Biology paper 1 Flashcards
what are living things made of
cells
what are the two types of cells
eukaryotic:
- have a nucleus
- complex cells including all animal and plant cells
prokaryotic:
- smaller and simpler like bacteria
what are eukaryotes and prokaryotes
eukaryote:
- organisms made of eukaryotic cells (have a nucleus/ animal and plant cells)
prokaryote:
- singe celled organisms
- a prokaryotic cell (small and simple like bacteria)
what subcellular structures does an animal cell have
- nucleus
- cytoplasm
- cell membrane
- mitochondria
- ribosomes
what subcellular structures does a plant cell have
- rigid cell wall
- large vacuole
- chloroplasts
what subcellular structures does a bacterial cell have
- chromosomal DNA
- ribosomes
- cell membrane
- plasmid DNA
- flagella
- slime capsule
what is the function of a nucleus, cytoplasm and mitochondria
nucleus - contains the genetic material that controls the activities of the cell, genetic material is arranged into chromosomes
cytoplasm - gel like substance where most of the chemical reactions take place and contains enzymes to control these reactions
mitochondria - energy released from respiration reactions
what is the function of the cell membrane and cell wall and ribosomes
cell membrane - holds the cell together and controls what substances move in and out of the cell
cell wall - made of cellulose it supports the cell and strengthens it
ribosomes - involved in the translation of genetic material to make proteins in protein synthesis
what is the function of the vacuole and chloroplasts
vacuole - contains cell sap, a weak solution of sugar and salts and it maintains the internal pressure to support the cell
chloroplasts - contain chlorophyll which absorbs light for photosynthesis reactions to happen
what is the function of chromosomal and plasmid DNA and flagella
chromosomal DNA - one long circular chromosome that controls the cell’s activities and replication, it floats free in the cytoplasm not in a nucleus
plasmid DNA - small loops of extra DNA that aren’t part of the chromosome and plasmids contain genes for things like drug resistance and can be passed between bacteria
flagella - a long hair like structure that rotates to make the bacterium move. It can be used to move away from toxins or towards things like nutrients or oxygen which are beneficial
what happens in sexual reproduction
the nucleus of an egg cell fuses with the nucleus of a sperm cell to create a fertilised egg which develops into an embryo
sperm and egg cells are haploid which means they only contain half the number of chromosomes needed for a normal body cell
what are the adaptations and function of the an egg cell or ovum
function:
- to carry the female DNA and to nourish the developing embryo in the early stages
adaptations:
- contains lots of nutrients in a large cytoplasm to be able to feed the embryo
- haploid nucleus
- straight after fertilisation, its membrane change structure to stop any more sperm getting in and this ensures the offspring has the right amount of DNA
what are the adaptations and function of a sperm cell
function:
- to transport the males DNA to the females egg
adaptations:
- long flagellum tail to swim to the egg
- packed with mitochondria in the middle section to provide energy from respiration to be able to swim the large distance to swim to the egg
- has an acrosome at the front of the head where it stores enzymes needed to digest its way through the membrane of the egg cell
- haploid nucleus
what are the adaptations and function of epithelial cells
function:
- the line the surface of cells to help move substances
adaptations:
- cilia ( hair like structures on the top) that beat in one direction along the surface of the tissue
- the lining of the airways has lot of ciliated epithelial cells which help to move the mucus and all of the particles from the air that it has trapped up the throat so it can be swallowed and doesn’t reach the lungs
what is the resolution of a microscope
how well it distinguishes between two points that are close together
a higher resolution means that the image can be seen more clearly and in more detail
how do light microscopes work
they pass light through the specimen and let us see things like nuclei and chloroplasts and we can also use them to study living cells
hence the need to take a thin slice of the cell to allow light to pass through
what are the advantages and disadvantages of using an electron microscope
advantages:
- higher resolution
- higher magnification
- more detail
- see internal structure of chloroplasts and mitochondria
- allow understanding of how cells work and the role of subcellular structures
