Topic 6 - Inheritance, Variation And Evolution Flashcards
1
Q
What does sexual reproduction involve and give examples ?
A
Involves the joining of male and female gametes, each containing genetic information from the mother and father (sperm and egg cells, pollen and egg cells)
2
Q
How many chromosomes does a human normal cell have ?
A
46
3
Q
What does asexual reproduction involve and what does it lead to ?
A
Involves one parent and no gametes joining, clones
4
Q
Describe the process of meiosis ?
A
- the cell makes copies of its chromosomes, so it has double the amount of genetic information
- the cell divides into 2 cells with half the amount of chromosomes (46)
- the cell divides again producing four cells each with 23 chromosomes
5
Q
Give some advantages of sexual reproduction ?
A
Produces variation :
- survival advantage, if the environment changes it is likely that a organism in the species has a characteristic that allows it to survive
- variation decreases the chance of the whole species becoming extinct
Allows us to use selective breeding :
- mixes genetic material from 2 organisms
- organisms with different desirable characteristics can be bred to produce offspring with even more desirable characteristics
- speeds up natural selection
6
Q
Give some examples of asexual reproduction ?
A
- only one parent needed
- less energy and is faster as organisms do not need to find a mate
- in favorable conditions lots of identical offspring can be produced
7
Q
How come malarial parasites use both sexual and asexual ways to reproduce ?
A
Produce sexually in a mosquito (the carrier) and then produce asexually in the human host (in the liver and blood cells)
8
Q
How come fungi reproduce both sexually and asexually?
A
- spores produced asexually are genetically identical
- spores are produced sexually when the conditions change in order to increase variation and avoid extinction
9
Q
How do flowering plants reproduce sexually ?
A
During pollination seeds are formed through the fusing of pollen with egg cells in the female parts of another flower
10
Q
Give examples of plants that reproduce asexually and why it’s advantageous?
A
- Strawberry plants producing runners
- Daffodil bulbs can grow new bulbs from old ones
11
Q
What is a gene ?
A
A small section of DNA on a chromosome which codes for a particular sequence of amino acids, which together can join to make a protein (and therefore contributes to a characteristic)
12
Q
What is the genome ?
A
All the genes coding for all the proteins within an organism
13
Q
What are some advantages and disadvantages to the human genome project ?
A
Advantages :
- can test and treat genetic disorders
- can predict and prevent diseases from occurring
- can create more efficient medication (such as dosage for breast cancer)
Disadvantages:
- Employers and insurers can use this to discriminate
- this knowledge can increase stress
- this knowledge could pressure people not to have children
14
Q
What is DNA ?
A
Deoxyribonucleic acid, a polymer that contains instructions for the body
15
Q
Describe the structure of nucleotides ?
A
- one sugar molecule, one phosphate molecule (which forms the backbone), and one of the four types of organic bases
- bases = A to T. C to G (complementary base pairs)
- each group of 3 bases codes for an amino acid (20 types) which join together to make a protein
16
Q
What is and describe protein synthesis ?
A
The process of producing a protein from DNA
1. DNA cannot move out of the nucleus as it is too big
2. The 2 strands pull apart from each other and mRNA nucleotides match to their complementary bases
3. The mRNA nucleotides are joined to create a mRNA strand
4. These move out of the nucleus move out of the nucleus onto the ribosomes
5. Then the bases are read in threes to code for an amino acid
6. The corresponding amino acids are brought to the ribosomes by carrier molecules
7. These amino acids connect to form a protein
8. When the chain is complete the protein folds to form a unique 3D structure
17
Q
What are the 3 main types of proteins ?
A
- enzymes (biological catalysts that speed up rate of reaction)
- hormones (chemical messengers that send signals around the body)
- structural proteins (to form structures such as collagen)
18
Q
What are the 3 ways mutations can change the sequences of bases in DNA ?
