Exam 2: The Beginning: From Conception to Birth

An allele is a variation that makes a gene different in some way from other genes for the same characteristic.

About ___ percent of natural conceptions never implant.

Dizygotic twins have _____ of their genes in common.

During the germinal period,the first task of the zygote's outer cells is:

In the United States,which is NOT a potential reason for the rise in the frequency of low-birthweight babies?

A teratogen is any agent or condition that increases the risk for:

Each variation of a gene is called a(n)_____.

Women become drunk on _____ compared to men.

The instructions for making amino acids are on about 3 billion pairs of chemicals called "_____ pairs."

When a sperm and an ovum combine,they create a new single cell called a "_____."