Topic 6 - Inheritance, Variation & Evolution Flashcards
1
Q
Where in a cell is the DNA of an animal or plant found
A
In The nucleus
2
Q
What are chromosomes made up of
A
Long strands of DNA
3
Q
What is the function of genes
A
They code for specific amino acids which in turn bind to make specific proteins
4
Q
What is meant by the term ‘genome’
A
The entire set of genetic material of an organism
5
Q
What is one reason that it is useful for scientists to know and understand genes
A
Helps scientists identify genes that are linked to diseases. Knowing which gene is linked to inherited diseases could help to develop an effective treatment for it
6
Q
What are the three subunits of a nucleotide
A
A phosphate
A sugar
A base (A,G,C or T)
7
Q
Explain how DNA bases in a gene code for specific amino acids
A
Each sequence of three bases codes for one specific amino acid, so the order of bases in the gene decides the order of amino acids
8
Q
Where in a cell does protein synthesis happen
A
In the ribosomes
9
Q
What role do the non-coding DNA play in protein synthesis
A
They switch on and off specific genes
10
Q
Explain how DNA is used in protein synthesis when it is unable to leave the nucleus
A
A molecule called mRNA is made by copying the code from the gene. The mRNA carries the code out of the nucleus to the site of protein synthesis
11
Q
Explain what happens to a chain of amino acids once they’ve been assembled
A
It folds up into a unique shape which allows the protein to carry out its function
12
Q
Explain how mutations can lead to a change in the protein being synthesised
A
A mutation changes the order of a sequence of DNA bases in the gene, the same sequence that codes for specific amino acids in a protein. Change in the order of amino acids could lead to a change in protein
13
Q
Name the three types of mutations that can occur
A
Insertion - a base if randomly inserted into the sequence where it shouldn’t be. Can change the amino acid and have a knock effect
Deletion - random base is deleted from the sequence also has a knock-on effect to the rest of the sequence
Substitution - random base is replaced by another
14
Q
Name one possible effect of a mutation that changes the shape of a structural protein
A
Could cause the protein to lose its strength meaning it can no longer provide support or strength
15
Q
Name a possible effect of a mutation in a gene that codes for an enzyme
A
It could change the shape of the active site so the substrate no longer bind to it which while make the enzyme unable to catalyse chemical reactions in your body
16
Q
Name the male gametes in an animal
A
Sperm
17
Q
Name the female gametes in an animal
A
Egg (cell)
18
Q
Which type of cell division are gametes made from
A
Meiosis
19
Q
What name can be given to the organisms produced from asexual reproduction
A
Clones
20
Q
Name the type of cell division used in asexual production
A
Mitosis
21
Q
Explain how a fertilised egg has the correct number of chromosomes
A
Gametes only have half the number of chromosomes of a normal cell, when two gametes fuse together the fertilised egg then has the the full number of chromosomes
22
Q
Give four differences between asexual and sexual reproduction
A
Any four of these:
Asexual needs only one parent, whereas sexual needs two
No fusion of gametes happens in asexual reproduction unlike in sexual reproduction
No mixing of chromosomes in asexual reproduction unlike in sexual reproduction
No genetic variation in asexual reproduction unlike in sexual reproduction
Asexual reproduction doesn’t involve meiosis where’s sexual reproduction does
23
Q
Where in the body does meiosis occur
A
In the sexual reproductive organs (testes and ovaries)
24
Q
What are the steps of meiosis
A
Cell starts with 46 chromosomes (23pairs), they are duplicated which leaves you with 92 chromosomes (46pairs). The cell divide which leaves you with two daughter cells each containing 46 chromosomes (23pairs). The cells divide again leaving you with four daughter cells contains 23 chromosomes.
