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GCSE Biology paper 2 > Inheritance, Variation and Evolution > Flashcards

Inheritance, Variation and Evolution Flashcards

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1
Q

9+10 =

A

21

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2
Q

What is DNA?

A

Deoxyribonucleic acid is a chemical that all the genetic material in a cell is made from. It contains coded information for all the instructions to put an organism together and make it work. DNA determines what protein the cell produces and in turn what type of cell.

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3
Q

Where is DNA found?

A

DNA is found in the nucleus of cels in really long structures called chromosomes. Chromosomes come in pairs.

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4
Q

Describe the structure of DNA

A

It is a polymer made of two stands coiled together to form a double helix.

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5
Q

What is a gene?

A

A gene is a small section of DNA found on a chromosome.Each gene codes for a particular sequence of amino acids which are put together to make a protein. Genes have the instructions to tell cells which order to put amino acids.

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6
Q

What is a genome?

A

It is the entire set of genetic material in an organism

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7
Q

What does the exploration of genomes do for humanity?

A

It allows scientists to identify genes linked to different diseases. Understand inherited diseases and develop effective treatment. The genome can be used to understand migration and the history of ancestors.

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8
Q

What is a nucleotide?

A

They are the repeating unit in the DNA polymer they are made of a sugar molecule, one phosphate molecule and one base. The sugar and phosphate molecule form the backbone of the DNA strands, these molecules alternate through the stand. One of four bases links with a sugar molecule.

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9
Q

What are base pairs?

A

The base pairs are what decides the order of amino acids in a protein they make up a gene. They are always complementary paired A pairs with T and C pairs with G.

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10
Q

Where are proteins made?

A

In the cytoplasm by ribosomes.

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11
Q

What is mRNA?

A

DNA in the nucleus is too large to leave the nucleus so mRNA is used to get the code from the DNA to the ribosome which is outside the nucleus.

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12
Q

Give three examples of proteins that can be formed in protein synthesis

A

Enzymes
Hormones
Structural proteins

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13
Q

What is a mutation?

A

Any random change in the organisms DNA, they can sometimes be inherited. Mutations change the sequence of the DNA bases in a gene which produces a genetic variant. Some mutations lead to a change in the protein it codes for.

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14
Q

What could increase the chance of a mutation?

A

Exposure to radiation or certain substances

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15
Q

How can a mutation be dangerous to your body?

A

In some cases the mutation can drastically change the protein it is suppose to code for, for example an enzyme if due to the mutation the enzymes active site was to change it can no longer bind to the substrate. Also structured proteins such as collagen could lose their strength making them useless.

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16
Q

What is an insertion?

A

It is a type of mutation where a base is inserted into the DNA base sequence where it shouldn’t be, an insertion changes the way the three bases are read which can change the amino acid they code for. Insertion mutation can change more than one amino acid as they can have a knock on effect on the base further on in the sequence.

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17
Q

What is deletion?

A

This is a mutation where a random base is deleted from the DNA base sequence. They change the way the base is read and have a knock on effect.

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18
Q

What is substitution?

A

This is a mutation where a base pair is randomly changed, this has no knock on effect to other bases in that gene.

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19
Q

What is sexual reproduction?

A

This is where genetic information from two organisms combine to produce an offspring. The mother and father both produce gametes through meiosis e.g. egg and sperm cells (LOL). Each gamete will contain 23 chromosomes, these two cells fuse together to form a cell with the full number of chromosomes.

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20
Q

What is variation?

A

This is the mixture of genetic information to achieve an offspring with different genetic code to the parenting DNA.

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21
Q

What is plant sperm?

A

Pollen

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22
Q

Describe asexual reproduction?

A

This is where there is only one parent so the offspring is genetically identical. This happens by mitosis and is called a clone. For example bacteria, some plants, some animals

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23
Q

Describe meiosis

A

The genetic information is copied, the chromosomes duplicate.
The chromosomes line up in the centre of the cell they are pulled apart by spindle fibres then the cell membrane pinches the middle and the cell splits.
The cell then splits a second time using the same process except the genetic information does not duplicate.
The chromosomes are pulled apart so each cell (gamete) has one set of chromosomes.

