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Lab reports: as printed in the X-linked cross lab write-up, you are expected to perform chi-square analysis on your data (both F1 and F2 for each cross - total of 4 chi-square tests); this will be basis for your discussion, ie. was there significant deviation between expected and observed ratios? New deadline: Fri. Nov. 8th at start of lecture.
Problem set 5 is graded and in folders in lab; avg. was 12/15. We’ll go over correct answers in lab this week; we’ll also take questions re. prob. set 6.
3. Ch. 17 rdg: skim pp.456-458; 460-461;
it’s more complicated being multicellular
2. The Promoter
5. Alternative splicing
I. Post-transcriptional gene regulations:
II. Classification of mutations
III. Detection of mutations in humans
IV. Different forms of mutations
If humans have approximately the same number of genes as a fruit fly, and we require more complex cellular functions (presumably with a larger number of proteins) - how do we accomplish this?
Making different forms of a protein from a single gene
Differential splicing of exons
1. Chromosomal ratio activates txn of Sxl in females only
2. SXL controls splicing of tra-2 mRNA
3. Females: exon 2 (which has a stop codon) is removed via SXL
Males: exon 2 is not removed.
Males: no active TRA
Females: TRA is made.
5. TRA directs splicing of dsx mRNA in specific manner; in males default splicing occurs.
A. Spontaneous vs Induced
B. Gametic vs Somatic
C. Phenotypic Effect:
- Dominant mutations easiest to detect
Where did original mutation occur?
Gamete of parent - gen.I
Could it be an X-linked mutation?
Most spontaneous mutations will occur in 95% of genome that does not encode genes - neutral mutations.
What is rate of deleterious mutations in humans?
1.6 deleterious genetic changes/individual/generation
Consequences to our species? Read short article by James Crow on page 465-466 in text.
1. Tautomeric Shifts: spontaneous
2. Base Analogues: chemical
3. Alkylating Agents: chemical
4. Intercalating Dyes: chemical
5. Deamination: chemical
6. UV Radiation and Thymine Dimers
7. High-Energy Radiation (X rays, gamma rays, cosmic rays)
Formation of a TA to CG Transition TimeDuring DNA Replication
Transition is a purine replaced by different purine or pyrimidine
replaced by different pyrimidine.
Incorporate 5-BU in place of Thymine
Changes T-A pair > C-G pair. T > C, and A > G are both Transitions
Sulfonate (EMS) Alkylates Guanine
Note: changes a G-C pair into an A-T pair
(G > A is a transition, C > T is a transition)
Another example: mustard gases first used in WWI.
Intercalate themselves into the DNA double helix, distorting it,
and causing insertion or deletion during DNA replication or
recombination. Other examples: Ethidium Bromide, DAPI.
(a) Causes: C -> T transition (and G -> A transition)
(b) Causes: A -> G transition (and T -> C transition). All.
Deamination can be spontaneous as well.
good for sterilization
of bacteria, bad for skin cancer.