A
- A bases is inserted into the code (which changes the way it’s read and may change all the amino acids afterwards)
- A base is deleted from the code
- A base is substituted (will only change one amino acid in the sequence or may not change the amino acid)
19
Q
What effect do mutations in DNA have ?
A
- most mutations do not alter the protein or only do so slightly
- however sometimes the substrate will not fit into the active site so it cannot act as a protein
- or a structural protein may lose its shape
20
Q
Gamete definition ?
A
An organisms reproductive cell
21
Q
Chromosome definition?
A
A structure found in the nucleus which is made up of a long strand of DNA
22
Q
A
23
Q
Alleles definition ?
A
The different forms of the gene
24
Q
Dominant allele definition?
A
Only one is needed for it to be expressed and for the corresponding phenotype to be observed
25
Recessive allele definition ?
Two copies needed for it to be expressed and for the corresponding phenotype to be observed
26
Homozygous definition ?
When both inherited alleles are the same (2 dominant or 2 recessive)
27
Heterozygous definition ?
When one of the inherited alleles is dominant and the other is recessive
28
Genotype definition ?
The combination of alleles and individual has
29
Phenotype definition ?
The physical characteristics that are observed in the individual
30
What are the 2 inherited diseases and what allele ?
Polydactyly :
- extra fingers or toes
- dominant allele
Cystic fibrosis :
- disorder of the cell membrane, resulting in thick mucus in the airways and pancreas
- recessive allele
31
What is embryonic screening ?
- allows scientists to observe whether the child will have a genetic condition
- if embryo is developed in the lab, cells can be taken from it and analyzed
- DNA from embryos in the womb can also be extracted
32
Arguments for embryonic screening
- reduces the number of people suffering (ethical)
- treating disorders is very expensive (economic)
- there are many regulations in place to stop it getting out of hand (social)
33
Arguments against embryonic screening
- could encourage people to pick desirable characteristics (ethical)
- it is expensive to carry out screening (economic)
- many promote prejudice as it suggests people with genetic disorders are unwanted (social)
- decisions about terminating a pregnancy have to be made (social)
- the procedure can lead to a miscarriage (social)
34
What are the X and Y combinations for female vs male sex ?
Female = XX
Male = XY
35
What 2 things is the phenotype of an organism depended by ?
1. Genotype, the genes it inherited
- genes are passed on from the parent in sex cells
- creates genetic variation
- only identical twins have the same genotype
2. Environment, the place it leaves
- scars, smaller and yellow leaves in plants
3. Weight depends on both
36
Evolution definition ?
A change in the inherited characteristics of a population over time through a process of natural selection selection which may result in the formation of new species
37
What is the theory of evolution ?
All species have evolved from simple life forms that first developed more than 3 billion years ago
38
How does natural selection work ?
1. Mutations occur which provide variation between organisms
2. If a mutation provides a survival advantage the organism is more likely to survive to breeding age
3. The mutation will then be passed onto offspring
4. Over many generations, the frequency of the mutation will increase within the population
39
What is speciation ?
When natural selection causes one population of species to become so different that they can no longer interbreed to produce fertile offspring
40
What is selective breeding ?
When humans choose organisms to breed in order to produce offspring with a certain desirable characteristic
41
What is the issue with selective breeding ?
- more likely to be breeding closely related individuals
- results in the reduction of the gene pool, as the number of different alleles reduce
- this means if the environment changes or if there is a new disease the species could become extinct as they all have the same genetic makeup
- small gene pool leads to a greater chance of genetic defects present in a offspring as recessive characteristics are more likely to present
42
Genetic engineering definition ?
Modifying the genome of an organism by introducing a gene from another organism to give a desirable characteristic
43
Process of genetic engineering?
1. Genes from chromosomes are 'cut out' using restriction enzymes leaving
'sticky ends' (short sections of exposed, unpaired bases)
2. A virus or bacterial plasmid is cut using the same restriction enzyme to also create sticky ends. This also contains an antibiotic marker gene.
