(P1) CB3: Inheritance, variation, & genetics Flashcards
1
Q
What are the male and female gametes in an animal?
A
Egg and sperm.
2
Q
What are the male and female gametes in plants?
A
Egg and pollen.
3
Q
Describe the process of meiosis.
A
The DNA is copied. The cell divides twice to form four gametes, each with a single set of chromosomes. All gametes are genetically different from each other.
4
Q
What is a gene?
A
A section of DNA which codes for a protein.
5
Q
What is an allele?
A
A version of a gene.
6
Q
What do dominant and recessive mean?
A
The dominant allele will take priority over recessive genes in the phenotype.
7
Q
What does homozygous mean?
A
Both alleles from each parent are the same.
8
Q
3 advantages of sexual reproduction:
A
Variation, increase in food production, a change in environment could be survived due to variation.
9
Q
What does heterozygous mean?
A
Both alleles from each parent are different.
10
Q
What is the genotype?
A
The complete set of genetic material for an organism.
11
Q
3 advantages of asexual reproduction:
A
One parent is required, takes less time, the offspring are identical.
12
Q
3 examples of organisms that can produce both sexually and asexually.
A
Fungi, plants, malaria parasites.
13
Q
What was one of Mendel’s observations when breeding plants?
A
Characteristics of an organism are determined by factors within that organism.
14
Q
Describe the basic structure of DNA.
A
Polymer made up of two strands forming a double helix. Each strand has a sugar-phosphate backbone with a sequence of bases attached.
15
Q
When did Mendel make his observations?
A
1865.
16
Q
How many chromosomes do human body cells have?
A
23 pairs (46 total).
17
Q
When was the behaviour of chromosomes during cell division first observed?
A
The late 1800s.
18
Q
What are the 4 bases of DNA and how are they paired?
A
Adenine + Thymine and Guanine + Cytosine
19
Q
What are the monomers of DNA called?
A
Nucleotides.
20
Q
How were Mendel’s observations and the observation of chromosome behaviour linked?
A
In the early 20th century, it was observed that chromosomes and Mendel’s ‘units’ behaved in similar ways. This led to the theory that the ‘units’, now called genes, were located on chromosomes.
21
Q
How does DNA code for a protein?
A
The sequence of bases in the DNA molecule determines the sequence of amino acids in the protein molecule.
22
Q
When was the structure of DNA discovered and who was it by?
A
1953, by Watson and Crick (and Franklin).
23
Q
What is an inherited disorder?
A
An inhereted disorder is when a disorder (such as ginger) is passed down genetically through inheritance.
24
Q
Describe how a protein is synthesised.
A
A template of the DNA sequence is made.
The ribosomes read the template and construct a protein by joining together amino acids.
When the chain is complete it folds up into the specific shape of the protein.
25
Give two examples of inhereted disorders.
Cystic fibrosis, Hungtington, Haemophilia, Sickle cell disease, Down syndrome, Type I diabetes.
26
How can a change in DNA structure lead to a change in the protein?
May lead to change in the amino acid sequence. This may affect the shape of the protein as it will fold differently. The protein may no longer be able to perform its function.
27
Is the allele for polydactyly dominant or recessive?
Dominant.
28
Is the allele for cystic fibrosis dominant or recessive?
Recessive.
29
Do all mutations alter the function of a protein?
Most do not change the protein, or affect its appearance or function.
30
List (in order) the 7 taxonomic groups.
Kingdom, phylum, class, order, family, genus and species.
31
Why have new models of classification been proposed?
Microscope technology has improved, allowing us to better observe the structures inside cells. Our understanding of biochemical processes has also progressed.
32
Describe the “three domain system” developed by Carl Woese.
Organisms are divided into:
Archaea (primitive bacteria usually living in extreme environments)
Bacteria (true bacteria)
Eukaryota (which includes protists, fungi, plants and animals)
33
Outline Darwin’s theory of evolution by natural selection.
There is variation between members in a population. More offspring are produced in each generation than there are resources for (so not all will survive). Certain characteristics may give an organism an advantage, so they are more likely to survive and reproduce , passing the genes for that characteristic on to the next generation. Over time, this characteristic will become more common within the population.
34
In what year was “On the Origin of Species” published?
1859.
35
Why were Darwin’s ideas only gradually accepted?
Evolution by natural selection could not be observed in action (it takes a long time). Many people felt it contradicted their religious beliefs.
36
What was Jean-Baptiste Lamarck’s theory of evolution?
Organisms gain characteristics over their life time (e.g a giraffe stretches its neck to reach the high leaves) and then these changes are passed onto their offspring.
37
Why do we not accept Jean-Baptiste Lamarck’s theory today?
We now know this is not the case as environmental variation is not inherited.
38
What process did Alfred Russel Wallace do pioneering work on?
Speciation.
