Genetics - Mutations Flashcards
What are the three types of chromosomal abnormalities?
Numerical
Structural
Mutational
What are numerical chromosomal abnormalities?
They are disorders in which whole chromosomes are missing or extra to the normal pair
What are structural chromosomal abnormalities?
They are disorders in which a part of an individual chromosome is missing, added or switched to another chromosome
What are the four subtypes of structural abnormalities?
Translocations
Deletions
Insertions
Inversions
What are the two types of chromosomal translocations?
Reciprocal
Robertsonian
What are reciprocal translocations?
It involve breaks in two chromosomes with formation of two new derivative chromosomes
What are the two types of reciprocal translocations?
Balanced
Unbalanced
What are balanced reciprocal translocations?
They are when the exchange of genetic material between the two chromosomes is equal, with no genetic information extra or missing
This means that full functionality is still achieved, and the individual is simply a carrier
What are unbalanced reciprocal translocations?
They are when the exchange of genetic material between the two chromosomes is uneven, with extra or missing genes resulting
This means that one chromosome will have partial trisomy (extra information) and another will have partial monosomy (missing information)
What are Robertsonian translocations?
It is a form of chromosomal rearrangement where the participating chromosomes break at their centromeres and the long arms fuse to form a single, large chromosome with a single centromere.
Is genetic material lost in Robertsonian translocations?
No
What are deletion chromosomal abnormalities?
This is the deletion of one or more nucleotide base pairs in a DNA sequence
What are the two types of chromosomal deletions?
Terminal
Interstitial
What is a terminal chromosomal deletion?
This is the loss of the end of a chromosome
What is an interstitial chromosome deletion?
This is the loss of the middle of a chromosome
What is an insertion chromosomal abnormality?
This is when a one or more nucleotide base pairs is added into a DNA sequence
What is an inversion chromosomal abnormality?
This is when a segment of chromosome is reversed end to end
This occurs when a single chromosome undergoes breakage and rearrangement within itself
What are the two types of chromosomal inversions?
Paracentric
Pericentric
What are paracentric chromosomal inversions?
They do not include the centromere and both breaks occur in one arm of the chromosome
What are pericentric chromosomal inversions?
They include the centromere and there is a break point in each arm
It results in balanced rearrangements as no genetic material is added or lost
What is the mechanism of chromosomal abnormalities?
Non-disjunction
What is nondisjunction?
It is the failure of homologous chromosomes or sister chromatids to separate properly during cell division (meiosis)
What occurs when nondisjunction occurs during anaphase I of meiosis I?
This means that at least one pair of the homologous chromosomes did not separate
This results in two cells that have an extra copy of one chromosome and two cells that are missing the chromosome
What occurs when nondisjunction occurs during anaphase II of meiosis II?
This means that at least one pair of sister chromatids did not separate
This results in two cells that have the normal haploid number of chromosomes
However, one cell will have an extra chromosome and one will be missing a chromosome.
What are autosomal aneuploidy syndromes?
They refer to all abnormalities that do not involve the sex chromosomes
Name three autosomal aneuploidy syndromes
Down’s syndrome
Patau syndrome
Edward’s syndrome
What are sex chromosome aneuploidy syndromes?
They refer to all abnormalities that involve the sex chromosomes
Name two sex chromosome aneuploidy syndromes
Turner’s syndrome
Klinfleter’s syndrome
What are germline gene mutations?
A gene mutation affecting germ cells
Can gremline gene mutations be passed onto offspring?
Yes
What are somatic gene mutations?
A gene mutations affecting somatic cells
Can somatic gene mutations be passed onto offspring?
No
What are non-coding gene mutations?
These are mutations that arise in non-coding DNA sequences
These are components of an organism’s DNA that do not encode protein sequences
What are coding mutations?
These are mutations that arise in coding DNA sequences, which are components of an organism’s DNA that encode protein sequences
What are the four types of coding mutations?
Silent
Missense
Nonsense
Frameshift
What are silent gene mutations? Give an example
They are mutations in DNA that do not have an observable effect on the organism’s phenotype
For example, CGA (Arg) to CGC (Arg)
What are missense gene mutations? Give an example
They are mutations in DNA that change a single nucleotide base
This causes the substitution of a different amino acid in the resulting protein
For example, CGA (Arg) to GGA (Gly)
What are the three potential affects of missense gene mutations?
No effect
It may cause the protein to have a different function
It may cause the protein to have no function at all
What are nonsense gene mutations? Give an example
They are mutations in DNA that cause substitution of a nucleotide with a stop codon - where previously there was a codon that coded for an amino acid
For example, CGA (Arg) to TGA (stop codon)
What is the effect of nonsense gene mutations?
The production of a shortened, likely non-functional protein
What are frameshift gene mutations? Give an example
This is a mutation caused by insertions or deletions of a number of nucleotides in a DNA sequence
.For example, CGA (Arg) to CCG A… (Pro)
What is the effect of frameshift gene mutations?
These insertions and deletions will affect the whole DNA sequence after the mutation, as it will result in the sequence shifting to forward or backwards so that each codon is read differently
