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1.4(CS) and Chemical analysis > Inheritance, variation and evolution (B2.6) > Flashcards

Inheritance, variation and evolution (B2.6) Flashcards

1
Q

What is a gene?

A

A gene is a small section of DNA on a chromosome. Each gene codes for a particular sequence of amino acids, to make a specific protein.

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2
Q

What is an allele?

A

Different versions of a gene we have 2 alleles per gene( 1 from each parent)

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3
Q

What is a genotype?

A

The alleles for a specific characteristic that are present

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4
Q

What is a gamete?

A

Gametes are sex cells eg sperm and egg cells but are not fused together.

They have 23 chromosomes (one copy of each chromosome called a chromatid)

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5
Q

What is a diploid and a haploid?

A

A gamete is a haploid as haploids are a single set of chromosomes of 23.

When the two gametes combine, they merge the two sets of chromosome to have 46, which are referred to as diploid. This produces a new cell called a zygote

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6
Q

What is a phenotype?

A

Observable physical characteristics as a result of genes

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7
Q

What is meant by a dominant allele?

A

The dominant allele is always expressed and is (B) even if only one copy is present

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8
Q

What is meant by a recessive allele?

A

The recessive allele needs 2 recessive alleles to be expressed (b)

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9
Q

What is meant by homozygous?

A

2 of the same alleles( bb= homozygous recessive or BB= homozygous dominant)

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10
Q

What is meant by heterozygous dominant?

A

Different alleles (Bb)

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11
Q

How many chromosomes do human cells have in their nucleus?

A

23 pairs (46)

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12
Q

What is sexual reproduction?

What is 2 advantages and 2 disadvantages?

A

2 parents have sex by mixing 2 sets of genetic information from 2 gametes and the offspring is genetically different

ADV- variation in offspring DIS- slower to reproduce and we need 2 partners.

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13
Q

What is asexual reproduction?

What is 2 advantages and 2 disadvantages?

A

1 parent makes identical copies of its cells and DNA and the offspring is identical to the parent (no gametes are required)

ADV- quick and no partners DIS- no variation and offspring will inherit diseases

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14
Q

What are the male and female sex organs in plants?

A

Male= stamen and female= stigma

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15
Q

Describe how sexual reproduction occurs and what type of cell division is used:

A

The gametes from each parent fuses and forms a zygote. Meiosis occurs

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16
Q

Describe the process of Meiosis

A

Cells in reproductive organs divide by meiosis to form gametes. Two cell divisions occur and the chromosomes replicate but only 1/2 of each chromosome goes to a new daughter cell. 4 new daughter cells are produced and the daughter cells are genetically different.

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17
Q

Describe the rough process of Mitosis

A

Only 1 cell division occurs and it produces 2 genetically identical daughter cells. The cell which has 46 will double to 92 and the split into 2 cells each of 46.
The chromosomes replicate which copies all genetic information (as a chromatid) and goes to each new daughter cell.

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18
Q

Why does Mitosis occur?

A

During growth, repair and asexual reproduction

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19
Q

Why does meiosis occur?

A

Meiosis only occurs in reproductive cells so the ovaries and testes in humans, to create haploid gametes that will be used in fertilisation

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20
Q

What is a chromatid?

A

one copy of each chromosome

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21
Q

Describe the organisation of our structure from small to large (8)

A

Genes, DNA, Chromosomes, Nucleus, Cell, Tissue, Organ , Organism

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22
Q

What is DNA?

A

Deoxyribonucleic acid. The genetic material in the nucleus of a cell is composed of DNA. DNA is made up of two strands forming a double helix. The DNA is contained in structures called
chromosomes.

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23
Q

What are the sex organs in flowering plants?

A

pollen and egg cells

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24
Q

What happens after meiosis?

A

Gametes join at fertilisation to restore the normal number of chromosomes. The new cell divides by mitosis. The number of cells increases and are identical. As the embryo develops cells start to differentiate.

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25
Q

What is a chromosome?

A

Coiled DNA- Humans have 46 chromosomes arranged in 23 pairs.

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26
Q

What is a genome?

A

The entire genetic material of an organism

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27
Q

What does the human genome allow us to understand?

