11. Genotype, Phenotype and Inheritance

Question 1

What is genotype?

Answer 1

• A genotype is an individual’s collection of genes

Question 2

What is phenotype?

Answer 2

• the set of observable characteristics of an individual resulting from the interaction of it’s genotype with the environment.

Question 3

What influences phenotypes?

Answer 3

Genotype and environment

Question 4

Can the environment affect our genotype?

Answer 4

Yes - radiation, mutagenic chemicals, smoking

Question 5

How many alleles are there of a gene?

Answer 5

2

Question 6

How many allele of a gene are there in the population

Answer 6

Many

Question 7

Define homozygous

Answer 7

Two alleles of a gene are the same

Question 8

Define heterozygous

Answer 8

Two alleles of a gene are different

Question 9

Define hemizygous

Answer 9

Only one allele of the gene on the X chromosome (Males only)

Question 10

Define dominant

Answer 10

The dominant allele in heterozygote determines the phenotype (only one allele is needed to be expressed)

Question 11

Define recessive

Answer 11

The non-dominant allele in a heterozygote is called recessive (Two of these alleles need to be present for the characteristic to be expressed)

Question 12

Define co-dominance

Answer 12

When both alleles are expressed (neither is dominant or recessive)

Question 13

What are the three alleles for blood type?

Answer 13

A B O

Question 14

Which two alleles of blood type are codominant?

Answer 14

A and B

Question 15

What are the different types of inheritance patterns?

Answer 15

Autosomal / sex-linked (Mendelian)

Mitochondrial

Polygenic / Complex or multifactorial

Question 16

Give an example of an autosomal recessive disease

Answer 16

Cystic fibrosis

Question 17

Give an example of an autosomal dominant disease

Answer 17

Huntington’s disease

Question 18

Why are diseases rarely found in the dominant homozygous state?

Answer 18

Diseases with dominant homozygous are very bad that its not viable for life

Question 19

What’s the chance that an affected individual has an affected offspring in an autosomal dominant disease?

Answer 19

50%

Question 20

Can an autosomal dominant disease skip a generation?

Answer 20

No

Question 21

Who are affected by x-linked recessive diseases?

Answer 21

Hemizygous males and homozygous

females affected

Question 22

Who are x-linked recessive diseases more common in?

Answer 22

Males

Question 23

What’s the chance of a heterozygous female carrier having affected sons of an x-linked recessive disease?

Answer 23

50%

Question 24

What’s the chance of an affected male carrier having affected sons of an x-linked recessive disease?

Answer 24

0%

Question 25

What is an example of an x-linked recessive disease?

Answer 25

Haemophilia A

Question 26

Who are affected in x-linked dominant diseases?

Answer 26

Hemizygous males and heterozygous

females affected

Question 27

Will affected males of x-linked dominant diseases give the trait to sons and daughters?

Answer 27

Affected males cannot give trait to sons,

but will give it to all their daughters

Question 28

Who do all individuals inherit their mitochondria and mitochondrial DNA from?

Answer 28

From their mothers

Question 29

What is the chance of children of a mother with a mitochondrial disease inherit the disease?

Answer 29

All the children will inherit it

Question 30

What is the chance of children of a father with a mitochondrial disease inheriting the disease?

Answer 30

None of the children will be affected

Question 31

What does polygenic mean?

Answer 31

When more than one gene is involved in producing a phenotype

Question 32

Is albinism inherited in a dominant or recessive manner?

Answer 32

Recessive manner

Question 33

When considering polygenic inheritance, what does linked and not linked mean?

Answer 33

• Genes on the same chromosome are
said to be ‘linked’
• Genes on different chromosomes are
said to be ‘not linked’

Question 34

What types of genes do not show independent assortment at meiosis?

Answer 34

Linked genes

Question 35

What is the recombinant frequency?

Answer 35

How often crossing over occurs

Question 36

What is the recombinant frequency between two linked genes dependent on?

Answer 36

The instance between the genes

Question 37

If two genes are close together, what is it called and what does t mean?

Answer 37

Tightly linked - the genes are more likely to travel together - less affected by crossing over

Question 38

What happens if two genes on the same chromosome are far apart?

Answer 38

They almost behave as unlinked genes

Question 39

Describe the effect of distance between genes on crossing over occurring

Answer 39

The further linked genes are apart, the more likely that crossing over occurs and more likely that new combinations are made