Lec 3 slides and reading Flashcards
theory of evolution
accounts for the diversity of life, and explains similarities between different species
Similarities between different groups of species
-Systems of biological classifications have been based on easily visible structural characteristics
-Species are essentially groups of similar individuals capable of interbreeding with each other
-Similar species are grouped in the same genus
-Another set of facts that strongly support the theory of evolution is provided by modifications of the same structure in different species
-E.g. bones of bats and birds wings indicate they are modified forelimbs; flippers of whales and fish fins, both well adapted for swimming
Embryonic development
-Provides many examples of similarity between different groups of organisms, clearly suggesting descent from common ancestors
-Embryonic forms of different species are similar, even when the adults are different
-E.g. at one stage in mammalian development, structures appear that look like the developing gill slits of fish embryos → makes sense if we descended from fish-like ancestors
Since it’s the adult structures that adapt the organism to its environ, they usually get modified by selection
Vestigial organs
remnants of structures that were functional in the ancestors of present day organisms
E.g. human appendix → reduced version of part of the digestive tract that’s bigger in orangutans
E.g. fossils of snakes have been found with hindlegs, showing snakes evolved from lizard-like ancestors
Similarities in cells
-Basic feature of all animal, plant and fungal life is that their tissues are made up of cells
-Cells→ basis of bodies of all organisms other than viruses
In eukaryotes (all cellular non-bacterial life) the cells are organized into cytoplasm and nucleus within it that contains genetic material
Cytoplasm → contains complex set of tiny pieces of machinery with many subcellular structures
Mitochondria → generate cell’s energy
Chloroplasts → photosynthesis in green plants’ cells occurs
It’s now known that both of these are descended from bacteria that colonized cells and became integrated into them as essential components
prokaryotes
bacteria that are cells but simpler with no nucleus or organelles
viruses
viruses are the only non-cellular forms of life and are parasites that reproduce inside the cells of other organisms, and consist of a protein coat surrounding genetic material
proteins
Proteins are enzymes that take a chemical and carry out a procedure for it (like chemical scissors)
-Also have storage or transport functions (haemoglobin in RBCs transports oxygen)
-Structural proteins (keratin) forms skin, hair and nails
-Communication proteins (hormones, signal to control cell behaviour during development)
effect of mutations in the myosin protein gene
deafness
how are enzymes categorized
Enzymes categorized by the jobs they perform (digestive enzymes snip molecules into pieces)
process by which cells generate energy from food sources
In process by which energy generated by cells from food sources, there’s an energy source (sugar or fats) and goes thru chemical steps, some release energy
Metabolic pathway organized like an assembly line and enzymes carry out the different steps
Cells have pathways to make chemicals and to generate energy from foods
what does the functioning of each chemical pathway depend on
Functioning of each biochemical pathway depends on enzymes
If any enzyme in pathway stops working → end product will not be produced
E.g. albino mutations result from lack of an enzyme necessary for production of pigment melanin
what is stopping a pathway useful for
Stopping a step in a pathway is useful to control the output of cell machinery (cells contain inhibitors to carry out control functions - e.g. control of melanin production)
dna structure
Sugar phosphate backbone (structure of DNA- sugars connected to nucleotides)
Nucleotides: adenine, guanine, cytosine and thymine: A&T, G&C
When DNA replicates during cell division, the 2 strands unwind and a complementary daughter strand is combined from each parent strand
genes
Inheritance is the control of individuals’ characteristics by physical entities called genes (Gregor Mendel)
The genes that control the production of metabolic enzymes and other proteins(and thus determine individuals’ characteristics) are stretches of DNA carried in the chromosomes of each cell
Discovery that chromosomes carry genes in a linear arrangement was made in the fruitfly (Drosophila melanogaster)
true or false: order of genes on a chromosome can be rearranged during evolution
true
Chromosome is a long DNA molecule encoding hundreds of genes DNA of a chromosome is combined with protein molecules that help package it in neat coils inside the cells nucleus
Each gene encodes a different protein
Chromosomes carry the info needed to specify the amino acid sequences of an organism’s proteins, together with the controlling DNA sequences that determine which proteins will be produced by organism’s cells
What is a gene, and how does it determine the structure of a protein?
Gene is sequence of four chemical letters of the genetic code, in which sets of 3 adjacent letters (codons) correspond to each AA in the the protein for which the gene is responsible
Gene sequence is translated into the sequence of a protein chain (has triplets marking the end of the AA chain)
Change in sequence of a gene causes mutation (some mutation don’t change the protein sequence)
Across living organisms, the genetic code differs slightly, suggesting that all life on Earth has a common ancestor
In order to produce its protein product, DNA…
DNA sequence of a gene is first copied into a ‘message’ made of RNA, whose sequence of letters is copied from the gene by a copying enzyme
RNA message interacts with proteins and other RNA molecules, to translate the message and produce the protein specified by the gene (occurs in all cells - in eukaryotes occurs in cytoplasm & message has to move outside of nucleus first)
