B5 - Growth and Development Flashcards
What does MRS GREN stand for?
Movement
Respiration
Sensitivity
Growth
Reproduction
Excrete
Nutrition
Tissue: what is it? Give an example
A group of cells doing the same job; e.g. Bone, blood, muscle skin…
Organ: what is it? Give an example
A group of tissues doing the same job; e.g. Heart, Lungs, Brain, Skin, Liver…
Organ system: what is it? Give an example
A group of organs working together; e.g. Circulatory, nervous, skeletal, digestive
Zygote
A fertilised egg
Up to what stage in humans, are all the cells embryonic?
The 8 cell stage
Differentiation
When stem cells become specialised to perform their job
Embryonic stem cells
Undifferentiated cells that can become any cell type
Adult stem cells
Stem cells that can either stay undifferentiated in certain parts of the body or become a limited number of cell types based on their location
Why and how are red blood cells specialised to do their job?
They are bio-concave giving them a larger surface area to allow rapid oxygen diffusion
What is Xylem and what does it do?
Xylem is a plant tissue that transports water, mineral salts and phloem (this transports the products of photosynthesis)
What are Meristems? (3) what are they? Why are they special? What do they do?
- Meristems are are the tissues in plants where stem cells are found
- These are the only tissues that contain stem cells
- They produce growth in height and width due to division and enlargement of a daughter cell
What growth does a meristem in the tip cause?
Increase in height/ flowers/ leaves
What growth does a meristem in the side bud cause?
Side growth/ leaves/ flowers
What growth does a meristem along the length of the stem cause?
Increase in girth
What growth does a meristem in the root tip cause?
Increase in length
Name two methods of cloning plants:
- Cuttings
- Tissue culture
What chemical is used to promote root growth in cuttings?
Hormone rooting powder
Describe the process of Tissue culture: (4)
- Cells or tissue are taken from a plant root or stem
- Enzymes are used to separate the cells
- Individual cells are placed on nutrient (agar) jelly to grow
- Plants are transferred to compost to grow
What plant hormones are used in agar jelly and hormone rooting powder?
Auxins
What do Auxins do? (3)
Increase cell division and enlargement and promote plant tissue growth
Phototropism
Response to the direction of light
“Plants are positively phototrophic”; why is this and how does this help them?
Plants grow towards light so are positively phototrophic and by growing towards light, they increase their chances of survival
Where is auxin produced in a plant?
Auxin is produced in the tip of growing shoots
Describe the events of phototropism (3)
- Light is shone on one side of the plant so Auxin is produced in the tip and moves towards the shaded side
- Auxin produces growth/ elongation on the shaded side
- The short grows towards the light
Chromosomes
Thread like structures made from DNA that are grouped in pairs
DNA
A double helix molecule called Deoxyribosenucleic Acid
What are the 3 components of DNA?
Base, Sugar and Phosphate
What are the four types of DNA base and how are they paired?
A, T, C, and G
A - T
C - G
Name the two single helix nucleotides:
Messenger RNA and Transfer RNA
Where does protein synthesis occur?
In the cytoplasm
3 bases in sequence make what?
An amino acid
The sequence of amino acids determines what?
The type of protein synthesised and its properties
What are the steps of protein synthesis? (6)
- DNA unzips - the hydrogen bonds between the bases break
- mRNA copies the gene for the required protein
- mRNA moves out of the nucleus
- mRNA moves to the ribosome
- Ribosome reacts with the mRNA code and tells tRNA to bring amino acids
- Amino acids are joined together to form a protein
Mitosis
Cell division that produces two new cells that are identical to each other and the parent cell
What are the purposes of mitosis?
For growth and repair
Describe the steps of Mitosis: (3)
- GROWTH: Cells produce more organelles, increase in size and the DNA in each chromosome is copied
- DIVISION: The cell divides by cytokinesis: chromosomes line up along the centre of the cell and it splits
- Two identical daughter cells are produced as each double chromosome splits and two nuclei form
Meiosis
Cell division that produces gametes
Gametes
Sex cells
How many chromosomes do human body cells have?
46; 23 pairs
How many chromosomes do human gametes have?
23
Describe the steps of meiosis: (5)
- The gamete parent cell (46 chromosomes)
- The chromosomes are copied and pair up (92 chromosomes)
- Chromosomes swap genes “crossing over”
- The cell divides then divides again
- This produces 4 daughter cells that are un identical and contain half the number of chromosomes the parent cell had
How can a gene be turned on or off? (2)
ON: to get produce protein from a gene, mRNA copies the base code of DNA and takes it to the ribosome where it is built “ON”
OFF: If the cell wants to stop a protein being made, a blocker protein attaches to the gene, blocking mRNA access, turning the gene “OFF”
What are stem cells used for? (4/5)
Replacing damaged or diseased cells Treating Parkinson's Rebuilding bones and cartilage Making replacement heart valves Repairing a damaged immune system
What sort of cells can bone marrow stem cells become?
Any blood cell
Why are there ethical issues surrounding the use of embryonic stem cells?
When the cells are removed from IVF embryos, the embryo is killed
How is a burn victim treated? (3)
- Take a skin cell from an unburied area
- Grow it in nutrient medium
- Cell divides to form new tissue which is transplanted to the burn
Describe the steps of Therapeutic cloning: (5)
- Remove the nucleus from and egg cell
- Put a body cell nucleus into that egg cell instead
- Stimulate the cell to divide to form an “embryo”
- Take the stem cells from this “embryo” and grow in nutrients
- Replace any type of cell with these cells
Why is therapeutic cloning good? (2)
It doesn’t require fertilisation and creates cells that are genetically identical to the patient so won’t be rejected
How can a cell be reactivated?
If the gene for creating blocker proteins is “turned off”, a cell will revert to its stem cell state
