Mod 2 Chap 6 - Cell Division Flashcards
Main phases of the cell cycle
The main phases of the cell cycle are the interphase and the mitotic (division) phase
What happens in the interphase of the cell cycle?
Interphase of the cell cycle
-Growth of cells
-No divisions taking place
-DNA is replicated
-Protein synthesis in the cytoplasm
-Mitochondria grow and divide
-Chloroplasts grow
-Metabolic processes occuring
Three stages of the interphase
3 stages of the interphase:
-G1 = synthesis of proteins, organelles replicate. Cells increase in size
-S = DNA replication
-G2 = cell increases more in size, energy stores increase, duplicated DNA checked for errors
The two stages of the mitotic phase of the cell cycle?
Mitosis (cell divides) and cytokineses (cytoplasm divides and two cells produced)W are the stages of the mitotic phase of the cell cycle
Why do cells leave the cell cycle?
Cells leave the cell cycle because of:
-Differentiation = specialised cells no longer divide
-DNA of the cell may be damaged, and so enters permanent cell arrest and no longer divides. This increases with age, or with diseases such as cancer
It is vital that the cell only divides when…
It is is vital that the cell only divides when it is big enough in size, DNA is error-free/repaired, chromosomes are in correct positions for mitosis
What are the control mechanisms of the cell cycle?
Checkpoints are the control mechanisms of the cell cycle to monitor that a phase has been done correctly
Where is the metaphase checkpoint of the cell cycle?
The metaphase checkpoint of the cell cycle is is the point in mitosis where all chromosomes are attached to spindles and have aligned
Why is mitosis important?
Mitosis is important for tissue growth and repair, and for asexual reproduction to produce genetically identical cells
Why is it important that chromosomes are kept together in cell division?
It’s important for chromosomes to be kept together in cell division so they can be precisely manoeuvred and segregated equally, one each into the new daughter cells
Stages of mitosis
Stages of mitosis are the prophase, metaphase, anaphase, telephase
What happens during prophase of mitosis?
Prophase of mitosis:
-Chromatin fibres coil and condense to form chromosomes, which takes up the stain to be viewed with a light microscope
-Nuclear membrane begins to break down
-Protein microtubules form spindle fibres that that link poles of the cell
-Nuclear envelope dissapeares at end of stage
What happens during the metaphase of mitosis?
Metaphase of mitosis:
-Chromosomes pulled to equator by spindle fibres to form a centre called metaphase plate
What happens during the anaphase of mitosis?
Anaphase of mitosis:
-Centrosomes divide, so chromosomes are pulled apart and the chromatids seperate to poles
What happens during the telophase of mitosis?
Telophase of mitosis:
-Nuclear envelope reforms around them
-Chromosomes uncoil and and nucleolus forms
-Cytokenesis (cell division) begins
Cytokenesis in animal cells
Cytokenesis in animal cells:
-Cell surface membrane forms and is pulled inwards by cytoskeleton until it’s close enough to centre to fuse around middle and form two cells
Cytokenesis in plant cells
Cytokenesis in plant cells:
-Vesicles from golgi apparatus form where the metaphase plate was
-Vesicles fuse with eachother and surface membrane to divide cell into two
What is a diploid?
A diploid is two chromosomes of each type (one inherited from each parent)
Term for a fertilised egg
A fertilised egg is a zygote
What is a haploid?
A haploid has half the number of chromosomes as the parent cell
What is meiosis also known as?
Meiosis is also known as reduction division - this is because cel;s go from diploid to haploid as the number of chromosomes are halved
What are alleles?
