Inheritance, Variation And Evolution Flashcards
(100 cards)
1
Q
What is mitosis
A
Formation of 2 genetically identical daughter cells from one cell
2
Q
What is meiosis?
A
Formation of 4 non- identical daughter cells from one cell
3
Q
What is mitosis used for?
A
Growth and repair
4
Q
What is meiosis used for?
A
Sexual reproduction (gametes)
5
Q
What type of cells are produced during mitosis?
A
Diploids - full set, 46 chromosomes in humans
6
Q
What type of cells are produced during meiosis?
A
Haploid- half set, 23 chromosomes in gametes
7
Q
How are gametes formed?
A
Through meiosis when the number of chromosomes in cell halves
8
Q
What are the gametes in humans?
A
Sperm cells - men
Egg cells - women
9
Q
What are the gametes in plants ?
A
Pollen - male
Eggs - female
10
Q
How many divisions occur in meiosis?
A
2
11
Q
What happens during fertilisation?
A
Each gamete (23 chromosomes) fuse together, producing full set of chromosomes
12
Q
Describe what happens during meiosis
A
-DNA is copied so it has double amount of genetic information, chromosomes are replicated, cell grows (46 -> 92)
- chromosomes line up along middles of cells
- chromosomes are pulled apart
- cell divide into 2 (genetically identical daughter cells), each with gang the amount of chromosomes (46)
- cell divides again producing 4 genetically different gametes, each with 23 chromosomes
13
Q
What happens during mitosis?
A
-Cells grows so number of organelles increases, DNA is copied so chromosomes are replicated
-chromosomes line up
- cells begins to split
- each set of chromosomes are pulled to polar ends of cell
- nucleus divides
- the cell divides into 2 producing 2 genetically identical daughter cells
14
Q
What are the advantages and disadvantages of sexual reproduction
A
Advantages
Produces variation in offspring- survival advantage, prevents extinction, better protected from diseases
Allows us to use selective breeding
Disadvantages
Mate is required- slower
2 parents needed
Uses more energy
15
Q
What is DNA?
A
A polymer with a double helix structure
Made up of 4 different repeating subunits called nucleotides
16
Q
What does DNA stand for ?
A
Deoxyribonucleic acid
17
Q
What does DNA hold?
A
The instructions (genetic code) that makes proteins
18
Q
What are the 3 parts that make up a nucleotide?
A
Phosphate
Deoxyribose sugar
Base
19
Q
What is complimentary base pairing?
A
A bases only connect to T bases
C bases only connect to G bases
20
Q
What determines a genetic code?
A
Order of bases on a DNA strand
21
Q
What do 3 bases code for?
A
An amino acid
22
Q
What is the sequence of bases used for?
A
To synthesise (build) chains of amino acids
23
Q
What does ha amino acid chain make ?
A
A protein
But proteins must be correct shape to carry out their function
The different order of amino acids determine what type of protein it is
24
Q
How may types of amino acids are there?
A
20
25
What is mRNA
A messenger molecule (different type of nucleotide) which acts as a template for DNA
It carries the same code as DNA but is small enough to leave the nucleus
26
What does mRNA do?
Carries instructions from a nucleus
27
What is protein synthesis ?
The process of producing a protein from DNA
28
Describe process of protein synthesis
- DNA hold the genetic code for making a protein, but can’t move out of nucleus as it’s too big
- 2 strands pull apart (unzips) and mRNA nucleotides match to their complimentary base on the strand
- the mRNA nucleotides themselves are joined together, creating a new stand called the mRNA strand, this is a template of the original DNA
- the mRNA moves out of nucleus to the cytoplasm onto ribosomes
- at ribosomes, the bases in mRNA are read in 3s to code for an amino acid
- the corresponding amino acids are brought to ribosomes by carrrier molecules (tRNA)
- the amino acids connect together to form a protein
- proteins then detaches and folds into its specific shape
29
What are the 3 types of proteins?
