Inheritance

Question 1

How many generations should you aim for as a minimum when taking a family history?

Answer 1

3 generations

Question 2

What is penetrance in relation to autosomal dominant inheritance?

Answer 2

The proportion of heterozygotes for a dominate a gene who express a trait, even if mildly

Question 3

What is expressivity in relation to autosomal dominant inheritance?

Answer 3

The variation in severity of the phenotypic features of a particular gene

Question 4

In which type of inheritance is population background information (e.g ethnicity) particularly useful? Why?

Answer 4

Autosomal recessive inheritance

Carrier frequency for different conditions can vary greatly between different populations

Question 5

What is consanguinity? Which type of inheritance is it particularly important in?

Answer 5

The blood relation of two individuals

Autosomal recessive

Question 6

How is mtDNA inherited?

Answer 6

Maternally

Question 7

In mitochondrial inheritance, the offspring of an affected female…

Answer 7

Will all be affected

Question 8

In mitochondrial inheritance, the offspring of an affected male…

Answer 8

Will not be affected

Question 9

What is the use of paternal mitochondria?

Answer 9

Used to power tail of sperm in fertilisation and then lost

Question 10

Most individuals affected by mitochondrial diseases have some normal and some mutated mtDNA, what is expression of the disease dependent on?

Answer 10

The burden of mutant vs normal mtDNA

Question 11

Give an example of a mitochondria-related disease.

Answer 11

Leber’s hereditary optic neuropathy

Question 12

Most common disease is not the result of mutations in single genes. It is….

Answer 12

Multifactorial

genes and non-genetic factors (e.g. Environment/behaviour) interact - on a spectrum

Question 13

Give an example of a largely genetic (unifactorial) disease?

Answer 13

Duchenne muscular dystrophy

Question 14

Give an example of a largely environmentally influenced disease?

Answer 14

Scurvy

Question 15

Each individual has how many alleles of each gene?

Answer 15

2

Question 16

What does homozygous mean?
What does heterozygous mean?
What does hemizygous mean?

In relation to alleles

Answer 16

Two alleles of a gene are the same

Two alleles of a gene are different

Only one allele exists for that gene on the x chromosome (only in males)

Question 17

What is an example of co dominance in the human body?

Answer 17

Human ABO blood types

Question 18

What is different between different blood types? What gene codes for these differences?

Answer 18

Different glycoproteins on surface of RBCs

Isoglutamin gene

Question 19

What are the 3 different alleles for blood type? Which 4 blood types exist?

Answer 19

A, B and O

A, B, AB and O

Question 20

Which alleles out of A, B and O are dominant over each other?

Answer 20

A is dominant over O
B is dominant over O
A and B show co-dominance

Question 21

How is the unknown sex of an individual displayed when drawing a pedigree? How is a deceased individual displayed?

Answer 21

Diamond

Diagonal line through the symbol

Question 22

By convention when drawing a pedigree the oldest child…

Answer 22

Is on the left of a line

Question 23

By convention when during a pedigree each generation is… (2)

Answer 23

Numbered (roman numerals)

Given a separate line

Question 24

In autosomal recessive inheritance, heterozygotes are…

Answer 24

Unaffected

Question 25

In autosomal recessive inheritance, males and females are...

Answer 25

Equally affected

Question 26

How can you recognise an autosomal recessive condition by a pedigree?

Answer 26

Males/females equally affected Can skip generations Disease 'comes out of nowhere'

Question 27

In autosomal dominant inheritance, heterozygotes are...

Answer 27

Affected

Question 28

In autosomal dominant inheritance, males and females are...

Answer 28

Equally affected

Question 29

Disease for autosomal dominant conditions is rarely found in the ______ state.

Answer 29

Homozygous

Question 30

Every affected individual has a _____% chance of having affected children (Autosomal dominant)

Answer 30

50%

Question 31

Two heterozygotes have a _____% chance of having affected offspring. (Autosomal recessive)

Answer 31

25% chance

Question 32

Give an example of a autosomal recessive condition and an autosomal dominant condition.

Answer 32

Cystic fibrosis Huntington's disease

Question 33

How can you recognise an autosomal dominant condition from a pedigree?

Answer 33

Males and females equally affected Disease does not skip generations Affected child will have at least 1 affected parent

Question 34

Which individuals are affected by an X-linked recessive condition?

Answer 34

Homozygous females | Hemizygous males

Question 35

X-linked recessive inheritance is more common...

Answer 35

In males

Question 36

In x-linked recessive inheritance affected males _____ pass on trait to their sons

Answer 36

Cannot

Question 37

In x linked recessive inheritance, what is the chance of a heterozygous female having an affected son?

Answer 37

50%

Question 38

Give an example of an x-linked recessive disease. | Give an example of an x-linked dominant disease

Answer 38

Haemophilia A Fragile X syndrome

Question 39

How can x-linked recessive inheritance be recognised?

Answer 39

Males and females unequally affected More common in males Every affected female will have an affected father and a carrier mother at least Every affected male will have at least a carrier mother

Question 40

Which individuals are affected by X-linked dominant inheritance?

Answer 40

Hemizygous males and heterozygous females

Question 41

In x-linked dominant inheritance, a heterozygous female has a ____% chance of having affected offspring.

Answer 41

50% chance

Question 42

Why is Y linked inheritance so rare? How is it passed? What is an example?

Answer 42

Small chromosome - so very few genes From father to son only Y chromosome infertility

Question 43

In which way is albinism inherited?

Answer 43

Autosomal recessive Result of multiple genes

Question 44

What is polygenic inheritance?

Answer 44

Where more than 1 gene is involved in producing a phenotype

Question 45

What are linked genes?

Answer 45

Genes on the same chromosome

Question 46

What are unlinked (not linked) genes?

Answer 46

Genes on different chromosomes

Question 47

Congenital cataract shows which inheritance pattern?

Answer 47

Autosomal dominant

Question 48

Tay-sachs disease shows which inheritance pattern?

Answer 48

Autosomal recessive

Question 49

Haemophilia A shows which inheritance pattern?

Answer 49

X-linked recessive

Question 50

Two genes that are close together on the same chromosome are _____ likely to be inherited together at meiosis

Answer 50

More likely to be inherited together