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Biology B2 > Genes And Enzymes > Flashcards

Genes And Enzymes Flashcards

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1
Q

What are the features of an animal cell

A

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

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2
Q

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

A

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

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3
Q

Describe a bacteria cell

A

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

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4
Q

What is the structure of DNA

A

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

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5
Q

How was the structure of DNA discovered

A

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

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6
Q

What practical can you do to extract DNA from cells

A

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

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7
Q

What does a triplet do

A

it codes for a particular amino acid

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8
Q

How do cells make proteins

A

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

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9
Q

What is transcription

A

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

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10
Q

What is translation

A

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

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11
Q

What is a mutation

A

A change to an organisms DNA base sequence

It could affect the shape of the protein of its function

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12
Q

What is a harmful mutation

A

It could cause a genetic disorder eg cystic fibrosis

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13
Q

What is a beneficial mutation

A

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

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14
Q

What is a neutral mutation

A

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

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15
Q

What are enzymes

A

Catalysts produced by living things

They are proteins

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16
Q

What is a catalyst

A

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

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17
Q

How do enzymes work

A

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

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18
Q

What is the lock and key mechanism

A

Enzymes only work with one substrate

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

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19
Q

How does iodine solution work

A

It will turn blue or black if starch is present

20
Q

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

A

Temperature - water baths
Ph
Varying substrate concentrations

21
Q

How does temperature effect the enzyme

A

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

22
Q

How does ph effect enzymes

A

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

23
Q

How does substrate concentration affect the enzyme

A

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

24
Q

What is the human genome project

A

Thousands of scientists worked together to find every single human gene

25
Q

What are the good things about the human genome project

A

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

26
Q

What are the bad things about the human genome project

A

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

27
Q

How does genetic engineering work

A

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

28
Q

How does genetic engineering reduce vitamin A deficiency

A

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

29
Q

How is genetic engineering used to produce human insulin

A

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

30
Q

How does genetic engineering increase crop yield

A

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

31
Q

Why do some people disagree with genetic engineering

A

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

32
Q

What does mitosis do

A

It creates two new genetically identical diploid daughter cells

33
Q

What does diploid mean

A

They have two versions of each chromosome

34
Q

What happens in mitosis

A

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

35
Q

How does asexual reproduction use mitosis

A

Eg in strawberry plants on runners

The offspring have the exact same genes as their parents so no genetic variation

36
Q

What are gametes

A

The eggs and sperm

They are haploid so only have one copy of The genes

37
Q

What does mitosis do

A

Creates four haploid gametes that are not genetically identical

38
Q

What happens in the first division of meiosis

A

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

39
Q

What happens in the second division of meiosis

A

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

40
Q

How is cloning done

A

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

41
Q

What are the uses of cloning

A

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

42
Q

What are the problems with cloning

A

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

43
Q

What are stem cells

A

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

44
Q

How can we use stem cells

A

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

45
Q

What are the opinions on stem cell research

A

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

Biology B2 (3 decks)

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