3rd LAB Practical 4 Flashcards
(23 cards)
What is the Law of Segregation?
During formation of gametes, 2 alleles for a trait separate, so each gamete carries only 1 allele for each trait.
What is the Law of Independent Assortment?
Different chromosomes assort independently into gametes due to random orientation of homologs during Metaphase of Meiosis 1.
What is crossing over and when does it occur?
Produces recombinant chromosomes by combining genes inherited from each parent. It occurs very early in Prophase I.
How is the distance between two genes on a chromosome related to crossing over?
Farther distance = more room for crossing over/recombination.
What happens if two genes on the same chromosome have a recombination frequency of 50%?
These genes will effectively assort independently.
Describe the Drosophila life cycle.
Eggs hatch to larvae, larvae pass through instar stages, form pupae where metamorphosis occurs, and adult flies emerge.
How are Drosophila mutant and wildtype alleles written?
e.g. allele for white eye mutation is w, allele for wildtype (red eye) is w+.
List some Drosophila mutations.
- Apterous
- White eyes
- Ebony body
- Eyeless
How can you distinguish male versus female Drosophila?
- Presence of sex combs in males
- Male external genitalia
- Abdominal structure and pigmentation (females are bigger and lighter colored)
What is a pure breeding strain?
Strains that are all homozygous for trait(s), created by inbreeding for many generations.
Provide an example of a genotype for a pure breeding strain.
TT for a pure-breeding strain of plants with a tall phenotype.
What is a tester strain?
Homozygous recessive strains used in crosses to test whether genes assort independently or are linked.
Provide an example of a genotype for a tester strain.
‘aa’ for a recessive allele.
What is the product rule in probability?
Probability of A and B occurring in a defined order equals the product of their individual probabilities.
What is the sum rule in probability?
The probability of one or the other occurring equals the sum of their individual probabilities.
What is the general Null Hypothesis for any Chi-Squared test?
There is no statistically significant difference between the observed and expected outcomes.
What is a p-value in statistics?
The probability of observing results as extreme as, or more extreme than, the ones obtained, assuming the null hypothesis is true.
How do you calculate degrees of freedom for a Chi-Squared test?
df = # of classes into which the data can fall minus 1.
What happens if the calculated χ2 value is less than or equal to the critical χ2 value?
We fail to reject the null hypothesis.
What happens if the calculated χ2 value is greater than the critical χ2 value?
We reject the null hypothesis.
What is the Null Hypothesis when testing independent assortment?
There is no difference between the observed and expected phenotypic ratios in the progeny.
What is the relationship between crossing over and recombinant phenotypes?
If there is crossing over, we will see some recombinant flies.
Fill in the blank: The farther the two genes are located from each other, the more ______ will occur.
crossing over
