Genes And Enzymes

Question 1

What are the features of an animal cell

Answer 1

Nucleus contains DNA and controls the cell

Cytoplasm a jelly like substance where chemical reactions are controlled

Cell membrane holds the cell together and controls what goes in and out

Mitochondria is where respiration happens and energy is released

Question 2

What are the features of a plant cell that are not in an animal cell

Answer 2

Rigid cell wall made of cellulose gives support for the cell

Large vacuole contains cell sap a weak solution of sugars and salts

Chloroplasts are where photosynthesis happens they contain chlorophyll

Question 3

Describe a bacteria cell

Answer 3

Chromosomal DNA is one long circular chromosome and controls the cells activities and floats free in the cytoplasm

Plasmids are small loops of extra DNA that contain genes for things like drug resistance and an be passed between bacteria

The flagellum is a long hair like structure that rotates to make the cell move

Cell wall supports the cell

Slime coat

No nucleus

Cell membrane

Question 4

What is the structure of DNA

Answer 4

Two strands coiled together in a double helix
Held together by complementary base pairs joined by weak hydrogen bonds
A-T
C-G

A gene is a section of DNA

Question 5

How was the structure of DNA discovered

Answer 5

Franklin and Wilkins worked out the helical structure by directing X-rays and crystallised DNA and looking at the patterns

Watson and crick used the ideas to make a model of a DNA molecule that fitted together

Question 6

What practical can you do to extract DNA from cells

Answer 6

Chop up onion and put it in a beaker containing a solution of detergent and salt
Put it in a water bath at 60c for 15 mins this denatures the enzymes and softens the onion cells
Put the beaker in ice to cool
Blend the mixture in a mixture
Cool the mixture again then filter out all of the lumps
Gently add some ice cold alcohol to the mixture and the DNA will start to come out and appear as white stringy pieces

Question 7

What does a triplet do

Answer 7

it codes for a particular amino acid

Question 8

How do cells make proteins

Answer 8

By stringing together lots of amino acids in protein synthesis
There are 20 different amino acids

Question 9

What is transcription

Answer 9

The two DNA strands unzip
The DNA is used as a template to make the mRNA
U is replaced with T

Question 10

What is translation

Answer 10

The mRNA moves out of the nuclear pores and joins the ribosome
Amino acids that match the mRNA are brought to the ribosome by the tRNA
The ribosome sticks the amino acids together using enzymes to make a chain of amino acids called a poly peptide

Question 11

What is a mutation

Answer 11

A change to an organisms DNA base sequence

It could affect the shape of the protein of its function

Question 12

What is a harmful mutation

Answer 12

It could cause a genetic disorder eg cystic fibrosis

Question 13

What is a beneficial mutation

Answer 13

A mutation could cause new characteristics that are beneficial to the organism eg herbicide resistance

Question 14

What is a neutral mutation

Answer 14

It is neither harmful of beneficial and doesn’t effect the organism at all

Question 15

What are enzymes

Answer 15

Catalysts produced by living things

They are proteins

Question 16

What is a catalyst

Answer 16

A substance that increases the speed of the reaction without being changed or used up in the reaction

Question 17

How do enzymes work

Answer 17

Chemical reactions usually involve things being split apart or put together
The substrate molecule is changed in the reaction
The substrate joins the active site of the enzyme

Question 18

What is the lock and key mechanism

Answer 18

Enzymes only work with one substrate

For the enzyme to work the substrate must fit into the active site

Question 19

How does iodine solution work

Answer 19

It will turn blue or black if starch is present

Question 20

What are the variables when measuring the rate of an enzyme controlled reaction

Answer 20

Temperature - water baths
Ph
Varying substrate concentrations

Question 21

How does temperature effect the enzyme

Answer 21

The higher the temperature the faster the rate of reaction at first
If it gets too hot some of the bonds holding the enzyme together break and the active site loses its shape so the enzyme becomes denatured so if it were to cool down it wouldn’t go back to its original shape
Most human enzymes have an optimum temperature of 37c

Question 22

How does ph effect enzymes

Answer 22

If the ph is too high or too low the active site is changed shape and the enzyme becomes denatured
All enzymes have an optimum ph and it’s mostly ph7

Question 23

How does substrate concentration affect the enzyme

Answer 23

The higher the substrate concentration the faster the reaction because there’s more chance the enzyme will find a substrate
After a point all of the enzyme is used up so the rate of reaction can no longer increase the graph will level off

