How does a gene leave the nucleus of a cell to assist with protein synthesis?
Genes cannot leave the nucleus, so a copy is made.
This copy leaves the cell and travels to the ribosomes so that proteins can be made by the cell.
What two main stages does protein synthesis involve?
1) transcription: the production of mRNA from the DNA in the nucleus of the cell
2) translation: the production of proteins from mRNA at the ribosomes on the cytoplasm
What is Messenger RNA?
The genetic information that is required to make a specific protein is transported from the DNA in the nucleus to the ribosomes in the cytoplasm by a specialised molecule called mRNA.
Genetically identical cells are produced by the cell division called .....
Gametes are produced by a cell division called .....
What is mitosis and when does it happen?
Mitosis is when the whole cell divides because more cells that are exactly the same as the parent cell are needed.
Mitosis is involved in cell growth and the replacement of damaged or worn out cells.
What is a cell cycle?
The whole process of cell growth and division.
The cycle begins with the number of organelles increasing, to ensure that each of the two new cells receive copies of all the organelles.
In mitosis, before a cell divides every chromosome must make a copy of itself. What is each new pair of chromosomes called?
A pair of sister chromatids.
What is meiosis?
The cell division which forms the male and female gametes.
What is meiosis sometimes referred to as, and why?
A reduction cell division.
It is called this because each gamete has only 23 chromosomes.
What are the two main features of meiosis?
- the chromosomes are copied
- the cell divides twice forming four gametes
Why do human body cells contain 46 chromosomes?
When the fertilisation of the nuclei occurs a sperm and an egg join to form the zygote.
The zygote contains 46 (23 pairs) chromosomes; 23 chromosomes from the sperm and 23 from the egg making 46 in total.
In sexual reproduction a male gamete fuses with a female gamete to produce a new cell. This fusion of the gametes is called...
Give three example is organs or tissues where mitosis takes place..
- the red bone marrow of the skelton, to produce blood cells
- the basal layer of the skin including hair follicles
- in tissue where growth is occurring, eg: ends of bone shafts or in the lining epithelium of the gut
Name two organs in which meiosis may take place..
- the testes
- the ovaries
Where in the cell are proteins made?
Briefly outline the stages of mitosis..
- multicellular organisms begin life as a single fertilised egg cell called a zygote
- the chromosomes in the nucleus are copied
- the nucleus splits in two and genetic information is shared between these two chromatids
- the cytoplasm then divides (in plant cells, a new cell wall develops) forming two smaller cells
- these take in food substances to supply energy and building materials so they can grow to full size
- the process is repeated and as the embryo grows, cells become specialised to carry out particular roles