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24
Q

What is a gamete?

A

A mature haploid male or female germ cell which is able to unite with another of the opposite sex in sexual reproduction to form a zygote

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25
Q

What happens after the gametes have fused after fertilisation?

A

The resulting new cell divides by mitosis to make a copy of itself . This repeats many times to produce lots of new cells in an embryo. As the embryo develops these cells start to differentiate into the different types of specialised cells that make up a whole organism.

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26
Q

Give some examples of organisms that can reproduce asexually and sexually.

A

Malaria-this is a parasite that reproduces sexually in the mosquito but asexually in a human
Fungi
Plants-production of seeds sexually but also asexually.

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27
Q

How many pairs of chromosomes do you have?

A

23

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28
Q

What does the 23 pair of chromosomes control?

A

Your sex

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29
Q

What distinguishes a male and female in their chromosomes?

A

xy as the 23rd pair - male

xx - female

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30
Q

What are alleles?

A

They are versions of genes, alleles are responsible for determining characteristics in the body such as hair colour, only the dominant allele will control the characteristic.

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31
Q

What is a genotype?

A

The combination of alleles you have.

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32
Q

What is a phenotype?

A

This is the molecular level of how your characteristics are determined.

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33
Q

What is the definition of homozygous?

A

It is an organism has two alleles for a particular gene that are the same.

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34
Q

What is the definition of hetrozygous?

A

Two alleles of a specific gene are different.

35
Q

How is polydactyly caused?

A

This is a disease where baby’s are born with extra fingers or toes this is caused through a dominant allele, the parent that carries the gene will also have that disease. There a 50% chance the child will have it if one parent has this disease.

36
Q

How is cystic fibrosis caused?

A

By recessive alleles - it is a genetic disorder of the cell membranes. Because its recessive allele people with only one copy won’t have the disorder.

37
Q

What are the symptoms of cystic fibrosis?

A

The whole body produces a lot of thick sticky mucus in the air passages and in the pancreas.

38
Q

What is embryonic screening?

A

This is where during in vitro fertilisation, embryos are fertilised in a laboratory, and then implanted into the mothers womb. Before being implanted, its possible to remove a cell from each embryo and analyse its genes. Many genetic disorders can be detected in this way. It is also possible to get DNA from an embryo in the womb to test for disorders.

39
Q

What are the advantages of embryo screening?

A

It will stop people suffering

Treats the cost of disorder treatment.

40
Q

What are the disadvantages?

A

It is unethical
It implies people with disorders are undesirable
Screening is expensive

41
Q

Who set the foundation of modern genetics?

A

Gregor Mendel - he noted how characteristics in plants were passed on. His work was published in 1866.

42
Q

What were Mendels three conclusions?

A

Characteristics in plants are determined y hereditary units
Hereditary units are passed on to offspring unchanged from both parents, one unit from each parent
Hereditary units can be dominant or recessive - if an individual has both the dominant and the recessive unit for a characteristic, the dominant characteristic will be expressed.

43
Q

When was the structure of DNA determined?

A

1953

44
Q

How are characteristics influenced by the environment?

A

The environmental variations can cause differences in growth for example light intensity for a plant.

45
Q

What is a mutation?

A

This is the change in the sequence of bases in DNA.

46
Q

What is the theory of evolution?

A

All of today’s species have evolved from simple life forms that first started to develop over three billion years years ago.

47
Q

What did Darwin state?

A

The organisms with the most suitable characteristics for that environment would be the most successful competitors. The organisms with the less suitable characteristics will be less likely to survive and reproduce so they will die out.

48
Q

Why was Darwin’s theory not accepted at the time?

A

Most people still believed in God

There was no evidence or explanation to why this is - genes were not discovered.

49
Q

What is speciation?

A

Over a long period of time, the phenotype of organisms can change so much because of natural selection that a completely new species is formed. This is called speciation. This happens when populations of the same species change enough to become re-productively isolated-this means that they can’t interbreed to produce fertile offspring.

50
Q

What is extinction?

A

A species that no longer exists.

