap 1 Phase (G1)
cells increase in size and synthesize proteins and enzymes needed for DNA replication
*G0 Phase- cells become specialized and are no longer active
S Phase
cells perform DNA replication; creating two sets of DNA
Gap 2 Phase (G2)
Microtubule Synthesis
cells synthesize materials such as microtubules necessary for cell division
Interphase Processes
DNA Replication and Protein Synthesis
A. DNA Replication
- DNA———> DNA
- cell’s DNA makes a duplicate of itself with the aid of various enxymes
- Helicase (unzipper)
- Single Strand Binding Protein (holder of two strands)
- DNA Polymerase (synthesizer)
- Gyrase (reliever)
- Ligase (joins)
- Template Strand (original)
- Leading Strand (continuous)
- Lagging Strand (fragments)
Helicase
“unzips” the two DNA strands
Single Strand Binding Protein
holds the two strands
DNA Polymerase
synthesizes new DNA strand using the original (3’—>5’); producing a complimentary strand (5’——> 3’)
I. DNA Polymerase I -synthesize lagging strand
II. DNA Polymerase III synthesize leading strand
Gyrase
relieves the strain cause from uncoiling
Ligase
joins the pieces of Okazaki Fragments together
Template Strand
original strand
Leading Strand
new strand, synthesized continuously
Lagging Strand
new strand. synthesized in fragments
B. Protein Synthesis
process by which cells synthesize proteins
relies heavily on the different RNA species: mRNA, tRNA, rRNA
Processes: Transcription and Translation
Transcription
- DNA———> RNA
- formation of RNA from DNA that encdoes functional protein
- inside the nucleus
Translation
- RNA———> Protein
- formation of proteins from an RNA strand
- Each mRNA strand is called a “ codon” which corresponds to one amino acid
- Occurs in cytoplasm with ribosomes
DNA-code
mRNA-codon
tRNA-anticodon
mRNA
“Messenger RNA”
synthesized during transcription; RNA copy of the DNA coding for the protein
tRNA
“Transfer RNA”
delivers amino acids to the ribosomes, the site of translation
rRNA
“Ribosomal RNA”
component of ribosomes
CELL DIVISION
Mitosis & Meisosis
Mitosis
-occurs in somatic or body cells
-undergoes division for the purpose of growth, tissue repair and cell proliferation
-Phases:
A. Prophase
B. Metaphase
C. Anaphase
D. Telophase
Prophase
- chromatin condenses into chromosomes
- centrioles migrate to opposite poles
- nuclear envelope disintegrates and nucleolus disappears
Metaphase
- centrioles and spindle fibers attach to chromosomes at the “kinetochore”
- chromosomes are assembled at the metaphase plate or equatorial plate
Anaphase
- sister chromatids break at the centromeres
- spindle fibers pull the chromatids at opposite poles
Telophase
- sister chromatids reaches the opposite poles
- nuclear envelope starts to form
- chromsomes uncoil
- nucleoli appear
*Cytokinesis-separation of the cytoplasm of the daughter cells
Kinetechore
point of attachment of spindle fiber
Centromere
entire middle region where kinetochore is found
Meiosis
- occurs in germ cells to produce gametes
- main purpose is to generate haploid sex cells
- Meiosis I & Meiosis II
Meiosis I
- reductional division
- Mother cell: diploid
- Daughter cell: haploid; genetically unique from the mother cell
Parts: Prophase I (L, Z, P, D) Metaphase I Anaphase I Telophase I
Prophase I
Parts:
a. Leptotene- condensation of chromatins
b. Zygotene- pairing of homologous pair
c. Pachytene- crossing over of homologous pair and exchange of genetic material
d. Diplotene- homologous pair appear as tetrads
Metaphase I
tetrads line up at the equatorial plate
Anapahase I
homologous pair separate and migrate to opposite poles
Telophase I
cytokinesis begins, giving rise to two haploid daughter cells
Meisosis II
-similar process to that of Meiosis.
-However initial cells are haploid instead of daughter cells giving rise to another set of haploid cells
-Parts:
Prophase II
Metaphase II
Anaphase II
Telophase II
Mitosis Cells
Mother Cell: Somatic No. of Divisions: 1 Ploidy of Daughter Cells: Diploid Genetic Variation: - Purpose: Growth, Repair
Meiosis Cells
Mother Cell: Germ cells No. of Divisions: 2 Ploidy of Daughter Cells: 4 Genetic Variation: + Purpose: Produce Gametes
Gametogenesis
Process:
- Growth and Maturation
- Meiosis
- Differentiation
Male: Spermatogenesis
Female: Oogenesis
Spermatogenesis
Organ Involved: Testes
Formation of Polar Bodies: No
Daughter Cells : 4 spermatozoa
Time of Occurrence: starts at puberty
Oogenesis
Organ Involved: Ovaries Organ Involved: Ovary Formation of Polar Bodies: Yes Daughter Cells : 1 ovum, 3 polar bodies Time of Occurrence: begins before birth, pauses, continues at puberty
Liptotene
“Condensation”
Zygotene
“Pairing”
Pachytene
“Crossing over”
Diplotene
“Formation of tetrads”
