Topic 15 Inheritance Flashcards
what do mutations form?
new alleles, which are alternative forms of genes, causing differences in inherited characteristics
eg gene for petal colour, one allele is red, one allele is yellow
what does dominant mean?
an allele that only needs to be inherited from one parent for it show in the phenotype of the organism
what does recessive mean?
an allele that only shows in physical characteristics of an organism when two copies are inherited, one from each parent
what does phenotype mean?
physical characteristics of an organism
what does genotype mean?
what alleles an organism has
what does homozygous mean?
when two alleles in an organism are the same
heterozygous
when two alleles in an organism are different
what is a carrier?
someone who is able to pass on a disease allele even though they are not suffering from disease
what is monohybrid inheritance?
characteristics involving a single gene
what is polygenic inheritance?
characteristics controlled by 2 or more genes working together
what kind of letter is the dominant allele given?
capital
what kind of letter is recessive allele given?
small letter
what is the allele pair for a phenotype called?
genotype
what is co dominance?
when both alleles within a genotype are expressed in the phenotype of an organism - neither allele is recessive, equally dominant
eg in a speckled hen, both black and white alleles are expressed in phenotype
what are most phenotypic features the result of?
polygenic inheritance rather than single genes
how to answer inheritance diagram questions
- show fully labelled working (parent genotypes, cross, offspring genotypes and phenotypes)
- show a conclusion with percentage chance
- do practice questions
how to answer inheritance diagram questions
- show fully labelled working (parent genotypes, cross, offspring genotypes and phenotypes)
- show a conclusion with percentage chance
- do practice questions
how to interpret family pedigrees
- always write on the genotypes of the people with recessive phenotypes first eg. if they a disorder caused by a recessive allele, they must be homozygous recessive
- for those with a dominant phenotype, you don’t know whether they are homozygous dominant or heterozygous dominant, so need to look at offspring -> only heterozygous individuals can pass on recessive allele to next generation
- only recessive alleles can ‘skip a gen’ ie not visible in heterozygous individuals, but can be passed on to offspring
- do practice question
what is inheritance?
transmission of genetic information from generation to generation
how is the sex of a person controlled?
- one pair of chromosomes, XX in a female and XY in a male
what is environmental variation?
variation caused by surroundings eg climate, diet, accidents, culture, lifestyle
how is sex of offspring determined?
- each male gamete may have an x or y chromosome, while each female gamete has an x chromosome
- tend to draw circles round gametes before placing them in punnett square
what is genetic variation?
inherited from parents due to genes recevied from sperm and egg (1/2 from each parent)
what is a mutation?
rare, random change in genetic material that can be inherited