What were oxygen levels in the atmosphere like when the first cells evolved?

Neelaredoxin is a 15-kda protein that is a gene product common in anaerobic prokaryotes. it has superoxide-scavenging activity, and it is constitutively expressed. in addition, its expression is not further induced during its exposure to o2 or h2o2 (silva, g., et al. 2001. j. bacteriol. 183: 4413–4420). which of the following statements best describes neelaredoxin synthesis? a-neelaredoxin is produced at all times; levels are constant even when exposed to o2 or h2o2.b-neelaredoxin is produced at all times; exposure to o2 or h2o2 increases expression.c-neelaredoxin is produced at all times; exposure to o2 or h2o2 decreases or prevents expression.d-neelaredoxin is only produced when there is exposure to o2 or h2o2.

Nhumans, abo blood types refer to glycoproteins in the membranes of red blood cells. there are three alleles for this autosomal gene: ia, ib, and i. the ia allele codes for the a glycoprotein, the ib allele codes for the b glycoprotein, and the i allele doesn't code for any membrane glycoprotein. ia and ib are codominant, and i is recessive to both ia and ib. people with type a blood have the genotypes iaia or iai, people with type b blood are ibib or ibi, people with type ab blood are iaib, and people with type o blood are ii. if a woman with type ab blood marries a man with type o blood, which of the following blood types could their children possibly have? in humans, abo blood types refer to glycoproteins in the membranes of red blood cells. there are three alleles for this autosomal gene: ia, ib, and i. the ia allele codes for the a glycoprotein, the ib allele codes for the b glycoprotein, and the i allele doesn't code for any membrane glycoprotein. ia and ib are codominant, and i is recessive to both ia and ib. people with type a blood have the genotypes iaia or iai, people with type b blood are ibib or ibi, people with type ab blood are iaib, and people with type o blood are ii. if a woman with type ab blood marries a man with type o blood, which of the following blood types could their children possibly have? a, b, ab, and o ab and o a, b, and o a and b

Will mark brainliest i only need the ! 1.use ten beads and a centromere of one color to construct the long chromosome. use ten beads and a centromere of a second color to construct the second chromosome in the long pair. make a drawing of the chromosomes in the space below. 2. for the second pair of chromosomes, use only five beads. 3. now model the replication of the chromosomes. make a drawing of your model in the space below. part b: meiosis i during meiosis i, the cell divides into two diploid daughter cells. 4. pair up the chromosomes to form tetrads. use the longer tetrad to model crossing-over. make a drawing of the tetrads in the space below. 5. line up the tetrads across the center of your “cell.” then model what happens to the chromosomes during anaphase i. 6. divide the cell into two daughter cells. use the space below to make a drawing of the result. part c: meiosis ii during meiosis ii, the daughter cells divide again. 7. line up the chromosomes at the center of the first cell, one above the other. separate the chromatids in each chromosome and move them to opposite sides of the cell. 8. repeat step 7 for the second cell. 9. divide each cell into two daughter cells. use the space below to make a drawing of the four haploid cells