Topic 1 Flashcards
Classical Genetics
inheritance of traits
“Transmission genetics” discovered by Gregor Mendel
Molecular Genetics
study of DNA & RNA structure, function, and molecular control of gene expression
Evolutionary/Population Genetics
interaction of genes and gene pools and the environment
Gene
hereditary unit of information
Gene Locus
positon of a gene on the chromosome
Allele
one of two (or more) versions of a gene that differs in sequenece and exists at the same loci
Genotype
combinations of alleles for any gene
Phenotype
observable characteristics, as determined by the genotype
Wildtype (phenotype)
most prevalent phenotype in the population under natural conditions
Mutant (phenotype)
a deviation to the wild-type phenotype as a result from an allelic change in the DNA sequence
Dominant (phenotype)
phenotype observed in heterozygous individuals (ie. genotype includes both allele variants)
Recessive (phenotype)
phenotype observed only in individuals that are homozygous for the recessive allele variant
A wild-type phenotype is produced when an organism has two copies of the ______________________, or when one copy is sufficient to meet the ____________________________.
wild-type allele; protein requirements
Loss of Function
significant decrease or complete loss of functional gene product
Gain of Function
gene product acquires a new function or expression increased above wild-type activity
Incomplete Dominance is where…
heterozygous individuals display intermediate phenotypes between either homozygous type
Codominance results when there is…
detectable expression for both alleles in the heterozygotes
Recessiveness is observed in mutations in genes that are….. The mutate allele is the …
functionally haplosufficient (+/m, where m is the mutate allele)
recessive allele
Dominance: In genes that are _________________, in a heterozygote (+/M), the single wild-type allele (+) cannot provide enough prouct for normal function. The mutated allele (M) is the ________________.
haploinsufficient
dominant allele
Nomenclature: What does upper case denote?
dominant allele
Nomenclature: What does lower case denote?
recessive allele
Nomenclature: What do slashes indicate?
alleles for genes on homologous chromosomes
Nomenclature: What do semicolons indicate?
genes on non-homologous chromosomes
What did Gregor Mendel do?
examined seven traits through crossing and selfing
What is Mendel’s 1st Law of Equal Segregation?
Half of gametes carry one member of gene pair, half carry the other member
What is a test cross?
cross use to determine the genotype of an individual that is expressing a dominant phenotype (the cross to homozygous recessive)
What are the parts of a chromosome?
telomere - ends
centromere - point between both arms
P arm - shorter arm
Q arm - longer arm
What is a metacentric chromosome?
centromere is in the centre - both arms of equal length
What is an acrocentric chromosome?
centromere is off centre - arms of different legnths
What is a telocentric chromosome?
centromere is on one end - only one arm
What does “n” refer to?
number of sets of chromosomes (not total number)
What does homogametic mean?
matching pair of sex chromsomes (ie. XX)
What does heterogametic mean?
no matching pair of sex chromosomes (ie. XY)
Sex chromosomes are…
non-autosomes
What is the test for sex linkage?
a reciprocal cross - parental cross but switches phenotypes between male and females
What does a reciprocal cross explain?
It explains the result of crosses if mutant allele was present on the X chromosomes
What is a pedigree analysis?
looking back through family trees and medical records as test crosses are not ethical for humans
- allows us to look for patterns suggesting dominance and sex-linkage
What is a propositus?
first member of the family who comes to the attention of a geneticist (usually has a disease)
What are the characteristics of an autosomal recessive pedigree?
- disease shows up from unaffected parents (heterozygous - hence carriers of the recessive allele)
- if both parents have the trait, all children will have it
- males and females have equal likelihood of showing the trait, although totals might not be equal
What are the characteristics of an autosomal dominant pedigree?
- no skipping of generations occurs – each affected individual MUST have at least one affected parent
- both males and females can transmit mutant allele to both sons and daughters with equal probability
- two affected parents CAN produce unaffected children, but two unaffected parents CANNOT have affected children
