Inheritance 1 Flashcards
What are the three generally recognised major classes of mutational change?
point mutations, transposable elements, chromosomal mutations (different morphology e.g plumage variations)
Which of the following lists include phenomena that are NOT likely to have been important mechanisms of major genome evolutionary change?
Exon shuffling and point mutations.
What is a phenotype?
Phenotype = the outward, physical manifestation of an organism’s genetic code
What is a character?
A character = a heritable feature (e.g. flower colour)
What is a trait?
A trait = a variant of each character (e.g. purple or white)
What is a genotype?
Genotype = the coded, inheritable information in an organism’s DNA
What is an allele?
An allele is one specific form of a gene that differs from other alleles by one or a few bases only and occupies the same locus (site/location) as other alleles of the gene
Explain the different kinds of alleles
Organisms can be homozygous at a locus (alleles both the same) AA or aa or heterozygous (two different alleles) e.g. Aa
Alleles can be dominant (A) or recessive (a)
More than 2 alleles can be present for one locus in the population, but only 2 alleles can be present at any one locus in any diploid individual
Explain in diploids
Each sperm or egg is haploid which can carry only one allele
heterozygotes (Aa) produce two gamete types
homozygotes (AA, or aa) produce only one
What is a monohybrid cross?
Finding only one [mono] character. (Using a Punnett square).
What was Mendel’s law of segregation?
The two alleles at any one locus in a diploid individual separate (segregate) during gamete formation. Each one has equal probability of being included in the resulting gametes (50%).
What is Mendel’s law of independent assortment?
each pair of alleles at any one locus segregates independently of other pairs of alleles at other loci
Reasons for why Mendelian’s rules don’t seem right?
*Codominance=Codominance is a heterozygous condition in which both alleles at a gene locus are fully expressed in the phenotype.
*Incomplete Dominance=A form of Gene interaction in which both alleles of a gene at a locus are partially expressed, often resulting in an intermediate or different phenotype.
*Lethal Gene - a gene where particular allele combinations lead to the death of an individual; can be either dominant or recessive
*Pleiotropic genes – those that have >1 distinguishable effect (more than one effect on the phenotypes)
*sex linkage- traits that are linked with a sex chromosome (e.g males and females will differ)
*epistatic genes (epistasis)= The expression of one gene is modified (e.g masked, inhibited or suppressed) by the expression of one or more other genes. Known as inhibiting genes.
