Midterm 1 - Notes 2 (Part 1) Flashcards
Phenotype
The observable character (including both physical appearance and behaviour) of a cell or organism
Genotype
Genetic constitution of an individual cell or organism. The particular combination of alleles found in a specific individual
How many copies of genes are in a diploid cell?
2
Gene
Region of DNA that is transcribed as a single unit and carries information for a discrete hereditary characteristic, usually corresponding to either a single protein (or set of related proteins) or a single RNA (or set of related RNAs)
What is the real name for a three-spine stickleback?
Gasterosteus aculeatus
What do three-spine stickleback have that make them harder to prey upon?
Series of plates along the sides of their bodies
What make three-spine stickleback easy prey?
Their size (they are small)
Are three-spine stickleback easy prey? Why or why not?
NO, because they have developed special defensive traits that make then harder to be eaten
Where are three-spine stickleback mostly found? (2)
- Circumpolar distribution in Arctic and temperate regions
2. Fresh water and coastal seawater (across the northern waters)
When did the phenotypic variation occur?
Recently
What are the 2 forms of fish found in Paxton Lake BC?
- Limnetic form
2. Benthic form
Limnetic form
- Mainly open water
2. Predation by larger fish and birds
Benthic form
- Shallow water
- Predation by macro-invertebrates
- May “grab them by the spine”
What is the adaptive advantage for the benthic form fish?
They are more round and smooth with reduced of absent spines and reduced armour plates
- makes them harder to grab onto and easy to slip away
What is the phenotypic difference on limnetic and benthic form fishes?
- Limnetic = contains dorsal and pelvic spines
- Benthic = reduction/ absence of the dorsal and pelvic spines
What kind of approach was used in the general outline of the experiment?
Classic genetic approach
- what happened and why/how
What happened in the classic genetic approach? (4)
- Lined them up along linkage groups
- establish crosses - Used markers to identify and locate the gene that is causing the absence of plates or spines
- genetic map - Takes a genome sequence and looks at the specific genes that could cause this phenotype
- candidate genes - These can identify a smaller number and compare them in other situations
- molecular changes
Did the Japanese marine fish have spines?
Yes
Did the Paxton benthic fish have spines?
No
What did they discover about the spines?
That it is dominant gene and that having no spine was a recessive gene
What are the 3 steps in classical genetics?
- Observe inheritable phenotype differences between individuals
- Find genetic markers distributed throughout the genome
- Identify markers that are linked (co-inherited) with phenotype (associated genotype with phenotype)
What is a genetic marker? (4)
- Defined segment of DNA
- Has a known position on a chromosome
- It has easily detectable allelic variations
- Only used for detection (it doesn’t actually cause the phenotype)
What is a huge part of genetic mapping?
Looking for co-inherited segments
Co-inheritance
Chromosomal regions in related individuals or the sharing of functional or marker alleles among phenotypically similar individuals
Co-segregation principle
Loci that are close together are co-inherited except a cross over occurred between them
What leads to a high chance of cross over?
Having the loci further apart from each other
Morphological
Any phenotypic difference cause by alleles of one gene
Biochemical
Allelic variants of enzymes
- eg. isozymes
Isozymes
Different versions of the same gene, but it might have a different function
Molecular (3)
- Allelic variations
- difference in the DNA (A vs T and G vs C) - Not related to a phenotypic difference
- No phenotypic consequence are the best
What are 3 advantages to molecular genetic markers?
- Evolutionary neutral
- unaffected by the environment/ development
- random changes that were inherited throughout the generations - Extremely abundant
- Can be easily chosen
What are 3 detection types of molecular genetic markers and an example for each?
- Restriction site based
- eg) RFLP - Repeat length based
- SSR or micro-satellites - Sequence based
- SNP
SSRs
Simple Sequence Repeats
Parallel evolution
Is the independent evolution of the similar traits, starting from a similar ancestral condition
What do the detection types allow you to do?
Allows you to detect differences in the DNA sequence
What detection type is more common?
SNPs
SNPs
Single Nucleotide Polymorphism
