UNIT 13 Flashcards
(15 cards)
Outline the diversity in structure of viruses.
Non-cellular structure;
Consist of protein coat and genetic material;
Genetic material can be DNA or RNA;
May be double stranded or single stranded;
Some are positive RNA viruses while others are negative RNA viruses;
Some viruses are covered in enveloped/naked capsid;
Some viruses/retroviruses have a reverse transcriptase component;
Describe the lytic pathway for a virus.
Bacteria inserts viral DNA into host genome;
Viral genetic material are made by the host cell by transcription and translation;
Viral proteins are made by host cell;
Lysis to release viral particles;
Describe the lysogenic pathway for a virus.
Occurs when a virus infects a cell but does not immediately replicate so the cell does not burst;
DNA of virus is incorporated into the host genome;
Replication and lysis will occur at a later time;
Describe the metabolic functions of reverse transcriptase.
Enzyme used in HIV replication;
Use viral RNA as template;
Synthesises/reverse transcription of viral DNA from RNA;
Viral DNA integrated into host chromosome with help from reverse transcriptase;
Viral DNA transcribed and translated to synthesise viral proteins;
Discuss the evidence supporting that the diversity of viruses exists as a result of convergent evolution.
Convergent evolution as the appearance of similar traits in unrelated organisms as a response to similar selection pressures;
Viruses exhibit a wide range of forms/structures/mechanisms to adapt to different hosts/environments;
Presence of a capsid surrounding genetic material/nucleocapsid is a shared feature that evolved independently in different viral lineages;
Presence of specific protein receptors or spikes have evolved independently to facilitate host cell attachment / suitable example such as similar spike proteins in coronaviruses and influenza viruses;
Independent evolution of similar replication enzymes / reverse transcriptase;
Viruses utilise either DNA/RNA as their genetic material, demonstrating molecular convergence in adapting to different replication strategies;
Convergent traits enhance viral fitness by aiding in host cell attachment/immune evasion/efficient replication;
Regressive hypothesis: originate from parasitic cells then evolved to lose cell content;
Progressive hypothesis: evolved from transposons;
Compare the structure of the coronavirus with the human immunodeficiency virus, HIV.
BOTH
Both are spherical in shape;
Both contain viral envelope;
Both contain capsid;
Both contain spikes;
Both spikes are made of glycoprotein;
HIV
Contains reverse transcriptase
Contains two single-stranded RNA / shorter genome
Enveloped capsid
Genome within enveloped capsid
Coronavirus
Does not contain reverse transcriptase;
Contains one single-stranded RNA / longer genome;
Nucleocapsid;
Genome is nucleocapsid / not in envelope;
Explain the difficulties with applying the biological species and morphological concepts to all organisms.
Morphological species concept cannot be applied to species that show variation due to reproductive isolation/species with different forms/polymorphism;
Morphological species concept does not take into account DNA/genetic information;
Biological species concept is defined in terms of sexual reproduction but not all organisms reproduce sexually;
Asexual reproduction e.g. budding in yeast/horizontal gene transfer in bacteria;
Biological species concept relies on ability to observe and study interbreeding in real-time which is not possible with extinct species/fossilised organisms;
Some different species can interbreed and produce viable offspring/hybrids might have reduced fitness or be sterile / challenges biological species concept;
Convergent evolution makes it difficult to group organisms based solely on morphological characteristics accurately;
Rapid evolution and morphological changes in response to the environment might make individuals appear distinct, even if they share a recent common ancestor, which challenges the reliability of morphological traits as indicators of species relationships;
Compare and contrast the biological species concept and the morphological concept.
BOTH
Both seek to define a species;
Both acknowledge there can be variation within a species;
Both are connected to the broader concept of evolution;
BIOLOGICAL SPECIES CONCEPT
Species as a group of organisms that can interbreed to produce fertile offspring
Proposed by Mayr
Proposed later
Applicable only to sexually reproducing organisms
Reflects evolutionary relationships
MORPHOLOGICAL CONCEPT
Species as a group of organisms with shared traits;
Proposed by Linnaeus;
Initially proposed;
Applicable to sexually and asexually reproducing organisms;
May not represent evolutionary relationships;
Outline the binomial naming system and its importance.
System used to name species;
Genus name and species name;
Species with the same genus share many characteristics/are closely related;
Internationally agreed;
Facilitates understanding and communication between scientists;
Explain how a sample of cells taken from a foetus can be used to determine whether the foetus will be biologically male or biologically female at birth.
Cells grown in a culture medium;
Cells stained;
Observed under a light microscope;
Photomicrograph taken during mitosis/metaphase;
Chromosomes arranged according to size/position of centromeres/into karyogram;
Look at chromosome pair 23;
Two large chromosomes mean foetus is XX;
One large chromosome and one small chromosome means foetus is XY;
XX is biologically female AND XY is biologically male;
Outline the outcomes of the human genome project and their impacts on different fields of science.
State a property that the genome of the same species will share.
Sequences entire genome;
Determined total number of base pairs in human genome;
Estimated number of genes in human genome;
Identified loci of genes;
Identified repeat sequences;
Identified locations of SNPs;
Identified gene sequences associated with certain diseases/biological processes/traits;
Stimulated further development/reduced price of sequencing technology;
Technology developed for HGP is now used to diagnose diseases/identify microorganisms/DNA matching in forensics and medicine/contribute information for personalised medicine;
Insight into evolutionary relationships/genetic similarities/differences;
Identification of regulatory elements/non-coding RNAs/components that play essential roles in gene expression/cellular function;
Emphasised importance of consideration of ethical/legal/social implications of genomic research;
Describe how the genome within a species could vary.
Genome can vary in size/base sequence;
Result of mutations/SNPs/insertions/deletions/tandem repeats;
Explain why cross-breeding between closely related species is unlikely to produce fertile offspring.
Parent chromosome numbers are different;
Explain how variations in specific molecules can indicate phylogeny.
Differences in DNA base sequence accumulate over long periods of time;
Differences in amino acid sequence in proteins also accumulate over long periods of time;
Differences accumulating at constant rate allow them to be used as evolutionary clock;
Number of differences is proportional to the time since they diverged;
Examples of genes/proteins that can be used as a molecular clock include rRNA, haemolglobin and cytochrome c oxidase;
Outline the principal taxonomic ranks in the modern classification system.
Domain is the largest rank;
Domains include Archaea, Eubacteria, and Eukarya;
Domain Eukarya is split into kingdoms;
From largest to smallest, kingdoms are divided into phyla/phylum, classes, orders, families, genera/genuses, and species;
Species are sometimes divided into subspecies;
