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Genetics
Each cell in a human’s body
contains 46 chromosomes:
The 46 chromosomes in each human cell
contains more than 3.2 billion base
pairs in their DNA and have more than
30,000 genes.
"If our strands of DNA were stretched out in a
line, the 46 chromosomes making up the
human genome would extend more than six
feet [close to two metres]. If the ... length of
the 100 trillion cells could be stretched out, it
would be ... over 113 billion miles [182 billion
kilometres]. That is enough material to reach
to the sun and back 610 times." [Source:
Centre for Integrated Genomics]
Genetics• The study of how traits are inherited
HeredityThe passing of traits from parent to offspring.
TraitA characteristic of organism. Traits may be visible,
such as eye color, or not visible, such as blood type.
AllelesDifferent forms a gene may have for a
trait.
Genetics
Genetics- the study of how traits are inherited.
Heredity- the passing of traits from parent to offspring.
Trait- a characteristic of an organism. Traits may be
visible, such as eye color, or not visible, such as blood type.
Alleles- the different ways a trait can look. For exampleeye color alleles would be blue, brown, green, hazel. Hair
color alleles would be blonde, brown, black, red.
The Father of Genetics
• Gregor Johann
Mendel was an
Austrian monk, who
in 1856 begin
experimenting with
pea plants.
Why peas you may ask?
• They have distinctive traits
• They grow fast
• He could control pollination and
fertilization.
What was Mendel's first
experiment?
• Mendel crossed (pollinated) two tall pea
plants.
• All of the
offspring
were tall pea
plants.
Next, Mendel crossed two of the
newly produced pea plants.
WOW!!!
For every three tall pea plants produced, there was on short
pea plant.
What did all this mean to Mendel?
•genes are always in pairs (each
one passed on from a parent)
•some forms of a gene (allele) are
stronger than others.
More notes:
• Gregor Mendel was an Austrian monk,
who in 1856 began experimenting with pea
plants. He found that genes are always in
pairs (each one passed on from a parent)
and that some forms of a gene (alleles) are
stronger than others.
In peas, the tall gene is stronger over the short gene.
If a pea plant receives a tall gene from one parent and a
short gene from the other parent the offspring will be
Tall
In genetics, the stronger gene is called dominant. It prevents
the other gene from being seen. Dominant alleles are written
as a capital letter (T).
While the weaker gene is known as recessive. The recessive
allele will not be seen is a dominant allele is present. It is
written as a lower case letter (t).
Even more notes:
Dominant- the stronger allele. It prevents the other from being
seen. Dominant alleles are written as a capital letter.
For example- Tall pea plants (T), Tongue roller (R)
Recessive- the weaker allele. The recessive allele will not be
seen if there is a dominant allele present. It is written as a lower
case letter.
For example- Short pea plants (t), Non-tongue roller (r)
Reginald Punnett
Reginald Punnett developed a
tool used to predict all the
possible gene combination of
offspring.
It is know as a Punnett
Square.
By knowing the combinations of alleles in the parents, we use
the Punnett square to predict the possible offspring.
•If a parent has two of the same alleles, either 2 dominant (TT)
or 2 recessive (tt), it is known as homozygous.
•If a parent has two different alleles, one dominant and one
recessive (Tt), it is know heterozygous.
From a Punnett Square we can tell what the genes the
offspring will have (genotype) and how the trait will appear.
(phenotype)
Yes, even more notes:
Punnett Squares- A tool used to predict all the possible
gene combination of offspring.
Homozygous- two of the same alleles. Having two
dominant alleles (TT) or two recessive alleles (tt)
Heterozygous- two different alleles, one dominant and
one recessive allele (Tt).
Genotype- the genes the organism has. For exampleTT, Tt, tt
Phenotype- the physical appearance of the organism.
How the trait appears. For example- Tall or short
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