topic 3 Flashcards
what is the operon?
A unit made up of linked genes which is thought to regulate other genes responsible for protein synthesis.
(Codes for a repressor protein which binds to the operator, preventing RNA polymerase from transcribing the gene of interest)
what is the lac operon?
The lactose operon is an operon required for the transport and metabolism of lactose in E. coli and many other enteric bacteria.
What happens during the mitotic phase?
The replicated DNA and cytoplasmic contents are separated and the cell divides
What happens during the interphase?
The cell grows and DNA is replicated
What are the 3 growth stages during interphase?
G1 - The cell grows
S - DNA synthesis happens
G2 - The cell grows some more before the mitotic phases begins
What is mitosis?
The part of the cell cycle in which a eukaryotic cell divides to produce two daughter cells, each with identical copies of DNA produced by the parent cell during DNA replication
Multicellular organisms go through mitosis to grow and repair damaged tissues
What are the 5 stages of mitosis?
Interphase
Prophase
Metaphase
Anaphase
Telophase
What happens during Interphase?
The cell prepares to divide
DNA is replicated (2 copies of every chromosome)
The organelles are replicated
More ATP is produced to be used in cell division
What happens during Prophase?
The nuclear envelope breaks down and the nucleolus disappears
The chromosomes coil tightly and become shorter and fatter (can be seen under a light microscope)
Small centrioles move to opposite poles of the cell
Microtubules form the mitotic spindle between the centrioles
What happens during Metaphase?
The chromosome line up along the mid-line of the cell
In the metaphase, the chromosomes are maximally condensed
They are attached to the spindle by the centromere
What happens during Anaphase?
The chromosomes break into two chromatids. The sister chromatids are separated at the centromere
The spindles contract and pull the chromatids to each pole of the cell
What happens during Telophase?
The chromosomes reach the opposite poles and begin to decondense, becoming chromosomes again
Nuclear envelopes form around the chromosomes so there are now two nuclei
The cytoplasm splits and two daughter cells are formed.
Only a few cells are able to continue dividing in a multicellular organism. In plants, the growing tips of roots and shoots contain meristem tissue that can divide by mitosis for growth.
What are the stages of Preparation of Stained Squashes of Cells from Root Tips?
1) Sample preparation
wear gloves, 5m hydrochloric acid, after 5min rinse tips
2) Cut the root tips
2mm long, place on clean slide
3) Staining
toluidine blue stain
4) Squashing
macerate
5) Viewing the sample
What is the role meiosis?
Meiosis is the process that produces haploid gamete cells from diploid cells. Meiosis is necessary for sexual reproduction to take place.
What does meiosis produce?
Meiosis produces 4 genetically different daughter cells
Each daughter cell receives a different combination of chromosomes
Meiosis increases genetic diversity in this way
Meiosis produces four genetically different daughter cells. Genetic variation is generated in each daughter cell in two ways. These are:
Crossing over
Independent assortment
How are sperm cells specialised for their function?
Tail helps produce movement (also streamline shape)
Mitochondria found in the midpiece to provide energy
The genetic material is contained in the head, inside a nucleus. The head is the only part of the egg to enter the egg
The head is covered by acrosome, which releases enzymes to break down the zona pellucida (eggs outer membrane)
Sperms are very small, so males can make many of them to increase the chance of feritlisation
How are egg cells specialised for their function?
The cytoplasm is high in nutrients which are used when the embryo is growing
The outer membrane of the egg is called the zona pellucida, which plays a role in preventing polyspermy, where more than one sperm fertilises the egg
What happens during the acrosome reaction?
A sperm finds the egg by following the chemicals the egg releases. (chemotaxis)
Once it reaches the egg, the acrosome reaction is initiated
The inner membrane of the acrosome fuses with the plasma membrane of the head of the sperm
This exposes the acrosome, which release enzymes to break down the zona pellucida
Sperm can the break through to the cell surface membrane of the egg and bind to it
What happens during the cortical reaction?
Once the head of the sperm has fused to the cell surface membrane, cortical granules (a type of vesicle) move to the cell surface membrane in the egg and fuse with the membrane
The contents of the cortical granules are exocytosis and it prevents any other other sperm from binding
What happens during nuclei fusion?
Once the head of the sperm cell has entered the egg cell, the second meiotic division occurs in the egg, so that a haploid egg nucleus can fuse together with the nucleus from the sperm. Fusion of the two nuclei produces a diploid zygote
What are the 4 types of stem cells?
Totipotent
Pluripotent
Multipotent
Unipotent
Describe totipotent cells.
Able to produce any type of body cell, as well as cells of supportive structures such as the placenta.
Most unspecialised
Only exist for a very limited time during embryonic development in mammals
They become specialised during embryonic development. (when specialised only some genes are activated (only activated genes are expressed))
Describe pluripotent cells.
Totipotent cells can develop into pluripotent cells in embryos
Pluripotent cells are able to divide in unlimited numbers and produce any type of that makes up the body (adults)
Can be used to treat human disorders
