Intro

Question 1

What is an allele?

Answer 1

A married form of the same gene and are found in the same place on a set of homologous chromosomes

Question 2

What does an allele do?

Answer 2

It codes for a specific trait of a certain gene.

Question 3

What are multiple alleles?

Answer 3

Are circumstances where 3 or more allelic forms of one gene are known but an individual will still only have 2 of these possible multiple alleles

Question 4

What is a gene for which only 2 alleles known called?

Answer 4

Polymorphic

Question 5

Give an example of multiple alleles.

Answer 5

ABO blood groups

Question 6

What is codominance?

Answer 6

This is when 2 alleles affect the phenotype in separate, distinguishable ways.

Question 7

Give an example of codominance.

Answer 7

A and B blood groups

Question 8

What are polygenic traits?

Answer 8

When a trait is controlled by more than one gene. This means a dominant allele will ad to the next dominant allele.

Question 9

Give an example of polygenic traits.

Answer 9

Height and skin colour.

Question 10

What happens in autosomal dominant disorder?

Answer 10

The normal allele is recessive and the mutated or abnormal allele is dominant.

Question 11

Give an example of an autosomal dominant disorder.

Answer 11

Achondroplasia, a type of dwarfism.

Question 12

How would you identify an autosomal dominant disorder in a pedigree analysis chart?

Answer 12

The phenotype appears in every generation and affected fathers and mothers pass on the phenotype to both sons and daughters. It also shows parents with the disorder passing it onto their children and/or having unaffected children.

Question 13

What happens in autosomal recessive disorders?

Answer 13

The affected phenotype is determined by the homozygosity for a recessive allele and the unaffected phenotype is determined by the presence of the corresponding dominant allele.

Question 14

Give an example of an autosomal recessive disorder.

Answer 14

Phenylketonuria (PKU) and cystic fibrosis (CF).

Question 15

How would you identify an autosomal recessive disorder in a pedigree analysis chart?

Answer 15

It affects both males and females equally and seen by an affected child coming from 2 unaffected parents.

Question 16

What happens in X- linked recessive disorders?

Answer 16

The affected gene is on the X chromosome which men only have one of so if they have the chromosome with the affected gene they will have the condition but if a female has an affected chromosome they may not have the condition because it can be over-ridden by having a dominant allele which will be unaffected.

Question 17

Give an example of X-linked recessive disorder.

Answer 17

Colour blindness. Haemophilia and duchess muscular dystrophy which is fatal.

Question 18

How would you identify a X-linked recessive disorder in a pedigree analysis chart?

Answer 18

It is displayed in more maps than females and none of the offspring of the affected male are affected.

Question 19

Give an example of X=linked dominant disorder?

Answer 19

Vitamin D resistant rickets.

Question 20

How would you identify a X-linked dominant disorder in a pedigree analysis chart?

Answer 20

Affected males pass the condition on to all of their daughters but none of their sons and females with the condition married to an unaffected male will pass it on to half of their sons and daughters.

Question 21

What are mitochondrial genes?

Answer 21

Genes that are inherited only through to egg,

Question 22

What happens with mitochondrial genetic diseases?

Answer 22

There are relatively few genetic diseases caused by mitochondrial mutations but they will always be passed from a mother onto the children.

Question 23

How would you identify a mitochondrial genetic disease in a pedigree chart?

Answer 23

All children of an affected female will be affected but none of an affected male.

Question 24

What is incomplete dominance?

Answer 24

Neither trait is dominant so an intermediate phenotype is apparent.

Question 25

What is pleiotropy?

Answer 25

Most genes are, they affect more than one phenotypic character.