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A-Level Biology > Genes And Diversity ( Year 12 content ) > Flashcards

Genes And Diversity ( Year 12 content ) Flashcards

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1
Q

What are the three components of nucleotides?

A

A pentose sugar, a phosphate group, and a nitrogenous base

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2
Q

Describe the structure of DNA

A

Made up of deoxyribose sugar, a phosphate group, and one of 4 bases (A,T,C,G). Its double-stranded and hydrogen bonds between the bases form a 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 ribose sugar, a phosphate group, and one of four bases(A,U,C,G). 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 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 cell?

A

●Eukaryotic cells=found in the nucleus,long and linear. Associated with histone proteins to form chromosomes
●Prokaryotic cells= short and 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-overlappinh=each triplet is only read once
●Degenerate= more than one codon can code for the same amino acid
●Universal= one codon codes for the same amino acid in most organisms

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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

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11
Q

What is a locus?

A

The fixed postion on a DNA molecule occupied by a gene

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12
Q

What is an allele?

A

A different version 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=region of DNA that code for amino acid sequence, separated by one or more introns
●Introns=regions of DNA that do not 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 entire 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 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 advantage of using mRNA rather than DNA for translation

A

●shorter and contain uracil=breaks down quickly, so no excess polypeptide forms
●single-stranded and linear=ribosomes move along strands, and tRNA binds to exposed bases
●contains no introns

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19
Q

Describe the structure of tRNA

A

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

Nucleus

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22
Q

Outline the process of transcription

A

●DNA helicase breaks the weak hydrogen bonds between bases, causing DNA to unzip, forming 2 template strands
●free nucleotides line up next to their commentary bases on the template strand
●RNA polymerase joins the adjacent RNA nucleotides by forming phosphodiester bonds in a condensation reaction
●pre-mRNA is formed, and introns are spliced using enzymes forming m-RNA

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23
Q

Outline the process of translation

A

●mRNA leaves the nucleus via nuclear pores and attaches to ribosomes
●ribosomes read the mRNA base sequence
●this causes tRNA to bring an anti-codon on one side that’s complementary to the codon on mRNA and a specific amino acid on the other side
●amino acids join together in a condensation reaction forming peptide bond
●this process requires ATP

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24
Q

Where does translation take place?

A

Ribosomes

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25
Q

What is a mutation?

A

A random change to the DNA base sequence

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26
Q

Why might a mutation not lead to change in the amino acid sequence?

A

●genetic code is degenerate, so mutations may end up coding for same amino acid as the original triplet
●Mutation may occur in intron

27
Q

What is a substitution mutation?

A

When a nucleotide in the DNA base sequence is replaced by another

28
Q

What is a deletion mutation?

A

When a nucleotide in the DNA base 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

29
Q

What is a mutagenic agent?

A

Factors that increase the rate of gene mutations
X-rays
UV Light

30
Q

What is meiosis?

A

A form of cell division that produces four genetically haploid cells( cells with half the number chromosomes found in the parent cell) known as gametes

31
Q

How does meiosis differ from mitosis?

A

●meiosis produces four genetically different cells with half the number of chromosomes as the parent cell
●mitosis produces two genetically identical cells with the same number of chromosomes as the parent cell

32
Q

What happens during meiosis I?

A

1) Homologous chromosomes pair to from bivalents
2) crossing over(exchange of alleles between sisters chromatids) occurs at chiasmata
3) Cell divides into two. Homologous chromosomes separate randomly

33
Q

What happens during meiosis II?

A

1) independent segregation of sister chromatids
2) Each cell divides again, producing 4 haploid cells

34
Q

In which two ways does meiosis produce genetic variation?

A

1) crossing over
2) Independent assortment

35
Q

Define population

A

All the organisms of a particular species that live in the same place

36
Q

Define genetic diversity

A

The total number of different alleles in a population

37
Q

What advantage does a high genetic diversity provide?

A

The ability to adapt to a change in the environment allows natural selection to occur

38
Q

Explain how natural selection results in the development of new characteristics

A

●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 alleles, and the frequency of advantageous allele increases

39
Q

What is directional selection?

A

Occur when phenotype of the extreme is favoured. Individuals with phenotype suited to the new condition will survive and pass on their genes

40
Q

Give an example of directional selection

A

Antibiotic resistance

41
Q

What stabilising selection?

A

Occurs when the environment is constant. Phenotypes closest to the mean are favoured, and phenotype of the extreme is favoured against

42
Q

Give an example of stabilising selection

A

Baby Birth weight
Heavy babies= problem in delivery
Light babies= complications

43
Q

What are the three types of adaptation?

A

1) chemical
2) physical
3) behavioural

44
Q

Define species

A

A group of organisms that can Interbreed to produce fertile offspring

45
Q

What are the advantages of courtship behaviour?

A

●individuals can recognise sexually mature members of their own species of opposite sex
●synchronises mating
●forms a pair bond

46
Q

Define classification

A

The process of arranging organisms into groups

47
Q

Name the eight groups in the classification hierarchy, from largest to smallest

A

Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species

48
Q

What system is used to give species a universal name?

A

Binomial naming system

49
Q

What are the two components to a binomial name?

A

Generic name= the genus the organism belongs to
Specific name= the species the organism belongs to

50
Q

What is phylogenetic classification?

A

The process of arranging organisms into groups based on their evolutionary origins and relationship

51
Q

How can we clarify evolutionary relationships between organisms?

A

Analyse their molecular differences
Advances in immunology sequencing

52
Q

Explain hierarchical classification

A

Smaller groups within larger groups with no overlap between the groups

53
Q

What is biodiversity?

A

The variety of living organisms

54
Q

Define community

A

All the different species that live in one area and interact with each other

55
Q

How do you calculate the index of diversity?

A

D= N(N-1) / Σn(n-1)

n = total number of organisms for a single species in the community
N = total number of organisms in the community
Σ = sum of

56
Q

What impact does agriculture
(Farming) have on species diversity?

A

Decreases species richness
●farmland is typically used for 1 species
● use of pesticides/ herbicides
● removal of hedgerows

57
Q

What impact does farming have on genetic diversity?

A

Decreases
●farmers select for certain characteristics, which reduces the number of different alleles in the population

58
Q

How can biodiversity be increased in areas of agriculture?

A

1) use of hedgerows instead of fences
2) rotate crops around after a season
3) Limit the use of pesticides and herbicides

59
Q

Name four ways we can measure genetic diversity

A

1) observable characteristics
2) base sequence of DNA
3) base sequence of mRNA
4) amino acid sequence

60
Q

Why do scientists prefer to use gene technology instead of observation?

A

Simply Inferring DNA differences by observing an organisms characteristics is not reliable; the characteristics could be coded for by more than one gene or could be influenced by the environment

61
Q

What is meant by interspecific and intraspecific variation?

A

Interspecific= differences between individuals of different species
Intraspecific= differences between individuals of the same species

62
Q

What is sampling?

A

Selecting a group of individuals to measure that will represent the whole target population

63
Q

How can random sampling be achieved?

A

Create a grid for the sample area, and then randomly generate coordinates where a quadrat can be placed. Repeat until the required sample size is reached

A-Level Biology (8 decks)

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