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AS Biology > 4 - Genetics > Flashcards

4 - Genetics Flashcards

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1
Q

Why do not all mutations cause a change in the structure of a polypeptide?

A
  • triplets code for same amino acid
  • occurs in introns
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2
Q

What is an exon?

A

Base sequence coding for sequence of amino acids

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3
Q

What are non-coding base sequences, and where are they positioned

A
  • DNA that does not code for protein
  • positioned between genes
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4
Q

How is DNA in a chloroplast different from DNA in the nucleus

A

chloroplast DNA is shorter and has fewer genes, and is circular not linear

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5
Q

Compare and contrast tRNA and mRNA

A

S - both single polynucleotide strand
D - tRNA is ‘clover leaf shape’, mRNA is linear
D - tRNA has hydrogen bonds, mRNA does not
D - tRNA is shorter but mRNA is longer

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6
Q

Give a difference between mRNA and pre-mRNA

A

mRNA has fewer nucleotides because of splicing

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7
Q

Describe how one amino acid is added to a polypeptide that is being formed at a ribosome during translation

A
  • tRNA brings specific amino acid to ribosome
  • Anticodon (on tRNA) binds to codon (on mRNA)
  • Amino acids join by condensation reaction
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8
Q

Describe how mRNA is produced from an exposed template strand of DNA

A
  • Free RNA nucleotides form complementary base pairs
  • Phosphodiester bonds form
  • by RNA polymerase
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9
Q

Describe transcription (5 marks)

A
  • helicase breaks Hydrogen bonds (between DNA bases)
  • Free RNA nucleotides align by complementary base pairing
  • Uracil base pairs with adenine
  • RNA polymerase joins nucleotides forming phosphodiester bonds
  • pre-mRNA is spliced to remove introns
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10
Q

Describe translation (6 marks)

A
  • mRNA attaches to ribosomes
  • anti codons bind to complementary codons
  • tRNA brings a specific amino acid
  • amino acids join by peptide bonds using ATP
  • tRNA released
  • ribosome moves along the mRNA to form the next polypeptide
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11
Q

What is a mutation?

A

A change in the base sequence of DNA resulting in the formation of a new allele

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12
Q

How can a mutation have no effect on an individual?

A
  • Genetic code is degenerate so amino acid sequence may not change
  • new allele is recessive so doesn’t effect phenotype
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13
Q

How can a mutation have a positive effect on an individual?

A
  • Results in change in polypeptide that positively changes the properties of the protein
  • may result in increased survival chances
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14
Q

Give two differences between mitosis and meiosis

A
  • in mitosis there is 1 division, in meiosis there is 2
  • in mitosis daughter cells are genetically identical, but in meiosis they are different
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15
Q

Describe the process of crossing over and explain how it increases variation (4m)

A
  • homologous pairs of chromosomes form a bivalent
  • chiasmata form
  • equal lengths of non sister chromatids are exchanged
  • producing new combinations of alleles
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16
Q

Give two ways meiosis produces genetic variation

A
  • independent segregation
  • crossing over
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17
Q

What happens during prophase 1 of meiosis? (4m)

A
  • nuclear membrane dissolves
  • crossing over between non sister chromatids
  • homologous pair associate through synapsis
  • bivalent forms
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18
Q

What happens during metaphase 1 in meiosis?

A
  • random orientation occurs
  • bivalents line up at equator
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19
Q

What’s the definition of genetic diversity?

A

the number of different alleles of genes in a
population

20
Q

What does natural selection cause?

A
  • beneficial alleles increase in frequency
  • negative alleles decrease in frequency
21
Q

Describe the process of evolution by natural selection (4m)

A
  • genetic variation is caused by mutation
  • overproduction of offspring leads to competition for survival
  • individuals with beneficial adaptations are more likely to survive
  • over many generations there is a change in allele frequency (evolution)
22
Q

How does variation occur?

A
  • random mutation in meiosis
  • sexual reproduction (crossing over in meiosis or random fertilisation)
23
Q

What’s the definition of phenotype?

A

The physical expression of a genotype

24
Q

What’s the definition of codominant alleles

A

Both alleles expressed in the phenotype

25
Q

What is a gene pool

A

All the alleles in a population

26
Q

What is a species?

A

Similar organisms that can reproduce to produce fertile offspring

27
Q

What are courtship behaviours?

A

Behaviours that animals exhibit to attract a mate (essential for successful mating)
- species specific
- indicate sexual maturity
- establishes a pair bond to raise young
- prevents interbreeding

28
Q

How can mating success and offspring survival be increased

A
  • attract same species
  • stimulates release of gametes
  • attraction of opposite sex
29
Q

What is the order of the taxon system?

A
  • domain
  • kingdom
  • phylum
  • class
  • order
  • family
  • genus
  • species
30
Q

What is the genus and species of this name : Homosapiens

A

Genus: Homo
Species name: Sapiens

31
Q

What are the different measures of biodiversity

A
  • Species richness: measure of no. of different species in a community
  • index of diversity: relationship between no. Of species in a community and no. of individuals in each species
32
Q

What are farming agriculture techniques that decrease biodiversity

A
  • monoculture (only 1 type of crop grown) limits food and habitats for other species
  • removal of woodland and hedges - destroys habitats forcing species to migrate/die
  • ploughing
  • herbicides - kills weeds so removes a food source for other organisms
  • spray crops with pesticides - kills pests which removes a food source for organisms
33
Q

Describe phylogenetic classification

A
  • there is a hierarchy
  • no overlap between groups at the same level
  • smaller groups within larger groups
34
Q

What are ways to compare genetic diversity?

A
  • order of amino acids sequence
  • base sequence of DNA
  • base sequence of mRNA
  • frequency of observable characteristics
35
Q

How could breeding experiments determine if 2 organisms belong to the same species

A
  • breed them together
  • if they produce fertile offspring they are from the same species
36
Q

Explain how the chromosome number is halved during meiosis

A
  • homologous chromosomes
  • one of each pair goes to each daughter cell
37
Q

What is the proteome?

A

The number of different proteins DNA is able to code for

38
Q

What is the genome

A

The complete set of genes in a cell

39
Q

What does it mean that the genetic code is universal

A

The same specific DNA base triplets code for the same amino acids in all living organisms

40
Q

What does it mean that the genetic code is non-overlapping

A

Discrete, each base can only be used once and in only one triplet

41
Q

What does it mean that the genetic code is degenerate

A

The same amino acid can be coded for by more than one base triplet

42
Q

What is a mutagenic agent?

A

Increases the rate of gene mutation

43
Q

Describe what is meant by non-disjunction

A
  • failure of chromosome pairs to separate
  • failure of chromatids to separate
  • During anaphase
  • So both chromatids go to one pole of spindle
44
Q

How do you calculate the number of possible chromosome combinations from the diploid number?

A

(2^n)^2.
- n = half the diploid number

Eg if diploid number is 12 then-> (2^6)^2

45
Q

What is a gene

A

A sequence of DNA bases that codes for the amino acid sequence of a polypeptide or a functional RNA

46
Q

What is a chromosome

A

Long linear DNA and its associated histone proteins in the nucleus of eukaryotic cells

AS Biology (6 decks)

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