IMMS genetics Flashcards
what does giesma stain?
G banding
what does quinacrine stain?
Q banding
which way does DNA polymerase read?
3’ to 5’
what is the function of topoisomerase?
unwinds the double helix- relieves supercoiling
what does DNA ligase join?
Okazaki fragments
what is a primer?
short strand of DNA that is the starting point for DNA synthesis
why does RNA detach from DNA?
hydrogen bonds are broken as DNA has a high affinity for re-bonding with its own complementary strand
what enzyme allows peptide bonds to form between amino acids during translation?
peptidyl transferase
what is a deletion variant?
out of frame deletion causing absence of a base- disrupts the protein
what is a splice-site variant?
nucleotide changes- no longer splice receptor site, affects accurate removal of an intron, intron translated into a protein
what is a non-sense variant?
changes codon into a stop codon, out of frame deletion site
what is a mis-sense variant?
single-base substitution, results in a change in amino acid- may be pathogenic, polymorphism or no functional difference
what happens during prophase?
chromatin condenses into chromosomes, centrosomes nucleate microtubules and move to opposite poles of nucleus
what happens during prometaphase?
nuclear membrane breaks down, microtubules invade nuclear space, chromatids attach to microtubules
what happens during metaphase?
chromosomes line up along metaphase plate
what happens during anaphase?
sister chromatids separate and are pushed to opposite poles of the cell
what happens during telophase?
nuclear membranes reform, chromosomes unfold into chromatin, cytokinesis begins
what is a spermatogonia?
undifferentiated male germ cell
how does the cytoplasm divide during gametogenesis in males?
it divides evenly
how does the cytoplasm divide during gametogenesis in females?
divides unequally- 1 egg and 3 polar bodies (which apoptose)
what is Mendels second law?
the law of independent assortment states that alleles for separate traits are passed independently of one another from parents to offspring
what is gonadal mosaicism?
occurs when precursor germline cells (to ova or spermatozoa) are a mixture of 2 or more genetically different cell lines
how does incidence of gonadal mosaicism change w/ paternal age?
incidence increases- more divisions= increased probability
what are the 3 groups can diseases be characterised into and which genetic variants fall under these?
- chromosomal
- mendelian- autosomal dominant, autosomal recessive and X- linked
- non-traditional- mitochondrial, imprinting, gonadal mosaicism
key characteristics of autosomal dominant conditions
- manifests in heterozygous state
- father to son
- 50% chance
key characteristics of autosomal recessive conditions
- manifests in homozygous state
- both parents must have recessive allele
- 25% chance
- males and females affected equally
key characteristics of X-linked conditions
- pathogenic variants on X- chromosome
- if mother has it- 50% of being unaffected male, 25% affected
- if father has it- all daughters will be carriers, boys will not be
what is lyonisation?
one of the females X-chromosomes becomes inactivated
what is the dominant negative effect?
an altered gene product is produced that acts antagonistically to the wild-type allele
what is Knudsons 2 hit hypothesis?
cancer is a result of accumulated mutations to a cells DNA
what is penetrance?
percentage of individuals with a specific genotype showing the expected phenotype
what is variable expression?
variable expressivity refers to the range of signs and symptoms that can occur in different people w/ the same genetic condition
what is sex limitation?
condition inherited in AD pattern that seems tot affect one sex more than another
what is allelic heterogeneity?
situation where different mutations within the same gene result in the same clinical condition (e.g. cystic fibrosis)
what is a telomere?
region of repetitive nucleotide sequences at the ends of each chromatid, protects the end of chromosomes from deterioration or from fusion to neighbouring chromosomes
