Question

1. when a sperm and an egg meet what cell is formed / how much dna does it have?. (2 pt)

1. where does a zygote get its dna? what must happen to this dna in order for the cell to divide?(2 pt)

1. which numbered steps above represent cellular division? ____ through ____ (numbers) (2 pts)

Explanation:

Question 1

When a sperm (male gamete) and an egg (female gamete) fuse, a zygote is formed. Sperm and egg are haploid (have $n$ DNA, 23 chromosomes in humans), so zygote is diploid with $2n$ DNA (46 chromosomes in humans).

A zygote gets its DNA from the sperm (contributing paternal DNA) and the egg (contributing maternal DNA). For the cell to divide (mitosis or later meiosis in germ cells), the DNA must replicate (during S - phase of the cell cycle) so that each new cell gets a complete set of genetic material.

Since the original problem does not provide the "numbered steps above", we assume typical steps in development: after zygote formation (step 1 maybe), steps involving cell division (like cleavage, mitotic divisions) would be from a lower number (e.g., 2) through a higher number (e.g., if steps are 1:fertilization, 2 - 5:cell divisions, then 2 through 5). But without the steps, we note that cellular division steps (like mitosis - based divisions of zygote into blastomeres, then embryo) follow fertilization. If we assume steps: 1 = fertilization (zygote), 2 = first cleavage, 3 = second cleavage, etc., then the steps representing cellular division would be from the step after zygote formation (e.g., 2) through the last division step (e.g., if up to 5, 2 through 5).

Answer:

A zygote is formed; it has a diploid (2n) amount of DNA (e.g., 46 chromosomes in human zygote, combining 23 from sperm and 23 from egg).

Question 2