Genetic info, variation and relationships between organisms

• DNA is a stable molecule that has strong phosphate bonds and is double stranded
• genes are strands of DNA that contain info for polypeptides
• genes combine to make proteins these determine the characteristics of an organism
• the sequence of bases on a gene determines which amino acids will be added together to form a protein
• a codon is three consecutive nucleotide base pairs that code for one specific amino acid
• each codon codes for only one amino acid
• an allele is an alternative form of the same gene
• organisms gain one allele from each parent
• degenerate code is when one codon codes for a few amino acids
• universal code means one codon codes for the same amino acid in all organisms
• there are 20 different amino acids but there are 64 possible combinations of bases so not every combination can be used to make proteins
• an intron is a non coding region
• an exon is the coding region
• transcription is when RNA polymerase reads the template strand which creates a complementary mRNA strand
• when transcription takes place the thymine gets replaced by uracil
• splicing is when introns are removed from the pre-mRNA and the remaining mRNA is spliced together
• tRNA has an anticodon that matches with the codons on the mRNA
• translation is where ribosomes read the codons on the mRNA and link them with tRNAs that have matching anticodons
• translation is when the sequence of bases in the mRNA determines the sequence of amino acids in the protein
• the genetic code is universal because it uses the same set of rules across all species
• a mutation is any change in the nucleotide sequence of DNA or RNA
• tRNA is specific as each type carries a specific amino acid to the ribosome
• a mutation is a permanent change to the DNA sequence of an organism
• point mutations are when a single nucleotide is changed in the DNA sequence
• the different types of point mutations are miscopying, substitution and 'nonsense mutations'
• nonsense mutations are mutations that result in a stop codon being read
• the different types of chromosomal mutations are inversion, deletion, duplication, translocation
• inversion mutation is when a segment of DNA is inverted, resulting in a frameshift
• translocation mutation is when a gene is moved from one chromosome to another
• deletion mutation is when a section of DNA is lost from the genome this can be a base or a whole section
• duplication mutation is when part of the DNA is copied and then inserted into the genome
• mutations can happen spontaneously or be caused by radiation or chemicals
• the first step of meiosis is when homologous chromosomes pair up and wrap around each other this is where crossing over happens
• crossing over is when homologous chromosomes exchange genetic material during meiosis
• the second stage of meiosis is when chromatids move apart and 4 cells are formed
• variation happens due to independent segregation of homologous pairs and crossing over
• crossing over happens when tension is created due to the twisting together of chromatids which causes portions to break off and then recombine
• genetic diversity is the total number of different alleles in a population of a species
• the first stage of natural selection is that populations must have genetic variation
• the second stage of natural selection is that different reproductive success happens between different phenotypes