Chromosome counts, chromatid counts and DNA content for one marked pair through mitosis and meiosis fill this SC435 Unit 2 worksheet, ending on nondisjunction and an XXY outcome. Searches like "sc 435 unit 2 assignment example", "sc435 unit 2 sample" and "sc435 unit 2 example" land here.
What a finished SC435 Unit 2 cell division worksheet looks like
Four pages of answered items with two tables and a set of labeled sketches. Table 1 covers mitosis, rows from G1 to cytokinesis, columns for chromosome number, chromatid number, DNA content in C units and whether sister chromatids are joined: 6 chromosomes and 2C in G1, then 6 chromosomes, 12 chromatids and 4C after S phase, and 12 chromosomes briefly at anaphase. Table 2 does the same for meiosis and adds a column for whether homologs are paired, ending at 3 chromosomes and 1C in each of four cells. Sketches at metaphase I and metaphase II show B and b in place. Short-answer items then explain why crossing over can delay the separation of B from b until meiosis II, and why an egg or sperm carrying two sex chromosomes can produce an XXY conception.
How a SC435 Unit 2 example is structured
Items build from counting to reasoning, so the tables establish the vocabulary the later answers depend on. Mitosis comes first as the baseline, one division producing two cells identical to the parent, which makes the reductions in meiosis visible by contrast. Every count is defined before use: a chromosome is counted by centromeres, a chromatid by DNA molecules, and C is the DNA of one unreplicated haploid set. The meiosis table adds homolog pairing, since that single column explains why anaphase I halves the chromosome number and anaphase II does not. The crossing-over item is where the worksheet shows depth: when a crossover falls between the centromere and the gene, each homolog carries B on one chromatid and b on the other, so the alleles part only at anaphase II. Nondisjunction closes the set, traced to both parents' possible origins.
Counting by centromeres
A chromosome is counted by its centromere and a chromatid by its DNA molecule. Stating both rules first prevents the most common counting error in the tables that follow.
Two tables, one extra column
Mitosis and meiosis share rows and columns except one: whether homologs are paired. That column carries the whole explanation of why meiosis halves the chromosome number.
Where B and b part
Without crossing over, B and b separate at anaphase I. With a crossover between the gene and the centromere, they separate at anaphase II instead, and a sketch shows both cases.
Three routes to XXY
An egg carrying two X chromosomes from either meiotic division, or a sperm carrying X and Y from a first-division error, can each yield XXY. The answer traces every route.
Sketches labeled with alleles
Metaphase I shows homologs paired at the plate, metaphase II shows single chromosomes lined up, and every chromatid carries its allele label so a reader can follow B and b through.
Where marks go in SC435 Unit 2
Cell division worksheets in this course are usually marked item by item, with the tables carrying heavy weight because later answers depend on them. The costliest error is confusing chromosomes with chromatids at the moment after S phase, which doubles or halves every later count in the row. DNA content causes the next set of losses when C values are not reset correctly after each division. Short answers earn credit through mechanism: saying that homologs separate in meiosis I and sister chromatids in meiosis II, with the crossover exception explained, rather than naming stages alone. The nondisjunction item rewards covering both parental origins and both divisions. Sketches lose points when alleles are missing or placed on the wrong chromatid. Unlabeled columns and inconsistent terms cost smaller amounts.
Get a SC435 Unit 2 example written to your instructions
Whatever diploid number or chromosome pair your SC435 Unit 2 worksheet uses, send the items in order with the rubric and any template file. The free first custom worksheet, completed within 24-48h, fills every count and content value, labels alleles on each sketch and explains where copies separate in a sentence apiece.
SC435 Unit 2 questions, answered
How do I count chromosomes when they are replicated?
Count centromeres. A replicated chromosome with two sister chromatids still counts as one chromosome until the centromere splits at anaphase of mitosis or anaphase II of meiosis. Chromatids are counted separately as DNA molecules. Keeping those two rules apart prevents most of the errors graders find in these tables.
What does C mean in DNA content?
C is the amount of DNA in one unreplicated haploid set of chromosomes. A diploid cell in G1 holds 2C, the same cell after S phase holds 4C, and a finished gamete holds 1C. Tracking C alongside chromosome number shows where replication happens and where each division halves the DNA.
Why does crossing over matter for where alleles separate?
Because it swaps segments between homologs. If a crossover falls between a gene and the centromere, each homolog ends up carrying one chromatid with each allele, so the two alleles are not separated until sister chromatids part at anaphase II. Items asking where alleles separate often test exactly this.