METHODS AND SYSTEMS FOR SAMPLE NORMALIZATION

1 . A method for nucleic acid processing or analysis, comprising:

(a) generating a mixture comprising (i) a first plurality of nucleic acid molecules derived from a biological sample of a subject, and (ii) a second plurality of nucleic acid molecules comprising sequences having at least one predetermined size;

(b) subjecting said (i) first plurality of nucleic acid molecules, or derivative thereof; and (ii) second plurality of nucleic acid molecules or derivative thereof, to sequencing to generate a plurality of sequence reads; and

(c) processing said plurality of sequence reads to identify (i) a first set of sequence reads corresponding to at least a subset of said first plurality of nucleic acid molecules, and (ii) a second set of sequence reads corresponding to at least a subset of said second plurality of nucleic acid molecules, which second set of sequence reads corresponds to said sequences having said at least one predetermined size; and

(d) using said second set of sequence reads to identify one or more nucleic acid molecules of said first plurality of nucleic acid molecules as having said at least one predetermined size.

2 . The method of claim 1 , further comprising subsequent to (a) using said first plurality of nucleic acid molecules and said second plurality of nucleic acid molecules to generate a third plurality of nucleic acid molecules.

3 . The method of claim 2 , wherein generating said third plurality of nucleic acid molecules comprises (a) ligating ends of a nucleic acid molecule of said first or second plurality of nucleic acid molecules, or a derivative thereof, to one another or (b) coupling an adapter to a 3′ end, a 5′ end or both a 5′ end and a 3′ end of a nucleic acid molecule of said first or second plurality of nucleic acid molecules, or a derivative thereof.

4 . (canceled)

5 . The method of claim 1 , further comprising, subsequent to (b) subjecting a nucleic acid molecule of said first plurality of nucleic acid molecules or said second plurality of nucleic acid molecules, or a derivative thereof, to nucleic acid amplification to generate a plurality of amplification products, wherein (b) comprises subjecting said plurality of amplification products or derivatives thereof to sequencing to generate a plurality of sequence reads.

6 .- 7 . (canceled)

8 . The method of claim 5 , wherein said nucleic acid amplification comprises contacting said nucleic acid molecule of said first plurality of nucleic acid molecules or said second plurality of nucleic acid molecules, or a derivative thereof, to an amplification reaction mixture comprising random primers.

9 . The method of claim 5 , wherein said nucleic acid amplification comprises contacting said nucleic acid molecule of said first plurality of nucleic acid molecules or said second plurality of nucleic acid molecules, or a derivative thereof, or a derivative thereof, to an amplification reaction mixture comprising one or more primers, each of which specifically hybridizes to a different target sequence via sequence complementarity.

10 . The method of claim 1 , wherein said second plurality of nucleic acid molecules comprises (i) a 5′ common sequence, (ii) a 3′ common sequence, or (iii) a 5′ common sequence and a 3′ common sequence.

11 . The method of claim 1 , wherein said second plurality of nucleic acid molecules comprises a fixed molar ratio of nucleic acid molecules of each predetermined size.

12 . The method of claim 11 , further comprising using said second set of sequence reads to normalize a molar ratio of said first plurality of nucleic acid molecules of each predetermined size.

13 . The method of claim 1 , wherein (c) further comprises processing said plurality of sequence reads to determine a size for at least a subset of said first or second plurality of nucleic acid molecules.

14 . The method of claim 1 , wherein said first or second plurality of nucleic acid molecules is single stranded.

15 . The method of claim 1 , wherein said first plurality of nucleic acid molecules of said biological sample comprises cell-free deoxyribonucleic acid (DNA) or cell-free ribonucleic acid (RNA).

16 . The method of claim 1 , wherein said first plurality of nucleic acid molecules of said biological sample is from a tumor.

17 . (canceled)

18 . The method of claim 1 , wherein said biological sample comprises a bodily fluid selected from urine, saliva, blood, serum, plasma, tears, sputum, cerebrospinal fluid, synovial fluid, mucus, bile, semen, lymph, amniotic fluid, menstrual fluid, or combinations thereof.

19 . (canceled)

20 . The method of claim 1 , wherein said biological sample is a cell-free biological sample.

21 . The method of claim 1 , further comprising, subsequent to (d) using said second set of sequence reads to normalize said one or more nucleic acid molecules of said first plurality of nucleic acid molecules having said at least one predetermined size.

22 . The method of claim 1 , further comprising processing said first set of sequence reads with a reference set of sequence reads to identify a change in said first set of sequence reads thereby determining that a subject has or is at risk of having a disease.

23 . The method of claim 22 , wherein said disease is cancer.

24 . The method of claim 23 , wherein said cancer is selected from the group consisting of colon cancer, non-small cell lung cancer, small cell lung cancer, breast cancer, hepatocellular carcinoma, liver cancer, skin cancer, malignant melanoma, endometrial cancer, esophageal cancer, gastric cancer, ovarian cancer, pancreatic cancer, brain cancer, leukemia, lymphoma, and myeloma.

25 .- 30 . (canceled)

31 . The method of claim 1 , wherein said second plurality of nucleic acid molecules comprises sequences having at least two predetermined sizes.

32 . (canceled)