lecture 9- tetrad analysis

Question 1

MI type segregation

Answer 1

4:4 segregation (one allele in top half and the other allele in the bottom half of the ascus

Question 2

MII type segregation

Answer 2

2:2:2:2 segregation (both alleles are present in both halves of the ascus

Question 3

independent assortment

Answer 3

the independent assortment of 2 genes will result in 50% parental ditype (PD) and 50% non-parental ditype (NPD or recombinant tyoe)

Question 4

complete linkage

Answer 4

complete linkage of 2 genes will result in only parental ditype ascus

Question 5

linkage of 2 genes with crossover

Answer 5

this will result in the number of PD&raquo_space;> number of NPD asci

Question 6

parental ditype (PD)

Answer 6

no crossing over between loci or double crossing over of the same 2 chromatids

Question 7

non parental ditype

Answer 7

all spores are recombinant- and all 4 chromatids are involved in the double cross over

Question 8

tretratype (T)

Answer 8

1/2 spores are recombinant- single crossing over of 2 chromatids or double crossing over involving 3 chromatids

Question 9

parental ditype WITH MII segregation

Answer 9

crossover between one locus and centromere, but no crossing over between loci

Question 10

penetrance

Answer 10

the frequency with which a genotype expresses a phenotype. A trait has low penetrance if few individuals with the gene(s) express it

Question 11

expressivity

Answer 11

the degree to which a trait is expressed in individuals having the gene(s)

Question 12

sex-limited traits

Answer 12

the expression of certain traits is only in one of the sexes. the traits encoded by genes on the autosomes but the character is expressed only in one sex

Question 13

sex-influenced traits

Answer 13

expression of certain traits is influenced by the sex. this appears in both of the sexes, but the frequency or degree of the phenotypic expression is different between the sexes

Question 14

effects of environment on phenotype

Answer 14

the phenotype results from the genotype interacting with the environment, changes in the environment can alter the phenotype

Question 15

multiple alleles

Answer 15

essentially all genes have not just two alleles, but many since there can be mutations at any of 1000 or more bases in a gene and result in many possible alleles

Question 16

blood type A

Answer 16

I^A I^A or I^A i

Question 17

blood type B

Answer 17

I^B I^B or I^B i

Question 18

blood type AB

Answer 18

I^A I^B

Question 19

blood type O

Answer 19

i i

Question 20

codominance

Answer 20

usually involves a system in which the 2 alleles of a single gene have slightly different products, both of which appear in the expression of the phenotype. this is usually molecular