Genetics PDF - Biology Past Paper

Punnett squares Pedigrees Gregor Mendel through his work on pea plants, discovered the fundamental laws of inheritance. Characteristics studied: seed shape, seed colour, flower colour, pod shape, pod colour, flower position + plant height. Dominant traits- a trait that appears more frequently tha...

Punnett squares Pedigrees Gregor Mendel through his work on pea plants, discovered the fundamental laws of inheritance. Characteristics studied: seed shape, seed colour, flower colour, pod shape, pod colour, flower position + plant height. Dominant traits- a trait that appears more frequently than another trait Recessive traits- both alleles of a gene at a locus are partially expressed Sex-linked traits- traits controlled by genes located on the sex chromosomes X or Y Codominance- both alleles are expressed fully and simultaneously in heterozygotes. Incomplete dominance- both alleles of a gene at a locus are partially expressed Multiple alleles-a single gene has more than one alete, multiple genes can result in more possible phenotypes. Polygenic inheritance- traits are controlled by two or more genes, phenotypes often show a range of variation. Heterozygous- two different alleles tHomozygous- two of the same alleles Phenotype vs. Genotype Phenotype- what you can see (what genes show) Genotype- type of genes/ alleles ​ ​ ​ ​ ​ ​ Gene flow-the movement of genes into or out of a population Genetic drift- the change in frequency of an existing gene variant in the population due to random chance Natural selection-Organisms that are more adapted to their environment are more likely to survive and pass on the genes that aided their success Chromosomes Law of segregation- each individual has two alleles for each trait, these separate during gamete formate Law of independent assortment- genes for different traits assort independently of one another during gamete formation Law of dominance- one of the pairs of inherited traits will be dominant and the others recessive unless both the factors are recessive Miosis Mutations Duplication- a section of the chromosome is copied and inserted into the genome Deletion- a section of the chromosome is lost or deleted inversion- a section if the chromosome breaks off, flips around and reattaches in the reverse order Translocation- section of one chromosome breaks off and reattaches to another chromosome Karyotypes Nondisjunction mutations homologous chromosomes don't separate so both chromosomes of the pair pass to the daughter cell. Down Syndrome- trisomy 21 (3 copies of chromosome Klinefeller syndrome- XXY ( extra X in males) Turner syndrome- monosomy ( missing X in females) Chargaff- made two important discoveries about molecules and DNA. with his discoveries, arised two important rules in genetics. Chargoff’s first rule states that the amounts of thymine and adenine are identical in any DNA molecule. His second rule states that DNA of different species differs in proportions of thymine and guanine. (discoveries of DNA’s structure and its method of replication) Franklin- used x-ray to prove that DNA is a double-helix polymer, a spiral consisting of two DNA strands wound around each other. Wilkins- provided direct evidence of the helical structure and helped them deduce the arrangement of bases within the DNA molecule double helix. Watson- molecular structure of DNA Crick- molecular structure of DNA Roles of DNA Messenger DNA -​ mRNA  -​ Starts in nucleus moves to ribosome -​ Delivers a copy of the DNA code to a ribosome -​ One the ribosome has the mRNA instructions it can then build a protein in the process of Translation Transfer DNA -​ tRNA -​ Located in the cytoplasm -​ Transfer amino acids from the cytoplasm to the ribosome -​ Ribosome will link the amino acids together to form a protein in the process translation Ribosomal DNA -​ rRNA -​ Main components of the ribosome -​ rRNA bonds with special proteins to form a ribosome -​ ribosome= organelle that builds protein Point mutations Base pair substitutions- a single nucleotide is replaced by another. This can be further categorized into: Translation- substitution of a purine for another purine (AG) or a pyrimidine for a pyrimidine (CT) Transversion- substitution of a purine for a purimidine or vise versa (AT)/(AU) and (GT)/(GC) Insertion- addition of one or more nucleotides into a segment of DNA Deletion-a section of the chromosome is lost or deleted Missense- a substitution that results in a different amino acid in the protein. This may after the proteins function, depending on the role of the affected amino acid. Nonsense- a substitution that changes a codon into a stop codon, leading to premature termination of protein synthesis that usually results in a nonfunctional protein. Neutrality- a substitution that results in an amino acid change but does not affect the protein's function. This is often because the change occurred in a less critical region