Heritable Variation Among Individuals (L11)

Exam 2 Lecture 11

Proteins

• polymers constructed from 20 types of amino acids

• catalyze chemical reactions, provide structural support, regulate the passage of substances across the cell membrane, protect against disease, and coordinate cell signaling pathways

• manufactured with help from the ER, Golgi, and ribosomes

Endoplasmic reticulum (ER)

• smooth ER - contains enzymes that produce lipids

• rough ER - contains ribosomes that produce proteins

Golgi apparatus

• finished, sorts, and ships cell products in vesicles

DNA

• composed of nucleotides (sugar, phosphate, base)

• A-T, C-G

• organizes into chromosomes, which wrap around histones

Ploidy

Number of copies of unique chromosomes in a cell

• Diploids- chromosomes come in homologous pairs

Autosome

A chromosome that does not differ between sexes

Codons

• A set of 3 bases read during translation

• Start → AUG

• Stop → UAA, UGA, UAG

Hormones

Flow through the body and alter the expression of genes

Reading RNA

Upstream - 5’ end towards the promoter

Downstream - 3’ end towards the terminator

Gene control region

• Upstream, includes the promoter and other regulatory sequences that control transcription of DNA

Transcription factor

A protein that binds to a specific DNA sequence to regulate the expression of a gene

• Activators and Repressors

microRNA

• Not the same as mRNA

• post-transcriptional regulators

• enhances or silences gene translation

RNA splicing

• removes introns and only keeps exons in mature mRNA

• Alternative splicing may also remove an exon

Prokaryotic gene expression

• Only occurs in the cytoplasm

• Regulation only occurs at the transcriptional level

Eukaryotic gene expression

• Occurs in the nucleus, then the cytoplasm

• Regulation occurs at pre-transcription, transcription, post-transcription, translation, and post-translation.

Plasmid

• A mobile genetic element

• A molecule of DNA in bacteria that can replicate independently of chromosomal DNA

Pseudogenes

• Nonfunctional genes

• Often form after a gene has been duplicated, and the original loses its function

Mutations

• Point mutation - a single base is changed to another

• Insertion - a segment of DNA is inserted

• Deletion - a segment of DNA is deleted

• Frameshift mutation - insertion of 1-2 bases changes the codon and shifts every codon downstream (changes the amino acids coded)

• Gene Duplication - A segment of DNA is copied a second time

• Inversion - A segment of DNA is flipped around and inserted backwards

• Chromosome fusion - 2 chromosomes get joined together

• Aneuploidy - Chromosomes are duplicated or lost

• Genome Duplication - Leads to increased ploidy

• Somatic Mutation - A mutation not passed down to offspring (affects the cells)

• Germline Mutation - A mutation that can be inherited by offspring (affects the gametes)

Albinism

• Point mutation of the FGFR3 gene

• Proline gets replaced with serine at one position

Polyphenic trait

• One genotype produces multiple phenotypes based on the environment

• A form of phenotypic plasticity

Ex: taurus beetle horns only appear if the beetle has sufficient nutrition

Morphogen

A signalling molecule that flows between nearby cells + alters the expression of target genes