Enzymes (biological catalysts)
Hormones (chemical messengers that send signals around body)
Structural proteins(strong proteins in order to form structures eg collagen)
30
What is a mutation?
A change to a base
31
What are the 3 things a mutation can cause ?
- a base is inserted into code- may change all the amino acids coded for after this mutation (insertion)
- a base is deleted from code- made change all amino acids coded for after this mutation (deletion)
- a base is substituted- only changes 1 amino acid in sequence or may not even change the amino acid
32
Explain how a mutation may affect an enzyme
Change in amino acids, changes the way the protein folds
Active site changes shape so is no longer complimentary to substrate
The enzyme is denatured
33
How will a mutation affect structural proteins
May cause it to lose it’s shape, becomes weaker
34
Why does variation between 2 organisms occur?
Because of the coding DNA that determines the proteins and their activity
The non coding DNA that determines which genes are expressed
35
Define gamete
An organism’s reproduction cells
36
Define chromosome
Long strand of DNA containing many genes
Found in nucleus
37
Define gene
Section of DNA that codes for a particular characteristic
38
Define allele
Version of a gene
39
Define dominant allele
Only 1 allele is needed for it to be expressed
40
Define dominant allele
Only 1 allele is needed for it to be expressed
41
Define recessive allele
2 alleles are needed for it to be expressed
42
What is cystic fibrosis and what is it cause by?
A disorder of the cell membranes, resulting in thick mucus in the airways and pancreas
Caused by a recessive allele, so both parents need to be carriers or one must have CF themselves and the other is a carrier
43
What does embryonic screening allow scientists to do?
Observe whether the child will have a genetic condition
If embryo is developed in lab, cells can be taken from it and analysed
DNA from embryos in the womb can also be extracted
44
What are the advantages of embryonic screening
Reduces the number of people suffering
Treating disorders is very expensive
Are many regulations in place for it
Healthy embryos implanted
45
What are the disadvantages of embryonic screening ?
Procedure can lead to miscarriage
Embryos destroyed
Expensive to carry out screening
Could encourage people to pick characteristics
46
What chromosomes do females have?
2 X chromosomes
So only pass on X chromosomes
47
What chromosomes do males have?
1 X chromosome
1 Y chromosome
48
What causes variation?
- genotype - the genes the organism inherits e.g eye colour
- environment- place it lives in e.g scars
- combination of both e.g weight, height
49
What does a genome and its interaction with the environment influence?
The development of the phenotype of an organism e.g identical twins
50
Define homozygous
When both inherited alleles are the same
51
Define heterozygous
When the inherited alleles are different
One is dominant and the other is recessive
52
Define genotype
The combination of alleles an individual has e.g Aa
53
Define phenotype
The physical characteristics that are observed in the individual e.g eye colour
54
How do u look at the probability of the offspring inheriting certain genotypes and phenotypes
Using the alleles the 2 parents have and a punnet square diagram
55
What is polydactyl and what is it cause by?
Having extra fingers or toes
Caused by a dominant allele
56
What is evolution?
A change in the inherited characteristics of a population over time through natural selection
Can lead to the formation of a new species
57
What is variation?
The differences in the characteristics of individuals in a population originally caused by mutations
58
What is theory of evolution?
All species have evolved from simple life forms
59
Describe natural selection
-Causes evolution
-The organism with the variants that produce the phenotypes best suited to the environment survive
-They then breed and pass their gene/ characteristics to their offspring
-Over many generations the frequency of the mutation will increase within the population
60
What is Charles Darwin’s theory of evolution
Individuals with characteristics that make them better suited/ adapted to their environment are more likely to survive and reproduce
61
Why wasn’t Charles Darwin’s theory initially accepted?
-Challenged the idea that God was the creator for all species on Earth
-Insufficient evidence to support this theory as few studies has been done
-mechanisms of inheritance were not known at the time, were only discovered 50 years later
62
What was Jean-Baptise Lamark’s theory?