of the protein or results in an amino acid with similar proteins. reading frame- the way nucleotides are grouped together into codons (sets of 3) for translation into proteins. The reading frame is critical because the insertion of deletion of a nucleotide can shift this frame. Frameshift- an insertion or deletion of one or two nucleotides (not in multiples of 3) that shifts the reading frame. This alters the entire sequence of amino acids downstream of the mutation, typically resulting in a nonfunctional protein. DNA proofreading and repair Correcting errors during DNA replication. Epigenetics Refers to the changes in gene expression that do not involve changes to the underlying DNA sequence. how your behaviors and environment can cause changes that affect the way your genes work Molecular geneticists techniques Agarose Gel Electrophoresis- a method used to separate DNA fragments based on their size. It is commonly used to analyze the results of polymerase chain reaction (building chains) check the quality of DNA, or estimate the size of DNA fragments polymerase chain reaction- a technique used to look at a specific chain of DNA. can be used for gene cloning, genetic testing and forensic analysis. DNA sequencing- the process of determining the exact order of nucleotides in a DNA molecule. DNA fingerprinting- also known as DNA proofing, is a technique used to identify individuals based on their unique DNA patterns. Using a codon wheel Use mRNA strand (bottom) Go in order: the inside of the circle to the middle and finally the outside following your sequence (CT)(AT)/(AU)(GT)/(GC) Biotechnology Selective breeding- Applications of fermentation- Genetic engineering- cloning - Gene therapy- Assistive reproduction technology - Synthetic technology- Societal pressure Food shortages- biotechnologies like GMO’s are developed to increase crop yield and food security (golden rice engineered to produce vitamin, and other necessary nutrients. Energy shortages- synthetic biology can be used to develop biofuels as alternative energy sources (algae based biofuels) Resource shortages- biotechnology can address resource scarcity, such as the development of biodegradable plastics. 3D bioprinting- uses cells and biomaterials to create tissue-like structures. These structures can be used for medical research, drug testing, and potentially creating organs for transplantation. personalized medicine- a medical model that tailors the therapeutic approach to the individual characteristics of each patient including genetic makeup, lifestyle and environment. Genetic testing/screening- testing involves analyzing DNA to identify changes or mutations that may lead to genetic disorders. Screening refers to testing a population for specific genetic conditions. Gene therapy- a technique that modifies a person's genes to treat or cure disease. Can involve adding, removing, or altering genetic material within patients cells. Recombinant DNA- combining DNA from different organisms to create new genetic combinations that are beneficial for research, medicine, agriculture and industry.( used in the production of insulin, growth hormones and GMO’s) Biofuels- renewable fuels derived from biological materials like plants or algae. They are also considered more sustainable compared to fossil fuels. Biomediation- is the use of living organisms such as bacteria, fungi or plants, to remove or neutralize contaminations from a polluted environment. Ethics ^ real life situations Human Genome Project HGP was an international research effort aimed at mapping and understanding all of the genes of the human species. Goals of the project were to identify all of the genes in human DNA. sequences of the 3 billion chemical base pairs. Importance 1.​ The collaborative nature of HGP 2.​ Impact on science and medicine 3.​ Ethical, legal and social implications Meiosis Meiosis I Prophase I The nuclear envelope disintegrates. Chromosomes begin to condense. Spindle fibres appear. Prometaphase II Spindle fibres attach to the chromosomes at the centromere. Metaphase I The homologous chromosomes align at the equatorial plate ensuring genetic diversity among offspring. Anaphase I The homologous chromosomes are pulled towards the opposite poles. Telophase I Spindle fibres disappear. Nuclear envelope is reformed. Cytokinesis I The cytoplasm and the cell division result in 2 non-identical haploid daughter cells. Meiosis II Prophase II The chromatin condenses into chromosomes. Nuclear envelope disintegrates. Centrosomes migrate to either poles. Spindle fibres are reformed. Metaphase II The chromosomes align along the equatorial plate. On the contrary, the chromosomes in metaphase I were in homologous pairs. Anaphase II Sister chromatids are pulled to the opposite poles. Telophase II Nuclear envelope redevelops and the spindle fibres disappear. Cytokinesis II The cytoplasm and cell divide producing 4 non-identical haploid daughter cells.