Level 2 Bio: Cell division & DNA Flashcards
What is the full name of DNA
Deoxyribonucleic acid
What is the full name of RNA
Ribonucleic acid
What are DNA & RNA made of
long chains of molecules called nucleotides.
What is the complimentary base pairing rule
A to T and C to G
What is the full name of A
Adenine
What is the full name of T
Thymine
What is the full name of C
Cytosine
What is the full name of G
Guanine
What are the 2 ends of strands of DNA
the 5’ end (5 prime end) and the 3’ end (3 prime end)
What is the nucleolus involved in
the construction of ribosomes
What are the nuclear pores involved in
the active transport of substances into & out of the nucleus.
What is the nuclear membrane
A double membrane enclosing the nucleus. It is continuous with the endoplasmic reticulum.
What is chromatin
The complex of DNA and proteins that makes up chromosomes. The DNA is coiled up so that the long DNA molecules can fit inside the nucleus.
What are the individual atoms involved in making deoxyribose sugars, phosphate and nucleotide base components
carbon, hydrogen, oxygen, phosphorus & nitrogen.
Where are chromosomes located in the cell
Nucleus
What are chromosomes made up of
Chromatin
What do chromosomes store
the information for controlling a cell.
What is the purpose of the cell cycle.
The cell cycle involves the production of new cells and the growth of those cells. New cells are produced by Mitosis.
What is the purpose of DNA replication
The purpose of DNA replication is to produce two identical copies of the cells’ DNA
Why is DNA replication necessary
It is necessary so that each new cell has the required identical genetic information.
When does DNA replication occur in relation to Mitosis
It occurs before Mitosis
What is semi-conservative
When DNA is replicated 1 strand is old (original) & has been conserved. The other strand is new.
What is the first step of DNA replication
The first step requires that the coiled DNA is allowed to uncoil by creating a swivel point. This is done by an enzyme called helicase.
What is the process that occurs between the first and second stages of DNA replication
New pieces of DNA are formed from free nucleotide units joined together by enzymes. Enzymes control the whole process.
What is the second stage of DNA replication
DNA is only read in the 3’ to 5’ direction so the new strand being created in the 5’ to 3’ direction. This only happens on one strand, the leading strand. The other strand is from 5’ to 3’ which bases can’t be added to (the lagging strand)
What is the third stage of DNA replication
The leading strand, can be made as a continuous, complete strand. An enzyme called DNA polymerase joins all the nucleotides together.
What is the fourth stage of DNA replication
This strand is made up of small fragments that are stuck together later by ligase enzymes. Each little fragment (1000 bases long) is reading the parent strand from 3’ to 5’. They are called Okazaki fragments.
What is the fifth stage of DNA replication
Once replicated the two new strands of DNA coil up into a helix. Each of the two newly formed DNA strands will go into forming a chromatid.
What are the stages of the cell cycle
G1, S, G2
What is the G1 stage
Growth phase- cell carrying out ‘normal’ cell processes’ growing
What is the S stage
Synthesis DNA replication- DNA condenses into chromosomes, then DNA replication occurs.
What is the G2 stage
Growth phase- cell checks replicated DNA, corrects any mistakes.
What is the purpose of Mitosis
The purpose of Mitosis is to produce 2 genetically identical cells for the growth of organisms and the repair of tissues/replacement of cells.
What are the 6 stages of Mitosis
1) Interphase
2) Prophase
3) Metaphase
4) Anaphase
5) Telophase
6) Cytokinesis
What happens in Interphase
Chromosomes are replicated (# doubles)
Chromosomes appear as threadlike coils (chromatin) at the start, but each chromosome and its copy (sister chromosome) change to sister chromatids at end of this phase.
What happens in Prophase
Mitosis begins (cells begin to divide)
Centrioles (or poles) appear and begin to move to opposite ends of cell.
Spindle fibres form between the poles.
What happens in Metaphase
Chromatids (or pairs of chromosomes) attach to the spindle fibers
What happens in Anaphase
Chromatids (or pairs of chromosomes) separate and begin to move to opposite ends of the cell.