disadvantages;
- expensive
- can’t be used to see living cells
how would you view a specimen using a light microscope
1) thin slice of specimen to light through
2) take a clean slide and put a drop of water on using a pipette to hold the specimen in place and place specimen on using tweezers
3) add stain if your specimen is completely transparent or colourless to make it easier to see e.g methylene blue for DNA
4) place cover slip at on end of the cover slip holding it at an angle with a mounted needle and carefully lower onto the slide. Press it down gently so that no air bubbles are trapped under it the clip slide to stage
5) select lowest objective lens
6) use the coarse adjustment knob to move the stage up so that the slide is just underneath the objective lens
7) look down the eyepiece and move stage downwards till specimen is nearly in focus
8) adjust the focus with the fine adjustment knob until you get a clear image
9) position a clear ruler on the stage and use it to measure the diameter of the circular area visible - your field of view
10) repeat with different objective lens
what are the two magnification calculations
total magnification = eyepiece lens x objective lens
magnification = image size divided by actual real size
convert mm to micrometres (um)
x 1000
what are enzymes
biological catalysts that reduce the need for high temperatures and we only have enzymes to speed up the useful chemical reactions in the body
what do chemical reactions normally involve
things being split apart or joined together
catalysed or synthesised
what molecule is changed in an enzyme reaction
substrate
discuss how temperature affects the rate of enzyme reaction
an increasing temperature will increase the rate of reaction at first until it reaches the enzymes optimum temperature. After this temperature the bonds holding the enzyme together begin to break so the shape of the enzymes active site changes and becomes denatured so it can no longer bind with its specific substrate. After the optimum activity decreases and stops.
discuss how pH affects the rate of enzyme controlled reaction
the pH must be at the optimum, either side of the optimum the enzyme won’t work as well because it will be denatured as the bonds holding the active site together will change shape
discuss how substrate concentration will affect the rate of an enzyme controlled reaction
the higher the substrate concentration, the faster the rate of reaction because it is more likely that an enzyme will meet up with a substrate molecule and react
however this is only up to a point. after that there are so many substrate molecules that there isn’t enough enzymes to react because all the active sites are full so the rate of reaction won’t change
what is the core practical for investigating the effect of pH on enzyme activity
the enzyme amylase catalyses the breakdown of starch to maltose and you can detect the starch using iodine
if starch is present it will turn from browny-orange to blue-black
1) a drop of iodine into every well of a spotting tile
2) place a Bunsen burner on a heat proof mat and a tripod and gauze over the top. Put a beaker of 25ml of water and heat till 35 degrees use thermometer to keep temp throughout the same
3) use a syringe to add 3cm cubed of amylase solution and 1 cm cubed of buffer solution of pH 5 to a boiling tube. Using test tube holders place the tube in the water for 5 mins
4) next use a different syringe to add 3cm of starch solution to the boiling tube
5) immediately mix the contents of the boiling tube and start a stop clock
6) Use continuous sampling to record how long it takes for the amylase to break down all of the starch. to do this use a dropping pipette to take a fresh sample from the boiling tube every ten seconds and put a drop into a well. When the solution remains browny-orange starch is no longer present
7) repeat with different pH values
how do you calculate the rate of reaction
rate = 1000/time
the unit of rate is s to the -1
or if an experiment measures how much something changes over time you can use
amount of product formed = change
change/ time
why is it important that organisms can break big molecules like proteins, lipids and carbohydrates into smaller molecules
so they can be used for growth and other life processes
many of the molecules we eat in food are too big to pass through the walls of our digestive system so digestive enzymes break them down into smaller soluble molecules.
these can easily pass through the walls of our digestive system allowing them to be absorbed into the bloodstream and pass into cells to be used by the body.
