Me ! i will give

a person with trisomy 21 has an extra copy of chromosome 21. what happened during meiosis that caused the person to get three, instead of two, copies of chromosome 21?

binary fission
crossing-over
genetic recombination
nondisjunction

Diego conducted an experiment to find out what kind of ball bounces the highest when dropped from a five-foot platform. he used a golf ball, a tennis ball, and a soccer ball. he dropped each ball from the balcony once. diego recorded his observations after each drop. what can diego do to best improve the reliability of his results? a) drop each ball from the platform three more times b) record his observations in more than one unit c) write at least two scientific questions after the experiment is complete d) share his results with other people who have done similar experiments you for the !

In which way are mercury and venus similar? they both rotate from east to west. they are both small and rocky. they both have thick atmospheres. they both are similar to earth in structure.

Plz ! what does it mean for an allele to be dominant?