What happens in Telophase
Two new nuclei form
Chromosomes appear as chromatin (threads rather than rods)
Mitosis ends.
Nucleus begins to form
What happens in Cytokinesis
Cell membrane moves inward to create two daughter cells - each with its own nucleus with identical chromosomes.
What are the factors affecting cell division
Just like every cell process many of the stages of the cell cycle are controlled by enzymes. Therefore, the factor that affect enzymes will also affect the rate of Mitosis.
Temperature, pH, substrate concentration
As an infant becomes an adult what occurs
Lot’s of growth will be occurring & therefore the rates of Mitosis are higher in infancy & childhood.
For plants when is the rate of Mitosis is highest
during seasonal growth
What animal cells are most likely to become damaged
Skin & hair cells are exposed to the environment & are therefore most likely to become damaged. Therefore the rate of Mitosis is higher in skin & hair cells as opposed to brain or heart cells.
For plant cells what cells are most likely to become damaged.
The roots & leaves are the most likely to be damaged, & so Mitosis rates are highest here.
What are the stages of Mitosis in plants
Interphase
Early Prophase
Late Prophase
Metaphase
Anaphase
Late Anaphase
Telophase
Cytokinesis
What happens in Interphase in plants
DNA is replicated, centrosome which later forms the spindle is also replicated, cell enters Mitosis
What happens in Early Prophase in plants
DNA continues condensing into chromosomes and the nuclear membrane begins to disintegrate.
What happens structurally in Prophase 1 (Meiosis)
Step 1: Chromosomes have shortened & thickened, becoming clearly visible as two chromatids held together by a CENTROMERE. The group of four chromatids is called a TETRAD or a BIVALENT.
Step 2: Parts of adjacent chromatids can CROSS OVER & recombine.
What happens structurally in Metaphase 1 (Meiosis)
Step 3: The chromosomes arrange themselves along the cell equator, with each member of a pair of homologous chromosomes orientated towards an opposite pole. SPINDLE fibres begin pulling the homologous chromosomes apart.
(Meiosis) What happens in Anaphase 1 (to do with chromosomes)
At the next stage of meiosis (Anaphase 1) any combination of chromosomes from each of the homologous pairs can move towards the cell poles.
(Meiosis) What happens structurally in Anaphase 1
Step 4: The homologous pairs separate & move towards the cell poles. The cell membrane begins to close up between them.
(Meiosis) What happens structurally in Telophase 1
Step 5: Two new cells form, both genetically unique because of the random assortment of alleles on the chromosomes that separated (& from crossing over) at Metaphase 1.
(Meiosis) What can the chromosomes now do after Telophase 1
The chromosomes can now undergo a resting time in which they unravel. Further shortening & thickening indicates the start of the second stage of divisions. This stage is known as Prophase 2.
(Meiosis) What happens structurally in Metaphase 2
Step 6: Chromosomes line up on the cell equator of each cell. Spindle fibres form. As in Metaphase 1, the positioning of chromosomes along the cell equator is random.
(Meiosis) What happens structurally in Anaphase 2
Step 7: Chromatids separate & move towards the cell poles. Cell membranes constrict between them.
(Meiosis) What happens structurally in Telophase 2
Step 8: Four new haploid daughter cells have formed, each of different genetic makeup from the other. These cells are the gametes.
(Meiosis) At step 7, which __________ gets pulled into each new cell is random. This random assortment of ___________ and __________, like the exchange of genetic material during step 2 and the different alleles present on each chromosomes, increases the genetic variability of the gametes formed.
At step 7, which CHROMOSOME gets pulled into each new cell is random. This random assortment of CHROMOSOMES and CHROMATIDS, like the exchange of genetic material during step 2 and the different alleles present on each chromosomes, increases the genetic variability of the gametes formed.
What is the full name of U
Uracil
Why is DNA classified as a polymer
Because its made up of many repeating units
What are Adenine & Guanine
Purines
What are Cytosine, Thymine & Uracil
Pyrimidines
What is reduction division used for
Used to form gametes (sex cells)
What happens in meiosis to do with cell divisions
In Meiosis the chromosomes are replicated once but the original cell undergoes 2 cell divisions.
