Week 1: Introduction and Tree of Life Flashcards
What is genetics?
The study of genome sequence variation
What is a genome?
the complete set of inherited instructions that contribute to the traits of an organism (DNA and RNA)
What was the previous definition of a gene?
a unit of inheriting traits from one individual to the next (defined before we knew what DNA was)
HEREDITY
What is a gene?
CURRENT:
specific locus of DNA that is transcribed into a single RNA molecule
OR
the entire sequence of DNA that is required to transcribe a single RNA molecule (all exons, introns, and sequences at beginning and end of RNA that are not translated, as well as rRNA, tRNA and non mRNA)
What is the broader definition of gene (that may be incorrect)?
“gene” includes things that are required to transcribe and encode RNA molecule - regulatory sequences (promotor, terminating regions)
Examples of genes?
- protein coding
- non coding RNA
- introns for protein coding genes
- tRNA, rRNAs
Characteristics of gene is a physical molecule?
- specific DNA sequence
- associated with a specific genome location
- encodes for 1+ RNAs/proteins
- part of genetic network that influences traits
What is an allele?
gene variant/version
characteristic of DNA?
chemically inert (just instructions for transcript)
where is the chemistry of life?
some RNA mainly protein
How do we know the origin of a majority of NY COVID 19 infections were from Europe?
- COVID-19 is an RNA virus
-single covid-19 genome infected a human and it replicated and infected other humans but during replication, new alleles arose - these alleles match the sequence in Europe
important property of genomes?
unstable (sequence information changes all the time due to replication errors)
What is the result of replication mistakes?
generation of alleles: a sequence variant
in a growing population of genomes with no selection pressure, the total number of alleles …
increases every generation
What is the mechanism for human genome sequencing?
human genomes have migrated and diverged -> assign origins with similar sequences in different locations
What happens if an allele is advantageous to the organism?
genomes containing advantageous alleles becomes dominant genome
Consequences of genome instability?
- genome of zygote accumulates alleles as it divides during development
- fibroblast cells in skin will have alleles not present in zygote
- new alleles can lead to cancer
- also no living fossils
What are the 3 things the study of genetics tells us?
- history of life and its evolution
- how inheritance works (Mendel and nuclear inheritance)
- chemistry of life
divergence in alleles leads to …
speciation
what does the tree of life look like?
side view: trunk = oldest, branches = newest
top view: middle = oldest, outside = newest
What are the 3 models for how life first arrived?
- protein world
- RNA world
- DNA world
What are the characteristics of the protein world?
- can catalyse chemical reactions
- can potentially alter other proteins conformation (ex. prions)
- “protocells” may have existed (concentrated proteins surrounded by lipid membranes)
What are the explanations of why the protein world is not the origin of life?
- generally unstable
- function but no heredity (can’t store genetic info)
What are the characteristics of the DNA World?
- stores genetic info
- very stable
What are the explanations of why the DNA world is not the origin of life?
without other molecules, DNA can’t do anything
What are the characteristics of the RNA world?
- can store genetic info (ex. covid)
- can catalyze reactions: ribosymes
- able to make proteins
- makes more stable template of self (DNA)
Characteristics of LUCA?
last universal common ancestor
- ~3.5 bya
- in DNA world
- diverged to 3 domains of life (bacteria, eukarya, archaea)
Characteristics of RNA world ancestor
- prior to DNA world
- ~4.1 bya
common feature found in all living organisms?
similar genetic systems (genome as nucleic acid)
What are the 2 eukaryotic genomes?
- nuclear
- mitochondrial
What are the types of genome found in animal/protist genomes?
- 1/3 alpha-proteobacteria
- 1/3 archae
- 1/6 other bacteria
- 1/6 novel (not found in bacteria or archaea)
What are the alpha-proteobacteria genomes involved in?
metabolism
What are the archaea genes involved in?
information storage and processing
What is the proposition for the origin of eukaryotes?
genetic merger (involving endosymbiosis) of alphaproteobacterium (bacteria) and loki (archaea)
What are the steps for creating a euyaryote according to the endosymbiosis hypothesis?
- host archaeal cell feeding on bacteria
- endosymbiosis
- sharing of metabolites
- entrapment (one organisms requires the other)
- transfer of control and genetic integration
