BIOL1020 MOD3 WEEK 1

What is evolution

In layman’s terms:

• Change in inherited characteristics of biological populations over successive generations

What is the difference between genotype and phenotype

GENOTYPE = Genetic Makeup

• genotypes are an individual’s unique sequence of DNA

• Inherited from each parent

PHENOTYPE = Observable Features

• Phenotypes are the expressed results of a genotype + environmental factors

What is Natural Selection

Individuals that are better suited to their environment survive and have more offspring. Over time, favourable traits accumulate in the population.

For Natural Selection to occur there must be: (4)

1. Variation within populations

2. Heritability of variation (= DNA basis)

3. Excess offspring per generation

4. Non-random survival and reproduction

What are the Three modes of Selection

1. Directional selection

2. Disruptive selection

3. Stabilising selection

Which is better Genetic drift or Natural selection in a larger or smaller generation

• Genetic drift works better in smaller populations as it works by chance. Smaller populations are more affected when a trait is randomly removed or a harmful trait is removed.

• Natural selection works better in a larger population as it driven by environmental fitness. Random chance events are averaged out allowing selected genes to be passed on.

What is a Genome?

GENOME:

• an individuals complete set of DNA, including all its genes and information required to build that organism for successful reproduction.

How do genomes differ depending on organism type

What is Lateral gene Transfer among Prokaryotes?

• induced by stress (e.g environmental perturbation)

• Occurs via conjugation and natural transformation

Is the movement of genetic material between different organisms, rather than between parent and offspring

What is the C-value paradox

In eukaryotes, there is no correlation between genome size and organismal complexity; genomes sizes vary widely.

What are Introns

“Intervening sequences”

• Nucleotide sequences in DNA and RNA that DO NOT code for proteins

• Are removed via RNA splicing during pre-mRNA stage

What are Exons

“Expressed sequences”

• Nucleotide sequence in DNA and RNA that are retained while creating mature RNA

• Typically includes 5’-end, 3’-end, start/stop codons, and protein coding genes

What are transposing

“Jumping genes”

• Nucleotide sequence in DNA which can move to different locations via copying or cut/paste mechanisms

2 Types:

• retrotransposons (revers transcription “copy/paste” using RNA)

• DNA transposons (direct “cut/paste” movement)

What are some mechanisms of evolution? (Mutations)

Deletion - removes a chromosomal segment

Duplication - repeats a segment

Inversion - reverses a segment within a chromosome

Reciprocal Translocation -moves a segment from one chromosome to another nonhomologous one.

What are other mechanisms of evolution?

1. Changes to existing genes - mutations, exon shuffling

2. Changes to existing regulatory non-coding DNA and RNA

3. Changes in genome composition - Lateral/Horizontal gene transfer, whole genome duplication (polyploidy), Duplication of one or more genes.

4. Transposable elements - moves genes and/or regulatory elements to new positions in the genome.