Download Wearing your Genes

Unit 1: Biological Diversity
TOPIC 4: HEREDITY
That’s genes…not jeans
I CAN…
Recognize the significance of genes in heredity
Identify dominant and recessive traits
THINK ABOUT IT:
Who do you look more like – your mom
or your dad?
Why do you think you don’t look exactly
the same as your brothers and sisters?
GENETICS
 Heredity is the passing down of traits to offspring
 The study of heredity is called genetics
 A trait is something measureable or observable
(eg. freckles, height)
GENES AND REPRODUCTION
At birth, you got information for ALL of your genes from:
Mom (23 chromosomes in egg)
Dad (23 chromosomes in sperm)
TOTAL = 46
chromosomes
CHROMOSOME WITH GENE
Individual genes
on a
chromosome
Chromosome pair
♀♂
Tongue
rolling
Eye colour
Blood type
DOMINANT & RECESSIVE TRAITS
DOMINANT TRAIT
 Will always be expressed if
present
 Use an UPPER CASE LETTER
to indicate a dominant trait
 EX. Tongue Rolling (T)
RECESSIVE TRAIT
 Will NOT be expressed in the
presence of a dominant trait
 Need two copies of trait to be
expressed
 Use a lower case letter to indicate
a recessive trait
 EX. Tonge Rolling (t)
WHAT TRAITS WILL THIS
INDIVIDUAL HAVE?
Tongue Roller
Brown Eyes
T
B
Chromosome pair
♀♂
Tongue
T
rolling
b Eye colour
DOMINANT OR RECESSIVE
Bent
thumb
Tongue roll
HOMOZYGOUS &
HETEROZYGOUS
HOMOZYGOUS
If you have two of the
SAME traits
EX.
TT – tongue roller
HETEROZYGOUS
If you have two
DIFFERENT traits
EX.
Bb – blue eyes
Can a recessive trait be expressed in a
Heterozygous pair? Explain your answer.
APPLY YOUR KNOWLEDGE
Homozygous
After mating…ALL
offspring look like
this
Homozygous
Which gene is dominant? Black fur or white fur?
2) DOMINANT OR RECESSIVE
Homozygous:
White fur
Homozygous:
Black fur
dominant
When a gene is dominant it will be
expressed when it is combined with a
recessive gene.
recessive
When a gene is recessive it will be
expressed when it is combined with
another recessive gene.
2) DOMINANT OR RECESSIVE
Purebred
Not a
purebred
Offspring can be…
Same as ONE parent
A combination
of the parents
Different
than the
parents
EXAMPLE: PUNNETT SQUARE
Brown Eyes (dominant) - B
Blue Eyes (recessive) - b
♀ = Bb
♂ = Bb
♂
B
♀
B
b
b
GENETIC DISEASE
MOTHER
FATHER
CHANGING OUR
GENETIC INFO
Mutation: a change in the DNA sequence
-can be an advantage (ex: hard beak) or
disadvantage (ex: cancer)
Mutagen: is a chemical or drug that changes your
DNA
CHANGING OUR
GENETIC INFO
Mutations can occur by…
X-rays
Radiation
Mutagens (chemicals in your body, example:
a pregnant woman takes drug X
and the baby is born blind)
Cancer is when cells divide uncontrollably. What causes it? There is a cancer
gene, but there may be other causes. Is it only genetic or is it from our
environment?
REEBOP ACTIVITY
Examine the offspring of Reebop parents
Use information about dominance and recessiveness
ANSWER THE FOLLOWING Q’S:
 From the characteristics you chose which traits are
discrete and which are continuous?
 Why did you choose the characteristics you did?
 Explain the leg colour you chose?
 If having red eyes is a recessive trait, how can you explain
the absence of red eyes on the Reebop?
 Use the rest of class time to answer the analysis Q’s
INDIVIDUALLY
WHAT EVER IS NOT DONE IN CLASS IS TO
BE COMPLETED AS HOMEOWORK!