Alelles are different types of the same gene
Two divisions involved in meiosis
The two divisions involved in meiosis:
-Meisosis I = pairs of homologous chromosomes seperated into two cells, the cells are haploid as each cell contains one full set of genes instead of two
-Meiosis II = pairs of chromatids in each daughter cell seperated, two more cells are formed
Meoisis: Meiosis I: Prophase I
Prophase I:
-Chromosomes condense
-Nuclear envelope disintegrates
-Nucleolus dissapears
-Spindle formation
-Chromosomes arranged in homologous pairs (forms BIVALENTS)
-Crossing over takes place
Meiosis: Meiosis I: Metaphase I
Metaphase I:
-Bivalents line at equator of spindle
-Independant assortment takes place: paternal and maternal chromosomes become independant > leads to genetic variance
Meiosis: Meiosis I: Anaphase I
Anaphase I:
-Homologous pairs seperated as chromosomes pulled to poles by spindle fibres - centromeres DON’T divide
Meiosis: Meiosis I: Telephase I
Telephase I:
-Chromosomes at poles
-Spindle fibres break down
-Nuclear envelope and nucleolus reforms
Meiosis: Meiosis II: Prophase II
Prophase II:
-Nuclear envelope breaks down and chromosomes condense
-Spindle formation
Meiosis: Meiosis II: Metaphase II
Metaphase II:
-Chromosomes line up single file at centre of cell
Meiosis: Meiosis II: Anaphase II
Anaphase II:
-Centromeres divide and individual chromosomes pulled to poles
-This creates four groups of chromosomes that have half the number of chromosomes compared to the original parent cell
Meiosis: Meiosis II: Telephase II
Telaphase II:
-Chromosomes at poles of cell
-Nuclear envelope and nucleolus reformation
Cytokenesis in meiosis II
In cytokenesis of meiosis II, 4 daughter cells have been produced, each being haploid due to the reduction division, and each is genetically different to eachother due to crossing over and independant assortment
Totipotent
Totipotent is when stem cells can differentiate into any cell type
Pluripotent
Pluripotent is when stem cells can differentiate into any cell type but cannot make whole organisms
Multipotent
Multipotent is when stem cells can only a form a certain range of cells within a certain type of tissue
Two sources of adult stem cells
Sources of adult stem cells;
-Embryonic = totipotent
-Adult stem cells = found in specific areas eg bone marrow = multipotent, but can be artificially triggered to become pluripotent
Advantages of harvesting adult stem cells from umbilical cords
Advantages:
-Plentiful supply
-By using own persons umbilical cord, stem cells will not be rejected
Source of plant stem cells
Plant stem cells come from meristematic tissue (located on tips of roots and shoots, and between phloem and xylem tissues. They are pluripotent
Diseases where stem cells can be used
Diseases where stem cells can be used:
-Heart disease - to replace heart tissue thats been damaged due to heart attacks
-Type 1 diabetes - to make insulin-producing cells
-Parkinsons disease - to make dopamine-producing cells
-Alzheimers disease - replacing damaged brain cells
-Macular degeneration
-Birth defects
-Spinal injuries
Where are stem cells already being used?
Stem cells are currently used in the treatment of burns and for drug trials and developmental biology
Erythrocytes adaptations
Erythrocytes adaptations:
Biconcave shape + having no nucleus allows erythrocytes to fit through narrow cappilaries
Neutrophils adaptations
Neutrophils adaptations:
Multi-lobed nucleus that makes it easier to squeeze through small gaps
Palisade cells adaptations
Palisade cells adaptations:
-Thin cell walls > allows for rapid diffusion of carbon dioxide
Describe how a gene is a code for the production of a polypeptide
-Base nucleotide sequence arranged in triplets which determines the amino acid sequence
What is the fixed position called that’s occupied by a gene on a DNA molecule?
Genes are located on loci/locus on DNA molecules
Difference between pre-mRNA and mRNA strands
Pre-mRNA has introns and exons for splicing wheras mRNA only has exons
Structural differences between tRNA and mRNA
Structural differences between tRNA and mRNA:
-tRNA contains hydrogen bonds wheras mRNA dont
-mRNA contains codons wheras tRNA contains anticodons
