W1 Classic Mendelian Genetics 1 Flashcards
Who is Gregor Mendel?
An Austrian who experimented with pea plants and correctly argued that parents pass on heritable factors - mendelian genetics
what is a character?
a heritable factor that varies between individuals (seed colour, seed shape, flower colour)
what is a trait?
the variations within a character (yellow or green seeds, round or wrinkled shape)
what is true-breeding?
self-fertilisation producing identical offspring to the parent (true-breeding parents = P generation)
what is a hybrid?
offspring of two different varieties ( called the F1 generation)
what is a cross?
fertilisation between two different individuals, between two F1 individuals (producing an F2 generation)
what is a heritable factor now known as?
a gene
what is the unit of genetic inheritance?
alleles, you get one allele from each parent which can be the same or different (homozygous = same, heterozygous = different)
what is the difference between a dominant and recessive allele?
a dominant is always expressed, a recessive is not expressed unless there is no dominant allele present
what is the idea/law of segregation?
alleles are separated/segregated randomly during gamete formation
what is independent assortment?
segregating pairs of alleles assort independently of each other
what are Mendels four postulates of genetics?
1 - unit of genetic inheritance
2 - dominance/recessiveness
3 - segregation
4 - independent assortment
What is an allele?
an alternative version of genes that account for variations in inherited characters
what is a gene?
a DNA segment that contains the regulatory and coding sequences for expression of the gene product
what does a gene encode?
an RNA transcript (may have its own biological activity)
what does a gene reside?
at a specific locus on a specific chromosome
what is a ‘wildtype’?
the more common allele / major allele (less common one is called minor allele)
how many alleles does an individual inherit from each parent for each character?
only one allele
if two alleles at a particular locus are identical what is this due to?
true-breeding from the P generation
if the alleles are different how many traits are visible?
only one
which type of allele determines phenotype?
the dominant allele
at what stage do the two alleles for a gene separate?
during gamete formation (end up in different gametes)
what does the segregation of alleles correspond to?
the distribution of homologous chromosomes to different gametes in meiosis
all cells except gametes have homologous pairs of chromosomes so they are diploid or haploid?
diploid
gametes have only a single copy of each chromosome so they are diploid or haploid?
haploid
at what stage of meiosis does recombination (crossing over) take place between homologous chromosomes?
during prophase 1 of meiosis
are alleles that are closer together or further apart more likely to become separated during crossing over?
ones that are further apart are more likely to separate
after crossing over are the homologous chromosomes separated into different or the same combinations in the gametes?
different
what is the definition of heritabilty (H2)?
the proportion of the variation in a population that is attributable to genetic differences
what is the calculation for heritabilty (H2)?
genetic variance / (genetic variance + phenotypic variance)
what is selective breeding?
only using males and females for breeding that have passed a certain quality criteria
what is the goal of selective breeding?
to genetically improve the heritable qualities of a population in a certain direction e.g. more muscle, higher milk yield
what is genotype?
the assortments of alleles an individual has (complete heritable genetic identity)
what is a phenotype?
the physical expression of the genes an individual has
what is complete dominance?
when phenotypes of the heterozygote and dominant homozygote are identical
what is incomplete dominance?
when the phenotype of F1 hybrids is somewhere between the two parents varieties (an intermediate phenotype)
what is codominance?
when two dominant alleles affect the phenotype in separate distinguishable ways
what is pleiotropy?
genes that have multiple but unrelated (e.g. colour and eye shape) phenotypic effects
what is epistasis?
when a gene at one locus influences the phenotypic expression of a gene at a second locus (e.g. coat colour is determined by two genes)
