Paper 2 Topic 6 Flashcards
1
Q
What does DNA stand for?
A
Deoxyribonucleic acid
2
Q
DNA has a double helix structure. How many strands is the helix made up of?
A
2
3
Q
The DNA in typical human cell is found in tight coils known as ___________.
A
chromosomes
4
Q
How many chromosomes are there in a typical human cell?
A
46
5
Q
Chromosomes exist in pairs. The chromosomes in the 23rd pair are known as the _____________.
A
sex chromosomes
6
Q
Do women have XX or XY sex chromosomes?
A
XX
7
Q
A small section of DNA that codes for a specific protein:
A
Gene
8
Q
What does the term ‘genome’ mean?
A
The entire set of genetic material in an organism.
9
Q
Where are the chromosomes found in the cell?
A
Nucleus
10
Q
______ are the different versions of a particular gene.
A
Alleles
11
Q
What is a phenotype?
A
The characteristics an organism has as a result of their genotype.
12
Q
Difference between heterozygous and homozygous?
A
Heterozygous - individual with two different alleles for a characteristic.
Homozygous - individual with two identical alleles for a characteristic
13
Q
What is a genotype?
A
the genetic makeup of an individual for a particular characteristic
14
Q
Which process is used to create gametes?
A
Meiosis
15
Q
What do we call the fusion of male of female gametes?
A
Fertilisation
16
Q
Difference between a gamete and a zygote?
A
Gametes are unfertilized reproductive cells.
A zygote is a fertilised egg or a fertilised egg.
17
Q
How many chromosomes in a haploid and diploid cell?
A
Haploid - 23
Diploid - 46
18
Q
During sexual reproduction in plants, which two gametes fuse together?
A
Pollen and egg
19
Q
When fungi and plants reproduce asexually, which process do they use?
A
Mitosis
20
Q
Do bacteria reproduce via sexual or asexual reproduction?
A
Asexual
21
Q
What is binary fission?
A
Asexual reproduction by a separation of the body into two new bodies.
22
Q
DNA can code for ________ by coding for the sequence in which ______ acids are joined together.
A
proteins
amino
23
Q
What is another name for gametes?
A
Sex cells
24
Q
Are gametes haploid cells?
A
Yes
25
How many chromosomes does a human gamete have?
23
26
When two haploid cells join, they form a _______ cell
diploid
27
During the process of meiosis, how many times does the cell divide?
2
28
As a result of meiosis, how many cells are produced?
4
29
Are the cells produced by meiosis genetically identical to each other, or genetically unique?
Genetically unique
30
How would you describe the genotype 'AA'?
**Homozygous dominant**
The letters are uppercase which means they represent dominant alleles, and both alleles are the same which means the genotype is homozygous.
31
How would you describe the genotype 'Hh'?
The two alleles are different, so the genotype is **heterozygous**.
32
How would you describe the genotype 'dd'?
**Homozygous recessive**
The letters are lower case which means they represent recessive alleles, and both alleles are the same which means the genotype is homozygous.
33
Is cystic fibrosis a dominant or recessive condition?
Recessive
34
What is polydactyly?
A condition in which an individual can be born with extra fingers or toes.
34
Polydactyly is an example of an 'inherited disease', what does this mean?
It can be inherited from an individual's parents
35
Is polydactyly caused by a dominant or a recessive allele?
dominant
36
Which part of a human body cell is affected by cystic fibrosis?
Cell membrane
37
Cystic fibrosis is an inherited condition that causes:
Thick, sticky mucus to build up in the lungs and digestive system
38
What does the term 'phenotype' mean?
The observable characteristics of an organism
39
Differences in the characteristics of individuals within a population is called ___________.
variation
40
Which two factors contribute to the variation between organisms?
The genes that individuals inherit
That environment that individuals are exposed to
41
A change in the DNA code is called a _________.
mutation
42
What factor(s) are involved in determining body mass?
Both genetic factors and environmental factors
43
A change in the genetical material of an organism is called a ___________.
mutation
44
What is this?: They generally have no effect, but are occasionally harmful, and very occasionally advantageous
mutations
45
What does the phrase 'survival of the fittest' mean?
The individuals with the most favourable characteristics are most likely to survive
46
___________ is the process by which the inherited characteristics of a population change over time due to natural selection. In some cases this may result in the formation of a new species.
Evolution
47
Who is credited with developing and proposing the theory of evolution?
Charles Darwin
48
Give one piece of evidence for the theory of evolution:
The spread of antibiotic resistance
Fossil records
49
Describe a series of events that might result in zebras evolving to run more quickly.
There is variation among the zebra population so that some can run faster than others.
A mutation arises that allows some zebras to run faster.
Those zebras that can run fastest are more likely to survive.
Therefore, they are more likely to reproduce and pass on their advantageous alleles.
This repeats over multiple generations.
The advantageous allele spreads throughout the population, until the species has 'evolved' to run faster.
50
Define Speciation
Speciation is the evolutionary process by which populations evolve to become distinct species.
