Genetic/ Geonomics Flashcards
What is a mutation?
- this is a permanent change in the sequence of DNA
- Mutations in gene 🧬Exon’s (regulatory elements) = if in non-coding regions.
- Caused by external (exogenous) or endogenous (nature) factors.
What are exogenous factors?
- Environmental factors such as sunlight, radiation and smoking
What are endogenous factors?
Errors during DNA 🧬 replication or toxic by products of cellular metabolism
What is point mutation?
A single base change in DNA 🧬 sequence a point mutation may be silent missense or nonsense
Example
CGTA a TCCTCGE
CGTA g TCCTCGE
What is silent mutation?
- This is a change in the genetic sequence thar does not change the protein sequence. This can occur because of redundancy in the genetic code where an amino acid may be encoded for by multiple codons
Example
TTC (PHE) TGt (CYS) AGT (SER) GGT (GLY)
TTC (PHE) TGc (CYS) AGT (SER) GGT (GLY)
Mutagens may be of physical, chemical or biological origin
What is a physical mutation?
- This is ionising radiation (x rays, Gamma rays and alpha particles) it causes DNA 🧬 breakages
- UV light also causes error in replication
Mutagens may be of physical, chemical or biological origin
What ate chemical mutagens?
- Chemicals interact directly with DNA or through the metabolic process in cells they produces mutagenic compounds
What is a missense mutation?
- A change in DNA base pair resulting in substitution of amino acids for another in the protein
For instance
Glutamine and Arginine are replaced/ substituted by a stop codon
What is a nonsense mutation (stop codon)?
This is a change in one DNA base pair the altered DNA sequence prematurely signals the cell to sto building protein
- This type of mutation results in a shortened protein that may function improperly or not at all
What is duplication?
- This consists of a piece of DNA that is abnormally copied one or more times
- This type of mutation may alter function of the resulting protein
What is frameshift mutation
- This changes the amino acids sequences from the site of mutation
- It is the addition or loss of DNA bases changing a genes reading frame
- A reading frame consists of 3 bases that each code for one amino acid ,
- Frameshift mutation shifts these bases and changes the code for the amino acid.
- The resulting protein is usually non- functional
- INsetion, deletion and duplication can all be frameshift mutations
What is a repeated trinucleotide?
- This adds a series do the amino acid glutamine to the resulting protein
- Nucleotide repeats are short DNA sequences that are repeated a number of times in a row
- A repeat expansion is a mutation that increases the number of times that the short DNA 🧬 sequence is repeated
- This type of mutation can cause the resulting protein to function improperly
E.g = Huntington’s disease
Facts about turners syndrome…GO
- Absence of Y chromosome/ dysfunctional SRY on the Y chromosome and therefore will develop into a female child
- 1 in 2500
- About 10% of the total number of miscarriages and still birth
- A female with turners syndrome has XO instead of XX
- Women with this condition are sterile
How do you conduct a genetic assessment/ what are the key areas if assessment?
- Age = The older the child bearer is the higher the chance of the baby developing downs
- Culture = Diabetes is common amount Asian people
- Gender = Prostate chancer doesn’t occur in women
- Race = Sickle cell disease in black African people
- Chemicals = e.g drugs
- Lifestyle = e.g smoking
- Family history = Inheritable diseases e.g Down’s syndrome
- Miscarriages =. Could be a reason as to why someone cant conceive
- Pregnancy history = Are you not getting pregnant because of lack of ovulation
- Employment history
Why is taking a genetic family history important?
- The genetic family history can reveal patterns of inheritance
- The genetic family history may help make to refine a diagnosis
- Helps assess the likelihood of the genetic disease in relatives
- The genetic family history can affect the testing treatment and management strategies
- The genetic family history may highlight the need for referral for specialist opinion
- Taking the genetic family history helps in building a rapport with the patient