25
How many cell division are there during meiosis
Two
26
Briefly describe the results of meiosis
Your left with four daughter cells (gametes) each containing 23 chromosomes (one set of chromosomes) which are all genetically different to each other
27
After fertilisation the cell divides repeatedly, what type of cell division is this
Mitosis
28
What happens to the cells in an embryo for it to become a whole organism
They differentiate into different types of specialises cells
29
How do strawberries reproduce asexually
| How do strawberries reproduce sexually
Using runners
| Producing seeds
30
What type of reproduction happens inside humans with parasites
Asexual
31
State two advantages of asexual reproduction over sexual reproduction
Any two of these:
Asexual reproduction used less energy as there is only one mate required
And is also faster
Many identical offspring can be produced in favourable conditions
32
Explain why sexual reproduction increases the chance of the population surviving
Sexual reproduction creates genetic variation in the offspring which means some individuals in the population have adaptations which help it to better survive in the new environment. Individuals with the gene are more like to survive and breed successfully passing in the gene to future generations which will allow them to also survive in the environment
33
How many chromosomes are there in normal body cells
46 chromosomes (23pairs)
34
How can you tell if an allele for a disease is dominant or recessive
It is recessive if someone cane be a carrier and not have the disease
35
What are the symptoms of polydactyly
Being born with extra fingers or toes
36
If a person only has to have one allele of polydactyly to have the disease what does this say about the allele that causes polydactyly
It is dominant
37
If two parents are carriers of cystic fibrosis explain why there is a small chance in their offspring having cystic fibrosis
Because the allele for cystic fibrosis is recessive so the offspring must have two in order to have the disease and the chance of that happening is 1 in 4
38
Suggest three arguments AGAINST the screening of embryos
Suggests that people with genetic problems are undesirable which may cause prejudice
Screening is expensive
People may want to screen all their IVF embryos to pick the most desirable ones
39
Suggest reasons FOR screening
Will stop people from suffering from genetic problems
Treating disorders costs the government and taxpayers money, screening reduces this amount by reducing number of people with disorders
Parents can’t use it to pick children with desirable features, there are laws to stop this
40
Name the two types of possible variations
Genetic and environmental
41
Explain how a mutation can lead to a rapid change in a species
The mutation leads to a new phenotype which is as it makes the species more suited to the new environment. It could become more common relatively quick within the species due to natural selection
42
What is the name of the process where a new species is formed
Speciation
43
What is speciation
When, over time, the phenotype of a organisms change so much due to natural selection a completely new species is formed
44
Explain how you would know for certain if two populations of one original species had become two new species
If the two populations can’t have fertile offspring then they have become two new species
45
How many years ago did simple life forms of new species develop
Over 3 billion years ago
46
Give two sources Darwin used to conclude his ideas of natural selection
Geology and fossils
47
What is the explanation for variation of phenotypes within a species
New phenotypes are produced because of genetic variants such as mutations
48
Explain how characteristics are passed on to offspring
Characteristics are passed on through genes from parents to their offspring
49
Explain fully Darwin's theory of the survival of the fittest
Individuals show variation in their characteristics due to differences in their genes. This variation causes them to survive longer and breed successfully and pass on the new gene to their offspring (survival of the fittest). The successful oragnisms are more likely to reproduce Over time this gene will have become more common in the species causing the species to evolve
50
Give two reasons as to why people didn’t believe Darwin’s theories back then
Because it went against religious beliefs at the time of there being a creator (God) of everything
There wasn’t enough evidence to convince other scientists as Darwin’s was one of the first experiments to explore this idea
51
What was Lamarcks theory
He believed that characteristics that are used a lot by an organism become more developed in that organisms lifetime and that its offspring will inherit the ACQUIRED characteristics
52
Give two examples of evidence that supports Darwin’s theory of evolution by natural selection
The fossil record which shows how changes in the organism developed slowly overtime
The discovery of how bacteria evolve to become resistant to antibiotics
53
What is another name for selective breeding
| What is selective breeding
Artificial selection