51
What is the difference between a genotype and phenotype?
A person's genotype is their unique sequence of DNA. More specifically, this term is used to refer to the two forms a person has inherited from their mother and father, for a particular gene. Phenotype is the observable expression of this genotype – a person's presentation.
52
Give a characteristic for why humans selectively breed plants.
Increased yield
Better taste
53
What type of variation can be passed on to the next generation?
Genetic variation only
54
What effect does selective breeding usually have on variation within a population?
It decreases variation
55
What is the term used to describe all the genes and their alleles found in a population?
Gene pool
56
What is the term used to describe the breeding together of closely related individuals?
Inbreeding
57
What are 2 drawbacks of inbreeding?
Rare inherited diseases are more likely to appear.
It reduces that size of the gene pool.
The population as a whole will be more at risk of disease.
58
Briefly describe how the process of selective breeding could be used to increase milk production in a population of cows. (4)
-> The cows that produce the most milk are selected...
-> ... and bred together
-> This process in then repeated with the offspring of those cows
-> And again for multiple more generations
59
What is genetic engineering?
The transfer of a piece of DNA from one organism to another organism.
60
What is another name for genetic engineering?
Genetic modification
61
Can genetic engineering only be done between two organisms of the same species?
False. Genetic engineering is possible between completely different species, and even between kingdoms such as from animals to bacteria.
62
Sheep have been genetically engineered to produce drugs in their _____.
milk
63
What has been genetically engineered to produce human insulin?
Bacteria
64
Give three traits that could have been altered by genetic engineering in crops.
Increased yield e.g. bigger fruit
Increase quality e.g. better taste
Resistance to disease
Resistance to insects
Resistance to herbicides
Resistance to droughts
65
What is gene therapy?
The treatment of an inherited disorder by giving the patient a healthy copy of the faulty gene
66
Give a disorder which could be treated with gene therapy:
Cystic fibrosis
67
Give a drawback of genetic engineering:
1) There is a small risk that genetically modified food could negatively affect our health
2) If the crops breed with wild plants they could spread the new genes and affect the gene pool
68
4 Steps of genetic engineering for human insulin:
1) Isolate the insulin gene from human DNA.
2) Insert the DNA into a vector, such as a plasmid.
3) Insert the plasmid into a host bacterium.
4) Let the bacteria divide and then produce the insulin protein.
69
What is the name of the small circles of DNA that are genetically modified in bacteria?
Plasmids
70
Why is the human genome important?
1) It helps us *understand* how genetic diseases work so preventative steps can be taken. People can get screened to detect health risks early and start treatment sooner.
2) It aids the *diagnosis and treatment* of inherited disorders by letting us quickly identify faulty genes. New personalised drugs and therapies can be tailored to a patient's specific genetic makeup (this is sometimes called personalised medicine).
71
In the context of the Human Genome Project, how does understanding genes contribute to the treatment of inherited disorders?
By tailoring treatments based on an individual's unique genetic makeup.
72
What key information does the Human Genome Project offer in tracing human migration patterns?
Genetic markers revealing ancestral origins and migration routes.
73
How does the Human Genome Project enhance our understanding of the link between genes and diseases?
By mapping the entire human genome and revealing genetic variations
74
What is a potential drawback associated with genetic screening?
1) Learning about their genetic risks can cause *stress* and mental health issues for some people.
2) Genetic *discrimination* may lead to unfair treatment in jobs and insurance for those with certain gene variants. Strict regulations are needed to prevent gene-based bias.
3) There are concerns about the misuse of genetic data by employers and insurers, emphasising the need for *privacy protections.*
75
What is the Human Genome Project?
The Human Genome Project (HGP) was a **major international research effort** that aimed to **map out the complete human genetic code**. From 1990 to 2003, scientists across the globe worked together to sequence all 3 billion DNA base pairs that make up the human genome.
76
Understanding the human genome has opened up new possibilities for... (give 2)
...medicine, genetic research, and personalised healthcare.
77
What is an explant?
A small piece of plant that can develop into a clone
78
What is micropropagation?
An alternative to using cuttings is to use cell cultures to clone a plant (this is also known as 'micropropagation').
79
Give a pro and con of micropropagation:
Con) It requires more expertise than using cuttings
Pro) It can produce many more clones.
80
Give two benefits of cloning via cuttings rather than micropropagation.
1) Cuttings is quicker
2) Cuttings is cheaper
3) Cuttings requires less technical expertise/equipment
4) Don't have to worry about sterilisation so much for cuttings
81
Micropropagation (using tissue cultures):
-> Find a plant with desirable characteristics that you want to clone.
-> Take very small pieces of plant tissue (called explants) from the tips of stems.
-> Sterilise the explants to remove any microorganisms.
-> Place the explants in a nutrient medium (agar) and let them grow into small masses of cells called calluses. The nutrient medium should also contain growth hormones.
-> Transfer the calluses to soil where they can grow into plantlets (basically baby plants).
-> The plantlets can then be transferred to their own pots to develop into genetically identical adult plants.
