bio - genetics (3)

• Asexual reproduction produces new organisms from one parent only, which are genetically identical to the parent.
• The advantages of asexual reproduction include its ability to produce lots of offspring very quickly and its requirement of only one parent.
• The disadvantages of asexual reproduction include the lack of genetic variation between offspring in the population and the need for organisms to reproduce when conditions are favourable.
• Rarely, a single mutation will significantly affect the phenotype.
• Sexual reproduction involves the combination of genetic information from two organisms to produce offspring, which are genetically different from parents.
• The advantages of sexual reproduction include the creation of genetic variation within the population and the production of genetically different haploid gametes.
• The disadvantages of sexual reproduction include the need for two parents and the fact that it takes more time and energy than asexual reproduction, hence producing fewer offspring.
• Meiosis is a form of cell division in which one parent cell produces four haploid daughter cells.
• DNA strands are polymers made up of nucleotides, which consist of a sugar, a phosphate group and one "base".
• A DNA molecule is coiled together in the shape of a double helix, with each base linking to the corresponding base from the opposite direction strand in the helix.
• Complimentary Base Pairing is when A pairs with T and C pairs with G.
• The genome is the entirety of an organism's DNA.
• It is possible to extract DNA from fruit using household ingredients: gently mix together 50ml cold water, half a teaspoon of salt and 10ml washing up liquid, heat this mixture at 50C for 5-10 minutes, add the solution to a kiwi, filter using a few sheets of kitchen paper and a sieve, pour the filtrate into a test tube, add 10ml of pineapple juice to the filtrate and allow to rest for a few minutes, add 2 teaspoons of cold ethanol to the solution and wait 10 minutes.
• DNA controls the production of proteins in a cell, proteins are made up of a chain called amino acids, the chains fold up to give the protein a different specific shape - hence they each have a different function, a gene is a section of DNA on a chromosome that codes for a particular protein, all of an organism's DNA makes up its genome, each amino acid is coded by a sequence of 3 bases known as base triplet, the amino acids join to make proteins, the different sequences of bases allows it to code for specific proteins, there are two stages in protein production: Transcription and Translation
• Transcription involves RNA polymerase binding to region of non-coding DNA in front of a gene, the two DNA strands unzip and the RNA polymerase moves along one of the strands of the DNA, it uses the coding DNA in the gene as a template to make the mRNA, base pairing between DNA and RNA ensures that the mRNA is complementary, the mRNA leaves the nucleus and joins with a ribosome.
• Translation involves the mRNA joining with a ribosome, the ribosome translates the mRNA into a sequence of amino acids, the amino acids join to make proteins, the different sequences of bases allows it to code for specific proteins.
• The enzyme RNA polymerase binds to non-coding DNA, and a change in the order of bases in this non-coding DNA can affect the amount of RNA polymerase that can bind to it.
• A base is substituted, which may change one amino acid in the sequence or may not change the amino acid, as the new sequence can sometimes still code for the same amino acid.
• Mendel in his garden cross bred his plants and recognised that characteristics could be passed down in the generations.
• A dominant allele only needs one copy to be expressed, while a recessive allele needs two copies to be expressed.
• Mutations change the sequences of bases in DNA.
• Coding DNA: A genetic variant will alter the sequence of bases and therefore will change the sequence of amino acids, altering the final structure of the protein produced.
• The tRNA have anticodons which is complementary to the codons.
• Alleles lead to differences in inherited characteristics because different alleles code for different forms of the same protein, an allele that codes for a damaged form of a protein can cause illness.
• If less RNA polymerase is able to bind, less mRNA can be formed, and the structure of the final protein is affected.
• Scientists argued that if the factors could not be changed when a species would not change (evolve ), which contradicted Darwin's theory of evolution.
• Genetic variants can affect the structure of proteins in different ways, depending on whether they occur in coding DNA or non-coding DNA.
• A zygote is the stage of development immediately after fertilisation - a diploid cell formed from the fusion of two haploid gametes.
• The amino acids are joined together by the ribosome, making a polypeptide.
• Genotype is the combination of alleles an individual has, while phenotype is the physical characteristics that are observed in the individual, such as eye colour.
• Amino acids are brought to the ribosome by another molecule called tRNA (transfer RNA).
• Genetic variants are small changes in the order of bases that make up a strand of DNA.
• Non-Coding DNA: A genetic variant in the coding DNA can affect phenotype differently.
• A base is inserted into the code, changing the way it is read and potentially altering all the amino acids coded for after this insertion.
• A base is deleted from the code, changing the way it is read and potentially altering all the amino acids coded for after this deletion.
• Monohybrid inheritance is the inheritance of a single characteristic.
• Mendel said that many factors were the cause of this, which scientists initially rejected as they could not explain how " factors " could explain the many variations in characteristics such as the human eye colour.
• The order of the amino acids matches the base triplets in mRNA (which can be known as codons).
• Homozygous refers to when both inherited alleles are the same, while heterozygous refers to when one of the inherited alleles is dominant and the other is recessive.
• Alleles are different forms of a gene, humans have two alleles – they inherit one from each parent.