8B- dihybrid crosses

Question 1

what are dihybrid crosses used for

Answer 1

if we want to predict the genetic outcome of two traits and calculate the likelihood of different combinations of genes being expressed in offspring a dihybrid cross can be used

Question 2

whats a dihybrid cross

Answer 2

a genetic cross used to observe the inheritance of alleles and phenotypes for two genes

Question 3

what are unlinked genes

Answer 3

genes located on different chromosomes or far apart on the same chromosome. unlinked genes have less chance of being inherited together

Question 4

how to determine the different gametes produced by an individual during meiosis

Answer 4

FOIL method

Question 5

what is the ratio for heterozygous dihybrid crosses

Answer 5

9:3:3:1

Question 6

what happens in unlinked genes that are on different chromosomes

Answer 6

they are subject to independent assortment

Question 7

what happens in unlinked genes that are far apart on the same chromosome

Answer 7

high chance of crossing over and not subject to independent assortment

Question 8

what happens in linked genes

Answer 8

as they are close together on the same chromosome, there is a low chance of crossing over and being subject to independent assortment

Question 9

how are the chances of crossing over calculated

Answer 9

map units- one map unit is equivalent to 1% chance of crossing over and the offspring containing a recombinant chromosome. this means that crosses with linked genes can result in stranger ratios

Question 10

how are genotypes written for linked genes

Answer 10

Aa/aa

Question 11

how to identify the type of linkage in genes (linked or unlinked)

Answer 11

linked genes: unusual genotypic ratios in offspring (i.e. a few genotypes that arise very rarely) or genotypes that were not present in the parents.

Question 12

what do linked dihybrid crosses indicate

Answer 12

parental/recombinant

Question 13

what are recombinant genes

Answer 13

chromosomes not identical to the parents
e.g. mother is be/be and father is Be/BE, recombinant gametes are BE/be

Question 14

dihybrid cross

Answer 14

a genetic cross used to observe the inheritance of alleles and phenotypes for two genes

Question 15

unlinked genes

Answer 15

genes located on different chromosomes, or far apart on the same chromosome. Unlinked genes have less chance of being inherited together

Question 16

linked genes

Answer 16

genes that are found close together on the same chromosome and are likely to be inherited together

Question 17

independent assortment

Answer 17

the random orientation of homologous chromosomes along the metaphase plate during metaphase I

Question 18

crossing over

Answer 18

the exchange of genetic material between non-sister chromatids during prophase I of meiosis, resulting in new combinations of alleles in daughter cells

Question 19

map units

Answer 19

a measure of the distance between two genes on the same chromatid. Genes that are closer together are more likely to be linked genes

Question 20

recombinant chromosomes

Answer 20

a chromosome which is not identical to one of the homologous chromosomes in a diploid cell

Question 21

parental chromosome

Answer 21

a chromosome which contains the same combination of alleles as one of the parents’ chromosomes