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A Level Biology > Genetics,Biodiversity and Classification > Flashcards

Genetics,Biodiversity and Classification Flashcards

1
Q

What are the 3 components of nucleotides?

A

A pentose sugar, a phosphate group, an organic base

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2
Q

Describe the structure of DNA

A

Made up of deoxyribose sugar,a phosphate group and 1 of 4 organic bases (A,C,G,T).It’s double stranded, and hydrogen bonds between the bases form a double helix shape

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3
Q

Describe the role of DNA

A

Carries genetic information, determines our inherited characteristics

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4
Q

Describe the structure of RNA

A

Made up of a ribose sugar,a phosphate group and 1 of 4 organic bases (A,C,G,U). It is single stranded

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5
Q

Describe the role of RNA

A

Transfers genetic information from DNA to ribosomes for protein synthesis

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6
Q

Which bases are purine and which bases are pyrimidine?

A

Purine (double ring):adenine,guanine
Pyrimidine (single ring):cytosine, thymine, uracil

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7
Q

How is DNA in eukaryotic cells different from in prokaryotic cells?

A

•Eukaryotic cells:found in nucleus,long &linear.Associated with histone proteins to form chromosomes. Mitochondria&chloroplasts contain prokaryotic-like DNA
•Prokaryotic cells:Short&circular, not associated with proteins

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8
Q

What is the genetic code?

A

The order of bases on DNA. Consists of codons (triplets of bases that code for a particular amino acid)

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9
Q

Identify features of the genetic code

A

•Non-overlapping:each triplet only read once
•Degenerate:more than 1 triplet codes for the same amino acid (64 possible triplets for 20 amino acids)
•Universal:same bases and sequences used by all species

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10
Q

What is a gene?

A

A sequence of bases on a DNA molecule that codes for a specific sequence of amino acids to make a polypeptide. Can also code for functional RNA

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11
Q

What is a locus?

A

The fixed position on a DNA molecule occupied by a gene

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12
Q

What is an allele?

A

Different versions of the same gene, found at the same locus on a chromosome

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13
Q

What are exons and introns?

A

Exons=regions of DNA that code for amino acid sequences.Separated by 1 or more introns
Intron=regions of DNA that don’t code for anything

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14
Q

Where are introns found?

A

Between exons, within genes

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15
Q

What is the genome?

A

The complete set of genetic information contained in the cells of an organism

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16
Q

What is the proteome?

A

The complete set of proteins that can be produced by a cell

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17
Q

Describe the structure of messenger RNA (mRNA)

A

A long,single strand.Its base sequence is complementary to the DNA it was transcribed from

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18
Q

Suggest advantages of using mRNA rather than DNA for translation

A

•Shorter&contains uracil=breaks down quickly so no excess polypeptide forms
•Single-stranded&linear=ribosome moves along strand & tRNA binds to exposed bases
•Contains no introns

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19
Q

Describe the structure of transfer RNA (tRNA)

A

A single strand of around 80 nucleotides thats folded over into a clover leaf shape. On one end is an anti-codon,on the opposite end is an amino acid binding site

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20
Q

What is produced by transcription?

A

mRNA

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21
Q

Where does transcription take place?

A

In the nucleus

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22
Q

Outline the process of transcription

A

•DNA uncoils into 2 strands with exposed bases. 1 used as a template
•Free nucleotides line up next to their complementary bases,and are joined together by RNA polymerase

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23
Q

What happens to mRNA after transcriptions?

A

In eukaryotic cells,pre-mRNA must be spliced to remove introns,leaving only the coding regions.Then it moves out of the nucleus and attaches to a ribosome

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24
Q

What is produced by translation?