plants store energy in the form of starch (a carbohydrate) and when plants need energy enzymes break down starch into smaller sugar molecules. These can then be respired to transfer energy to be used by the cells
how are proteins made
by joining amino acids together using enzymes that synthesise
what is the test for sugars
BENEDICTS REAGENT
there are lots of different types of sugar molecules. due to their chemical properties many sugars are called reducing sugars
add Benedict’s reagent (which is blue) to a sample and heat it in a water bath that’s set to 75 degrees. If the test is positive it will form a coloured precipitate
the higher the concentration of reducing sugars the further the colour change goes
blue - green - yellow - orange - brick red
what is the test for starch
IODINE
add iodine
if starch is present the sample changes from browny-orange to blue-black
what is the test for lipids
ETHANOL SHAKE WATER MILKY EMULSION
add 20ml of ice cold ethanol and shake for about a minute until it dissolves and pour the solution in water
if there are any lipids present they will precipitate out of the liquid and show up as a milky emulsion
the more lipid the more noticeable the milky colour will be
what is the test for proteins
BIURET TEST
add a few drops of potassium hydroxide solution to make the solution alkaline
then add 10ml of copper (II) sulphate solution which is bright blue
if there are no protein the solution will stay blue
if proteins are PRESENT the solution will turn purple
what is the core practical for seeing how much energy food contains
CALORIMETRY
1) collect some food that will burn easily - something that is dry like pasta, dried beans or crisps
2) weigh 2grams of the food and then skewer it on a mounted needle
3) add 50ml of water to a boiling tube (held with a clamp) so you can measure the amount of energy that is transferred when the food is burnt
4) measure the temperature of the water, then set fire to the food using a Bunsen burner but make sure the Bunsen isn’t near the water or your results will be inaccurate
5) immediately hold the burning food under the boiling tube until it goes out. Then relight the food and hold it under the tube and repeat until the food won’t catch fire again
6) measure the end temperature of the water
then do…
energy in food = mass of water x temperature change of water x 4.2
then do…
energy per gram of food = energy in food / mass of food
how can you reduce energy loss to the surroundings in the food energy (calorimetry) core practical?
insulate the boiling tube with foil or cotton wool
discuss osmosis
a partially permeable membrane is just one with very small holes in it so bigger molecules like sucrose can’t pass through
the water molecules actually pass both ways through the membrane during osmosis because the water molecules move about randomly all the time
but because there are more water molecules on one side than the other, there’s a steady net flow of water into the region with fewer water molecules, e.g the more concentrated solute solution
this means the solute solution gets more dilute and the water acts like it is trying ‘even up’ the concentration either side of the membrane
define diffusion
passive process
no energy needed
ya know the rest :)
define active transport
active transport is the net movement of particles across a membrane against a concentration gradient (from an area of low concentration to an area of high concentration) using energy transferred during respiration
the process requires energy
discuss active transport with nutrient in the blood
when there’s a higher chance of nutrients in the gut than in the blood the nutrients diffuse naturally into the blood
but sometimes there’s a lower concentration of nutrients in the gut than in the blood
active transport allows nutrients to be taken into the blood despite the fact that it is against the concentration gradient to stop us from starving
what is the core practical for investigating osmosis
1) prepare sucrose solutions of different concentrations ranging from pure water to a very concentrated sucrose solution
2) use a cork borer to cut potato into the same sized pieces of about 1cm diameter and from the same potato
3) divide the cylinders into groups of three and use a mass balance to measure the mass of each group
4) place on group in each solution
5) leave the cylinders in the solution for at least 40 minutes
6) remove the cylinders and pat dry gently with a paper towel to remove excess water from the surface of the cylinders so you get a more accurate measurement of their final masses
7) weight each group again and record your results
8) the only thing you should change in this experiment is sucrose solution concentration. Everything else must stay the same
then do percentage change = final mass - initial mass over initial mass and times your answer by 100
positive = gained mass
negative = lost mass
what does the nucleus contain
genetic information in the form of chromosomes which are coiled up lengths of DNA molecules
why are body cells normally diploid
because it has two copies of each chromosomes one from your mother and one from your father
discuss interphase in mitosis
in a cell that’s not dividing the DNA is all spread out in long strings. Before it divides the cell has to grow and to increase the amount of subcellular structure such as mitochondria and ribosomes.