Question 24

What is the human genome project

Answer 24

Thousands of scientists worked together to find every single human gene

Question 25

What are the good things about the human genome project

Answer 25

We can predict and prevent diseases so doctors can find out what diseases were likely to get and help us to not get them or treat them early We can develop new and better medicines We can get more accurate diagnoses so we could find genetic causes for diseases to know if people have them Improve forensic science, forensic scientists can make a DNA fingerprint

Question 26

What are the bad things about the human genome project

Answer 26

It can cause increased stress if people know from an early age that they are susceptible to a disease People with bad genes could feel under pressure not to have children People could be discriminated by employers and insurers if they are more likely to get a particular disease

Question 27

How does genetic engineering work

Answer 27

A useful gene is cut out from one chromosome using enzymes The same enzyme is used to cut another organisms chromosome and insert the useful gene This produces genetically modified organisms

Question 28

How does genetic engineering reduce vitamin A deficiency

Answer 28

Beta carotene is used in our body to make vitamin a In South Africa and Asia millions of children go blind due to a lack of vitamin a Golden rice is a variety of gm rice and allows the rice to produce beta carotene So when people eat It they are less likely to get a vitamin a deficiency

Question 29

How is genetic engineering used to produce human insulin

Answer 29

The human insulin gene can be placed into bacteria to produce human insulin This produces insulin quickly and cheaply to treat diabetes

Question 30

How does genetic engineering increase crop yield

Answer 30

Gm crops have there genes modified to make them resistant to herbicides So fields of crops can be sprayed with herbicide and all of the plants die except the useful gm one this increases the yield and makes more food

Question 31

Why do some people disagree with genetic engineering

Answer 31

Using gm crops reduces the amount of weeds and flowers so reduces biodiversity People may develop allergies to the gm crops Transplanted genes could get out into the environment e.g. Creating super weeds that are resistant to herbicide

Question 32

What does mitosis do

Answer 32

It creates two new genetically identical diploid daughter cells

Question 33

What does diploid mean

Answer 33

They have two versions of each chromosome

Question 34

What happens in mitosis

Answer 34

The DNA is duplicated The nucleus breaks down The chromosomes line up at the centre and the spindle fibres pull the two chromosome arms apart Membranes form around each set of chromosomes which are the two new nuclei The cytoplasm divides and you get two new cells

Question 35

How does asexual reproduction use mitosis

Answer 35

Eg in strawberry plants on runners | The offspring have the exact same genes as their parents so no genetic variation

Question 36

What are gametes

Answer 36

The eggs and sperm | They are haploid so only have one copy of The genes

Question 37

What does mitosis do

Answer 37

Creates four haploid gametes that are not genetically identical

Question 38

What happens in the first division of meiosis

Answer 38

A diploid cell duplicates and the chromosomes line up and the nucleus breaks down The chromosome arms are pulled apart by the spindle fibres and the nuclei reforms and the cytoplasm splits

Question 39

What happens in the second division of meiosis

Answer 39

The chromosomes line up in the centre of the cell the arms are pulled apart and four new nuclei form and the two cytoplasms split It's the same as before but the chromosomes don't duplicate

Question 40

How is cloning done

Answer 40

Take an unfertilised egg cell and remove the nucleus A diploid nucleus is taken from an adult body cell The diploid nucleus is inserted into the egg The egg is stimulated by a shock to undergo mitosis When the embryo is a ball of cells is it inserted into the adult female This was used to create dolly the first cloned sheep

Question 41

What are the uses of cloning

Answer 41

It could help with the shortage of organs for transplants genetically modified pigs are being tested to do this It can give us a deeper understanding of the ageing process and age related disorders It can help preserve endangered species

Question 42

What are the problems with cloning

Answer 42

There's a reduced gene pool so it would be much easier for a whole species to be wiped out by disease The cloned mammals might not live as long and could age faster Cloning often fails or the clones are born with genetic defects or unhealthy immune systems

Question 43

What are stem cells

Answer 43

To start all cells in the embryo are undifferentiated so all the same They can reproduce to get more stem cells or different specialised cells When cells become specialised it is called differentiation Most animal cells lose their ability to differentiate at an early stage Adults only have stem cells in their bone marrow and they aren't as good as the ones in the embryo

Question 44

How can we use stem cells

Answer 44

To cure diseases such as sickle cell anaemia by giving the person a bone marrow transplant We can take embryonic stem cells and grow them so later in life they could be used to replace cells damaged by disease of injury

Question 45

What are the opinions on stem cell research

Answer 45

Some people believe embryos are potential human life so shouldn't be used in experiments Others think curing live patients is more important than potential life In some countries it is banned