39
Describe the steps which give rise to new species.
Speciation occurs when two groups of organisms (of the same species) become isolated from each other. Members of one group are prevented from breeding with members of the other group. Over time, the two groups become so genetically different that they would no longer be able to breed together to produce fertile offspring: therefore, two new species have been formed.
40
What evidence exists to support Darwin’s theory of evolution?
Fossils and antibiotic resistance to bacteria.
41
What is a fossil?
Fossils are the ‘remains’ of organisms from millions of years ago, which are found in rocks.
42
Give 3 ways in which fossils may be formed.
From parts of organisms that have not decayed because one or more of the conditions needed for decay are absent.
When the parts of the organism are replaced by minerals as they decay.
As preserved traces of organisms, such as footprints, burrows and rootlet traces.
43
Why is the fossil record incomplete for early life forms?
Many early life forms of life were soft-bodied, which means that they have left few traces behind. What traces there were have been mainly destroyed by geological activity. This is why scientists cannot be certain about how life began on Earth.
44
What can we learn from fossils?
We can learn from fossils how much or how little different organisms have changed as life developed on Earth.
45
When does extinction occur?
Extinctions occur when there are no remaining individuals of a species still alive.
46
What factors can contribute to the extinction of a species?
Destruction of wild habitats, introduction to invasive species, climate change, hunting, illegal trafficking, over harvesting.
47
Why can bacteria evolve rapidly?
Bacteria can evolve rapidly because they reproduce at a fast rate.
48
How does antibiotic resistance develop in bacteria?
Mutations of bacterial pathogens produce new strains. Some strains might be resistant to antibiotics, and so are not killed. They survive and reproduce, so the population of the resistant strain rises. The resistant strain will then spread because people are not immune to it and there is no effective treatment.
49
What is MRSA?
A strain of bacteria that causes disease and is resistant to antibiotics.
50
Give 3 ways we can reduce the rate of development of antibiotic resistant strains.
Doctors should not prescribe antibiotics inappropriately, such as treating non-serious or viral infections.
Patients should complete their course of antibiotics so all bacteria are killed and none survive to mutate and form resistant strains.
The agricultural use of antibiotics should be restricted.
51
What is a major problem in the fight against antibiotic resistance?
The development of new antibiotics is costly and slow. It is unlikely to keep up with the emergence of new resistant strains.
52
What is variation?
Differences in the characteristics of individuals in a population.
53
What two types of factor can cause variation?
Environmental and genetic.
54
What causes genetic variation?
Mutations (changes to the DNA).
55
What is evolution?
A change in the inherited characteristics of a population over time through a process of natural selection.
56
What does the theory of evolution by natural selection state about the origin of all species of living organisms?
All species of living things have evolved from simple life forms.
57
How long ago is it theorised that life began?
More than three billion years ago.
58
How can evolution lead to the formation of a new species?
If two populations of one species become so different in phenotype that they can no longer interbreed to produce fertile offspring they have formed new species.
59
What is selective breeding?
Selective breeding (artificial selection) is the process by which humans breed plants and animals for particular genetic characteristics.
60
Describe the process involved in genetic breeding.
Selective breeding involves choosing parents with the desired characteristic from a mixed population. They are bred together. From the offspring those with the desired characteristics are bred together. This continues over many generations until all the offspring show the desired characteristic.
61
Give 4 examples of characteristics that can be selectively bred for.
Usefulness, appearance, disease resistance in food crops, animals which produce more meat or milk, domestic dogs with a gentle nature, large or unusual flowers.
62
What is one drawback of selective breeding?
Selective breeding can lead to ‘inbreeding’ where some breeds are particularly prone to disease or inherited defects.
63
What is genetic engineering?
A process which involves modifying the genome of an organism by introducing a gene from another organism to give a desired characteristic.
64
Give 2 ways plants have been genetically engineered.
Resistant to diseases or to produce bigger better fruits.
65
Give an example of how bacteria have been genetically engineered.
Bacterial cells have been genetically engineered to produce useful substance such as human insulin to treat diabetes.
66
Describe the process of genetically engineering.
Enzymes are used to isolate the required gene; this gene is inserted into a vector, usually a bacterial plasmid or a virus.
The vector is used to insert the gene into the required cells.
Genes are transferred to the cells of animals, plants or microorganisms at an early stage in their development so that they develop with desired characteristics.
67
What are GM crops and what are the benefits?
Crops that have had their genes modified by genetic engineering. GM crops include ones that are resistant insect attack or to herbicides. GM crops generally show increased yields.
68
What are some of the concerns about GM crops?
The effect on populations of wild flowers and insects. Some people feel the effects of eating GM crops on human health have not been fully explored.
69
What is a potential use of genetic engineering in medicine?
Modern medical research is exploring the possibility of genetic modification to overcome some inherited disorders.
70
What is tissue culture?
