A Closer Look at Conception

Chapter 3 Section 2

The Genetic Package

• Nature– Genetics/ Heredity– Physical build– Skin color– Hair texture/color– Color/shape of eyes– Shape/size of ears,

hands, and feet– Blood type

Moment of Conception

• _____ chromosomes– 23 from ______ (father)– 23 from mother (_____)

• Each contains genes– Determine

characteristics • ____ genes for each

characteristic– One from mom, one

from dad

Dominant Vs. Recessive• When both genes

________, the child will receive that trait– Ex: both parents pass the

blue-eyed trait, child will have blue eyes

• When different, the _________ trait will win– Ex: brown-eyed trait (D) vs

blue-eyed trait (R): the child will have _______ eyes

Gene Pool

• How are the genes picked?– Matter of _________

• Create an _________ individual

• Siblings will look similar but ________________ __________________

How Does it Work???

• What does this mean?– BB: 2 dominant= brown– Bb: brown– bb: Blue eye

• 1 in 4 chance of blue eyes

Sex Determination

• Gender is determined by 2 chromosomes– ____________

• The _____ contains ___• Sperm – __________• During fertilization– XX= ______________– XY= ______________

Multiple Births

• Beginning of _____________the cell divides into 2– Continue until they divide

into millions• Sometimes the growing

mass divides into 2– Grow into separate

______________• Produces _____________

twins

Identical Twins• Dividing mass of cells• Form 2 embryos• Same ______• Very similar characteristics

– Due to the same _______ and same _________

If the split is not complete- ___________ twins occurs

Fraternal Twins

• Results when 2 eggs are released at the _________________– Each fertilized by

different _________• Not always the same

sex• No more alike than

ordinary ___________

Multiple Births

• In more than 2 births:– Can be identical,

fraternal, or both• Example: triplets– One ovum could divide

into 3 parts (_________)– 2 eggs are fertilized and

one splits (2 identical & one fraternal)

– ______ eggs released at once (_____________)

Genetic Worksheet