A

We can: search for genes linked to different types of disease
• understanding and treatment of inherited disorders
• use in tracing human migration patterns from the past( allows people to understand their ancestry)

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28
Q

Why could climate change affect asexually reproducing organisms more than sexually reproducing organisms?

A

If parents are unable to adapt to a certain condition there offspring will also die as the offspring is a clone- whereas in sexual reproduction there is more variation

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29
Q

Who determines the sex of an foetus?

A

The father

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30
Q

What are the sex chromosomes for a boy and for a girl? What pair of chromosomes code for gender?

A

Boy= XY and Girl= XX

The last 23rd pair

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31
Q

Describe sex determination

A

We have 2 sex chromosomes of x and y chromosomes. Males have one of each whereas females have XX chromosomes. This means the male gamete determines the sex of an embryo. So the mother has XX and the father has XY so the baby will be either ( XX,XY,XX,XY- so there’s a 1:1 chance of a boy or a girl)

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32
Q

In the human sex chromosomes, what is the recessive and what is the dominant? Why is it important that the dominant chromosome is DOMINANT?

A

Male dominant= Y and Female recessive= X

Otherwise the world would only have females

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33
Q

What is an inherited disorder?

A

These disorders are caused by the inheritance of certain alleles

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34
Q

What is Cystic Fibrosis and the symptoms?

A

Disorder of cell membranes which affects lungs and causes breathing difficulty as hairs don’t waft mucus up which blocks tubes- symptoms= difficulty breathing and walking

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35
Q

What is the allele and genotype that causes Cystic Fibrosis?

A

STRICTLY Homozygous recessive allele and the persons genotype is (cc)

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36
Q

What is a carrier?

What is a mutation?

A

If a person receives only one recessive allele, their one dominant allele means they do not have symptoms of the disorder. However, they are able to pass it to their children. They are called a carrier.
A mutation is a random change in the DNA/gene

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37
Q

What is polydactyly?

A

Having an extra toe or thumb

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38
Q

What type of allele and genotype causes polydactyly?

A

1 dominant allele ( PP or Pp)

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39
Q

How can we see (or prevent) if an embryo has genetic disorders?

A

Screening techniques i.e. IVF, Amniocentesis or Chorionic Villus Sampling

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40
Q

What is Amniocentesis?

A

Carried out at 15 weeks or so and we take amniotic fluid from foetus and test the fluid for genetic disorders using foetal cells.

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41
Q

What is Chorionic Villus Sampling?

A

Carried out at 10-12 weeks and we take a sample of the tissue of placenta and test foetal cells

42
Q

What are the downsides to both embryo testing methods?

A

Can cause/ increases risk of miscarriage and in case of false result- a healthy pregnancy can be terminated

43
Q

Describe IVF

A

Gametes are removed from both parents and are fused outside the body via in vitro ( in a lab). Then the embryo develops via fertilised egg and we test embryo cells for a disorder. Embryos with good alleles are implanted into mother and develop whilst embryos with bad alleles are destroyed

44
Q

Why do identical twins look identical?

A

Have the same DNA

45
Q

What is variation?

A

Differences in the characteristics of individuals in a population

46
Q

What are the 3 causes of variation?

A

1) The alleles that individuals have inherited (genetic causes i.e. hair and eyes)
2) Environment i.e. languages or scars
3) Combination of both genes and environment like: height/weight

47
Q

Why do genetic variations occur and what do they lead to ?

A

Due to mutations causing phenotypes to change

48
Q

Explain the process of genetic variation

A

The DNA of an organism randomly changes due to a mutation. Therefore the genotype changes sometimes resulting in a change of the phenotypes causing variation

49
Q

What’s the difference between discontinuous and continuous data?

A

Discontinuous= specific groups like hair colour/ blood group

Continuous= data with a range i.e. height/weight

50
Q

What difficulties can arise when testing identical twins?

A

Hard to control EVERYTHING?

Ethical issues i.e. pressurising or separating twins

51
Q

What is natural selection?

A

How species change and adapt so best adapted organisms with desired phenotypes survive/ reproduce whilst other less adapted organisms die

52
Q

Describe the process of natural selection using rabbits and foxes

A

Lets say some rabbits have alleles for good sight/hearing and others dont- when a fox is around the rabbits with good eyesight/hearing will run away and survive but the other rabbits with non adapted alleles will die= natural selection

53
Q

What is evolution?

