Download 1 What makes a family? Cells, Genes, Chromosomes and Traits

Cells
What makes a family? Cells, Genes, Chromosomes and Traits
Genes
All living things – people, plants, and animals – are made of cells
(say: sels). Our bodies are made of cells. All people or humans
have 100 trillion (100,000,000,000,000) cells. All humans have
about 200 types of cells.
Each cell has twenty-five thousand (25,000) to thirty-five
thousand (35,000) genes (say: jeenz).
NO
YES
Genes are on chromosomes (say: KRO-moh-somes).
Chromosomes are inside cells. Chromosomes are in
pairs (2).
1 Chromosome
Each human cell has one nucleus (say: NOO_clee-us). The
DNA
Chromosomes have DNA. DNA gives cells directions. DNA tells
cells what to do.
nucleus is the brain of the cell. In humans, the nucleus has forty-six (46) chromosomes or 23
pairs of chromosomes. (23 x 2 = 46)
Half (1/2) of the chromosomes are from your mother. Half (1/2)
of the chromosomes are from your father.
23
Same
Difference
Fraction
99/1000
1/1000
Decimal
.999
.001
Percent
99.9%
.1%
2 X and Y Chromosomes
The last pair (2) of chromosomes are the “sex chromosomes” – X
and Y. A girl has two XX chromosomes. A boy has one X and
one Y chromosome.
Traits
Genes have information. The information makes our traits (say:
trates). Some traits are inherited. The traits are from our
ancestors. Parents, grandparents, great grandparents, great-great
grandparents and more are ancestors. We are the offspring or
children of our parents.
Ancestors
Great Grandparents
Grandparents
girl XX
boy XY
Parents
Offspring
Children
(kids)
3 Inherited Traits
Acquired Traits
Not all traits are inherited. Other traits are acquired. You learn
acquired traits. You practice. You learn how to ride a bike. You
learn how to read. You learn how to play sports. You learn how
to play music. Eye color is an inherited trait. What is your eye color?
Hair color
Red
Brown
Black
Acquired traits are also events that happen to you. You break
your arm. You cut your hair. You hit your head.
Eyesight
Glasses
No glasses
Hair color is an inherited trait. What is your hair color?
Eyesight is an inherited trait. Do you wear glasses?
Skin color, height, foot size, and birthmarks are inherited traits.
4 Dominant Gene
Recessive Gene
A dominant gene has one (1) A recessive gene is one (1)
strand of DNA that is
strand of DNA that is weaker
stronger than the other strand than the other strand of DNA.
of DNA.
Domianant Gene
Recessive Gene
Dominant?
Recessive?
Dominant?
Recessive?
Eye color: We have BOTH a dominant and recessive gene for
eye color. Why does a mother and father with brown eyes have a
child with blue eyes? (B = dominant / brown eyes; b = recessive /
blue eyes)
Dominant
Recessive
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