3. The loop and gene sticky ends are then joined together by DNA ligase
enzymes
4. The combined loop is placed in a vector, such as a bacterial cell, and then allowed to multiply as it will now contain the modified gene. As the bacteria grows we can see which ones are resistant to antibiotics. The colonies that are will be the bacteria that are also producing the modified gene, as they were inserted together.
In plants the vector is put into meristematic cells (unspecialised cells) which can then produce identical copies of the modified plant.
44
Examples of genetic engineering ?
- genetically modified crops to be resistant to insects which will result in increased yields
- may be possible to use gene therapy to cure inherited disorders
45
Benefits of genetic engineering ?
- can be useful in medicine to mass produce certain hormones in microorganisms
- in agriculture it can be used to increase yields by : improving growth rates, introducing modifications that allow the crops to grow in different conditions, introducing modifications that allow plants to make their own pesticide/herbicide
- crops with extra vitamins can be produced
- greater yields can help solve world hunger (population growth)
46
What is cloning ?
Creating genetically identical copies of an organism
47
What are the 2 methods of plant cloning ?
1. Tissue culture : (important to preserve rare plant species or commercially in plant nurseries)
- plant cells are taken
- they are placed in a growth medium with nutrients and hormones
- they grow into new plants and are clones as they are genetically identical to the parent
2. Cuttings : an older easier method to produce clones
- cuttings are taken from a plant with a desirable feature
- they are planted and produce clones as they are genetically identical to the parent
48
How does embryo transplant cloning work ?
- sperm and egg cells form parents with desirable features are obtained
- In the lab they are fertilized to form an embryo
- the embryo divides many times and is then inserted into a host mother
- the offspring which is eventually born is genetically identical
49
How does adult cell cloning work ?
- the nucleus is removed from an uncertified egg cell
- the nucleus is removed from an adult body cell and is placed in the denucleated egg cell
- through the stimulation of an electric shock the egg cell begins to divide to form an embryo
- the embryo is implanted into the womb of a female
- The offspring born is a clone of the adult body cell
50
Benefits of cloning ?
- produces lots of offspring with a specific desirable feature
- the study of clones could help research into embryo development
- can help extremely endangered species or even bring back species that have been extinct
51
Risks of cloning ?
- the gene pool is reduced meaning it is less likely that the population will survive if a disease arises with low diversity in the population
- clones have a low survival rate and tend to have genetic problems
- may lead to human cloning
52
Charles Darwin ?
- scientist and naturist
- put forward the theory of evolution
- supported by experimentation and his knowledge of geology and fossils that he discovered on a round the world expedition
- Published ‘On the origin of species’ in 1859
53
What is cloning ?
Creating genetically identical copies of an organism
54
Theory of evolution :
• Variation exists within species as a result of mutations in DNA
• Organisms with characteristics most suited to the environment are more likely to survive to reproductive age and breed successfully - called survival of the fittest.
• The beneficial characteristics are then passed on to the next generation
• Over many generations the frequency of alleles for this advantageous characteristic increase within the population
55
Why was there controversy towards Darwin’s ideas ?
1. Contradicted the idea that God was the creater of all species on Earth
2. Not enough evidence or studies
3. Mechanism of inheritance and variation not known at the time
56
What did Jean-Baptiste Lamarck believe in regard to evolution ?
- changes that occurred during the lifetime of an organism were passed onto offspring
- if an individual continually repeated an action the characteristic that allowed it to do this would develop further
57
What is speciation ?
The process of new species developing through the selection of different alleles which increases the genetic variation until the new population cannot breed with those in the old population to produce fertile offspring
58
Who developed the theory of speciation ?
