Biology Answers

what is product of light reaction in photosynthesis

Tay-Sachs disease is an inherited disease that is caused by a recessive allele. If a man and his wife, who are both carriers, have three children, what is the probability of each of the following? Show your calculations and give your answers as fractions.

a) All their three children do not have the disease.

d) At least one child is phenotypically normal without the disease.

b) One or more of their three children have Tay-Sachs disease.

c) All three children have the Tay-Sachs disease.

1. You are a Geneticist employed by Thato Biotech Pty Ltd in a criminal case, which could not be solved due to the integrity of DNA used as evidence. You are requested to ascertain the integrity of DNA evidence. You decided to resuspend the purified DNA in a volume of 100uL of double-distilled nuclease-free sterile water. You then diluted 10uL of the DNA sample to a total volume of 100uL with water quality for spectrophotometric analyses. On measuring the absorbance of this diluted sample at 230, 260, and 280nm she obtained the following readings:

A280nm= 0.494; A260nm = 0.364; A230nm= 0.191

a) What is the DNA concentration of the 100uL aliquot, in 3 significant figures

b) How much total DNA was purified by the procedure?

c) Is this DNA pure? If yes, how do you know? if not, what is the most likely contaminant?

d) if this DNA was contaminated with salts what would you expect in the absorbance readings?

e) If DNA was contaminated with RNA, how would you purify your DNA?

recall the structures found in animal and plant cells including algal cells

If height were entirely genetically controlled, what concordance would you expect between monozygotic twin pairs?

1. Based on Rosa’s symptoms, which parts of her brain may have been affected by Alzheimer’s disease? 
2. How are messages sent between cells in the nervous system? What molecules are involved in this process? In what ways can drugs alter this process? 
3. Why can’t Rosa’s brain simply grow new cells to replace the ones that have died? 
4. How do certain classes of drugs help with neurotransmission in the brain? Could this help Rosa? 

A cross was made between pure breeding plants differing in two characters (colour and shape of seed) and the progenies were intercrossed to produce F2 population. Four types of phenotypes; yellow round (1200), yellow wrinkled (386), green round (372) and green wrinkled (144) were observed in F2. Use the chi-square test to determine if these results are due to independent assortment 

How do motility and secretions of the stomach contribute to the digestive process?

explain why mismatch repair is the more important for the accuracy of DNA Replication