the breeding of an organism so that genes for particular useful or attractive characteristics stay in the population. When individuals with the most desirable characteristics are bred to produce the most desirable offspring
54
Suggest why dairy farmers may use selective breeding
In order to produce cows with a high milk yield
55
Why are species produced by selective breeding more susceptible to genetic defects
Because selective breeding leads to there being less variation in genes/ alleles which reduces the gene pool so there’s more of a chance of the offspring inheriting diseases if it's present in the population
56
Why might a new diseases within a selectively bred species cause a problem for the offspring
Because selective breeding causes less variation in alleles/ genes in offspring so if there’s less chance of there being an allele in the population which is resistant to the disease. If one individual gets the disease the others are likely to get it as well
57
What is genetic engineering
It’s the transfer of the desired gene from one organism's genome to another
58
Describe the steps of genetic engineering
The useful gene in an organism is isolated/ cut from its DNA using an enzyme and is then inserted into a vector. The vector is normally a virus or bacteria plasmid. When the vector is introduced to the target organism the useful gene is then inserted into the cell which leads to the organism developing the desired characteristic
59
Give two examples of how scientists are using genetic engineering to human diseases/ how it could potentially be used
Scientists cut insulin from human DNA using ana enzyme and then insert it into bacteria DNA plasmid which rapidly reproduces and is then inserted into someone who lacks insulin (a diabetic person)
Sheep’s have been genetically engineered to produce a drug in their milk which will help treat human diseases
60
1) What does ‘GM’ stand for
2) Suggest two ways in which a plants genes can be modified to increases it yield
3) Give two cons of GM
1 - Genetic Modification
2 - Any two of these:
To make them resistant to herbicides
To make them resistant to diseases
To make them resistant to insects
3 - People aren’t convinced that eating genetically modified crops are good for you and may have bad side effects on humans
Transplanted genes may be passed onto weeds which will make them resistant to things and become sort of super weeds
61
1) Give two types of cloning used in plants
| 2) Give two uses for them
1 - Cuttings and Tissue culture
| 2 - to produce plants with desirable features and to preserve rare plants that are hard to reproduce naturally
62
Describe fully how embryo transplants work
Sperm from a male member of the species (with desirable characteristics) and egg cells from a desired female member of the species are taken
a fertilised egg is created in vitro
developing embryo is split, before they’re specialised, to form clones
they're implanted into lots of other female members of the species
they produce genetically identical offspring with desirable characteristics
63
Describe fully how adult cell cloning works
First you remove the nucleus of an unfertilised egg and also remove the nucleus of another persons body cell (e.g. skin cell) and insert it into the ‘empty’ egg cell. The egg cell is stimulated by electric shocks so that it divides like a normal embryo. This ball of cells/ embryo is inserted into the female womb which grows into a genetically identical copy (clone) of the original adult body cell
64
Describe transcription
RNA molecules line up against the strand of DNA, making a copy of it with corresponding bases, changing 'T' to 'U'. RNA joins the molecules together creating what is known as mRNA. The mRNA is able to leave the nucleus as its single-stranded
65
Describe how translation works
mRNA is sent out of the nucleus where it joins to a ribosome in the cytoplasm. The start tRNA binds to the mRNA and brings a specific amino acid to it depending on what the codon reads (order of three bases). Another tRNA molecule joins and the first leaves. A peptide bond between the tRNA’s amino acids is formed. This continues until a stop codon is reached, the completed polypeptide leaves the ribosome.
66
True or false: ‘Most mutations have little or no effect on the protein coded for a gene
True
67
What are alleles
They’re different forms of the same gene
68
What is it called when someone has two of the same alleles, and what is it called when they don’t
Homozygous and heterozygous
69
What did Gregor Mendel discover?
He noted how characteristics in plants were passed on from one generation to the next, through experiments on pea plants
70
What three conclusions did Gregor Mendel reach after his experiment on pea plants?
1 - Characteristics in plants are based on hereditary units
2 - hereditary units are passed on unchanged, one unit from each parent
3 - hereditary units can be dominant or recessive
71
What do fossils show us?
They provide evidence that organisms lived a long time ago and how living things have evolved over time
72
What are fossils?
Remains of organisms from millions of years ago and are found in rocks
73
What are the three ways fossils are formed?