it then duplicates its DNA so there is one copy for each new cell. The DNA is copied and forms X-shaped chromosomes. Each arm of the chromosomes is an exact duplicate of the other
explain the stages of mitosis from prophase to cytokinesis
prophase - the chromosomes condense getting shorter and fatter. The membrane around the nucleus breaks down and the chromosome lie free in the cytoplasm
metaphase - the chromosomes line up at the centre of the cell
anaphase - spindle fibres pull the chromosomes apart. The two arms of each chromosome go to opposite arms of the cell
telophase - membranes form around each of the sets of chromosomes. These become the nuclei of the two new cells - the nucleus has divided
cytokinesis - the cytoplasm and cell membrane divides to form new cells
what is produced by mitosis and what is mitosis used for
2 diploid genetically identical daughter cells
growth and repair
describe mitosis
the division of a cell to form 2 diploid genetically identical daughter cells that are used for growth and repair
how do you calculate the number of cells after multiple divisions
2 to the power of n where n is the number of divisions
how does a cell grow
cell DIVISION by mitosis
cell ELONGATION where a plant cell expands making the cells bigger and the plant grow
cell DIFFERENTIATION - the process by which a cell changes to become specialised for its job. having specialised cells allows multicellular organisms to work more efficiently
discuss growth in animals
all growth in animals happens by cell division. Animals tend to grow while they’re young and then they reach full growth and stop growing. So when you’re young cells divide at a fast rate but once you’re an adult most cell division is for repair - the cells divide to replace old or damaged cells. This also means in most animals cell differentiation is lost at an early stage
discuss growth in plants
in plants growth in height is mainly due to cell elongation - cell division usually just happens in the tips of the roots and shoots (in areas in called meristems) but plants often grow continuously - even really old trees will keep putting out new branches. So, plants continue to differentiation to develop new parts e.g leaves or roots
how is cancer caused
uncontrolled cell division
the rate at which cells divide by mitosis is controlled by the chemical instructions (genes) in an organisms DNA
If there’s a change in one of the genes that controls cell division (a mutation), the cell may start dividing uncontrollably
this can result in a mass of abnormal cells called a tumour
if the tumour invade and destroys surrounding tissue it is called cancer
what chart is used to measure growth
why do we use these charts
what does it mean to be on the 75th percentile
percentile chart
assess a child’s growth over time so that an overall pattern in development can be seen and any problems like obesity, malnutrition and obesity can be highlighted
25% of babies are bigger at that age
75% of babies are smaller at that age
what are stem cells
undifferentiated cells
why can embryonic stem cells divide into any type of cell
because the first few cells of the human embryo need to develop into all of our body cells
what can adult stem cells do
only divide into some cells
only found in certain places like bone marrow
used to replace damaged cells like skin or blood cells
what are the cells in plants that divide by mitosis
meristems
meristem tissue is found in the areas of a plant that are growing e.g tips of roots and shoots
meristems produce unspecialised cells that are able to divide and form any cell type in the plant - they act like embryonic stem cells but unlike human stem cells these cells can divide and differentiate to generate any type of cell for as long as the plant lives
the unspecialised cells go on to form specialised tissues like xylem and phloem
how do doctors use stem cells in medicine
- doctors use adult stem cells to cure some diseases
- scientists have experimented with extracting stem cells from very early human embryos and growing them. Under certain conditions the stem cells can be stimulated to differentiate into specialised cells
- it might be possible to use stem cells to create specialised cells to replace those which have been damaged by disease or injury e.g new cardiac muscle cells could be transplanted into someone with heart disease
- this potential for new cures is the reason for the huge scientific interest in stem cells
what are the potential risks associated with stem cells treatment
tumour development:
stem cells divide very quickly. If scientists are unable to control the rate at which the transplanted cells divide inside a patient, a tumour may develop
Disease transmission:
viruses live inside cells. If donor cells are infected with a virus and this isn’t picked up the virus could be passed on to the recipient and make them sicker
Rejection:
if the transplanted cells aren’t grown using the patients own stem cells the patients body may recognise the cells as foreign and trigger an immune response to try to get rid of them. The patient can take drugs to suppress this response but this makes them susceptible disease.
