The Cell Cycle & Differentiation Flashcards
What is the first stage to DNA replication?
The enzyme DNA helicase breaks the hydrogen bonds between the two polynucleotide DNA strands.
The helix unzips to form two single strands.
What is the second stage to DNA replication?
Each original single strand acts as a template for a new strand.
Free-floating DNA nucleotides join to the exposed bases on each original template strand by specific base pairing- A with T and C with G.
What is the third stage to DNA replication?
The nucleotides on the new strand are joined together by the enzyme DNA polymerase.
Hydrogen bonds form between the bases on the original and the new strand.
Each new DNA molecule contains one strand from the original DNA molecule and the one new strand.
What is DNA replication type of copying called?
Semi-conservative replication because half of the new DNA molecules are from the original piece of DNA.
What is the cell cycle?
The process that all body cells from multicellular organisms use to grow and divide.
The cell cycle starts when a cell has been produced by cell division and ends with the cell dividing to produce two identical cells.
What does the cell cycle consist of?
A period of cell growth and DNA replication, called interphase
A period of cell division, called mitosis.
Interphase (cell growth) is subdivided into three seperate growth stages- G1, S and G2.
What are the stages?
Mitosis- the cycle starts and ends here.
Gap phase 1- cells grows and new organelles and proteins are made.
Synthesis- cell replicates its DNA, ready to divide by mitosis.
Gap phase 2- cell keeps growing and proteins needed or cell division are made.
What happens during interphase?
The cell carries out normal functions, but also prepares to divide.
The cell’s DNA is unravelled and replicated, to double its genetic content.
The organelles are also replicated so it has spare ones, and its ATP content is increased ATP provides the energy needed for cell division.
What form of cell division happens during the cell cycle?
Mitosis.
The structure of chromosomes.
As mitosis beings, the chromosomes are made of two strands joined in the middle by a centromere.
The separate strands are called chromatids.
Two strands on the same chromosome are called sister chromatids.
There are two strands because each chromosome has already made an identical copy of itself during interphase.
When mitosis is over, the chromatids end up as one strand chromosomes in the new daughter cells.
What is 1. prophase?
Chromotin condenses into chromosomes
The nucleolus disappears.
Tiny bundles of protein called centrioles start moving to opposite ends of the cell, forming a network of protein fibres across it called the spindle.
The nuclear envelope breaks down and chromosomes lie free in the cytoplasm.
What is 2. metaphase?
The chromosomes (each with two chromatids) line up along the middle of the cell and become attached to the spindle by their centromere.
What is 3. anaphase?
The centromere divide, separating each pair of sister chromatids.
The spindles contract, pulling chromatids to opposite ends of the cell, centromere first.
What is 4. telophase?
The chromatids reach the opposite poles on the spindle.
They uncoil and become long and thin again.
They’re now called chromosomes again.
A nuclear envelope envelope forms around each group of chromosomes, so there are now two nuclei.
The cytoplasm divides and there are now two daughter cells that are genetically identical to the original cell and to each other.
Mitosis finished and each daughter cell starts interphase ready for next round of mitosis.
How many cells are produced during mitosis?
2
