Genetics Flashcards
Karyotype
picture of an individuals 23 pairs of chromosomes
How many autoosomal chromosomes pairs do we have?
22
acro-centric chromosome
centromere is closer to the head of the chromosome than the bottom, chromosomes 13, 14, 15, 21, and 22
2 alleles for eye color
dominant (brown)/recessive (blue)
what is the area of crossing over between homologous chromosomes called?
chiasma
In which phase of meiosis does crossing over occur?
prophase I
disjuction
when sister chromatids separate during Meiosis II
when do alleles for a single gene separate?
anaphase I (mendel’s 1st law)
what is mendel’s 2nd law?
independent assortment - gametes get one maternal or paternal chromosome (though he did not understand linkage- so law is true unless alleles are linked)
incomplete dominanace
heterozygous exhibit intermediate phenotype
penetrance
proportion of individuals in a population with a genotype, who actually express the phenotype
expressitivity
the degree to which an individual expresses a given genotype as a phenotype
mutagens
things that cause mutations - chemicals (free radicals, carcinogens), ionizing radiation (xrays, UV light), spontaneous mutation
point mutation
one nucleotide is swapped for another
silent - no amino acid change, no affect on protein (usually the 3rd base - wobble, in intron or junk DNA)
missense - 2nd base is swapped, changes one amino acid (if amino acids are similar, may not affect protein)
nonsense - creation of a stop codon, severely alters protein
frameshift mutatin
insert or delete a nucleotide
changes from entire reading frame from mutation foreward - every AA after that is different from original
severely affects protein
chromosomal mutations
large parts of the chromosome are affected - can get rid of, duplicate, or invert sections of the chromosome.
some involve multiple chromosomes
insertion - DNA is moved from one chrom to another
translocation
DNA from one chromosome is swapped with DNA from another
nondisjunction
chromosomes fail to separate
ex: turner syndrome monosomy X, klinefelter syndrome trisomy XXY, down syndrome trisomy 21
How can yo tell if a trait is dominant?
parents exhibit trait, any # of children do not
how can you tell if a trait is X-linked recessive?
affects only or mostly males, parents may not show the trait but offspring do
codominance
multiple traits are expressed
Incomplete dominance
the trait is a combination from the two alleles
point mutation
replaces a single nucleotide with a different nucleotide
missense mutation
changes a codon to encode a different amino acid
nonsense mutation
changes a codon to a stop condon
frameshift mutation
inserts or deletes a nucleotide; shifts the sequence, affecting all subsequent codons
In a familial genetic tree, what type of trait is indicated by two unaffected parents having two affected children?
autosomal recessive - parents are both carriers, but neither of their children are affected
In a familial genetic tree, what type of trait is indicated by two affected parents having two unaffected children?
autosomal dominant - both parents are heterozygotes, yet they express the trait/disease
How does gene regulation work in prokaryotes?
Either inducible system or repressible system.
inducible: repressor is bound to the operator site unless an inducer inhibits it and RNA polymerase is allowed to transcribe the genes. (positive feedback)
repressible: regulator is non-functional unless a corepressor binds with it to stop transcription (negative feedback)