discuss the spinal cord
a long column of neurones (nerve cells) that run from the base of the brain down the spine. At several places down the cord, neurones branch off and connect with other parts of the body.
The spinal cord relays information between the brain and the rest of the body
what is the brain made up of
billions of interconnected neurones and different parts of the brain have different functions
what does the cerebrum part of the brain do
the cerebrum is the largest part of the brain
divided into two halves called cerebral hemispheres.
the right side controls muscles on the left side and vice versa
different parts of the cerebrum are responsible for movement, intelligence, memory, language and vision
[conscious activities]
what does the cerebellum part of the brain do
responsible for muscle coordination and balance
what does the medulla oblongata part of the brain do
controls unconscious activities like breathing and heart rate
how can a CT scanner be used to investigate the brain
- uses an X-ray to produce an image of the brain
- shows the main structures of the brain but doesn’t show the function of them
- However if a CT scan shows a diseased or damaged brain structure and the patient has lost some function, the function of that part of the brain can be worked out. E.g if an area of the brain shows up damaged and the patient can’t see then that area is involved in vision
how can a PET scanner be used to investigate the brain
- PET scanners are a bit more fancy than CT scanners
- they use radioactive chemicals to show which parts of the brain are active when the person is inside the scanner
- they are very detailed and can be used to investigate both the structure and the function of the brain in real time
- PET scans can show if areas in the brain are usually inactive and active so they are useful for studying disorders that change the brain’s activity. E.g in Alzheimer’s disease, activity in certain areas of the brain is reduced - PET scans show this reduction when compared to a normal brain
what things can go wrong with the CNS and why is this a problem
injuries to the brain or spinal cord, tumours and diseases but these can be difficult to treat
it’s hard to repair damage to the CNS because the neurones in it don’t readily repair themselves and scientists haven’t developed a way to repair nervous tissue in the CNS
If a problem occurs in a part of the nervous system that’s not easy to access it can be hard to treat e.g it’s not possible to surgically remove tumours growing in certain parts of the brain
treatments for problems in the nervous system may lead to permanent damage. For example, a person who has injured their spinal cord may need surgery on their spine near the injury. There is a risk that the spinal cord could be damaged further during the operation leading to permeant damage
discuss the CNS response (reflex arc)
the nervous system is made up of neurones which go to all parts of the body
the body has a lot of sensory receptors that detect a stimulus (change in the environment). different receptors detect different stimuli
when a stimulus is detected by receptors the information is converted into electrical impulses and sent along sensory neurones to the CNS
The CNS coordinates a response and impulses travel through the CNS along relay neurones
the CNS sends information along a motor neurone to an effector (muscle or gland)
the effector responds accordingly e.g a muscle may contract or a gland may secrete a hormone
what is your reaction time and the typical one of a human
the time it takes you to respond to a stimulus
0.25 seconds
what do all neurones have
- a cell body with a nucleus plus cytoplasm and other subcellular structures
- the cell body has extensions that connect to other neurones - dendrites and dendrons carry nerve impulses towards the cell body, and axons carry nerve impulses away from the cell body
- some axons are surrounded by a myelin sheath which acts as an electrical insulator speeding up the electrical impulse and preventing energy loss
- neurones can be very long which also speeds up the impulses because connecting with another neurone slows the impulse down so one long neurone is much quicker than lots of short ones joined together
discuss sensory neurone
- one long dendron carries nerve impulses from receptor cells to the cell body which is located in the middle of the neurone
- one short axon carries nerve impulses from the cell body to the CNS
discuss motor neurone
- many short dendrites carry nerve impulses from the CNS to the cell body
- one long axon carries nerve impulses from the cell body to effector cells
discuss relay neurone
