|

How Genes Are Passed On

Through the generations

Through each generation, genes are shuffled and re-shuffled. Half of a baby's genes come from its father and half from its mother. The baby's parents in turn inherited half each of their genes from each of their own parents. One quarter of each person's genes therefore come from the grandparents. So how does this happen? Instead of containing the full complement of 46 chromosomes, each egg and each sperm has just half, or 23, chromosomes each. When they meet at conception the chromosomes pair up to again make up the full complement that now forms the genetic blueprint for the new individual. One of the 23 pairs of chromosomes are sex chromosomes, so gender is also determined at conception. Each egg carries an X chromosome and each sperm either an X or Y. If two X chromosomes combine, the baby will be a girl; if an X and Y chromosome combine, the baby will be a boy (see How gender is determined).

Inheriting genes

Genetic inheritance means that successive generations can share certain characteristics.

excerpted from:

Excerpted from Pregnancy Day by Day.
Copyright © 2009 Dorling Kindersley Limited.
Buy this book now!

Pregnancy Day by Day

Tell us your due date to receive our daily newsletter and find out what is happening in this day of your pregnancy!

Already a member? Log-in here

Name of the Day

stay connected

highlights

Printable Fall Fun To-Do List
Celebrate the cooler weather with this printable checklist of fun fall activities for your whole family.

Kindergarten Readiness App Wins Gold
Our Kindergarten Readiness app won the Gold Award of Excellence in the educational category at the 2014 Communicator Awards. This valuable checklist comes with games and activities to help your child practice the essential skills she needs for kindergarten. Download the Kindergarten Readiness app today!

Top 10 Care Package Items for College Students
Show your college student that you love and miss her by mailing a care package full of dorm room essentials and comforting treats. Whether it's her birthday, exam time, or just because, get care package ideas to brighten her day.

Find Today's Newest & Best Children's Books!
Looking for newly released books for your child? Try our new Book Finder tool to search for new books by age, type, and theme, and create reading lists for kids!

© 2000-2014 Pearson Education, Inc. All Rights Reserved.