- changes that occurred during the lifetime of an organism were passed on to offspring
- these changes were caused by their environment
- thought the way organisms behaved affected the features of their body
- if an animal used a feature a lot, this feature would grow and develop
- these changes would be passed to their offspring
63
What is speciation
Is the process of a new species developing
64
What is the process of speciation?
- variation exists within a population as a result of genetic mutation
- a species becomes isolated due to a geographical barrier
- a barrier is formed between the 2 populations preventing them from breeding
- overtime in each population natural selection will cause the most adapted individuals to survive
- eventually the selection of different alleles will increase the genetic variation between the 2 populations
- so when they meet again they are no longer able to breed together to produce fertile offspring
- a new species is formed
65
Who produced the theory of speciation?
Alfred Russel Wallace
66
What is selective breeding?
When humans choose which organisms to breed in order to produce offspring with a certain desirable characteristic
67
Why do humans selectively breed?
Characteristics can be chosen for usefulness or appearance e.g :
- disease resistance in plants
- animals that produce more meat/milk/ wool
- domestic dogs with gentle natures/ dosile animals
- large or unusual flowers
68
Define process of selective breeding
- parents with describable characteristics are chosen
- they are bred together
- from the offspring those with desired characteristics are bred together
- the process is repeated for many generations until all offspring have the desired characteristic
69
What are the problems with selective breeding?
Can lead to inbreeding due to small gene pool
Inbreeding can cause same breeds to be more susceptible to diseases or genetic defects
70
What is genetic engineering?
Modifying the genome of an organism by introducing a gene from another organism to give a desired characteristic
71
Give examples of genetic engineering
Plant cells become engineered for disease resistance or to have larger fruits
Bacterial cells engineered to produce substances useful to humans e.g insulin
72
Define genetically modified crops
Engineered to be resistant to insects and herbicides resulting in increased yield as less crops will die
73
Describe genetic modification in medicine
Possible to use genetic engineering to cure inherited disorders
Called gene theory and involves individuals transferring normal genes into patients so correct proteins produced
74
Describe process of genetic engineering
- there is a human cell containing the normal insulin gene and a bacterial cell containing plasmids
- enzyme is used to isolate required gene and used to cut open plasmid
- gene is inserted into a vector e.g bacterial plasmid or virus
- vector is used to insert gene to required cells
- genes are transferred during early development so that all cells develop with desired characteristic
75
What is cloning?
Creating genetically identical copies of an organism
76
Describe how cloning occurs in animals
Embryo transplant- sperm and egg cells from parent with desirable features are obtained
In the lab they are fertilised to form a embryo
Embryo divides many times and is inserted into host mother
Embryos are split into several smaller embryos before the cells differentiate
The offspring is genetically identical as they have genetic information from the same mother and father
77
Describe how plants are cloned
Tissue culture- small groups of cells are taken from plant to grow identical new plants
Are placed in a growth medium with nutrients and hormones
Sample is developed into tiny plantlets and grow into new plant that are genetically identical to parent
Advantages: preserves rare species, nurseries are able to grow many identical plants
Cuttings- cuttings are taken from a plant with a desirable feature
Then dipped into rooting powder (contains hormones to encourage root formation)
Pushed into a pot of compost and kept moist
Produces clones genetically identical to parent
Advantages: desirable characteristics from parent passed on, cheap, large number of plants produced quickly
78
What are the advantages and disadvantages of embryo transplant
+
Genetically identical offspring with desirable characteristic
Multiple births (high yield)
-
All will carry genetic defects
Small gene pool
79
Describe process of adult cell cloning
-nucleus removed from an unfertilised egg cell
- nucleus removed from an adult body cell and placed in the denucleated egg cell
- electric shock stimulates the egg to begin to divide into an embryo
-embryo inserted into surrogate- womb of a female
- the embryo contains the same genetic information as the body cell
80
What are the advantages and disadvantages of adult cell cloning?
+
Large number of identical offspring
Guaranteed desired features
Quick
Cheap
Save animals from extinction
-
Reduce gene pool/ limits variation
Any genetic defects will be passed into all offspring
Ethical objections
All may succumb to unexpected disease
81
What did Gregor Mendel do?
