P2: Inheritance, Variation And Evolution Flashcards
(97 cards)
1
Q
What is mitosis used for?
A
Growth, repair to damaged tissue and replacement of worn-out cells.
2
Q
Explain the process of mitosis.
A
Chromosomes in the nucleus are copied.
Chromosomes and their copies are pulled apart and moved towards the opposite sides
Chromosomes separate
Cell divides into two genetically identical daughter cells
3
Q
What is produced when the nuclei of the male and female gametes fuse?
A
A zygote.
4
Q
What are the gametes in flowering plants?
A
Pollen and eggs
5
Q
What is a haploid?
A
A cell that contains one set of chromosomes
6
Q
What is the starting cell before meiosis occurs?
A
A diploid cell.
7
Q
Describe the process of meiosis.
A
A diploid cell copies its genetic information,
The cell divides twice to form four gametes, each with a single set of chromosomes (haploid)
All gametes are genetically different from eachother
8
Q
What are the products of meiosis?
A
4 genetically different daughter cells.
9
Q
What is meiosis?
A
A type of cell division exclusive to gametes (sex cells)
10
Q
What are the advantages of sexual reproduction?
A
-Produces variation in the offspring.
-The species can adapt to new environments due to variation.
-A disease is less likely to affect all the individuals in a population.
-Humans can speed up natural selection through selective breeding, which can increase food population.
11
Q
What are the advantages of asexual reproduction?
A
-The population can increase rapidly when the conditions are favourable
-Only one parent is needed
-It is more time and energy efficient, as you don’t need a mate
-It is faster than sexual reproduction
12
Q
What are the disadvantages of sexual reproduction?
A
-Time and energy are needed to find a mate
-It is not possible for an isolated individual
13
Q
What are the disadvantages of asexual reproduction?
A
-It does not lead to variation in a population
-The species may only be suited to one habitat
-Disease may affect all the individuals in a population
14
Q
How do fungi reproduce asexually?
A
By releasing spores
15
Q
When do malarial parasites reproduce sexually?
A
In the vector mosquito
16
Q
What is DNA?
A
Deoxyribonucleic acid. The material inside the nucleus of cells, carrying the genetic information of a living being. It is a polymer.
17
Q
What is the shape of DNA?
A
A double helix.
18
Q
What is a gene?
A
A small section of DNA in a chromosome.
19
Q
Who discovered the structure of DNA?
A
Rosalind Franklin.
19
Q
What does a gene do?
A
Codes for a particular sequence of amino acids in order to make a specific protein.
20
Q
State the four bases, and which ones pair with which.
A
A, G, C & T. A-T, C-G
21
Q
Explain the structure of DNA.
A
Each base is connected to a sugar. These sugars are connected to eachother by phosphate sections. Opposite bases have chemical cross-links between eachother.
22
Q
What determines the shape of the protein?
A
The specific order of the amino acids.
23
Q
What does the shape of the protein determine?
A
Its function.
24
What does each triplet of bases do?
Encodes for a specific amino acid in the protein. The cell reads the DNA sequence in these triplets.
25
What is the name of the first stage of protein synthesis?
Transcription
26
Explain the process of transcription.
-The base sequence of the gene is copied into a single complementary template molecule, called mRNA.
-mRNA passes out of the nucleus and into the cytoplasm
27
What is the name of the second stage of protein synthesis?
Translation
28
Explain the process of translation.
-The mRNA molecule attaches to a ribosome.
-Amino acids are brought to the ribosome on carrier molecules, or tRNA.
-The ribosome reads the triplets of bases on the mRNA and uses this to join together the correct amino acids in the correct order.
-Once the protein chain is complete, it folds into its unique shape.
29
What does the non-coding part of DNA do?
Switches genes on and off.
30
What is a mutation?
A random change in the structure of a gene or chromosome
31
What can be some of the causes of mutations?
-Ionising radiation
-Chemical mutagens
32
Gives examples of how mutations may change the DNA.
-May change the activity of a protein
-Might result in phenotype changes
-Might change how genes are expressed if the change is in a non-coding section of DNA
-Might result in development of a genetic disease (eg cystic fibrosis)
33
What are alleles?
Different forms of the same gene.
34
What is the phenotype?
The visible characteristics of an organism which occur as a result of its genes.
34
What is the genotype?
The alleles that an organism has for a particular characteristic.
35
What is a recessive allele?
An allele that is only expressed if the individual has two copies, and no dominant allele of that gene.
35
What is a dominant allele?
An allele that always expresses itself, whether it is partnered by a recessive allele or by another like itself.
36
What does homozygous mean?
