PSYB21H3 Chapter Notes -Low Birth Weight, Bulimia Nervosa, Teenage Pregnancy
Document Summary
Human zygote = cell formed by union of sperm and ovum, contains 23 chromosomes from mother and 23 chromosomes from father. Chromosome are composed of molecules of deoxyribonucleic acid (dna) Polygenetic traits = human characteristics such as skin color and height that result from interplay of multiple genes. Recessive gene inherit a gene but it is not manifested as it is masked by dominant gene. Gender is determined by 23rd chromosome (sex chromosomes: blond hair = recessive, brown hair dominant, males have 1 x and 1 y, females have 2 x. Sex linked traits = recessive genes that are carried on sex chromosome. Some genetic defects are caused by defects in chromosomes occur when genetic instructions go awry during early pregnancy. Down syndrome = due to presence of extra 21st chromosome or piece of one, causes a range of physical and mental handicaps: mother over 35 are at greater risk because of their longer exposure to environmental substances.
