Week 4 Flashcards
Who and when create the process of DNA fingerprinting?
Sir Alec Jeffries 1984
What is an overview of the function of DNA?
DNA sequence codes for an allele
Alleles = genetic variants at specific locus (gene)
Alleles encode proteins…..and thus everything!
Pairs of chromosomes in diploid organisms
What does both alleles impact?
At a locus (gene) alleles from both chromosomes combine to
produce the Genotype and its effects
What produces the phenotype?
Genotype and environment
What is polymorphic DNA?
Variation in some part of the genome
How can polymorphism vary?
Polymorphism in, or among - individuals, groups, populations or species
What is an overview of exons?
Transcribed part of genome
Nucleotide sequence variation can be mapped
Different alleles directly influence phenotype
What is an overview of non coding DNA (neutral markers)?
Part of genome with no direct function (not transcribed)
Neutral to selection
Highly polymorphic
Provides many highly informative markers
What are the different types of DNA?
Nuclear autosome – bi-parentally inherited
Sex chromosomes e.g. Y = males, X = both sexes
Mitochondrial - maternally inherited
What are examples of DNA markers?
Microsatellite repeats, e.g. CTTT(inverse^)10
Sequence data
SNPs – single nucleotide polymorphisms
How can you co-oridinate individuals with DNA results?
Place spots or tags to identify the individual
Where can you get DNA from?
Blood
Tissue
Faeces
Hair follicles
Feathers
Sloughed skin
Where can you store collected DNA?
100% Ethanol
Specialised buffers
Dried
Why do we need only to collect a small amount of DNA?
As we can undego PCR to amplify the DNA regions we are investigating
What are and what happens during the 3 main stages of PCR?
Denaturing – when the double-stranded template DNA is heated to separate it into two single strands.
Annealing – when the temperature is lowered to enable the DNA primers to attach to the template DNA.
Extending – when the temperature is raised and the new strand of DNA is made by the Taq polymerase enzyme
How can molecular techniques be useful in the field?
Distinguishing similar species
Determining prey species
* Observations = difficult or time consuming
* Gut contents or faecal samples
What is DNA barcoding?
Library of species barcodes
What is used in DNA barcoding?
Short, easy to amplify section of DNA
That has lots variation across spp……but little within species variation
Same sections used across all (or at least whole groups of) species
In animals - e.g. 600-700bp of mitochondrial COI region
Why are molecular techniques used for sex determination?
In the majority of organisms sex is genetically determined- these genes can be used to identify sex
How can molecular techniques be used for sex determination?
Amplify a piece of DNA on sex chromosomes
What is a case study of molecular techniques being used for sex determination?
Allele on W chromosome is shorter than on the Z
Run on a size separation electrophoresis gel
Females (ZW) have two bands - Males (ZZ) have one
Birds
What is a case study for sex determination in whales?
Baleen whales lack obvious secondary sexual
characteristics.
A Y-chromosome probe used in humpback whales (identifies males)
Determine gender of free ranging whales using skin biopsies
What can be used to determine biological age?
DNA methylation and Telomeres
What is a case study of usinf DNA methylation for age determination?
Key DNA loci show increased methylation with age
Can be used to calculate age
Polanowski et al 2014 - humpback whales
Determine age structure of pods and populations - pods are all male or all female with calves
Why can telomeres be used to determine age?
Telomere attrition with cell replication
Thus telomeres shorten with age
Can be used to determine chronological age
May cause senescence /age related disease
What causes telomeres to shorten?
Oxidants – also erode telomeres
* Product of metabolism
* Affected by stresses
What can increases telomere shortening?
Higher oxidants and telomere shortening with, for example:
1) infection
2) reproductive effort
3) Psychological stress
What is a case study of the relationship between telomere length and post-sampling lifespan?
Seychelles warbler, Acrocephalus sechellensis
Measured teleomere length and then recorded when the birds died
Positive correlation - telomere length predicts future
lifespan after controlling for age
What did the experiment with the Seychelles warbler prove?
Marker of biological age
In Seychelles warbler what was shown to increase life span?
The cost (stress) of fighting with new and/or unrelated neighbours
Having helpers delays ageing in breeding females
Why are telomeres a good tool for estimating lifespan?
Telomeres as a generic currency to measure the costs of different behaviours in life
How can molecular tools be useful for monitering infections?
Who has an infection e.g. malaria
When they get it
How they behave when infected
Survival and reproductive success
Behavioural changes selected for
What bird in Hawaii escape malaria througha change in behaviour?
Hawaiian Honeycreeper
How did the Hawaiian honeycreeper reduce eposure to malaria?
They move nest up in the mountains where it was too cold for mosquitos before moving down in the day to find food
What is the overview of the spread of Wolbachia?
Detected using PCR of ribosomal DNA from the bacteria
Ca 60% of insects infected!
Transmitted in egg cytoplasm therefore only by female hosts
Cause female bias in hosts’ offspring e.g. override sex
determination, induce parthenogenesis, kill male eggs etc
How did the wide spread nature of Wolbachia impact mating behaviour?
Acraea butterflies:
Skews sex ratio to mainly females - reversing the sex that
competes for a mate - results in female lekking
What are the problems with determining parentage without genetics?
Difficult to watch individuals or groups
Matings may be secretive/difficult to observe
Females may copulate with multiple males
Offspring from multiple females may be mixed