A genotype in which the two alleles for the characteristic are identical.
37
What does heterozygous mean?
A genotype in which the two alleles for a particular characteristic are different.
38
What are the sex chromosomes for males?
XY
39
What are the sex chromosomes for females?
XX
40
What is the possibility of any offspring being female?
50%
41
What is cystic fibrosis?
A disorder that mainly affects the lungs, pancreas, liver and intestine. The lungs produce too much mucus, causing the lungs to become damaged and eventually stop working.
42
What type of allele carries cystic fibrosis?
Recessive
43
What type of allele carries polydactyly?
Dominant
44
What does polydactyly do?
It gives a person extra fingers or toes
45
What are the problems with gene therapy?
Can have major ethical implications in society, as people believe it is unnatural to alter genes.
46
What are the problems with genetic tests?
-Can give false positives and false negatives
47
What are the benefits of gene therapy?
-Prevents unnecessary suffering in affected individuals
-Prevents future generations from inheriting similar diseases
48
What was Gregor Mendel?
A monk from the 19th century who studied the inheritance of different characteristics in pea plants.
49
Why was Mendel’s work not accepted by most scientists when he was alive?
-He did not communicate his work well to other scientists
-It was published in a scientific journal that wasn’t well known
-He could not explain the science behind why characteristics were inherited
50
What did Mendel observe?
That characteristics were inherited in “units”
51
What is variation?
Difference between individuals
52
Give examples of genetic variation in humans.
Blood group, skin colour and natural eye colour
53
Give examples of environmental variation in humans.
Scars, language and accent
54
What is natural selection?
A process where organisms that are better adapted to an environment will survive and have more offspring, meaning their genes are passed onto the future generations.
55
What is selective breeding?
An artificial process in which organisms with desired characteristics are chosen as parents for the next generation.
56
What are the benefits of selective breeding?
-New varieties may be economically important, by producing more or better quality food.
-Animals can be selected that cannot cause harm
56
Describe the main steps for selective breeding.
1- Decide which characteristics are important enough to select
2- Choose parents that show these characteristics from a mixed population and breed them together
3- Choose the best offspring with the desired characteristics to produce the next generation
4- Repeat the process continuously over many generations until all offspring show the desired characteristics
57
What are the risks of selective breeding?
-Reduced genetic variation can lead to attack by specific insects or disease, which could be extremely destructive
-Rare disease genes can be unknowingly selected as part of a positive trait, leading to problems with specific organisms
-Can create physical problems in specific organisms
58
What are the current uses of genetic engineering?
-Bacterial cells have been genetically modified to produce human insulin
-Crops modified to be resistant to herbicides
-Rice has been modified to produce beta carotene
58
What is genetic engineering?
A process which involves the artificial transfer of genetic information from one donor cell or organism to another.
59
Describe the main steps of genetic engineering.
-Enzymes are used to isolate the required gene, which is inserted into a vector (usually a bacterial plasmid or a virus)
-The vector inserts the gene into required cells
-The genes are transferred to animal, plant or microorganism cells, during early development, which allows them to develop with the desired characteristics
60
What are the benefits of genetic engineering?
-Genetic modification is a faster and more efficient way of getting the same results as selective breeding
-Improves crop yields and quality
-Introduces herbicide resistance
-Insect and pest resistance can be developed and inserted into plants
-Sterile insects could be created such as a mosquito
61
What are the risks of genetic engineering?
-Transfer of the selected gene into other species may be harmful
-Some people believe it is not ethical to interfere with nature in this way
-GM crop seeds are expensive
-GM crops could be harmful
-GM crops could cause allergic reactions in people
-Pollen produced by the plants could be toxic
62
Explain how a bacteria is used to produce insulin through genetic engineering.
-Enzymes are used to isolate the insulin gene. This insulin gene is cut from a human chromosome
-A plasmid is removed from the bacterial cell and cut using enzymes
-The insulin gene is inserted into the plasmid
-The plasmid is inserted into another bacterial cell
63
What are the two methods of cloning plants?
Cuttings and tissue culture
64
Explain how cuttings work.
-Take a cutting of a plant
-Remove its lower leaves
-Plant the stem in damp compost, and cover it in a clear plastic bag to keep it moist and warm
65
Explain how tissue culture works.
-Scrape tissue samples from a parent plant
-Place it in Agar jelly that contains auxin and nutrients
-The samples will develop into tiny plantlets
-Plantlets planted into compost
66
What are the two methods of cloning animals?
Embryo transplants and adult cell cloning
67
Describe embryo transplants
-Sperm is taken from an animal
-The female of the species is artificially inseminated
-Zygotes develop into embryos and then are removed from the uterus
-The embryos are split into several smaller cells before they become specialised
-The identical embryos are transplanted into host mothers
68
Describe adult cell cloning.
