UNIT 10 LESSON 1 – TRAITS 2

INTRODUCT IO

N TO GENET IC

S

FATHER OF GENETICS

• Gregor Mendel was an Austrian monk who lived in the 1800’s.

• He discovered how traits are inherited by studying pea plants.

http://www.rjwsciencestm.com/AP-Bio/Unit-Two.html

GREGOR MENDEL’S EXPERIMENTS• Tested at least 28,000 pea

plants!• He studied their seed

shape and color. Also whether the stems were tall or short.

• He self-pollinated the plants and collected and grew the seeds (their offspring)

GREGOR MENDEL’S EXPERIMENTS• Mendel’s observations:When I cross yellow with green I get all yellow!

When I cross two yellow I get some yellow and some green!• He discovered that traits

are either dominant or recessive.

http://www.mun.ca/biology/scarr/MGA2-05-05smc.html

WHAT’S THE DIFFERENCE?

Dominant: the gene or allele that “wins” over another allele.

Recessive: the gene or allele that gets masked or covered by the dominant gene.

http://www.biologycorner.com/bio2/genetics/notes_mendel.html

GENETICS• Genetics is the science of genes and

how traits are passed from one generation to the next.

• People who study genes are geneticists.

http://thepersonalgenome.com/2007/12/shortage-of-geneticists-in-the-united-states/

DNA AND GENETICS• We get our DNA from our parents.• DNA is found inside the egg cell and sperm

cell.• When an egg and sperm join to become a

new cell, all the necessary genetic information is created.

• This process is called fertilization.

• This new single cell will grow and divide into trillions of cells!

• DNA tells that single cell to divide into two cells, then four, then eight… until a whole body forms.

• DNA controls individual traits, such as whether you are a boy or a girl… or whether you are tall or short. The list is endless!

DNA

CHROMOSOMES• Genes come in pairs. • You get half of your genes from your

mother, the other half from your father.• Genes are found on chromosomes.• Every human cell has 46 chromosomes

(23 pairs of chromosomes)

This picture shows the 23 pairs (46 total) of chromosomes in every cell. The last two chromosomes are the sex chromosomes. This person has one large X and one small Y so it’s a boy! Two large X’s would be a girl.

KARYOTYPES• A karyotype is a picture of the 23 pairs of chromosomes.

XY = maleXX = female

The first 22 pairs of chromosomes

are called autosomes.

(#1-22)

Sex chromosomes are pair #23

Male (XY)

Female (XX)

• Karyotypes are used to determine if an offspring has the right number of chromosomes (46 in humans)

• Example: Down’s Syndrome47 chromosomes because there are 3 copies of

chromosome #21Causes developmental differences in the child.

LET’S REVIEW!• At the end of your notes there’s a

short crossword puzzle you can try.• Use the vocabulary from your notes

to complete the puzzle.