ch 10 lo

Recall what variation is and distinguish the different types

Variation is the differences among individuals in population
Types: Genetic Variation, Environmental Variation, and GxE

Genetic, Environmental, GXE variation

Genetic - caused by differences in DNA (mutations, recombination, independent assortment
Environmental - caused by differences in surrounding
GxE - when the same genotype produces different phenotypes depending on the environment

Define phenotype plasticity (aka ‘reaction norm’); understand how assess presences or absence of it

The ability of a single genotype to produce different phenotypes in response to environmental conditions
Ex: Hydrangea flowers can be pink in basic soil but blue in acidic soil.
To understand presence or absence: Grow organisms from different environments in the same controlled environment
If differences disapper → variation was environmental
If differences remain → variation is genetic

Swap individuals between environments
If they change phenotype to match new environment → phenotypic plasticity is present


Graph: X-axis = environment, Y- axis = phenotype
Steeper slope → more plasticity
Flat line → no plasticity

Define mutations and distinguish random vs induced mutations

Mutation - a change in DNA sequence
Random - occurs naturally during DNA replication without an external cause
Induced - caused by mutagens such as UV radiation and chemicals

Identify a point mutation (SNP) and be able to rank how much they can affect phenotype

Point mutation - a change in a single nucleotide base
Ranked by least to most harmful:Synonymous, nonsynonymous, nonsense, frameshift

Synonymous, non-synonymous, non-sense, indels

Synonymous (silent) - no change in amino acid → usually no phenotype change
Non synonymous (missense) - changes in amino acid → may affect protein function
Nonsense - creates a premature stop codon → usually harmful
Indels - insertions/deletions that can cause frameshift mutatio

Gene duplications (what can happen to duplicated genes? WHY?)

When an organism ends up with an extra copy of a gene in its genome
It matters bc the extra copy can mutate and evolve indepedently, leading to new functions, specialized roles, or nonfunctional genes
It happens due to erros in DNA replication or recombination events

Retroposition; unequal cross over; inversions; whole genome duplications

Retroposition: mRNA transcript of gene is reverse transcribed into DNA by reverse transcriptase
This cDNA is inserted back into the genome at a new location
- lacks introns and may have poly A tail
Fate: usually nonfunctional

Unequal cross over: During meiosis, homologous chromosomes misalign during crossing over. One chromosome gets extra copies of a gene, the other loses copies

Inversions: A chromosome segment breaks into two places, flip 180, and reattaches
- can reduce recombination

Whole genome duplications: entire set of chromosome duplication often due to errors in meiosis or hybridization between plants
- common in plants (wheat is a hexaploid; 6n)

Differentiate paralog vs ortholog

Paralog - genes that arise by duplication within the same species
Ortholog - genes in difference species that evolved from a common ancestor

Review and understand Meiosis - how sexual reproduction leads to variation

Crossing over, independent assortment, random fertilization

• Crossing over (prophase I) – homologous chromosomes exchange segments.

• Independent assortment (metaphase I) – chromosome pairs align randomly.

• Random fertilization – any sperm can fertilize any egg, multiplying variation

Recall and distinguish homozygous dominant, heterozygous, homozygous recessive

• Homozygous dominant (AA) – two dominant alleles → dominant phenotype.

• Heterozygous (Aa) – one dominant, one recessive allele → dominant phenotype.

• Homozygous recessive (aa) – two recessive alleles → recessive phenotype.

Calculate observed genotype freq and observed allele freq

• Genotype frequency = (# individuals with genotype) / (total individuals).

• Allele frequency = (# copies of allele) / (total alleles in population).