- many short dendrites carry nerve impulses from sensory neurones to the cell body
- an axon carries nerve impulses from the cell body to the motor neurones
discuss the synapses
the gap between two neurones
the nerve signal is transferred by chemicals called neurotransmitters which diffuse across the gap
the neurotransmitters then set off a new electrical signal in the next neurone
the transmission of a nervous impulse is very fast but it is slowed down a bit at the synapse because the diffusion of neurotransmitters across the gap takes time
discuss the reflex to help prevent injury from the sting of a bee
reflexes are automatic, rapid responses to stimuli - they can reduce the chances of being injured. The passage of information in a reflex (from receptor to effector) is called a reflex arc. The neurones in a reflex arc go through the spinal cord or an unconscious part of the brain
1) when a stimulus (a bee sting) is detected by receptors impulses are sent along a sensory neurone to a relay neurone in the CNS
2) when the impulses reach a synapse between the sensory neurone and the relay neurone the trigger neurotransmitters to be released and these carry impulses to be sent along the relay neurone
3) when the impulses reach a synapse between the relay neurone and a motor neurone the same thing happens. Neurotransmitters are released and cause impulses to be sent along the motor neurone
4) the impulses then travel along the motor neurone to the effector of a muscle (in this case but it could be a gland)
5) the muscle then contracts and moves your hand away from the bee
6) because you don’t have to spend time thinking about the response, it’s quicker than normal response
how does a reflex help to protect the eye
very bright light can damage the eye so you have a reflex to protect it
light receptors in the eye detect bright light and send a message along a sensory neurone to the brain
the message then travels along a relay neurone to a motor neurone which tells circular muscles in the iris to contract making the pupil smaller
what is the function of the cornea
refracts (bends) light into the eye
what is the function of the iris
controls how much light enters the pupil
what is the function of the lens
refracts light, focusing it onto the retina
what is the function of the retina
the light sensitive part of the eye and it is covered in receptor cells called rods and cones
what is the function of rods and cones
rods - sensitive in dim light but can’t detect colour
cones - sensitive to different colours but can’t detect light
what is the function of the optic nerve
information from light is converted into electrical impulses and the optic nerve carries these impulses from the receptors to the brain
what does the eye do to look at distant objects
the ciliary muscle relaxes which allow the suspensory ligaments to pull tight
this pulls the lens into a less rounded shape so light is refracted less
what does the eye do to look at close objects
the ciliary muscle contrasts which slackens the suspensory ligaments
the lens becomes a more rounded shape, so light is refracted more
why are some people long sighted and what lens can correct this
the lens is the wrong shape and doesn’t bend light enough
the eyeball is too short
light from near objects is brought into focus behind the retina
you can use a convex lens to correct it
why are some people short sighted and what lens can correct this
the lens is the wrong shape and bends light too much
the eyeball is too long
light from distant objects is brought into focus in front of the retina
you can use a concave lens to correct this
what is colour blindness
can’t tell the difference between certain colours
the most common form of the disorder is red-green colour blindness
caused when red or green cones in the retina are not working properly
there is no cure for colour blindness because the cone cells can’t be replaced
what is a cataract
a cloudy patch on the lens which stops light from being able to enter the eye normally
people with cataracts are likely to have blurred vision
they may also experience colours looking less vivid and have difficulty seeing in bright light
a cataract can be treated by replacing the faulty lens with an artificial one
what is mitosis also known as
the cell cycle
what are three uses of mitosis
asexual reproduction
growth
repair
discuss the process of sexual reproduction
where genetic information from two organisms (a father and a mother) combine to produce offspring which are genetically different to either parent
in sexual reproduction the father and mother produce gametes (egg and sperm) which are reproductive cells
gametes only contain half the number of chromosomes of normal cells and are haploid