51
Q

Why do some species become extinct?

A 
The environment changes
A new predator kills them 
A new disease kills them
They can't compete with another species
A catastrophic event happens that kills them all
52
Q

What was Lamarcks ideas?

A

Changes during an organisms lifetime will be passed on to its offspring. If a characteristic was used more it will become more developed and the offspring will obtain this.
For example if a rabbit used its legs to run the legs will grow longer, the offspring’s legs will then be longer.
He believed that everyone originated from one species.

53
Q

What is selective breeding?

A

This is where humans artificially select the plants or animals that are going to breed so that particular genes remain. They are selected to be more attractive or useful.

54
Q

Why would we want to selectively breed some animals?

A

For more meat or milk
Crops resistant to diseases
Dogs with good temperament
Decorative flowers or unusual flowers

55
Q

What is the main drawback in selective breeding?

A

It reduces the gene pool - the number of different alleles in a population. Inbreeding can cause health problems because there is more chance of inheriting harmful genetic diseases.
New diseases can appear because there’s not much variation in the gene pool the whole population will suffer.

56
Q

What is genetic engineering?

A

This is the basic idea of transferring a gene responsible for a desirable characteristic from one organism’s genome into another.

57
Q

Describe the process of genetic engineering

A

The useful gene is isolated using enzymes and is inserted into a vector
A vector is usually a virus or bacterial plasmid
When the vector is introduced to the target organism, the useful gene is inserted into its cell - the bacteria cell reproduces quickly and asexually so it will be a clone.

58
Q

What are GM crops?

A

These are crops that get modified to improve there size and quality of their fruit or that make them resistant to disease.

59
Q

What is the controversial topic in genetic engineering?

A

There are long term effects that could create genetic unplanned problems for future generations.

60
Q

How can plants be cloned?

A

Through tissue culturing - this is where a few plant cells are put in a growth medium with hormones, and they grow into new plants. These plants can be made very quickly, in very little space and be grown all year round.. Tissue culture is used by scientists to preserve rare plants that are hard to reproduce naturally.
Cuttings - This is where the gardener cuts a bit of the plant off and they put it in soil, this is quick, cheap and simple.

61
Q

How would you make animal clones?

A

Sperm cells are taken from the specific animal and so are egg cells the sperm is used for artificial fertilisers. The embryo that develops is then split many times before any cells become specialised. These cloned embryos can then be implanted into lots of other cows where they grow into genetically identical offspring.

62
Q

What is adult cell cloning?

A

This involves taking an unfertilised egg cell and removing its nucleus. The nucleus is then removed from an adult body cell and is inserted into the empty egg cell.
The egg cell is then stimulated by an electric shock - this makes it divide, just like a normal embryo.
When the embryo is a ball of cells, its implanted into the womb of an adult female. It grows into a genetically identical copy of the original adult body cell.

63
Q

What are the issues with cloning?

A

You get a reduces gene pool making them more susceptible to a certain disease. Cloned animals will not be as healthy. Some people worry that humans might be cloned in the future.

64
Q

What are the advantages of cloning?

A

It allows us to understand more more about the development of the embryo. This can save a dying species - endangered.

65
Q

What are fossils?

A

They are the remains of organisms from many thousands of years ago, which are found in rocks. They provide the evidence that organisms lived ages ago. Fossils can tell how much or little organism have changed.

66
Q

How do fossils form - gradual replacement?

A

Gradual replacement by minerals - things like teeth, shells, bones which don’t decay when buried. They’re eventually replaced by minerals as they decay, forming a rock like substance shaped like the original hard part. The surrounding sediments also turn to rock, but the fossils stay distinct inside the rock and eventually someone digs it up.

67
Q

How do fossils form - casts and impressions?

A

Sometimes fossils are formed when an organism is buried in a soft material like clay. The clay later hardens around it and the organism decays, leaving a cast of itself - footprints can also leave these impressions.

68
Q

How do fossils form - preservation?

A

In amber and tar pits there’s no oxygen or moisture so decay microbes can’t survive. In glaciers it’s too cold for the decay microbes to work. Peat bogs are too acidic for decay microbes.

