Neurogenetics Flashcards
what is a pecometre?
trillionths of a metre
how many pairs of nucleotides are in one’s genetic code?
3 billion
what is a genome?
someone’s genetic code
what are the building blocks of proteins?
methionine?
what are the building blocks of genetic code?
nucleotides or bases
what are the 4 different bases in DNA?
adenine, cytosine, guanine, and thymine
what are amino acids/what do they do?
they are the building blocks of proteins
what happens to proteins?
they are encoded by one’s genetic code
what constitutes the genetic code for a particular amino acid?
a specific sequence of 3 building blocks
what is gene transcription?
the gene is read out into a protein
how many bases are in the whole human genome?
3 billion
how many genes in a human code for proteins?
20-25 thousand
how do genes always pair?
cytosine always with guanine C-G
adenine always with thymine A-T
t or f, the dna helix is double stranded ?
true
What is dna bundled into in cells?
chromosomes
how many chromosomes does the human karyotype consist of? what is the make up?
46
22 pairs of autosomal chromosomes
two sex chromosomes
XX sex chromosomes are….
female
what determines how proteins interact with other proteins in the body?
how the proteins are folded
the function of a protein is determined by what?
its structure
what is the structure of a protein determined by?
its sequence of amino acids
an amino acid is represented in the genetic code by what?
a sequence of three bases
what is a sequence of 3 bases called?
a codon
true of false, each amino acid has only one codon that can represent it
false
t or f, a change to a single base in a codon cannot change an amino acid
false
what codons represent alanine, name 4
GCT, GCC, GCA and GCG
t or f, changing the amino acid cannot change the structure and function of the protein
false
what is a single nucleotide polymorphism
a position on the genome where the base differs between individuals or between chromosomes within same individuals
what are the alternative bases of an SNP called?
alleles
what is an individual’s genotype at a SNP determined by?
the two alleles on the two copies of the chromosome
what is a phenotype
the presence, absence or value of a trait of interest
what are the 4 types of structural genetic variants?
insertion - deletion
- block substitution
- inversion
- copy number
what happens to bases in an insertion deletion variant?
bases are added or are missing
what happens to bases in an block-substitution variant?
multiple bases are substituted
what happens to bases in an inversion variant?
bases are replaced with the reversed sequence from the other stand
what happens to bases in a copy number variant?
sequence of bases are repeated one or more times
what is a mutation?
something that is rare (less than 1% of alleles in pop)
what is a polymorphism?
something that is common (more than 1% of alleles in pop)
where does the gene XIST live
on the X chromosome
to avoid excess dosage of x chromosome proteins in females, what happens?
one copy of the x chromosome in each cell is silenced or inactivated
in many mammals, the process of silencing one x chromosome in each cell is random, true or false
true
what is an RNA transcript?
an intermediate step in the process of converting a gene encoded in DNA to a protein
what functionally happens when two x chromosomes are in one cell?
XIST gene produces RNA transcript that coats one chromosome, which is then inactivated
what is a barr body?
an inactive chromosome
what does TSIX do ?
produces RNA transcript that suppresses transcription of XIST
what are antisense partners?
encoded by same stretch of DNA but transcribed in opposite directions
what is the classical equation in heritability?
what do all terms refer to?
P = G + E p = phenotypic variance G = variance from Genes E = variance from environment
what is missing from classical heritability equation?
variance from gene and environment interaction
and covariance between genes and environment
what is covariance between genes and environment?
how some genetic variance are more likely to exist in certain environments
what is heritability?
it is the proportion of phenotypic variability that can be attributed to variance from genes
what are two key things about heritability?
that it is an estimate of a specific population at a specific time
before molecular genetics, how did we measure heritability?
genetic epidemiology
what does genetic epidemiology rely on?
the fact that related individuals share a predictable amount of genetic material
what are concordance rates?
if one twin has a trait, does the other twin possess it?
what are MZ twins, what are DZ twins?
how much genetic inheritance is shared ?
MZ = monozygotic = 100% DZ = dizygotic = about 50%
what do dominant traits require for expression of the phenotype?
mutation on one copy of the chromosome
what do recessive traits require for expression of the phenotype?
mutation on both copies of the chromosome
exception, male sex chromosome as there is only one
what can be inferred from a pedigree chart?
modes of inheritance
how are males v females and affected v unaffected represented in pedigrees?
filled in circle = affected female
outlined circle = unaffected female
filled in square = affected male
outlined square = unaffected male
what bases repeat in the FMRI protein?
CCG
what triggers a process of methylation?
the large increase of the CCG repeat in the FMRI protein
what is FMRI essential to?
the strength and capabilities of synapse
also its plasticity
what is fragile x syndrome?
a monogenic disorder that results from a copy number variant in the 5 untranslated region of the FMRI gene
what is a monogenic disorder?
a disorder that can be trace to a single gene
what does the 5 untranslated region of a gene contain?
the promoter region where chemicals bind to start the process of transcribing a gene into a protein
what are the 4 quadrants of modes inheritance using pedigree maps?
dominant - recessive
autosomal - x linked
what can dominant traits not do?
cannot skip generations
in recessive traits, two affected parents cannot have unaffected offspring, t or f?
True
true or false, autosomal disorders are equally common in both sexes
true
do sons ever receive the x chromosome from their father?
no they can only receive the y chromosome
if daughter of an affected father has to be affected, what sort of trait is this?
and why is this the case?
x linked
because a daughter has to get her fathers X chromosome
what is a must of an x linked recessive trait?
father of affected daughter must be affected
x linked recessive disorders are more common in males or females?
males
what are some monogenic disorders
huntington’s and fragile x syndrome
what are polygenic disorders?
where there is no single gene that causes a certain disorder or influences cog outcomes
what do genome wide association studies examine?
the statistical association between a phenotype and many SNP markers throughout a genome
how many markers do GWAS typically look at
500,000 to 2,000,000 markers
what does linkage disequilibrium allow?
allows us to observe indirect associations, allowing us to sample common variation sparsely