Using small groups of cells from part of a plant to grow identical new plants.
71
What is the practice of taking cuttings?
An older, but simple, method used by gardeners to produce many identical new plants from a parent plant.
72
What are embryo transplants?
Splitting apart cells from a developing animal embryo before they become specialised, then transplanting the identical embryos into host mothers.
73
Describe the process of adult cell cloning.
The nucleus is removed from an unfertilised egg cell.
The nucleus from an adult body cell, such as skin cell, is inserted into the egg cell.
An electric shock stimulates the egg cell to divide to form an embryo.
These embryo cells contain the same genetic information as the adult skin 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.
74
What are the sex chromosomes in mammals?
M = XY
F = XX
75
What are the sex chromosomes in birds?
M = XX
F = XY
76
How is sex determined in crocodiles?
Egg incubation temperature
77
What are the two types of reproduction, and how are they different?
Asexual (one organism)
Sexual (two organisms)
78
Gene
short section of DNA which codes for a protein
79
How is sex determined?
NOT BY CHROMOSOMES
caused by genes (eg: Sry for males)
80
Parthenogenesis
Unfertilised egg develops to a new individual
Asexual reproduction
Very rare. Lizards (eg: Komodo dragons)
81
What are the characteristics of gametes in sexual reproduction?
Haploid, formed by meiosis
82
What are the pros and cons of sexual reproduction?
+ Genes from two parents (variation occurs)
- A mate must be found (time consuming)
83
What are the key characteristics of sexual reproduction?
* Gametes
* Genes from 2 parents - offspring show variation
* Dominant and recessive genes
* Haploid gametes formed by meiosis
* Mate must be found
84
What are the characteristics of gametes in asexual reproduction?
There aren't any
85
What are the key characteristics of asexual reproduction?
* One parent
* No gametes
* Bacteria and fungi - also starfish
* One cell splits into 2
* Clones: same genes, basically copy and paste. This is often done by farmers.
* Aphids: born pregnant, but can also have sex. Extremely fast population growth.
86
Which organisms reproduce asexually?
Bacteria, fungi, starfish, aphids (but they can also have sex)
87
What is a clone?
An organism created with identical genetic information
88
Proper term for an egg cell
Oocyte
89
How many daughter cells are produced by meiosis?
4
90
When is meiosis used?
Making more gametes
91
What process does meiosis follow?
**Basically mitosis twice.
**
**MEIOSIS I:**
1. Prophase I
2. Metaphase I
3. Anaphase I
4. Telophase I
**MEIOSIS II:**
1. Prophase II
2. Metaphase II
3. Anaphase II
4. Telophase II
92
What forms the "backbone" (frame) of the DNA?
Sugar phosphate.
93
What does DNA stand for?
Deoxyribonucleic acid
94
What will the phenotype of the heterozygous pair "mM" be?
M
95
Phenotype
Observable characteristics
96
Genotype
Characteristics in genetic code
97
What's the difference between RNA and DNA?
RNA - single stranded and smaller
DNA - double stranded
98
What does mRNA do?
Messenger RNA
Transfers DNA code to ribosomes for translation
99
What is translation?
Synthesis of proteins in the ribosomes
100
What does tRNA do?
Transfer RNA
Brings amino acids to ribosomes for translation
101
What is rRNA?
Ribosomal RNA
Ribosomes are made of rRNA and protein
102
What is transcription?
making RNA from DNA. The RNA is complementary to the DNA.
103
What is RNA polymerase?
an enzyme which binds to DNA and seperates strands for transctiption. A strand of DNA is used as a template for mRNA.
104
Proper name for proteins
polypeptide chains
105
DNA is read in groups of...
3
106
Describe the process of transcription.
* Takes place in the nucleus
* mRNA moves to the cytoplasm and then the ribosomes
* tRNA "read" the mRNA and obtain the amino acid coded for
* ribosomes attach amino acids to form a polypeptide chain (protein)
* the chain grows until a stop codon is reached
107
What are mutations?
Random changes in genetic code
108
What are the two kinds of mutation?
Gene mutations
Chromosomal mutations
109
What is a gene mutation? Give examples of what these can be.
changes in a single gene
(eg: substitution (single letter change), reverse order, deletion, insertion)
110
What are chromosomal mutations?
whole chromosome changes
111
genetic disorder
disease caused by mutation
112
What causes mutation?
radiation (eg: UV, X-ray)
chemicals (eg: cigarette smoke, barbecueing, benzyol peroxide)
infectious agents (eg: HPV)
113
What is sickle cell anemia?
* stops malaria
* 2 alleles for sickle cell, which is bad!
* affects haemoglobin
* one letter change - substitution mutation
114
In blood, which alleles are dominant, and which are recessive?
A, B = dominant
O = recessive
115
Where in DNA are genes found?
the coding strand
