Acase-control study was performed to determine whether head injury was associated with an increased risk of brain tumors in children. two hundred cases with brain cancer were identified from the state cancer registry and 200 controls were recruited from the same neighborhoods where the cases lived. the mothers of the children completed a questionnaire that asked them to describe their child's past history of head injury. the investigators found that the mothers of the children with brain tumors reported a past head injury for 70 of the cases while a past history of head injury was reported in 30 of the controls. what type of bias was likely to have influenced the findings of this study? length bias recall bias surveillance, diagnostic, or referral bias interviewer/recorder bias

This is due ! matching pairs of chromosomes from parents are called a. homologous chromosomes b. heterozygous chromosomes c. herterogenes d. homologous bands

Analyze how the water cycle affects a food web. now list 3 examples for each below using complete sentences, on how too much water would affect the same web? how about to little water?

Penicillin is hydrolyzed and thereby rendered inactive by penicillinase (also known as β-lactamase), an enzyme present in some resistant bacteria. the mass of this enzyme in staphylococcus aureus is 29.6 kd. the amount of penicillin hydrolyzed in 1 minute in a 10-ml solution containing 10-9 g of purified penicillinase was measured as a function of the concentration of penicillin. assume that the concentration of penicillin does not change appreciably during the assay. penicillin(μm) amount hydrolyzed(nmol) 1 0.11 3 0.25 5 0.34 10 0.45 30 0.58 50 0.61 (a) plot v0 versus [s] and 1/v0 versus 1/[s] for these data. does penicillinase appear to obey michaelis-menten kinetics? if so, what is the value of km? (b) what is the value of vmax? (c) what is the turnover number of penicillinase under these experimental conditions? assume one active site per enzyme molecule.