Alfred Russel Wallace
59
Alfred Russel Wallace :
- on his travels he had the idea that individuals who did not have characteristics to help them survive would die out
- he published joint studies with Darwin
- the publication of ‘On the origin of species’ meant that Darwin received the credit for the theory
- continued to work across the world to collect evidence
60
The process of speciation :
1. Variation exists within a population as a result of genetic mutations
2. Alleles which provide a survival advantage are selected for through natural selection
3. Populations of a species can become isolated
4. Different alleles may be advantageous in the new environment leading to them being selected for
5. Over time the selection of different alleles will increase genetic variation between the two populations
6. When they are no longer able to breed together to produce fertile offspring a new species has formed
61
Who is Gregor Mendel
• Trained in mathematics and natural history in Vienna
• Worked in the monastery gardens and observed the characteristics passed on to the next generations in plants
• He carried out breeding experiments on pea plants.
• He used smooth peas, wrinkled peas, green peas and yellow peas and observed the offspring to see which characteristics they had inherited
• Through keeping a record of everything he did and eventually publishing his work in 1866, he came to the conclusions that:
• Offspring have some characteristics that their parents have because they inherit 'hereditary units' from each.
• One unit is received from each parent.
• Units can be dominant or recessive, and cannot be mixed together.
62
How was Mendels theories proved ?
- in late 19th century chromosomes as a part of cell division was observed
- in 20th century, it was understood that chromosomes and units had similar behaviors. It was decided that units (now genes) were on the chromosomes
- the structure of DNA was determined in 1953
63
Where is evidence for evolution seen in ?
1. Fossils
2. Antibiotic resistance in bacteria (the selection of pressure of antibiotics leads to advantageous mutations being selected for in bacteria populations so they are no longer killed when exposed to antibiotics
64
What are the 3 things fossils are formed from ?
1. Parts of organisms that have not decayed because oxygen or moisture were not present, meaning that the microbes that cause decay cannot survive
2. Parts of organisms such as teeth, shells and bones are replaced with minerals as they decay forming a rock structure of the original part
3. Preserved traces such as footprints, burrows and trails
65
Why can’t fossils be used to tell us how life started on earth ?
- most early life forms are soft bodies and therefore decay completely
- any traces have been destroyed by geological activity
66
Extinction definition ?
When an entire species has died out
67
Name (6) factors that can contribute to extinction?
- changes in environment which the species cannot adapt fast enough to
- new predators which have evolved or migrated
- a new disease and there are no resistant alleles
- they have to compete with a species which has advantageous mutations for the same food source
- a catastrophic event can wipe out a species
- destruction of habitat
68
How can bacteria become resistant ?
- bacteria reproduce at a fast rate
- mutations during reproduction can result in new genes, such as the gene for antibiotic resistance
- exposure to antibiotics creates a selection pressure as those with antibiotic resistant genes survive and those without die
- as a result those with resistance can reproduce and pass on the advantageous gene to their offspring
- this population of antibiotic resistant bacteria increases
69
What is an example of resistant bacteria ?
MRSA, called a ‘superbug’ common in hospitals and spreads when doctors and nurses move to different patients
70
How can you slow the development of resistant bacteria ?
1. Antibiotics should not be given to viral or non-serious infections
2. Specific antibiotics should be given for specific bacteria
3. Patients should complete their course of antibiotics
4. Antibiotics should be used less in agriculture
71
How can you slow the transmission of bacteria ?
1. Maintain high standards of hygiene in hospitals
2. Medical staff and visitors should wash hands regularly
3. Medical staff should wear disposable clothing/ clothing that is regularly sterilized
72
What is the Linnaean system ?
- Carl Linnaeus put this forward in the 1700s
- living things divided into kingdoms, phylum, class, order, family, genus, species
73
What is the binomial system ?
Gives each organism a name which is used worldwide. The first part is their genus and the second part is their species
74
What is the three-domain system ?
- developments in science (microscope and increased knowledge in biochemistry) found that some species were more distantly related than first thought
- Carl Woese added 3 large groups called domains above kingdoms :
• archaea - primitive bacteria which live in extreme environments
• bacteria - true bacteria
• eukaryota - organisms who have a nucleus enclosed in membranes
75
What are evolutionary trees used for ?
To show how closely related organisms are
76
