Gene Linkage And Epigenetics

Question 1

What does di and hybrid mean in a dihybrid cross

Answer 1

Di: two
Hybrid: different and heterozygous

Question 2

Un-linked autosomal genes, Dihybrid cross ratio

Answer 2

9:3:3:1

Total of 16 punnet squares

Question 3

Test-cross explained.

Answer 3

Crossing an organism with a dominant phenotype to an organism with a recessive phenotype in order to find if it is homozygous or heterozygous. The offspring will tell you all you need to know; if only dominant phenotypes show, then the original dominant phenotype must be homozygous dominant. If a recessive phenotype shows in any offspring then we know it is heterozygous.

Question 4

Phenotypic ratios of test crossing a monohybrid

Answer 4

1:1

Question 5

Phenotypic ratios of test crossing a dihybrid

Answer 5

1:1:1:1

Question 6

Independent assortment and it’s paradox?

Answer 6

Genes are assorted independently when switching chromosomes and synapsis occurs. Only exception to this law is genetic linkage.

Question 7

Recombination frequency

Answer 7

The likelihood of 2 genes or alleles that begin together on the same chromosome and recombine on another chromosome after meiosis.

Question 8

A greater recombination frequency correlates strongly with

Answer 8

the greater distance along the chromosome.

Question 9

A low recombination frequency correlates strongly with

Answer 9

A low distance on the chromosome.

Question 10

The closer the alleles are on the chromosome the more

Answer 10

Highly linked the alleles are.

Question 11

In a complementary dihybrid crossed gene you would expect a …….ratio?

Answer 11

9:7

Question 12

Complementary gene or epistasis

Answer 12

A particular set of alleles at one gene can mask a particular set of a second gene. Epistatic relationships.

Question 13

Unlinked genes

Answer 13

Genes on different chromosomes assort independently into gametes

Question 14

Linked gene

Answer 14

Genes on the same chromosome generally stay together in gametes

Question 15

What ratio would you expect to get in a self cross of a dihybrid with both dominant alleles on the same chromosome?
AB/ab x AB/ab

Answer 15

3:1

Question 16

What ratio would you expect to get in a test-cross of a dihybrid with both dominant alleles on the same chromosome?
AB/ab x ab/ab

Answer 16

50/50 or 1:1

Question 17

When to use a Chi-squared test?

Answer 17

Testing wether genes are significantly linked or not, with a goodness of fit test.

Question 18

Epigenetics

Answer 18

External and environmental influences impacting genes and how they work.

Question 19

Epigenetic trait

Answer 19

Are stable both mitotically and meitically, and result in a heritable phenotype by changing gene expression without altering DNA sequence.

Question 20

External signs that stimulate a cellular response; stress, pathogens, toxins are termed ……. In genetics

Answer 20

Epigenators

Question 21

RNA and DNA binding proteins that interact with genetic elements to trigger a response are termed……

Answer 21

Initiators

Question 22

Enzymes / proteins that interact with DNA to sustain change are termed…..

Answer 22

Maintainers

Question 23

siRNA

Answer 23

Small interfering RNA

Question 24

End result of an epigenetic pathway is…

Answer 24

A functional gene that does not always result in expressed phenotype.