Patterns of Inheritance

Question 1

What does the genotype influence?

Answer 1

The phenotype

Question 2

What is the phenotype?

Answer 2

What it looks like

Question 3

What does the environment influence?

Answer 3

The genotype and the phenotype

Question 4

Give 5 environmental factors

Answer 4

• Radiation
• Mutagens
• Chemicals affecting cell growth
• Diet
• Life style

Question 5

Give an example of how an environmental factor can influence the DNA

Answer 5

Radiation can damage DNA

Question 6

Give an example of a disease that is purely genetic

Answer 6

Cystic fibrosis

Question 7

Give an example of a disease that is purely environmental

Answer 7

Infection

Question 8

Give 2 examples of diseases that are a mixture of genetic and environmental factors

Answer 8

NAME?

Question 9

What are genetics down to?

Answer 9

NAME?

Question 10

What is variation caused by?

Answer 10

NAME?

Question 11

How many genes does each human have?

Answer 11

25,000

Question 12

How many copies of each gene does each individual have?

Answer 12

2

Question 13

Where do the 2 copies of each gene come from?

Answer 13

One maternal, one paternal

Question 14

What does each individual have of each gene?

Answer 14

2 alleles

Question 15

How many alleles of a gene are there within a population?

Answer 15

Many

Question 16

What does homozygous mean?

Answer 16

Two alleles of a gene are the same

Question 17

What does heterozygous mean?

Answer 17

Two alleles of a gene are different

Question 18

What does hemizygous mean?

Answer 18

Only one allele of a gene on the X chromosome

Question 19

What does dominant mean?

Answer 19

The allele that determines the phenotype in heterozygote

Question 20

What does recessive mean?

Answer 20

The non-dominant allele

Question 21

Is the heterozygote affected in an autosomal recessive disease?

Answer 21

No

Question 22

Are males or females more affected in an autosomal recessive condition?

Answer 22

Equal

Question 23

What is the chance of two heterozygotes having a child affected with an autosomal recessive condition?

Answer 23

25%

Question 24

What is chance of two individuals affected by an autosomal recessive condition having affected children?

Answer 24

100%

Question 25

Are heterozygotes affected with an autosomal dominant condition?

Answer 25

Yes

Question 26

Is an autosomal dominant disease usually found in the homozygous state?

Answer 26

No

Question 27

Why is an autosomal dominant disease not usually found in the homozygous state?

Answer 27

Often, disease is so important, that the homozygous state is incompatible with life

Question 28

What is the chance of an affected individual having affected offspring in the case of an autosomal dominant disease?

Answer 28

50%

Question 29

What does every individual affected with an autosomal dominant condition have?

Answer 29

At least 1 affected parent

Question 30

Can an autosomal dominant disease skip a generation?

Answer 30

No

Question 31

Who is affected with an X-linked recessive disease?

Answer 31

Hemizygous males and homozygous females

Question 32

Who is a X-linked recessive disease more common in?

Answer 32

Males

Question 33

What is the chance of a heterozygous female carrier or an X-linked recessive disease having an affected son?

Answer 33

50%

Question 34

Can a male affected with a X-linked recessive disease give the trait to their sons?

Answer 34

No

Question 35

Why can’t a male affected with a X-linked recessive disease give the trait to their sons?

Answer 35

Because the trait is on the X chromosome, but males can only give the Y chromosome to their songs

Question 36

What does every female affected with an X-linked recessive disease have?

Answer 36

A carrier mother and an affected father

Question 37

What is the genotype of daughters of males with an X-linked recessive condition?

Answer 37

Heterozygous

Question 38

What is co-dominance?

Answer 38

When both alleles contribute to the phenotype

Question 39

Give an example of where co-dominance is shown?

Answer 39

In blood types

Question 40

What is complementation?

Answer 40

When more than one gene contributes to the phenotype

Question 41

Give an example of where complementation is found?

Answer 41

Albinism

Question 42

How does complementation work?

Answer 42

A gene may code for an enzyme that converts the substrate to an intermediate. Another gene may code for a different enzyme that converts the intermediate to the product. Therefore, both genes have contributed

Question 43

What is said of genes on the same chromosome?

Answer 43

They are ‘linked’

Question 44

Do linked genes show independent assortment at meiosis?

Answer 44

No

Question 45

Why don’t linked genes show independent assortment at meiosis?

Answer 45

Because they are carried together

Question 46

Why do you only have two combinations of gametes with linked genes?

Answer 46

As the alleles are carried together

Question 47

How can you get other combinations with linked genes?

Answer 47

If crossing over between locus of the linked genes

Question 48

Why is the ratio of gametes for linked genes not 1:1:1:1?

Answer 48

Because dependant on how often crossing over occurs

Question 49

What is recombination frequency between two linked genes dependant on?

Answer 49

The distance between two genes

Question 50

What is said of genes close together?

Answer 50

They are ‘tightly linked'

Question 51

How do genes far apart on the same chromosome behave as?

Answer 51

Almost as unlinked genes