Unit 06: Genetic Linkage and Mapping

Question 1

what is a recombination map?

Answer 1

the mapping of loci of genes where the units of distance are relative to their ability to crossover

Question 2

what is a physical map?

Answer 2

mapping of specific gene loci on a chromosome where the units of distance are the numbers of nucleotides

Question 3

what is another term used for genes located on the same chromosome?

Answer 3

syntenic genes

Question 4

what is a result of syntenic genes being very close together?

Answer 4

genetic linkage (inability to assort independently)

Question 5

what is the result of a test cross involving linked genes?

Answer 5

F1 generation with a LOT of parental phenotypes

Question 6

who discovered the concept of linked genes?

Answer 6

bateson and punnett

Question 7

who confirmed genetic linkage by creating one of the first linkage maps?

Answer 7

thomas morgan

Question 8

describe cis formation.

Answer 8

when the dominant alleles are on one homolog and the recessive are on the other

Question 9

describe trans formation.

Answer 9

when the dominant alleles are NOT on the same homolog

Question 10

who first discovered cytological evidence recombination in corn?

Answer 10

mcclintock and stern

Question 11

what would be the result if we had no crossing over?

Answer 11

only 2 types of gametes - both parental and no recombinants

Question 12

what is a double crossover?

Answer 12

when two crossovers occur between 3 linked traits

Question 13

what percent of morgan’s flies were recombinant?

Answer 13

10.7%

Question 14

what is the recombination frequency in complete linkage?

Answer 14

0

Question 15

what is the recombination frequency in incomplete linkage?

Answer 15

between 0 and 50

Question 16

a dihybrid produces how many unique gametes?

Answer 16

2 parental and 2 recombinant

Question 17

linked genes are always _____

Answer 17

syntenic and located near each other on the same chromosome

Question 18

frequency of cross over is roughly proportionate to _____

Answer 18

distance between genes

Question 19

who de we credit using recombination frequencies to map genes?

Answer 19

alfred sturtevant

Question 20

how can we find the proportion of each parental phenotype using recombination frequencies?

Answer 20

100-RF/2

Question 21

how can we find the proportion of each recombinant phenotype using recombination frequencies?

Answer 21

RF/2

Question 22

what is the formula to calculate recombination frequency?

Answer 22

(number of recombinant offspring)/(total offspring) x 100%

Question 23

what are some examples of linked genes in humans?

Answer 23

• hair and eye colour
• hereditary eliptocytosis

Question 24

the gene for HE is how many mu apart from the gene for Rh factor?

Answer 24

4

Question 25

what is the function of a three point testcross?

Answer 25

determining the recombination frequencies between 3 genes, and therefore the distances between them

Question 26

do male flies undergo recombination?

Answer 26

naur

Question 27

rank the following genotypes in order of abundance in a three point test cross: parental, DCO, SCO

Answer 27

parental>SCO>DCO

Question 28

what is interference?

Answer 28

when we get less DCO than expected if the SCOs occurred independently due to some factors limiting the number of double crossovers

Question 29

what is the formula to find expected number of DCOs?

Answer 29

(SCO1) X (SCO2) = expected DCO freq x total progeny = expected DCO progeny

Question 30

what does interference acc mean?

Answer 30

the number of DCOs expected but not observed

Question 31

what is the formula for coefficient of coincidence ?

Answer 31

observed dco/expected dco

Question 32

what does the coefficient of coincidence represent?

Answer 32

likelihood that crossovers occur tgr

Question 33

what is the formula for interference?

Answer 33

1 - c

Question 34

what happens if we get a negative value for interference?

Answer 34

we got more DCOs than expected!

Question 35

what genotypic ratio do we test when doing a chi square test to infer gene linkage?

Answer 35

1:1:1:1

Question 36

what can influence recombination in genomes?

Answer 36

- sex - age - temperature - genetic hot/cold spots

Question 37

recombination frequency _____ the actual physical distance between genes

Answer 37

underestimates

Question 38

what type of organisms have lower recombination?

Answer 38

heterogametic

Question 39

what is the difference between genetic hot and cold spots?

Answer 39

hot - recombination occurs more than average based on # of nucleotides present cold - recombination occurs less than average bc of # of nucleotides present