69
Q

What is RNA and what is the use of RNA?

A

DNA is too long to fit through the pores of the nucleus. The activator proteins recruit transcription factors - which makes RNA. These proteins unwind the double helix structure of DNA and RNA polymerase. This makes RNA this is a single stranded small copy of the DNA which can leave the nucleus.

70
Q

What does RNA polymerase do?

A

It moves along the DNA template, making RNA complementary to one of the DNA strands. This is called transcription.

71
Q

What is RNA made of?

A

Ribonucleotides

72
Q

How is RNA read when it has copied the genetic code from DNA?

A

The RNA is split up by splicing so the RNA corresponds to the introns. This is then called messenger RNA it is ready to be used as a template for protein production. The three base pairs read are called codons.

73
Q

What is speciation?

A

Is the development of new species. It occurs when when populations of the same species become so different they can no longer successfully interbreed to produce fertile offspring.

74
Q

How does isolation and natural selection lead to speciation?

A

When the population is separated - isolation. This can occur through natural barriers such as floods or earthquakes. Conditions on either side of the barrier will be slightly different, because the environment is slightly different on each side different characteristics will become more common due to natural selection.

75
Q

What was Alfred Russel Wallace’s theory?

A

He worked on the idea of speciation. During his career he independently came up with the idea of natural selection and published his work with Darwin.

76
Q

How can bacteria evolve?

A

Bacteria sometimes develops random mutations in their DNA. This can lead to changes in their characteristics. This can lead to antibiotic-resistant strains forming as the gene for antibiotic resistance becomes more common in the population.Bacteria reproduce rapidly so they evolve by natural selection quickly.

77
Q

What are the simple steps of evolution? For full marks every time

A

Mutation - variation
Natural selection - competition
Over time that gene becomes more common

78
Q

Why does bacteria evolving dangerous?

A

The antibiotics will no longer be able to kill the bacteria therefore a suberbug is made which can be fatal. This is becoming more common.

79
Q

How can be prevent bacteria becoming resistant to the antibiotic?

A

Only prescribe this antibiotic if it is needed

Always take the full dosage so all the bacteria are destroyed

80
Q

How can we classify organisms into groups?

A

Organisms are classified according to a system first proposed in the 1700’s by Carl Linnaeus which groups organisms according to their characteristics.
In this system living things are first divided into kingdoms. They are then subdivided into smaller and smaller groups - phylum,class,order,family,genus,species.

81
Q

How has the classification system changed over time?

A

Carl Woese in 1990 proposed the three domain system. He used research in RNA sequence analysis.
Archaea - Different type of prokaryotic cell thought to be primitive bacteria
Bacteria - this is true bacteria they are biochemically different to the archaea domain
Eukaryota - This includes a broad range of organisms including fungi, plants, animals and protists.

82
Q

What is the binomial system?

A

It is a naming system for animals there is two parts in the Latin name. The first part refers to the genus that the organism belongs to - this gives you information on the organisms ancestry. The second part refers to the species. It is used worldwide so scientists who speak different languages all refer to a particular species by the same name.

83
Q

What are evolutionary trees?

A

This shows how species are related to each other through common ancestors. The more recent the common ancestor the more closely related the species are and the more characteristics they are likely to share.

84
Q

What is the method for Protein synthesis?

A

There are 2 stages: Transcription and translation.
Transcription:
- Gene base patterns in the nucleus are converted into complimentary template molecule,
- This is because the gene sequence is too large to leave the nucleus membrane so it must be converted into mRNA (message RNA),
- The mRNA then leaves the nucleus and goes into the cytoplasm,

Translation:

  • The mRNA attaches to a ribosome,
  • Then tRNA brings amino acids to the ribosome, for pairing with the base triplets,
  • The ribosome then reads the mRNA and assigns an appropriate amino acid to the base triplets, this creates one part of an amino acid chain,
  • Once the whole mRNA is read, and amino acids are assigned, an amino acid chain is complete and creates a protein,
  • This protein will have a set shape which will help it carry out its function (e.g. enzymes active site).

GCSE Biology paper 2 (3 decks)

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