A

The change in inherited characteristics of a population through the process of natural selection over a long period of time

54
Q

What can happen when 2 populations of the same species become VERY different in phenotype?

A

The 2 populations become 2 separate species and cannot breed successfully with the other population

55
Q

What is selective breeding (artificial selection)?

A

When humans choose which organisms to breed to produce offspring with desired characteristics

56
Q

What is the point of selective breeding in the future?

A

Next generation will be likely to have desired characteristics

57
Q

Describe selective breeding (detailed)

A

1) Organisms show variation in features and humans select organisms with desired characteristics i.e. good nature/ temperament
2) 2 chosen organisms are mated/ bred and offspring is produced.
3) Offspring with good features and bred all over again and again for many generations UNTIL all of the population have these characteristics.

58
Q

What are some desired features we want in animals?

A

Good milk yield
Produces lots of meat
Good temperament
Gentle domestic pets

59
Q

What are some advantages of selective breeding?

A

Unique/ unusual plants– Genetic manipulation leads to unusual genetic combinations– economic profit— speeds up evolution– better genes/alleles in a population overall

60
Q

What are some disadvantages of selective breeding?

A

Reduces variation of phenotypes in a population—

In case of a new change to environment, all animals/ plants share genotypes so none are able to survive–

More inherited diseases

Inbreeding means breeding related animals/plants for a specific look– which can cause inherited defects/diseases

61
Q

What is genetic engineering?

A

genes from 1 organisms i.e. humans are cut out and transferred to cells of a different organism i.e. bacteria——– Genetic engineering involves the modification of genetic material of an organism

62
Q

What is an example of how we have genetically modified bacteria?

A

People with T1 diabetes cannot produce their own Insulin (a hormone for blood glucose regulation)and must inject themselves with insulin regularly

We have genetically modified bacteria to contain the human insulin gene which means the bacteria reproduce and produce lots of human insulin which we take for T1 diabetes

63
Q

How can we make GM crops better than regular crops?

A

Transfer the gene into plants to make GM crops that are bigger( greater yield) or disease resistant or resistant to herbicides

64
Q

What is gene therapy?

A

Genetic modification to treat human inherited disorders

65
Q

Describe the process of genetic engineering

A

Find the gene you want to transfer

Use enzymes to isolate and cut out gene from the organism

Transfer the gene into vector like: a plasmid or virus

Insert the gene into the cells of the target organism i.e. animal/plant

66
Q

What is a plasmid?

A

A small circle of DNA useful for transferring DNA from one organism to another

67
Q

At what stage of the organism do we transfer the gene?

A

Early stages of development (i.e. for animals at early embryo stage) to make sure ALL cells receive the transferred gene so that the organism develops with the characteristic we want

68
Q

What are some advantages of Genetic engineering in agriculture?

A 
Better Growth rates 
Bigger yield (more food)
Disease/Drought resistant 
Herbicide/ pesticide resistant 
Mass production of desired genes
69
Q

What are some concerns of Genetic Engineering?

A 
New science
We dont know long term effects
Encourages more human engineering
Expensive
People feel eating GM crops is unsafe
Effect on population of flowers/insects
70
Q

How could genetic engineering be used to cure genetic disorders?

A

Healthy cells inserted into affected cells and the affected cells begin to work properly so we can alter peoples genes to make sure they dont have the disorder

71
Q

Why might the government not allow the production of certain GM foods?

A
  • Extinction of the natural food

- They dont know long term effect

72
Q

What do fossils provide?

A

Good evidence for evolution

73
Q

What are fossils?

A

Remains of organisms from millions of years ago which are found in rocks

74
Q

What are the 3 ways fossils can form?

A

1) Parts of an organism have not decayed when conditions for decay are absent i.e. temp= too cold or if there is not enough oxygen
2) When parts of the organism are replaced by minerals during the decay process
3) Preserved traces of organisms i.e. footprints or burrows or plants leaving preserved spaces in area of roots

75
Q

What do we need for decay to occur?

A

Oxygen

76
Q

What conditions can cause fossilisation?

A

Lack of oxygen, extreme cold temperatures and absence of bacteria

77
Q

What is an issue about fossils?

