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  • Created by: Faith16
  • Created on: 07-12-15 19:37
Decribe a DNA molecule.
It has two strands which are coiled together to form a double helix. Each strand is made up of lots of small units called nucleotides. Each nucleotide contains small molecules called bases.
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What are the bases called and what bases is paired to what?
Adenine (A) is paired to Thymine (T) and Cytosine (C) is paired to Guanine (G). This is called base pairing.
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What is a gene?
A section of DNA that contains instructions for one particular protein.
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How do cells make proteins?
By joining amino acids together in a paricular order. The order of bases in a gene tells the cell in what order to put the amino acids. Each set of 3 bases (triplet) codes for one amino acid.
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What are ribosomes?
Organelles that make proteins within the cell cytoplasm.
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How is information for DNA taken to the ribosomes?
A copy of the DNA is made using messenger RNA. This is similar to a DNA molecule but it is much shorter and only a single strand.
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How does messenger RNA work?
The two DNA strands upzip and a mRNA is made using one strand of the DNA as a template. The mRNA moves out of the nucleus to join with a ribosome in the cytoplasm.
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What is the job of the ribosome?
To stick amino acids together in a chain to make a protein following the order of bases in the mRNA.
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What is mitosis?
When your cells divide in order to make new ones. Mitosis produces two new genetically identical new cells (clones of each other and parent cell)
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What is the process of mitosis?
1.The cell has two copies of DNA that spread out in long strings. 2. The DNA forms X-shaped chromosomes. These are duplicates.3. The chromosomes line up in the centre and the cell fibres pull them apart.
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Process of mitosis continued.
4. Membranes form around each of the sets of chromosomes, these become nuclei for the two new cells. 5. the cytoplasm divides.
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What is meiosis?
The dividing of gametes- sperm and egg cells. This produces four not identical cells.
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What is the process of meiosis?
1. The DNA duplicates itself so it has an exact copy of itself. 2. the chromosome pairs line up in the centre of the cell. 3. The pairs are pulled apart so each cell only has one copy of each chromosome (each from father and mother).
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Process of meiosis continued.
4. The chromosomes line up in the centre of the cell again and the arms of the chromosomes are pulled apart. 5. You get four gametes each with only a single set of chromosomes in it (they all have random sets of chromosomes)
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What is a zygote?
A fertilised egg
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What are embryonic stem cells?
The cells that a zygote begins with. They are all undifferentiated.
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When do the cells being to become specialised in a zygote?
Eight cell stage.
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Where do adults have stem cells?
In places such as bone marrow.
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Why can adult stem cells only become certain types of cells?
Because all body cells contain the same genes but in specialised cells most of the genes are not active. They only product specific proteins that they need in order to be a certain cell.
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What are adult stem cells used for?
They are used to cure diseases. For instance people with blood diseases can be treated by bone marrow transplants as they contain stem cells that can turn into new blood cells to replace the bad ones.
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What do scientists do to embryonic stem cells to get a certain type of cell?
Scientists put stem cells under different conditions to activate certain genes.
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What is the negative side of embryonic stem cells?
People think it is unethical as the embryos used to provide the stem cells are destroyed and they could of become a person.
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How can cloning make stem cells?
An egg cell is taken and you remove its genetic material. The nucleus is put into an 'empty' egg cell. Under the right conditions inactive gene in the nucleus can be reactivated so that an embryo forms. The stem cells can be extracted from the embryo
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Where in plants are the only cells that divide mitotically active?
Meristems which is found in roots and shoots.
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What are meristems?
They are like embryonic stem cells- they can divide into any cell for as long as the plant lives.
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What do unspecialised cells form when specialised in plants?
Tissues like xylem and phloem (water and food transport tissues) which can group together to form organs such as leaves, roots, stems and flowers.
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What is a cutting?
Where you tale a bit of a plant to clone it. They are taken from an area where it contains unspecialised meristem cells which can differentiate to make any cell.
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What do people do to make cuttings grow?
Add rooting powder which contains plant hormones like auxins to the soil. The cuttings will produce roots rapidly and start growing new plants.
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What is phototropism?
Growth towards or away from light.
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What is positive phototropism?
Growing towards the light.
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What is an example of positive phototropism?
Plants need sunlight for photosynthesis else they will not survive as they won't produce the food they need for energy and growth. Photosynthesis occurs mainly in the leaves so it is important for plant shoots to grow towards the light.
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What is negative phototropism?
Growing away from the light.
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What is an example of negative phototropism?
Plants need nutrients and water from the soil to grow. Therefore phototropism causes the roots to grow away from the light and down into the soil. This is where they can absorb the water and nutrients that plants need for healthy growth.
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What is auxins?
Plant growth hormones that control the growth of the tips of shoots and roots.
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What happens when auxins are produces in the tips of plants?
The auxins diffuse backwards to stimulate the cell elongation (enlargement) process. This happens just behind the tips.
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What are auxins involved in in the plant?
Responses to light, gravity and water.
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Why do auxins make shoots grow toward the light?
When a shoot tip is exposed to light more auxin accumulate on the side thats in the shade than the side thats in the light. This makes the cells grow (elongate) faster on the shaded side so that the shoot grows towards the light.
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Other cards in this set

Card 2


What are the bases called and what bases is paired to what?


Adenine (A) is paired to Thymine (T) and Cytosine (C) is paired to Guanine (G). This is called base pairing.

Card 3


What is a gene?


Preview of the front of card 3

Card 4


How do cells make proteins?


Preview of the front of card 4

Card 5


What are ribosomes?


Preview of the front of card 5
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