Biology Review

Cells divide because large cells have trouble moving, ____ and ____ across the membrane.

nutrients; waste

Another reason cells must divide is to avoid __________ “overload.”

DNA

When a cell divides, it forms two __________ cells that are genetically __________.

Daughter; Identical

Mitosis is the process by which __________ cells divide.

eukaryotic

Unicellular organisms use mitosis for __________, while multicellular organisms use it for __________ and __________

5. asexual reproduction; growth; repair

A chromosome is made of tightly coiled __________.

DNA

7. Loose, uncoiled DNA is called __________.

chromatin

Two identical copies of a chromosome attached together are called __________ __________.

8. sister chromatids

Humans have __________ chromosomes, or __________ pairs.

46; 23

10. The three phases of interphase are __________, __________, and __________.

G1; S; G2

11. During the S phase, the cell __________ its DNA.

replicates

12. The first phase of mitosis is __________, and the chromosomes become __________.

prophase; visible

13. During metaphase, chromosomes line up along the __________ of the cell.

equator

14. In anaphase, the __________ split and sister chromatids move to opposite __________.

centromeres; poles

15. During telophase, the nuclear __________ reappears and chromosomes begin to __________.

membrane; uncoil

16. The division of the cytoplasm is called __________.

cytokinesis

17. In animal cells, cytokinesis occurs when the cell membrane __________.

pinches

18. In plant cells, a __________ __________ forms instead of pinching.

cell plate

19. Uncontrolled cell growth is known as __________.

cancer

20. A mass of cancer cells is called a __________.

tumor

21. DNA stands for ________________________________________.

Deoxyribonucleic Acid

22. DNA is made of repeating units called __________.

nucleotides

23. The three parts of a nucleotide are: __________, __________, and __________.

phosphate; sugar; nitrogen base

24. The four DNA bases are __________, __________, __________, and __________.

adenine; thymine; cytosine; guanine

25. According to Chargaff’s Rule, __________ pairs with __________, and __________ pairs with _________

adenine; thymine; cytosine; guanine

26. DNA has a shape known as a __________ __________.

double helix

27. The scientist who took the famous X-ray image of DNA was __________ __________.

Rosalind Franklin

28. The two scientists who built the DNA model were __________ and __________.

Watson; Crick

29. A group of three DNA bases is called a __________.

codon

30. A gene is a stretch of DNA that codes for a __________.

protein

31. DNA replication happens before __________ and __________.

mitosis; meiosis

32. The first step of DNA replication is that DNA __________.

unzips

33. DNA replication is called semi-conservative because each new DNA molecule contains one __________ strand and one __________ strand.

original; new

34. DNA never leaves the __________ because it must be protected.

nucleus

35. RNA can leave the __________ because it is only a __________ of DNA.

copy

36. In RNA, the base __________ replaces __________.

uracil; thymine