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Zoology Y1 > APS11006 Principles of Evolution- Slate Lectures > Flashcards

APS11006 Principles of Evolution- Slate Lectures Flashcards

1
Q

First theory of inheritance

A
  • Jean Baptiste de Lamarck (1744-1829)
  • Inheritance of acquired characteristics
  • WRONG
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2
Q

Causes of mutations

A
  • Tend to be spontaneous but can be induced
  • Radiation, UV, X-Rays
  • Mutagens, any agent that increases mutation rate
  • Disasters such as Chernobyl provide a ‘natural laboratory’ for testing the effects of radiation on mutation rates across Western Europe
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3
Q

Karyotype

A

-Number or organisation of chromosomes in an individual

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4
Q

Polyploidy

A
  • More than diploid
  • Dispermy occurs when two sperm simultaneously fertilise egg, resulting in 3 complete sets of chromosomes, happens in 1-3% conceptions, always lethal
  • Bacteria usually monoploid
  • Plants can be diploid, tetraploid, hexaploid…
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5
Q

Aneuploidy

A
  • One set of chromosomes is incomplete (missing or extra)
  • On autosomes can be nullisomy (both missing, lethal), monosomy (one missing, lethal in humans) or trisomy (one extra, usually lethal)
  • On sex chromosomes, missing chromosome (45X, turners syndrome, causes infertility, 45Y inviable), extra chromosomes (minor effects, reasonably common)
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6
Q

Translocations

A

Exchange of parts between non-homologous chromosomes, evolutionary dead end

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7
Q

Deletions

A
  • Part of chromosome missing
  • Consequence depends on size
  • Deletion on chromosome 5, Cri-du-Chat syndrome
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8
Q

Inversions

A
  • Chromosome breaks during replication but is repaired in different order
  • Paracentric doesnt include centromere, no problems in meiosis
  • Pericentric inversions include centromere, possible meiosis problems
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9
Q

Human genome length

A

3 billion base-pairs long

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10
Q

Codon

A
  • Three nucleotides
  • Specifies one amino acid
  • An amino acid can be encoded by more than one codon
  • Start (met) and stop codons
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11
Q

Organisation of human genome

A
  • 20-30,000 genes
  • 1.5% encodes proteins, most conserved
  • 3% regulate protein expression, highly conserved
  • 45% caused by transposons
  • 6.6% not transcribed
  • 44% non conserved, repetitive DNA, regulating DNA and structure and folding
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12
Q

DNA substitutions

A
  • Most common mutation form
  • E.g., CAT<>CAC, switching of one base to another
  • Can be silent or synonymous, CAT and CAC both code for histidine, however CAA and CAG code for glutamine
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13
Q

DNA insertions and deletions

A
  • Indels
  • Causes change in amino acid from indel onwards
  • Serious consequences, different protein is encoded
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14
Q

Albinism

A
  • Caused by a single substitution in codon for tyrosinase

- Stops melanin production in gorillas

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15
Q

Sickle cell anaemia

A
  • Caused by mutation from GAA to GTA in the haemoglobin beta gene
  • GAA codes for glutamic acid, and GTA valine
  • Valine causes individuals to have sickled red blood cells
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16
Q

Single nucleotide polymorphisms

A
  • 100,000,000 SNPs discovered in humans
  • Non-coding region mutations
  • Around 3% of genome contains polymorphisms, leading to variation amongst individuals
17
Q

Satellite DNA, or simple tandem repeats

A
  • Nearly always harmless
  • Sequences with repeated parts
  • Widely used in finding disease genes, conservation genetics, evolutionary genetics, agricultural improvement
18
Q

Pisum sativum

A
  • Garden pea
  • Wide variety of phenotypes
  • Single gene, readily available
  • Short generation time
  • Self-pollinates (true breeding)
19
Q

Cross-pollination

A
  • Anthers removed before they shed pollen, stops self-pollination
  • Transfer pollen by brushing
20
Q

Chi-square goodness-of-fit test

A
  • X^2 = sum of (((O-E)^2)/E)
  • Degrees of freedom = categories - parameters - 1
  • Null hypothesis always that O and E are good fit
  • To reject null when df = 1, chi-square must be greater than 3.841
21
Q

Exceptions to independent assortment law

A

-Two genes physically proximate on same chromosome do not assort independently

22
Q

Mendel-Fisher controversy

A
  • Ratios were always very close to expected
  • Probability of this is 7x10^-5
  • Fisher attributed the alleged forgery to an unknown assistant
23
Q

Mendelian or monogenetic disease

A

One gene involved

24
Q

Multifactorial or polygenic disease

A
  • Many genes involved

- Most diseases

25
Q

Pedigrees

A
  • Show several generations

- Used to infer mode of inheritance or genetic counselling

26
Q

Consanguineous

A

-Inbreeding

27
Q

Autosomal dominant diseases

A
  • Achondroplasia, form of dwarfism
  • Polydactyly, extra digits
  • Hairy mid-digit
  • Widow’s peak
28
Q

Autosomal recessive diseases

A
  • Carriers and non-carriers indistinguishable without genetic testing
  • 2 carriers mate, 1 in 4 chance of affected offspring, 1 in 2 carrier
  • Albinism, sickle cell disease, cystic fibrosis, attached ear lobes
29
Q

Cystic fibrosis

A
  • Two inactive copies of the CFTR gene (CF transmembrane conductance regulator)
  • Large gene, lots of mutations, some more severe
  • Most common is at codon 508
30
Q

Examples of x-linked recessive disorders

A
  • Duchenne’s muscular dystrophy
  • Red-green colour blindness
  • Haemophilia
31
Q

Lyonization

A
  • X-inactivation
  • In each cell of females, one X chromosome is randomly inactivated
  • Occurs early in development
  • Some cells express one X, others will express the other
32
Q

How many genes do humans have?

A

Around 20,500

33
Q

Recombination/crossing over

A
  • Non-independent assortment of linked genes

- Closer the genes together, less likely to cross over

34
Q

Recombination fraction

A
  • Recombinant individuals/total individuals

- Measure of distance between two genes in centiMorgans

35
Q

Loci

A

Physical position of a gene or genetic marker along chromosome

36
Q

Estimating allele frequencies example in scarlet tiger moth (Panoxia dominula)

A
  • Three forms controlled by 2 alleles A1 (p) and A2 (q)
  • Sample of 18,385 moths, 17,062 were A1A1, 1,295 A1A2, 28 A2A2
  • p + q = 1
  • Number of A1 alleles is (2 x 17,062) + (1,295) =35,419
  • A1 frequency = 35,419/36,770 = 96.3%
  • A2 = 1 - 0.963 = 3.7%
37
Q

Hardy-Weinberg equilibrium

A
  • p^2 + 2pq + q^2 = 1
  • Assumes random mating, no natural selection at that gene, a large pop size, no migration, no mutation
  • Useful as it provides description of how genetic variation is maintained in population

Zoology Y1 (5 decks)

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