Genetics, Genome Structure and Organisation, and Gene Function

Question 1

How many characters are changing in a monohybrid cross?

Answer 1

One

Question 2

How many characters are changing in a dihybrid cross?

Answer 2

Two

Question 3

What does a monohybrid cross demonstrate?

Answer 3

Allelic segregation

Question 4

What does a dihybrid cross demonstrate?

Answer 4

Independent assortment of alleles

Question 5

What is the probability relationship between each assortment in independent assortment?

Answer 5

Each assortment is equally probable

Question 6

What is the phenotype ratio in partial dominance?

Answer 6

1:2:1

Question 7

What is partial dominance?

Answer 7

When the phenotype is an intermediate between the two alleles

Question 8

What are the two alleles labelled when there is no clear dominance relationship?

Answer 8

R^1 and R^2

Question 9

Define co-dominance

Answer 9

When two alleles produce distinct and detectable gene products and distinct and detectable effects on phenotype

Question 10

How is co-dominance different to partial dominance?

Answer 10

In partial dominance, a mixture of the alleles in the genotype are seen in the phenotype but in co-dominance both alleles in the genotype are seen in the phenotype.

Question 11

How do multiple alleles occur?

Answer 11

A mutation occurs producing a new allele so one gene exhibits multiple alleles

Question 12

What is a null mutation?

Answer 12

A mutation that abolishes function

Question 13

What are recessive lethal alleles?

Answer 13

Null mutations in essential genes that can be tolerated in the heterozygous state but homozygous alleles are embryo lethal

Question 14

Why are dominant lethal alleles usually lost from the population?

Answer 14

Individuals with dominant lethal alleles die before reproducing

Question 15

Why might dominant lethal alleles not be lost from the population?

Answer 15

When the phenotype exhibits late onset e.g. Huntington’s

Question 16

Define epistasis

Answer 16

One gene masks or modifies the expression of another gene

Question 17

What does gene interaction imply?

Answer 17

More than one protein may be required for the development of a single phenotype

Question 18

What does the mutation fut1 do?

Answer 18

In relation to blood group: prevents synthesis of complete H substance so A and B antigen production is supressed

Question 19

Which antibodies do Bombay individuals produce?

Answer 19

Anti-H antigen antibodies

Question 20

What are Bombay individuals at risk of?

Answer 20

Haemolytic transfusion if they receive blood containing H antigens

Question 21

What is duplicate recessive epistasis?

Answer 21

When a recessive allele is masking the expression of dominant alleles at two loci

Question 22

In duplicate recessive epistasis, what would aa do?

Answer 22

Mask any genotype at locus B

Question 23

In duplicate recessive epistasis, what would bb do?

Answer 23

Mask any genotype at locus A

Question 24

What is novel phenotype?

Answer 24

A phenotype that is unique in comparison to the parent phenotypes

Question 25

What are males described as for X-linked genes?

Answer 25

Hemizygous

Question 26

What is gene drive?

Answer 26

A form of genome editing

Question 27

What is the aim of forward genetics?

Answer 27

To identify mutations that produce a certain phenotype

Question 28

Is forward genetics a controlled or random process?

Answer 28

Random; randomly generates mutations hoping that differences are phenotypically observed

Question 29

What is the aim of reverse genetics?

Answer 29

To identify the phenotype that results from specific mutations

Question 30

What is the role of gene knock out in reverse genetics?

Answer 30

Confirms that the phenotype is a direct result of the mutation

Question 31

What are the main 3 advantages of unicellular model organisms?

Answer 31

• Very short reproductive cycles
• Can be grown easily
• Large numbers produced allow rapid identification of rare organisms

Question 32

Describe the prokaryotic genome

Answer 32

Single, circular chromosome with less junk DNA than eukaryotes making it more efficient

Question 33

What can add functionality to the prokaryotic genome?

Answer 33

Extra DNA in the form of plasmids

Question 34

How can reverse genetics be carried out on unicellular organisms?

Answer 34

Using recombinant DNA technology to construct a mutated version of the target gene which can be transformed into E. coli and the phenotype can be analysed

Question 35

Give 5 advantages of zebrafish as a model organism

Answer 35

• Fast early development
• Many eggs
• Eggs develop outside the mother
• Eggs are transparent
• Can be used for both forward and reverse genetic screens

Question 36

Give 3 disadvantages of zebrafish as a model organism

Answer 36

• Need to be bred for 2 generations until homozygous offspring are observed
• Requires significant resources
• More licensing needed

Question 37

Define syntenic

Answer 37

Genes that occur on the same chromosome

Question 38

What are orthologues?

Answer 38

Homologous genes where a gene diverges after a speciation event but the gene and its main function are conserved

Question 39

What technique can be used in mice to investigate human gene function and simulate human disease phenotypes?

Answer 39

Gene knockouts (reverse genetics)

Question 40

Where are embryonic stem cells derived from?

Answer 40

Inner cell mass of the blastocyst

Question 41

What is the aim of targeted mutagenesis using ESC?

Answer 41

To inactivate genes to investigate their function