GENETICS Flashcards
What is gonadal mosaicism?
where more than one set of genetic information is found specifically within the gamete cells
What is non-disjunction?
Failure of homologous chromosomes or sister chromatids to separate properly
What is autosomal dominant inheritance, the chance of offspring having the condition and an example condition?
offspring to be heterozygous
huntingtons disease
What is a centromere and telomere
centromere- how chromosomes are attached to each other
attached to spindle fibre during cell division
telomere- the end of a chromosome. Telomeres are made of repetitive sequences of non-coding DNA that protect the chromosome from damage
How does meiosis produce genetically different cells?
through crossing over and independent assortment
what is a mis sense mutation
point mutation in which a single nucleotide tide change results in a codon that codes for a different amino acid
What is a non-sense mutation , and an example?
where a codon is changed to a premature stopcodon that results in a truncation of the resulting protein, can render the protein non functional
what is aneuploidy
Aneuploidy is the presence in a cell of an atypical number of chromosomes.
Stages in mitosis
Interphase dna replicates
Prophase dna condenses and formation of spindles
Metaphase chromosomes line up along the centre and spindles attach to centromeres
Anaphase chromosomes split and go to opposite poles
Telophase nuclear membrane begin to form , microfilament ring tightens
Cytokinesis two seperate daughter cells when the membrane seperates
Steps in meiosis
M1- mitosis 1
Dna replicates prophase
Crossing over for genetic diversity
Independent segregation in metaphase maternal and paternal chromosomes line up along the equator
Anaphase 1 dna is divided in 2
Telophase 2 haploid cells
Same process again but with 4 genetically different cells at the end
Define penetrance
Proportion of individuals carrying a particular variant
Variable expression
Degree in which a genotype is expressed in the phenotype
Define sex limitation
Genes that are present in both sexes but are only expressed in one gene
What is gametogenesis
Process by which diploid or haploid cells undergo cell division and differentiation to make mature haploid cells
What is a Mendelian trait
One that is controlled by a single locus in an inheritance pattern
What is the knudson hypothesis
Hypothesis that most tumor supressor genes require both alleles to be inactivated
what parts of the cell cycle are classed as interphase
g1 g2 s1
what happens in g1 s and g2
g1 organelles replicate
s dna replication
g2- preparation for mitosis,
what happens at g1 and g2 checkpoint
g1- checks dna damage pre dna repl
g2- checks dna damage after rep, damaged bases are removed
define polymorphism
Two or more variants of a particular DNA sequence
what is wild type
the normal expression of a genen
what is anticipation
eg huntingtons
wider nucleotide repeats through generations
what is autozygocity
mutation from both parents
Rules of inheritance for autosomal recessive
Appears in both sexes with equal frequency
Tends to skip a generation
more frequent in consanguineous marriages
Rules of inheritance for autosomal dominant
Does not skip generation
Male and female equally affected
Unaffected parents do not transmit the trait
X linked dominant rules
More often female than male affected
No skipping of generations
Affected sons must have an affected mother
X linked recessive rules
More males than females affected
Affected sons are born to unaffected mothers
Trait does skip generation
Never passed from father to son
Mitochondrial inheritance rules
Trait inherited from mother only
All children of mother are at risk to be affected or carriers