A

Proteins

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25
Where does translation take places?
In the cytoplasm (or ribosomes)
26
Outline the process of translation
•The anti-codon of tRNA attaches to complementary bases on the mRNA •Amino acids bonded to tRNA form peptide bonds,continuing to form a polypeptide chain until a stop codon is reached •This process requires ATP
27
What is a mutation?
An alteration to the DNA base sequence.Often arise spontaneously during DNA replication
28
Why might a mutation not lead to change in the amino acid sequence?
•Genetic code is degenerate so mutation may end up coding for same amino acid as the original triplet •Mutation may occur in intron
29
What is a substitution mutation?
When a nucleotide in the DNA sequence is replaced by another. This is more likely to be a quiet mutation, meaning no change occurs in the amino acid sequence
30
What is a deletion mutation?
When a nucleotide in the DNA sequence is lost.This is more likely to be harmful and significant,as it leads to a frame shift which means the entire amino acid sequence will be different
31
What is a mutagenic agent? Give examples of this?
Factors that increase the rate of gene mutation.Examples:X-rays,UV light, gamma rays,certain chemicals e.g in alcohol and tobacco
32
What is a polyploidy chromosome mutation?
When an individual has 3 or more sets of chromosomes instead of 2
33
What is chromosome non-disjunction?
When chromosomes fail to separate correctly in meiosis,resulting in gametes with 1 more or less chromosome than normal
34
What is meiosis?
A form of cell-division that produces 4 genetically different haploid cells (cells with half the number of chromosomes found in the parent cell) known as gametes
35
How does meiosis differ from mitosis?
•Meiosis produces 4 genetically different cells with half the number of chromosomes as the parent cells •Mitosis produces 2 genetically identical cells with the same number of chromosomes as the parent cells
36
What happens during meiosis 1?
•Homologous chromosomes pair to form bivalents •Crossing over(exchange of sections of genetic material)occurs at chiasmata •Cells divide in 2.Homologous chromosomes separate randomly. Each cell contains either maternal or paternal copy
37
What happens during meiosis 2?
1.Independent segregation of sister chromatids 2.Each cell divides again,producing 4 haploid cells
38
Give 2 ways meiosis produces genetic variation?
1.Crossing over during meiosis 1 2. Independent assortment (random segregation)of homologous chromosomes and sister chromatids. •Results in new combinations of alleles
39
Define population
All the organisms of a particular species that live in the same place
40
What is an allele?
Different forms of a particular gene, found at the same locus on a chromosome.A single gene could have many alleles
41
Define genetic diversity
The total number of different alleles in a population
42
What advantage does a high genetic diversity provide?
Ability to adapt to a change in environment;allows natural selection to occur
43
Explain how natural selection results in development of new characteristics
•Random mutations result in new alleles •Some alleles provide an advantage, making an individual more likely to survive and reproduce •Their offspring receive the new allele, and frequency continues to increase over many generations
44
What is directional selection?
Occurs when environmental conditions change.Individuals with phenotypes suited to the new conditions will survive & pass on their genes.Over time the mean of the population will move towards these characteristics
45
Give an example of directional selection
Antibiotic resistance.Bacteria with a mutation allowing them to survive in the presence of antibiotics will reproduce.So frequency of this allele will increase&the population will shift to have a greater antibiotic resistance
46
What is stabilising selection?
Occurs when environmental conditions stay the same.Individuals closest to the mean are favoured&any new characteristics are selected against.Results in low diversity
47
Give an example of stabilising selection
Birth weight;babies that way around 3kg are more likely to survive than those a lower or higher weights
48
Define a niche
The role of a species within its environment.Species sharing the same niche will compete with each other
49
What are the 3 types of adaption? Give examples of each
•Anatomical (changes to body structure) e.g oily fur •Physiological (changes to bodily processes) e.g venom production •Behavioural (changes to actions) e.g hibernation
50
Define species
A group of organisms that can interbreed to produce fertile offspring
51
What are the advantages of courtship behaviour?
Individuals can recognise sexually mature members of their own species of the opposite sex,synchronise mating,form a pair bond,&successfully breed
52
Define classification
The process of arranging organisms into groups
53
Name the 8 groups an organism can be classified into, from largest to smallest
domain->kingdom->phylum->class->order->family->genus->species
54
What system is used to give species a universal name?
Binomial naming system
55
What are the 2 components to a binomial name?
•Generic name=the genus the organism belongs to.2 closely related species will share the same genus •Specific name=the species an organism belongs to
56
How are binomial names handwritten?
The first letter of the generic name should be capitalised,with the rest in lowercase.The whole name should be underlined
57
What is phylogenetic classification?
The process of arranging organisms into groups based on their evolutionary origins and relationships
58
How can we clarify evolutionary relationships between organisms?
Analyse their molecular differences. Advances in immunology/genome sequencing provide clear pictures of how related 2 organisms are
59
Explain hierarchical classification
•groups within groups •no overlap between groups
60
What is biodiversity?
The variety of living organisms.It can be measured in terms of species diversity(no. of species in a community),ecosystem diversity(range of different habitats)and genetic diversity
61
Define community
All the different species that live in one area and interact with each other
62
How do you calculate index of diversity (d)?
d=N(N-1)/Σn(n-1) N=total number of organisms of all species n=total number of organisms of each species Σ=sum of
63
What impact does farming have on species diversity?
decreases species richness •farmland is typically used for only 1 species (monoculture) •use of pesticides/herbicides
64
What impact does farming have on genetic diversity?
decreases •farmers select for certain characteristics,which reduces number of different alleles in the population
65
How can biodiversity be increased in areas of agriculture?
1.Use hedgerows instead of fences 2.Grow different crops in the same area,or rotate crops around after a season 3.Limit use of pesticides and herbicides
66
Name 4 ways we can compare genetic diversity between organisms
1.Frequency of observable characteristics 2.Base sequence of DNA 3.Base sequence of mRNA 4.Amino acid sequence
67
What is meant by gene technology?
Sampling DNA or mRNA in order to read and compare the base sequence of organisms.Alternatively,the amino acid sequence can be studied as this will also provide information on the organisms mRNA and DNA sequences
68
Why do scientists prefer to use gene technology instead of observations?
Simply inferring DNA differences by observing an organism’s characteristics is not reliable;the characteristics could be coded for by more than one gene,or could be influenced by the environment
69
What is meant my interspecific and intraspecific?
Interspecific=differences between individuals or different species Intraspecific=differences between individuals of the same species
70
What is sampling?
Selecting a group of individuals to measure that will represent the whole target population
71
How can a random sample be achieved?
Created a grid for your sample area,and then randomly generate coordinates where a quadrat or transect can be placed. Repeat until required sample size is reached

A Level Biology (7 decks)

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