Genetic Screening

Question 1

What are Pedigree charts used for ?

Answer 1

To analyse patterns of inheritance in genetic screening and counselling

Question 2

How can a pattern of inheritance be revealed?

Answer 2

By collecting information about a particular characteristic from the family members or the information used to construct a family tree

Question 3

When can most genotypes be determined ?

Answer 3

Once phenotypes are know

Question 4

What does a genetic counsellor do?

Answer 4

Construct a family tree

Uses information from the family tree to advise parents of the possibility of passing a genetic condition to their child

Question 5

What do pedigree charts show ?

Answer 5

Sex
Matings
Siblings
Affected individuals 
Twins 
Heterozygotes
Carrier of sex linked allele
Deceased

Question 6

What does autosomal inheritance mean?

Answer 6

genes carried by normal body cells

Question 7

What does recessive mean ?

Answer 7

A gene whose effect does not show it there is a dominant allele too, a recessive characteristic only shows if there are two recessive genes , traditionally represented by small letters.

Question 8

What does the term dominant mean?

Answer 8

A gene whose effect always shows, they are normally represented by capital letters

Question 9

What is an example of autosomal recessive inheritance ?

Answer 9

Cystic fibrosis

Question 10

What does homozygous mean?

Answer 10

Both genes for a particular characteristic are the same

Question 11

What does heterozygous mean?

Answer 11

The two alleles are different, one dominant, one recessive

Question 12

What appears in every generation?

Answer 12

Autosomal dominant inheritance

Question 13

What is an example of autosomal dominant inheritance?

Answer 13

Huntington’s chorea

Question 14

What is incomplete dominance ?

Answer 14

Where the recessive gene still has an effect and there is an intermediate phenotype

Question 15

What is an example of autosomal incomplete dominance ?

Answer 15

Sickle cell anaemia

Question 16

What is an example of sex linked recessive trait?

Answer 16

Haemophillia

Question 17

How are sex linked genetic problems different ?

Answer 17

Only the X chromosomes carry an effective gene

Question 18

Female chromosomes?

Answer 18

They have Two X chromosomes

Question 19

Male chromosomes?

Answer 19

They have an X chromosome and a much shorter Y chromosome which has fewer genes

Question 20

What is likely to happen if one female X chromosome has a recessive gene?

Answer 20

The other X chromosome will have a dominant gene to prevent the recessive condition having an effect

Question 21

What will happen if a male has a recessive gene on their only X chromosome?

Answer 21

There will be no allele in the shorter Y chromosome and so the condition will show in their phenotype

Question 22

Which chromosomes do males receive from their parents?

Answer 22

Y from their father

X from their mother

Question 23

What will sons always inherit from their mothers if there is any recessive genes on their X chromosome?

Answer 23

The sex linked condition

Question 24

What are females who are normal for a given characteristic and heterozygous known as?

Answer 24

A carrier

Question 25

What will the children of a normal male and a normal but carrier female be?

Answer 25

It is expected that:
Half the daughters will be normal and half will be carriers
Half the sons will be normal and half will be effected

Question 26

What is pre implantation genetic diagnosis (PGD) used for?

Answer 26

To identify single gene disorders and chromosomal abnormalities before selecting embryos to be implanted into the uterus

Question 27

What is PGD used in conjunction with?

Answer 27

IVF