-The nucleus is removed from an unfertilised egg cell
-The nucleus from an adult body cell is inserted into the egg cell
-An electric shock stimulates the egg to divide to form an embryo
-These embryo cells contain the same genetic information as the adult body cell
-When the embryo has developed into a ball of cells, it is inserted into the womb of an adult female to continue its development.
69
State the order of classification subdivisions
Kingdom, Phylum, Class, Order, Family, Genus, Species
70
What are the three domains?
Archaea, Bacteria, Eukaryota.
71
What is “survival of the fittest”?
-Individuals with characteristics most suited to their environment are more likely to survive and reproduce. The genes that allow these individuals to be successful within their environment are passed on to their offspring, which results in these specific genes becoming more common.
72
What happens if two populations of one species become increasingly different in phenotype?
They can no longer interbreed to form fertile offspring, which results in the formation of two species.
73
What did Lamarck’s theory of evolution involve?
-A characteristic which is used more and more by an organism becomes bigger and stronger, and one that is not used eventually disappears.
-Any feature of an organism that is improved through use is passed to its offspring
74
What is the problem with Lamarck’s theory of evolution?
-His theory implies that all organisms would gradually become complex and all simple organisms disappear
75
What did theories did Darwin propose?
-Individual organisms within a particular species show a wide range of variation for a characteristic
-Individuals with characteristics most suited to the environment are more likely to survive to breed successfully
-The characteristics that have enabled these individuals to survive are then passed on to the next generation
76
Why were Darwin’s theories originally not accepted?
-The theory challenged the idea that God made all animals and plants that live on Earth (creationism)
-There was insufficient evidence when the theory was published to convince many scientists
-The mechanism of inheritance and variation was not known until 50 years after the theory was published
77
What is speciation?
The formation of a new and distinct species in the course of evolution.
77
How can a new species arise?
Due to genetic variation, natural selection, isolation and speciation
77
How do fossils support Darwin’s theory of evolution?
Fossil remains have been found in rocks of all ages. Fossils of the simplest organisms are found in the oldest rocks, and more complex ones in the newest rocks. Darwin’s theory of evolution states that simple life forms gradually evolved into more complex ones.
78
Explain how isolation can result in a new species arising.
-Two populations of a species can become geographically separated because of the environment
-Isolation can prevent interbreeding and the combination of genes within a species
-Different mutations can take place in the isolated groups and create different phenotypes within a particular location
-Over time, species may evolve to be different to each other, and they will not be able to interbreed.
79
What can fossils be formed from?
-Bones and shells that do not decay easily, or are replaced by minerals as they decay
-Parts of organisms that have not decayed because one or more of the conditions needed for decay are absent
-Preserved traces of organisms, such as footprints, burrows and rootlet traces become covered by layers of sediment, which eventually become rock.
80
What can scientists learn by studying fossils?
How much organisms have changed as life developed on Earth.
80
What is amber?
Hardened tree sap or resin.
81
Why are peat bogs good for preserving dead animals and plants?
Because they are waterlogged, and do not have the conditions needed for decay.
82
What are the main steps in the development of resistance in bacteria?
-Random mutations occur in the genes of individual bacterial cells
-Some mutations protect the bacterial cell from the effects of the antibiotic
-Bacteria without the mutation die or cannot reproduce when the antibiotic is present
-Resistant bacteria can reproduce with less competition from normal bacterial strains.
83
What should we do to reduce the rate of development of antibiotic resistant strains of bacteria?
-Doctors should not prescribe antibiotics inappropriately, such as for the treatment of non-serious infections
-Patients should always complete the full course of antibiotics to ensure all bacteria are killed and none survive to mutate and form resistant strains
-The agricultural use of antibiotics should be restricted
84
What factors cause a species to become extinct?
New diseases, new predators, new competition, changes to the environment, a single catastrophic event, speciation
85
What was the first antibiotic to be produced on a mass scale?
Penicillin
86
How do fossil fuels provide evidence for the theory of evolution?
They show types of animals/plants that no longer exist, and show the changes in species, demonstrating natural selection and survival of the fittest
86
Explain how meiosis and sexual reproduction give rise to variation.
Sex cells fuse, offspring receives alleles from both parents, alleles in a pair can vary
87
What is tissue culture?
When an group of cells are grown into a new organism.
88
Explain how a change in DNA causes a different protein to be produced.
-Different genes mean different DNA, leading to different codes for making proteins, and a different order of amino acids in proteins
