Topic 1 - Introduction Flashcards
Cell Doctrine (1838) - 3 Key Players
- Schwann
- Schleiden
- Virchow
Cell Doctrine - 3 main points
1) Cells are the smallest living unit
2) Cells are distinct units with specific tasks
3) A cell is only derived from another cell (Virchow) - put to rest spontaneous generation
* * Viruses are the only exception
Commonalities between all cells?
- store hereditary information
- replicate hereditary information
- transcribe part of the genetic information into RNA
- translate RNA into proteins
- proteins are used as catalysts for function
- biochemical factories use the same molecular building blocks
- enclosed in plasma membranes
What are the 4 basic features of all cells?
- membranes
- DNA
- ribosomes
- cytosol
What is significant about the Mycoplasma?
- only has 500 genes (the smallest amount for life)
4 Metabolic Pathways & general sizes of cells
- photoautotroph
- photoheterotroph
- chemoautotroph
- chemoheterotroph
- 1-10 micrometers
2 Methods of identifying bacteria?
1) Culture dishes - however we have only grown and named 5000 species of bacteria (>90% not cultivated yet)
2) DNA sequencing
2 unique features to Animal Cells
- centrosomes
- lysosomes
4 unique features of Plant Cells
- chloroplasts
- central vacuoles
- plasmodesmata
- cell walls
Feature shared by plant and animal cells
mitochondria
What are the advantages of compartamentalization
1) Each area has a distinct pH - allows enzyme functionality to depend in specific pH’s - as a fail safe
2) Gradients across membranes do work
3) Arrangements of protein complexes in membranes allow reactions to occur faster
What do bacteria and mitochondria have in common?
- the both have their own genome, membrane, own ribosomes and machinery
What organelle was taken up first - chloroplast or mitochondria
- only plant cells have chloroplasts while all eukaryotes have mitochondria
Number of Prokaryotes genes
roughly 4000 genes , mycoplasma exception
Number of Eukaryotic genes
21000-30000 genes
Comparisons between prokayotes and eukaryotes - genes?
- Eukaryotes have 3-30X more genes than prokaryotes
- Eukaryotes have 1000X more NON-CODING DNA
Why do eukaryotes have gene splicing or post translational modifications?
Eukaryotes have hybrid genomes - the human genome has about 98% non-coding for proteins compared to prokaryotes with 11% of its DNA being non-coding for proteins
Is there a correlation between genome size and level of organization?
1) NO - compare a human genome to amoeba*
2) YES - correlation with function requirement - meaning tissues with higher level of organization
Is there a correlation between genome size and level of organization? (2) - house renter vs house buyer
1) Prokaryotes are house renters - require mobility thus only produce essential structures, smaller genomes are used to compete for nutrient since there is a pressure to replicate
2) Eukaryotes are house buyers - takes 12hours to replicate its genome, has sites for storage, and contains coding & non-coding regions in its genome
Once you double genome size…
… you do NOT double in size
Does the number of chromosomes correlate with the level of organization?
NO CORRELATION - in the example, each species have the same number of genes, but one has a significantly larger genome size
Genes and NON-coding regions on Chromosomes
- repeated sequences consist of 50% of a chromosome
- 40% of these are transposons
- segmental duplication of bases
Define pseudogenes
- segments related to genes however they have lost their functionality to a complete gene (in terms of cellular gene expression or protein coding ability)
Are genomes of Humans Identical?
NO
a) SNP (single nucleotide polymorphism)
- variation in single nucleotides occurring in a specific position in a genome - each variation is present to some degree within a population
b) duplication/deletion - of large areas of a genome
How do we generate Junk DNA?
- accumulation of mistakes during DNA replication which never got fixed 100%
4 ways to accummulate Junk DNA
1) Intragenic Mutation - insertion/deletions
2) Gene Duplication - via transposons
3) DNA segment suffling
4) Horizontal Gene Transfer - integration of genes into other organisms (Vertical gene transfer - normal transfer of genes from parent to offspring)
Explain an Ortholog
when an ancestral organism with gene G undergoes SPECIATION giving: Gene Ga and Gene Gb - these two genes are called ortholog’s since they descended from a common ancestor & and encode for a protein with the same function
Explain a Paralog
when an ancestral organism with Gene G undergoes GENE DUPLICATION and DIVERGENCE allowing later ancestral organisms to have Gene G1 and Gene G2 - these homologous genes involved in gene duplication encode for a protein with sSIMILAR but NOT IDENTICAL function
Eukaryotes have regulatory DNA which allows them to (2)
- selectively use the genetic information
- use environmental signals to activate selective sets of genes
Regulatory DNA through signalling cascades turn genes on and off having what 3 effects
- metabolic enzymes
- transcription regulatory proteins
- cytoskeletal proteins