A

Many earlier forms of life were soft bodied so they dont form fossils so we dont have evidence about evolution from the start

Also some fossils have been destroyed due to tectonic hazards i.e. volcanoes

78
Q

How can fossils give evidence for evolution?

A

We see how older fossils change and how younger ones developed

79
Q

What does extinct mean?

A

When there are no remaining individuals of a species alive

80
Q

How can species become extinct?

A

Due to a catastrophic event (i.e. asteroids)

Environmental changes

new disease or predator

If a new species evolves and competes with the old species for food/water

81
Q

How do fossils form?

A

Dead bodies of animals buried via mud/sand
Layer of sediment presses down on them
Pressure increases
The pressure leaves the remains to stone or minerals fill in the hole

82
Q

What is the name of the type of organism that evolves extremely rapidly? Why?

A

Bacteria— they reproduce at such a fast rate so they evolve rapidly

83
Q

How did doctors begin to treat bacterial diseases ?

A

Antibiotics like Penicillin KILL bacteria

84
Q

How are antibiotics used?

A

Widely used in medicine and in farming to prevent animals from developing bacterial disease

85
Q

What has occurred due to the evolution of bacteria?

A

Certain strains of bacteria are no longer killed by antibiotics so they are “ antibiotic resistant”

86
Q

Name 1 common strain of antibiotic resistant bacteria

A

MRSA

87
Q

How does antibiotic resistance happen?

A

In any population of an organism- there are genetic variations due to mutations

Some bacterium have a mutation that makes them resistant to antibiotics

We use antibiotics to kill the bacteria without the mutation BUT the antibiotic resistant bacteria still survive

These resistant strains reproduce causing the population of the resistant strain to rise and spread and there is no treatment

88
Q

How can we reduce the development of antibiotic resistant strains of bacteria?

A

Doctors mustn’t prescribe antibiotics inappropriately i.e for a virus as this wouldn’t work

Patients must complete their course of antibiotics to make sure ALL bacteria is killed and none can survive to mutate

We must restrict use of antibiotics in farming

89
Q

Why dont researchers just develop new antibiotics?

A

Takes a very long time

Very Expensive

New strains emerge all the time so its unlikely we can keep up!

90
Q

What can we observe from lots of species?

A

They have similar characteristics in common despite being different species

91
Q

Who and how have species been classified by?

A

Traditionally living things have been classified into groups
depending on their structure and characteristics in a system
developed by Carl Linnaeus.

92
Q

How did Linneaus do this?

A

Divided all living organisms into 2 kingdoms of “ the animal kingdom” and the “plant kingdom”

He then divided each kingdom into smaller categories

93
Q

What are the names of linneaus’ classification categories?

A

Linnaeus classified living things into: kingdom, phylum, class, order,
family, genus and species.

94
Q

What mmemonic can we use to remember this?

A

King Phillip came over for good soup

95
Q

How are organisms named?

A

Organisms are named by the binomial

system (2 names) of genus and species.

96
Q

We have a polar bear–

The Family is called Ursidae
The Genus is called Ursus and the species is called Maritimus

What is the binominal name of this organism?

A

Genus+ species= Ursus Maritimus

97
Q

What do we base this classification system on?

A

Characteristics we can see (phenotypes)

98
Q

What advances have been made since this classification system?

A

As evidence of internal structures became more developed due to
improvements in microscopes, and the understanding of
biochemical processes progressed, new models of classification
were propose.

We can use microscopes to look at internal structures or analyse DNA

99
Q

What system do scientists now use?

A

The 3 domain system developed by Carl Woese.

100
Q

What is the 3 domain system?

A

. In this system
organisms are divided into:
• Archaea (primitive bacteria usually living in extreme environments)
• Bacteria (true bacteria i.e in our digestive system)
• Eukaryota (which includes protists like amoeba, fungi, plants and animals)

101
Q

What are evolutionary trees?

A

Evolutionary trees are a method used by scientists to show how they believe organisms are related.

102
Q

What do we need to make an evolutionary tree for living and extinct species?

A

They use current classification
data for living organisms

Fossil data for extinct organisms= issue as many fossils are incomplete

1.4(CS) and Chemical analysis (11 decks)

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