genetics questions Flashcards
Q2.
(a) Mutation is one cause of genetic variation in organisms.
Give two other causes of genetic variation.?
= crossing over and independant segregration
(b) Give one piece of evidence from the diagram above to show that the allele
for grey body colour is dominant.
= for these types of questions find 2 affected or unaffected with an opposite child, this means they both must be carriers to pass on a recessive allele
(c) Explain one piece of evidence from the diagram above to show that the
gene for body colour is not on the X chromosome.
= to check for sex linkage look at fathers and opposite daughyers, possile with recessive genotype
(a) In genetic crosses, the observed phenotypic ratios obtained in the offspring
are often not the same as the expected ratios.
Suggest two reasons why
= random fertilisation
= sample size too small
= epistasis sometimes
What is meant by the term phenotype?
= observerable charactertiscs, determined by the genotype
In fruit flies, the genes for body colour and wing length are linked. Explain
what this means.
= gene is found on the same chromosome
when would you use a chi sqaured test?
= catergorical data
What is the expected ratio for dihybrid crosses?
9:3:3:1
Why cant males have heterozoygous?
= males can only express an allele in the X chromosome, therefore cannot be heterozoygous
How do we explain the autosomal linkage?
= state the most common phenotypes (observerable characteristic),
= gametes are more common, not formed from crossing over- crossing over creates new combinations of alleles
= few of one particular phenotype as it is recessive
= crossing over is rare so less of a particular phenotype
= therefore not many of a partiault genotype
= if u do not get expected ratio, crossing over took place.
Whatdi we do when it mentions that the genes are not on the sex chromosome?
= linked together, th genes are linked on the sam chromosome- autosomal linkgae
= talk about crossing over
= high ftequency and name the