at fertilisation a male gamete fuses with a female gamete to produce a fertilised egg known as a zygote ]the zygote ends up with a full set of chromosomes so is diploid
the zygote then undergoes cell division by mitosis and develops into an embryo
the embryo inherits characteristics from both parents as it has received a mixture of chromosomes and therefore genes from its mum and dad
how are proteins made
proteins are made by reading the code in DNA
1) DNA controls the production of proteins (protein synthesis) in a cell
2) proteins are made up of chains of amino acid molecules. Each different protein has its own particular number and order of amino acids
3) the amino acid chains fold up to give each protein a different, specific shape which means each protein has a different function
4) remember a section of DNA that codes for a particular protein is called a gene. Its the order of bases in a gene that decides the order of amino acids in a protein
5) each amino acid is coded for by a sequence of three bases in the gene - a base triplet
6) the amino acids are joined together to make proteins following the order of the bases in the gene
7) each gene contains a different sequence of bases - which is what allows it to code for particular protein
what is a base triplet
each amino acid is coded for by a sequence of three bases in the gene and this is called the base triplet
what is a triplet code
a code based on base triplets
discuss non-coding regions in DNA
may regions of DNA are non-coding meaning they don’t code for any amino acids
despite this some of these regions are still involved in protein synthesis
all of an organisms DNA (including the non-coding regions) makes up the organisms genome
how can genetic variants arise by mutations
a mutation is a rare random change to an organisms DNA base sequence that can be inherited
if a mutation happens in a gene it produces a genetic variant - a different version of the gene
the genetic variant may code for a different sequence of amino acids which may change the shape of the final protein and so its activity
for an example the activity of an enzyme nay increase, decrease or stop all together
this could end up changing the phenotype of an organism
mutations can also happen in non-coding regions of DNA
discuss transcription (stage 1 of protein synthesis)
proteins are made in the cell cytoplasm in the ribosomes
DNA is found in the nucleus and can’t move out because it is too big so the cell needs to get the information from the DNA to the ribosome in the cytoplasm
this is done using a molecule called messenger RNA (mRNA) - like DNA mRNA is a polymer of nucleotides but it is shorter and only a single strand. It also uses uracil (U) for a base instead of thymine (T).
RNA polymerase is the enzyme involved in joining together RNA nucleotides to make mRNA.
1) RNA polymerase binds to a region of non-coding DNA in front of a gene
2) The two DNA strands unzip and the RNA polymerase moves along one of the strands of DNA
3) It uses the coding DNA in the gene as a template to make the mRNA. Base pairing between the DNA and RNA ensures that the mRNA is complementary to the gene
4) Once made the mRNA molecule moves out of the nucleus and joins with a ribosome
discuss translation (stage 2 of protein synthesis)
Once the mRNA is bound to a ribosome, the protein can be assembled - translation
1) Amino acids are brought to the ribosome by another RNA molecule called transfer RNA (tRNA)
2) The order in which the amino acids are brought to the ribosome matches the order of the base triplets in mRNA. Base triplets in mRNA are known as codons
3) Part of tRNA’s structure is called an anticodon - it is complementary to the codon for the amino acid. The pairing of the codon and anticodon makes sure that the amino acids are brought to the ribosome in the correct order.
4) The amino acids are joined together by the ribosome. This makes a polypeptide (protein)
how does a mutation of non-coding DNA affect the binding of RNA polymerase
before any transcription can happen RNA polymerase has to bind to a region of non-coding DNA in front of a gene. If a mutation happens in this region of DNA then It could affect the ability of RNA polymerase to bind to it. It might make it easier to bind to or more difficult
how well RNA polymerase can bind to this region of DNA will affect how much mRNA is transcribed and therefore how much of the protein is produced. And depending on the function of the protein, the phenotype of the organism may be affected by how much of it is made
So genetic variants in non-coding regions can still affect the phenotype of an organism even if they don’t code for proteins themselves