-carried out breeding experiments on pea plants
- used smooth, wrinkled and yellow peas and observed the offspring to see which characteristics they had inherited
- in 1866 concluded 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 can’t be mixed together
82
Why was Mendel not recognised until after his death?
As genes and chromosomes were not yet discovered so people couldn’t understand
83
Describe how the understanding of genetics evolved
Late 19th century - chromosome as a part of cell division were observed
20th century- understand that chromosomes and units had similar behaviours. Was decided that units (now know as genes) were on the chromosomes
1953- structure of DNA was determined, so we could understand how genes worked
84
What is the evidence for evolution?
Fossils and antibiotic resistant resistance in bacteria
85
How are fossils formed?
- parts of organisms that have not decayed because oxygen or moisture were not present, meaning the microbes that cause decay can’t survive
- parts of the organism (teeth,shell,bones) are replaced by minerals as they decay, forming a rock structure of the original part
- preserved traces such as footprints, burrows and rootlet traces (plant roots) remain due to ground hardening around them and forming a cast
86
What can fossils be used for ?
- to show how the anatomy of organisms has changed over time
They can be used to compare how closely related 2 organisms are, through looking at the number of similarities they have
87
Why can’t fossils be used to tell us how life started on earth?
As most early life forms are soft-bodied and therefore decay completely so are few fossils of them and any traces left have been destroyed by geological activity
88
What is extinction?
When an entire species has died out
89
What are the factors which can contribute to extinction?
- changes in environment which the species can’t adapt fast enough to
- new predators may have evolved or migrated to the area
- a new disease arises and there are no resistant alleles to it
- have to compete with a species which has a advantageous mutations for the same food source
- a catastrophic event can wipe out a species
- destruction of a habitat
90
What are antibiotic resistance bacteria?
Bacteria that are not killed by antibiotics which previously were used as cures against them
91
Describe how bacteria become resistant
-Bacteria reproduce at a fast rate
- mutations during reproduction can result in new genes (gene for antibiotic resistance). This is the creation of a new strain
- exposure to antibiotics crates a selection pressure, as this with antibiotic resistant genes survive and those without die
- as a result those with antibiotic resistance can reproduce and pass on the advantageous gene to their offspring
- this population of antibiotic resistant bacteria increases
- bacterial diseases spread rapidly because people aren’t immune to these new resistant bacteria and is no treatment
92
Name a resistant bacteria
MRSA - resistant to many different types of antibiotics and is common in hospitals
93
How do u slow the development of resistant bacteria
Antibiotics shouldn’t be given for viral or non serious infections
Specific antibodies should be give for specific bacteria
Patients should compete their course of antibiotics - so no bacteria can survive meaning they can’t mutate to become resistant
Antibiotics should be used less in agriculture
94
How do u slow the transmission of bacteria?
Maintain high standards of hygiene in hospitals
Medical staff and visitors should wash hands regularly
Medical staff should wear disposable clothing or clothing that is regularly sterilised
95
Why is it difficult to keep up with the development of resistant strains?
As development of antibiotics is expensive and slow
96
What is classification?
Involved putting organisms into groups depending on their structure and characteristics
97
what did Carl Linnaeus do?
Studies the similarities and differences between organisms to classify them
He developed the binomial system which is used worldwide to name organisms by genus and species , the 1st part is their genus and the 2nd species
He divided living things into
Kingdom
Phylum
Class
Order
Family
Genus
Species
98
What are powerful microscopes used for today in classification!
Used to see internal structures
This and biochemical analysis has led to new classification systems
99
What did Carl Woese develop?
The 3 domain system to classify organisms by adding 3 large groups (domains) above kingdom: archea - primitive bacteria which live in extreme environments
Eukarya- eukaryotes (have nucleus enclosed membranes)
Prokarya- true bacteria
100
What are evolutionary trees used for?
To show how closely related organisms are to
To compete this they use classification data and fossils from extinct species
