Download Genetics

• All will know which chromosomes make a boy
and which chromosomes make a girl.
• Most will be able to explain what a genetic
counsellor is.
• Some will understand the importance of
genetic counselling and identify at least 3
reasons when genetic counselling maybe
needed.
What are genes?
Genes are what makes you the person that you are and
how much you look like your parents.
Every cell in your body has 46 chromosomes, except for
the sex chromosomes which are made up of 23 from the
sperm and 23 from the egg.
Some genes are dominant and can be clearly seen, e.g.
The colour of your hair
Some genes are recessive genes for example you may
have brown eyes but be the carrier of blue and so could
pass this on to your children.
How sex chromosomes are passed on
Girl
x
X
y
X
XX
XY
Boy
What is a congenital abnormality?
When a baby is born with a major birth defect.
These can be caused by environmental or genetic
factors.
Genetic abnormalities can be inherited from
one or both parents.
A genetic counsellor is someone who
understands a range of conditions that can be
passed on in different genetic ways and can
advice couples on how great the risk might be.
If a couple feel that they may pass on a
condition they can ask their GP for genetic
counselling. People may approach a GP to be
referred to a genetic counsellor if:
•There is a repeated history of miscarriages
•If there is a blood relationship between the mother
and her partner e.g. cousins
•If a women has previously given birth to a child with a
genetic condition e.g. cystic fibrosis or a chromosomal
disease e.g. Down’s syndrome.
•If there is a family history of inherited disorders e.g.
Haemophilia
•If either partner belongs to an ethnic group in which a
genetic disorder occur frequently e.g. Sickle cell
disease is common mainly in people whose families come
from Africa, the Caribbean and eastern Mediterranean.
•If there is a high rate of some forms of cancer within
families
•If the couple are having problems conceiving.
Down’s syndrome
Genetic abnormalities can be created during
conception, for example down’s syndrome. Babies
with down’s syndrome generally have a broad head
with a very round face, with slightly smaller ears and
mouth.
Activity
Think about your own physical features. Which do
you think you inherited from your mother and which
from your farther? Do the same for your brothers
and sister.
How many features do you have the same?
How many are different?