lecture 16 - how are we different? Flashcards
What are Mendel’s 3 Laws of Inheritance?
Segregation, Independent Assortment, Dominance
What is the Law of Segregation?
When gametes form, alleles are seperate so that each gamete carries only one allele for each gene, one from each parent
What is the Law of Independent Assortment?
The segregation of alleles for one gene occurs independently to that of any other gene (though this is not true for genes on the same chromosome)
What is meiotic recombination?
When parts of homologous chromosomes combine to form new chromosomes with alleles from both.
What is genetic linkage?
A principle whereby the closer 2 genes are on a chromosome, the less likely they are to be recombined onto different chromosomes. You are more likely to have both genes rather than just 1
What is the Law of Dominance?
Some genes are dominant while others are recessive. An organism with at least one dominant allele will express the dominant.
Do recessive alleles encode functional proteins?
No - the protein has a different sequence, which often results in loss of fucntion
How is phenylalanine breakdown influenced by genes?
Mutations to certain genes means that the proteins required for steps in phenylalanine breakdown do not work, leading to accumulation of phenylalanine or other steps in the process (e.g. tyrosine)
What is the genetic condition caused by the inability to break down phenylalanine?
PKU - phenylketonuria
What are the symptoms of phenylketonuria?
Intellectual disability, seizures, behavioural/mental problems,
How can environmental factors influence phenotype of individuals with PKU?
Eating a low phenylalanine diet can reduce symptoms
How can genetics further influence phenotype in individuals with PKU?
genetic variation alters the efficiency of the phenylalanine transporter across the blood-brain barrier, meaning some people have less cumulative of Phe in the brain
What is translation?
The process in which mRNA is used by a ribosome to produce polypeptide chains
What are the 3 steps of translation?
initiation, elongation, termination
What are the 3 key types of single amino acid mutations?
substitution, deletion, insertion
What is a substitution mutation?
Change of one amino acid, resulting in a point mutation
What is a deletion mutation?
Loss of one amino acid, resulting in a frameshift mutation
What is an insertion mutation?
Insertion of an amino acid into the sequence, resulting in frameshift mutation
What elements are required for PCR?
DNA nucleotides, DNA from cells, Primers specific to the gene being isolated, Taq DNA polymerase
What does PCR stand for?
Polymerase Chain Reaction
What are the steps in PCR?
Heat DNA to 95C to seperate DNA strands, Cool to 60C to anneal/pair the primers to the DNA sequence. heat to 72 to allow Taq DNA polymerase to copy the DNA. Repeat to exponentially amplify
What temperature must DNA be heated to to seperate the strands in PCR?
95 degrees
What temperature must DNA strands be heated to to anneal with primers in PCR?
~60 degrees
What temperature must DNA be heated to to allow Taq polymerase to copy the DNA?
72 degrees
How many base pairs make up typical PCR primers?
~20 nucleotides
What technique is used to determine wild-type sequences from mutants?
Restriction enzymes are added that will only cut the DNA if a specific sequence (e.g. mutation) is present
What restriction enzyme is used to identity and cut the MODY2 mutation?
HindIII
When a restriction enzyme has been added to a sample, how can the wild type and cut mutant DNA be differentiated?
Via gel electrophoresis- differentiates molecules based on size, so normal will have one line while the mutant will have 2, representing the two pieces on either side of the cut (sometimes three if they are heterozygous)
