Evolution

Question 1

Evolution def

Answer 1

Process by which organisms change over time through changes in the genome.

Question 2

Biological evolution def

Answer 2

Refers specifically to genetic change occurring in a group of organisms. Can’t just be one organism.

Question 3

Steps of evolution

Answer 3

1. Genetic variation arises: mutation and recombination
2. Increase and decrease in frequency variants occur . Caused by environmental forces and changes the gene pool.

Question 4

2 Types of evolution

Answer 4

1. Anagenesis- evolution taking place in a single lineage over time
2. Cladogenesis- splitting of one lineage into two. No longer a common gene pool

Question 5

Hypotheses of molecular protein variation prevails

Answer 5

1. Neutral-mutation hypothesis- most molecular variation is neutral with regard to natural selection. Shaped largely by mutation and genetic drift.
2. Balance hypothesis- the genetic variation in natural populations is maintained by selection that favours variation.

Question 6

What is a RFLP? And how is it used?

Answer 6

Restriction fragment length polymorphism is variation in the presence of a restriction site. They can be used to estimatee the variation in the DNA and the proportion of nucleotides that differ between organisms.
PCR-RFLP analysis of the mtCyt-b gene identifies species of donkey and horses.

Question 7

What are microsatellites?

Answer 7

They are short DNA sequences in multiple copies. Variation in number of copies is common and microsatellites can be detected by by OCRs

Question 8

How is variation detected by DNA sequencing?

Answer 8

DNA sequence data often reveals processes that influence evolution
DNA seuqencinv was used to reassess the genetic relationships between African elephants
Analysis showed large difference between forest and Savannah elephants, suggesting limited gene flow. Know that they’re two different species.

Question 9

Prezygotic reproductive isolation examples

Answer 9

Ecological- habitat differences
Temporal- reproduce at different times
Mechanical- anatomical differences
Behavioural- differences in mating behaviour
Gametic- incompatible gametes

Question 10

Post-zygotic reproductive isolation examples

Answer 10

Hybrid inviability- hybrid zygote doesn’t survive to reproductivity
Hybrid sterility- hybrid is sterile
Hybrid breakdown- F1 hybrids are viable and fertile but F2are inviable or sterile.

Question 11

Speciation def

Answer 11

Process by which new species arise. Comes about through the evolution of reproductive isolating mechanisms

Question 12

Allopatric speciation def and examples

Answer 12

When a geographical barrier splits a population in 2 or more groups and prevents gene flow.
Ex rivers separating fish, mountains separate plants, finches separated from everything on Galapagos island.

Question 13

Sympatric speciation def and examples

Answer 13

Arises in the absence of geographical barrier to gene flow. Reproductive isolating mechanisms evolve within a single interbreeding population.

Question 14

Polyploidy and alloploidy def

Answer 14

Polyploidy- organisms that have two or more sets of chromosomes common among plants, some fish, frogs and leeches.
Alloploidy- organisms that have more than two sets of chromosomes that are from different species. Often when two diploid species hybridize. Ex. Gossypium, a hybrid species of cotton formed from two diploid species of cotton.

Question 15

Nondisjunction def

Answer 15

A pair of homologous chromosomes that failed to separate at anaphase so both pairs of chromosomes are passed to the daughter cell.

Question 16

Rates of molecular evolution def

Answer 16

Different genes and different parts of the same gene evolve at different rates. We can look at the rate of substitution for nucleotides, how many substitutions taking place per nucleotide site.
Rates are highest in regions of the gene that have the smallest effect on function. Very high from introns.
Lowest rates are seen in non synonymous changes in the coding region. They alter the amino acid and are often deleterious.

Question 17

The molecular clock def

Answer 17

Mutations may build up in a stretch of DNA at a reliable rate. This gene could be used as a molecular clock and becomes a tool for estimating the dates of lineage-splitting events

Question 18

Exon shuffling def

Answer 18

Molecular mechanism for the formation of new genes, where 2 or more exons from different genes are recombined between introns, giving rearranged genes with altered functions.

Question 19

Gene duplication def

Answer 19

Any duplication of a DNA that contains a gene. Used to acquire new genes.

Question 20

Whole genome duplication def

Answer 20

When an entire genome is copied and pasted so that a species has twice the genetic material it did before

Question 21

Horizontal gene transfer def

Answer 21

The movement of genetic material between organisms, includes the spread of antibiotic resistant genes among bacteria

Question 22

3 mechanisms of horizontal gene transfer

Answer 22

1. Transformation- bacteria take up DNA from their environment
2. Conjugation- bacteria directly transfer DNA to another cell
3. Transduction- bacteriophages move gene spas from one cell to another