inheritance and evolution Flashcards
(23 cards)
genotype
the genetic constitution of an organism. For a particular gene this refers to the alleles present e.g BB, Bb or bb
phenotype
is the appearance of a characteristic due to the expression of the genotype and its interaction with the environment
alleles
different forms of the same gene. e.g B codes for brown eyes and b codes for the blue eyes these are both alleles of the gene controlling eye colour.
alleles can be dominant, recessive or codominant
dominant allele
the allele that is always expressed
recessive allele
the allele that is only expressed if the genotype is homozygous recessive (bb)
codominant alleles
is where both alleles are expressed in the phenotype
locus
the position of a gene on a chromosome
homozygous
both alleles being the same (BB) (bb)
hetrozygous
alleles being different (Bb)
sex linked gene
where the gene is carried on only one type of sex chromosome usually X chromosome
how to prove that an allele is recessive
2 unaffected parents who have an affected child .
therefore the parents must be hetrozygous carriers
how to prove that an allele is not sex-linked (when known to be recessive)
2 unaffected parents who have an affected daughter
how to prove that its dominant
2 affected parents who have unaffected children
how to prove that an allele is not sex-linked (when know to be dominant)
2 affected parents who have an unaffected daughter
what is the chi-squared test
used to determine if there is a statis
explain why people with the genotype IA
IB have the blood group AB
because both alleles are codominant so bot are expressed so produces antigens A and B
Explain how meiosis results in people with the blood group AB producing two different types of gamete
with respect to the gene for the ABO blood groups.
because allele IA and IB are on different chromosomes on a homologous pair so in meiosis i they are separated. only one allele on each gamete
what stats test is used for this topic
chi squared
explain the reason for using a stats test
-to determine if difference between expected and observed ratios is significant
-to determine whether the probabilty of chance is greater or less than 0.05
male fruit flies are more likely than female fruit flies to show a phenotype produced by a recessive allele
carried on the X chromosome. Explain why.
because females have to inherit two recessive alleles, but males only need to inherit one recessive allele.
Natural selection
-Variation presents due to mutations and meiosis
-those with advantageous allele due to mutation survive and have reproductive success to pass on advantageous allele
-allele frequency increases
-this continues from generation to generation
Assumptions for hardy weinburg
-large populations
-no mutations
-no selection
-no migration
-mating random