1 - most are created because they are gradually replaced by minerals as they decay, forming a rock-like substance which forms a distinct shape of the organism and is dug up many years later
2 - preservation in places where there is no oxygen or moisture (amber and tar pits), water or high enough temperatures (glaciers) for the microbes to decay
3 - preserved traces of organisms such as footprints and burrows or plant roots in soft mud which leaves an impression and hardens as the organism decays leaving its shape
74
What are the problems with fossils?
1 - Many early forms of life were soft-bodied organisms with soft tissue which decays away completely so the fossil record is incomplete
2 - many fossils not formed millions of years ago could have been destroyed by geological activity such as the movement of tectonic plates
3 - many fossils still haven't been found yet
75
What is meant by extinction?
there are no remaining individuals of a species still alive
76
What are the reasons for a species to become extinct?
1 - A catastrophic event e.g an asteroid hitting Earth
2 - A new predator kills them all
3 - A new disease kills them all
4 - drastic environmental changes e.g destruction of habitat
5 - a new competitor for food or water
77
Describe the steps of the formation of a new species
Isolation - percentage of population become isolated
Genetic variation/mutations occur
Natural selection - variation leads to individuals surviving longer in new environment and passing on their genes
Speciation - isolated population change completely over thousands of years and can no longer produce fertile offspring with original population of the species
78
What is meant by a species?
a species is a group of organisms with similar characteristics and can interbreed to produce fertile offspring
79
Why didn't people believe in Gregor Mendels' work at the time?
1 - lack of evidence available
| 2 - he was a monk, not a scientist
80
Why can bacteria evolve so quickly?
Because they reproduce at a fast rate
81
How do bacteria become resistant to antibiotics?
1 - bacteria develop random mutations in their genes leading to antibiotic-resistant strains being created
2 - these bacteria live inside a host even if they're being treated increasing the population size of antibiotic-resistant strain bacteria as there's no more competition
3 - they reproduce rapidly and evolve very quickly
4 - resistant bacteria spreads because people are not immune to it and there are no effective treatments for it
82
What is a common strain of antibiotic-resistant bacteria called?
MRSA - which can be fatal and often affects people in hospitals
83
How can you reduce the production of antibiotic-resistant bacteria?
1 - don't take antibiotics when it's not needed
| 2 - take the full course of antibiotics so none can live on to mutate
84
Who created the classification system based on the characteristics of an organism and its structure?
Carl Linnaeus in the 1700s created the Linnaeus system
85
Why did classification systems change over time?
Because biochemical processes were understood in further depth and microscopes improved, allowing us to find out more about the internal structures of an organism
86
What was the new classification system in 1990 called and who created it?
Carl Woese posed the three-domain system
87
Why did Carl Woese change the Linnaeus system to the three-domain system?
Using evidence gathered from RNA sequence, derived from new chemical analysis techniques, he found that species thought to be closely related weren't as close as they were originally thought to be, therefore making the info provided by the Linnaeus system somewhat invalid
88
What are the three large groups in the three-domain system?
Organisms are first split up into
1 - Archaea, which are primitive bacteria found in extreme places such as salt lakes or hot springs
2- Bacteria, which contain true bacteria such as E.coli and staphylococcus. Although physically similar to archaea there are many different biochemical differences
3 - Eukaryota - includes a broad range of organisms including fungi, plants, animals and protists
89
What were the names of the 7 subdivisions included in the three-domain system by Carl Woese?
```
kingdom
phylum
class
order
family
genus
species
```
90
How was the Linnaeus system divided?
```
All organisms fit into one kingdom and then was divided by :
Phylum
class
order
family
genus
species
```
91
How are organisms named?
using the binomial system, creating a two-part name.
Genus-species e.g homo-sapiens
This is because the binomial system is used worldwide so that people refer to the same species by the same name to avoid possible confusion
92
What do evolutionary trees show?
They show how scientists think different species are related to each other
93
What does the evolutionary tree include?
Common ancestors among different species - the more recent the ancestor the more closely related the species are and the more characteristics they are likely to share
94
How do scientists work out evolutionary data?
for living things, they use the current classification system based on DNA analysis and structure
for extinct species, they use info from the fossil record
