genetics Flashcards
gregor mendel
In school bright but not successful
Financial difficulties lead to joining the monastery in Moravia (Czech) (1840s)
1860s published his genetic theories
Not thought important until rediscovered in the early 1900s
mendel’s contributions
Discrete physical unit responsible for each trait
Passed from parent to offspring and through generations
Passage determined by mathematical laws
Trait doesn’t disappear if it’s not shown
mendel’s reasons for success
Followed progress of hybrids through a number of generations
Selected plants that possessed contrasting characteristics
Used a large number of plants
mendel’s experiments
Hypothesized that green trait not lost or altered
Yellow trait simply dominant and green trait recessive
principle of segrigation
Genes occur in pairs. During the production of gametes, the pair is separated and each gamete contains only one of the pair
principle of independent assortment
Distribution of one pair of genes does not influence the distribution of other pairs of genes
gene
Entire sequence that codes for a protein
mitosis
Normal cell division Results in 2 daughter cells identical to the mother cell Growth of organism Replace old cells Occurs only in somatic cells
meiosis
Reduction division
Preparation of DNA for transmission to the offspring
Results in the formation of gametes
meiosis functions
Diploid becomes haploid
Combination of mother’s and father’s genetic material
Recombination and crossing over
Transmission of mother’s mtDNA
replication of dna
Two strands unwind
Strands separate
2 single strands attract free DNA nucleotides
Result is 2 identical double strands of DNA
Transcription
Two strands of DNA unzip
One strand of DNA attracts RNA
RNA copies the DNA in complimentary form (mRNA)
Translation
mRNA migrates out of the nucleus
mRNA is attracted to a string of ribosomes (rRNA)
Ribosome moves along the mRNA strand “reading” the genetic message
tRNA is attracted via the ribosome who brings with it the anticodon
Chain of amino acids is formed
proteins
Structural components Enzymes (chemical reactions) Hormones Direct and perform all physiological and cellular functions “Genes” code for proteins
codominence
both traits are present and distinguishable
incomplete dominance
traits blend together
polygenetic inheritence
Many genes code for the same thing
Continuous traits
Influenced by alleles at two or more loci, each make a contribution to the phenotype
Genetic and environmental factors
Many polygenic traits influenced by environmental conditions
pleiotropy
One trait codes for many things
Several seemingly unrelated phenotypic effects are influenced by the action of a single gene
Evolution is a two stage process
Production and redistribution of variation
Natural selection acting on the variation differentially affect successful reproduction
modern synthesis
Until 1930’s either mutation or natural selection was viewed as the prime mover of evolutionary change
mutation
Molecular alteration in genetic material
To be evolutionary significant must occur in sex cells
Only way to produce new genetic variation
gene flow
Exchange of genes between populations
genetic drift
Random factor in evolution directly tied to population size
Some individuals can contribute a disproportionate share to genes to succeeding generations
Founder effect
founder effect
A few members of on population start a new population with different allele frequencies than the original
recombination
Both parents contribute genes to offspring so genetic information is reshuffled
Does not change allele frequencies but does produce new genetic combinations for natural selection to act on
four causes of evolution
natural selection
mutation
gene flow
genetic drift