82
Give two nutrients that should be added to the agar medium.
**Nitrates** for amino acids / proteins / DNA / genetic material etc
**Phosphates** for DNA / genetic material / ATP / cell membranes etc
**Glucose/sucrose** for energy/ATP/respiration
**Magnesium** for chlorophyll/chloroplasts
83
Plants can be cloned by micropropagation.
Suggest 2 precautions/ conditions needed to ensure healthy growth of the small plants.
sterile/aseptic conditions
temperature
light
humidity
growth hormones
84
What are fossils?
Fossils are the remains of organisms from millions of years ago, which are found in rocks.
85
Why are fossils used as evidence for evolution?
Fossils show us how species have changed over millions of years
86
Give one reason why the fossil record is incomplete.
- Some organisms are soft-bodied so do not fossilise well.
- Some fossils formed long ago may have been destroyed since
87
Give 2 ways fossils can form
1) Hard body parts, such as bones and shells, which decay very slowly, are gradually replaced by minerals, forming rock-like substances.
2) Animals can leave impressions or casts, such as footprints or burrows. These become covered by layers of sediment, which eventually become rock.
3) Some parts of organisms may not decay at all. For example, dead animals and plants can be preserved in amber, peat bogs, tar pits, or in ice.
88
Why might a dead animal be preserved in a tar pit, rather than decay?
Not enough oxygen for decay to take place.
The lack of oxygen means that microorganisms can't respire aerobically and so can't carry out the decay process.
89
What does it mean for a species to become extinct?
There are no remaining individuals of a species still alive.
90
Suggest 2 ways a species may become extinct.
-> Rapid environment change such as an increase in temperature
-> Reduction in habitat as it could reduce food and living space
-> Increase hunting as individuals are directly killed
-> The spread of a new disease
-> Introduction of a new competitor or predator
-> A catastrophic event, such as an asteroid strike
91
When bacteria evolve to become able to survive exposure to antibiotics, we say that they have developed:
Antibiotic resistance
92
Describe how antibiotic resistance arises.
1) A population of a bacteria infect somebody.
2) That person takes antibiotics to kill the bacteria
3) Some bacteria have (or get) a random mutation that makes them less susceptible to the antibiotic than others (or completely resistant to it)
4) The antibiotics kill all the bacteria except those that are resistant
5) The resistance strains of bacteria now have more resources to grow and multiply
6) More mutations may arise, leading to greater resistance
7) There is now a strain of bacteria that can't be killed by antibiotics, which we call antibiotic resistance
93
To reduce the rise and spread of antibiotic resistance, should we increase or decrease the use of antibiotics?
Decrease use
94
Are antibiotics effective at treating viral diseases?
No, because antibiotics only kill bacteria, not viruses.
95
If we want to reduce the rise and spread of antibiotic resistance, should doctors prescribe antibiotics for mild bacterial infections?
No. Our bodies can generally fight mild bacterial infections themselves, so we don't really need antibiotics.
96
Should you take the whole course of antibiotics, or stop taking them once you feel better?
It is important to take the full course so that they can kill all of the bacteria.
97
Give 2 reasons why antibiotic resistance is becoming more common.
1) Doctors often prescribe antibiotics in cases where they aren't necessary. For example, mild or viral infections.
2) Many people don't take the full course of antibiotics, so not all the bacteria are killed.
3) Huge amounts of antibiotics are given to farm animals in order to make them grow faster
98
Why is the spread of antibiotic resistance a problem?
If more bacteria are resistant to antibiotics, we won't be able to treat those infections.
This means more people will die of bacterial infections.
99
What is one advantage of using a binomial system to name species?
Each species has a unique name.
It lets scientists discuss individual species.
100
Which 18th Century scientist developed the traditional classification system for classifying living things?
Carl Linnaeus
101
Which international system is commonly used to classify organisms?
The Linnaean classification system
102
What is the correct order of groups in the Linnaean classification system?
Kingdom, phylum, class, order, family, genus, species.
103
Which two groups in the classification system are used in the binomial naming system?
Genus
Species
104
What is the binomial name for humans?
*Homo sapiens*
105
How do we write the binomial name of a species? Give 1
All in italics
All lower case except the first letter of the genus
106
The binomial name for grey wolves is *Canis lupus*.
What are the species and genus names for the grey wolf?
The binomial name tells you the genus and species. So for *Canis lupus*, *Canis* is the genus and *lupus* is the species.
107
Which 20th century scientist used microscopes and modern technology to develop the three domain system to classify organisms?
Carl Woese
108
Carl Woese developed the three domain system to classify organisms. What are the three domains?
Archaea
Eukaryotes
Bacteria
109
Give 4 examples of Eukaryotes.
Protoctists
Fungi
Plants
Animals
110
What do evolutionary trees show?
The evolutionary relationship between the organisms being studied.
111
What do the branch points show on an evolutionary tree (circled red in the above diagram)?
The divergence of a single population/species into two separate populations/species.
