BI107 Quiz 3

Central Dogma of Molecular Biology

genetic info flows in one direction. DNA→RNA→Protein. DNA is transcribed to RNA then translated into a protein. Amino Acids code for proteins.

Is all DNA transcribed?

No. Non-coding DNA/Regulatory DNA is never transcribed.

Does all RNA code for proteins?

No. There is non-coding RNA like tRNA and rRNA. Transfer RNA and Ribosomal RNA.

Molecular evolution

evolutionary change at the level of the DNA sequence.

genome

complete set of genetic material in an organism. entire genome is in every cell. genome is expressed differently in different cells.

diploid

two complete sets of chromosomes.

codon

3 nucleotides. 1 codon codes for 1 amino acid

what does it mean for genetic code to be redundant

multiple codons can code for the same amino acid.

synonymous substitution

change to gentic sequence that produces the same amino acid and does not affect protein function.

non-synonymous substitution

change in genetic sequence that results in different amino acid. usually deleterious but also selectively advantageous or neutral.

point mutation (spontaneous)

change in single nucleotide in DNA sequence due to errors during DNA replication

induced mutations

chemicals or radiation

chromosomal mutations

happen at the geene or chromosome level and result in non-viable gametes

non viable gametes

not passed to next generation

lethal mutations

not passed to offspring, unviable zygote

deleterious mutation

can be passed to offspring, fitness disadvantage

advantageous mutation

can be passed to offspring, selective advantage, can become fixed in a popilation (only alelle present for a trait)

neutral mutation

can be passed on to offspring, doesnt change fitness.

3 mechanisms that generate new phenotypes

sexual reproduction, lateral gene transfer, gene duplication

sexual reproduction

genetic info from two individuals combine to form offspring.

advantages of sexual reproduction

new gene combos that increase evolutionary potential, large diversity of genotype combos

disadvantages of sexual reproduction

reduced overall reproductive rate compared to asexual reproduction. recombination can break up beneficial combinations of genes.

lateral gene transfer

genetic material transferred from one organism to another

• DNA fragments can be picked up from environment

• genes can be transferred to new host throguh viruses

• hybridization results in transfer of many genes related species.

• common in bacteria and viruses

• new genotypes

lateral gene transfer advantages

• new genetric material and traits are introduced. genetic diversity is increased quicker than random mutations.

• organisms can quickly adapt to new environments or challenges.

gene duplication

one or more extra copies of a DNA segment are produced.

• led to trichromatic vision in primates

psuedogene

mutations leading to a non-functional promotor, or mutations in the coding sequence that lead to a nonfunctional protein.

• one copy keeps original function

• other copy changes and evolves a new function.

Evolutionary Developmental Biology (EVO-DEVO)

the comparative study of organismal development and how it has evolved. Most animals share a common set of genes.

what types of fenes determine the structure and developmental direction of animal embryos?

homeotic genes

genetic toolkit

highly conserved genes found in nearly all animals.

homeotic genes

subset of genetic toolkit

• direct development of particular body segments or structures.

• most animal homeotic genes are HOX GENES

Hox Genes

Provide positional info during development

• determine what type of body part will develop in a certain location.

• control expression of many other genes that develop the body parts.

• transcription factors

homologous genes

genes in a different species that are inherited from a common ancestor.

heterometry

different levels of gene expression

• "how much the gene is expressed

• can change how body is developing the gene

• different amounts of gene expression during development.

heterochrony

timing of gene expression

• different time

• chronological

• how long the gene is expressed

heterotopy

spatial differences in gene expression

• “different space”

• instead of when, its where the gene is expressed

heterotropy in the evolution of rodent cheek pouches

• differences in location of gene expression for cheek pouches

• the pouches could be internal or external depending on how the gene is expressed.