Transcript What is Inheritance?

What is Inheritance?
Standard Grade Biology
What is Inheritance?
By the end of this lesson you should be able to:
 Know how many chromosomes are in body cells
 Understand the word phenotype
 Give examples of phenotypes
 Understand what true breeding means
 Know what the letters P, F1 and F2 represent
 Understand what dominant and recessive mean and
be able to give examples
What is Inheritance?

What makes us who we are?
Your environment
The genetic information
and your experiences you got from your
parents
YOU
What is Inheritance?



The characteristics that an organism has
have mostly been inherited from the
parents.
They are determined by the genetic
information from their mother and their
father
E.g. eye colour, blood type, flower colour
Genes & Chromosomes



We inherit information in the form of genes.
Each gene controls a different characteristic
Genes can be found on CHROMOSOMES
(thread like structures)
Genes & Chromosomes
Chromosomes
Chromosomes can be found in the NUCLEUS of a
cell
 Every cell in an individual contains a full set of
chromosomes in the nucleus (except sex cells)
 The number of chromosomes varies between
species
 Some species can have as few as 2 chromosomes
and others as many as 100!
 Humans have 46 chromosomes

Chromosomes



Each chromosome can have thousands of
genes on it
Chromosomes are passed from parents to
offspring during fertilisation.
This is how we acquire inherited information
PHENOTYPE

The PHENOTYPE is the organism’s
appearance which has resulted from the
genetic information inherited from the
parents. There can be a number of
different forms of the phenotype e.g. wing
type of fruit flies can be normal or
vestigial.
PHENOTYPE
Fruit flies
“normal” wings/Vestigial wings
PHENOTYPE

Fruit flies can have grey bodies or ebony
bodies
PHENOTYPE

Copy the table 21.1 from P158 in Torrance
True Breeding

Sometimes two organisms with the opposite phenotype can be
crossed (mate) and produce offspring with the different
phenotypes
X
True Breeding

However if all the offspring show the
same phenotype, the parents are said to
be TRUE BREEDING
True Breeding

So if a true breeding
black cat and a true
breeding white cat are
crossed all the offspring
will be…….

BLACK!
Why?????????



This is because the gene for a black
coat is ‘stronger’ than the gene for
white coat.
The gene for a black coat is
DOMINANT
The gene for white coat is RECESSIVE
Task


Insert the “Guinea Pig Cross- diagram 1”
into your jotter.
Answer the following questions in
sentences:
1.
2.
What letter is used to represent the
parents?
What letter and number are used to
represent the first generation?
Task….
Copy and complete the following paragraph:
The parents in both crosses are described as
true breeding. This means that, when bred
together, black guinea pigs will always
produce
offspring. True breeding
white guinea pigs, when bred together, will
always produce
offspring.
An example



The gene for a long coat is dominant to the gene for short
coat in dogs
Imagine a cross between a true breeding short haired dog and
another true breeding short haired dog.
What will the hair of the puppies be like?
Task


Insert the “Guinea Pig Cross- diagram 2”
into your jotter.
Answer the following questions in
sentences:
1.
2.
3.
4.
What colour coat do the parents have?
What colour coat are the F1 generation?
What colour coat are the F2 generation?
Which phenotype does not show in the F1
generation?
Task
5.
6.
7.
8.
9.
Which phenotype does show up?
In which generation are both phenotypes
present?
In the F2 generation, which phenotype is
most common?
Which phenotype is dominant?
Which phenotype is recessive?
Task
Copy and complete the following paragraph:
true-breeding
If two
individuals, of
different phenotypes are crossed, all of the
offspring will have the phenotype of one of
the parents.
dominant
This phenotype is
, the other
phenotype is recessive
dominant
recessive
phenotype
true-breeding
What do you know?
Can you do the following?:
 Say how many chromosomes are in body cells
 Say what the word phenotype means
 Give examples of phenotypes
 Say what true breeding means
 Say what the letters P, F1 and F2 represent
 Say what dominant and recessive mean and be able
to give examples