Test 2

Question 1

cytogenetics

Answer 1

Study of behavior and properties of chromosomes

Question 2

molecular genetics

Answer 2

Genetic studies at the molecular level

Techniques to investigate and handle qualitative and quantitative traits.

Question 3

heredity-

Answer 3

Variations that result from heritable causes (genes) and are transmitted to progeny.

Question 4

gene-

Answer 4

basic unit of heredity, located on a specific chromosomal locus

Question 5

Allele –

Answer 5

Allele – an alternative gene; alleles located on corresponding loci of homologous chromosomes

Question 6

homozygous

Answer 6

having like genes at corresponding loci on homologous chromosomes

Question 7

Heterozygous –

Answer 7

having unlike alleles at corresponding loci of homologous chromosomes

Question 8

dominant allele-

Answer 8

an allele that masks the expression of another allele

Usually designated with an uppercase letter

Question 9

Recessive allele –

Answer 9

an allele whose expression is masked by another allele

Question 10

What do P, F1, F2, F3, etc. refer to?

Answer 10

generations of parents

Question 11

What is a monohybrid cross? What is a dihybrid cross?

Answer 11

– cross involving one pair of contrasting traits

- two traits

Question 12

What is a test cross?

Answer 12

cross to see if test plant has homozygous or heterozygous phenotype.

Question 13

What is incomplete or partial dominance?

what ratio would you expect?

Answer 13

Expression of heterozygous phenotype which is distinct from, and often
25,25,50

Question 14

Genotype by environment interaction –

Answer 14

Genotype by environment interaction –relative performance of genotypes in different environments.

Question 15

Additive effects –

Answer 15

each gene (from same locus or from multiple loci) adds an increment, aabb= 0, Aabb= 1, AaBb=2, AABb=3, AABB=4

Question 16

Dominance effects-

Answer 16

heterozygote is more like one parent than the other,hetero and one homo have equal effects.
aa=0, Aa=2, AA=2, A_B_= 4

Question 17

Epistatic effects-

Answer 17

interaction of non-allelic genes, two genes have no effect individually, yet have an effect when combined.
aabb=0, AAbb=0, aaBB=0, A_B_=4

Question 18

Overdominance effects-

Answer 18

each allele contributes a seperate effect, but together they contribute a greater effect.
aa=1, Aa=3

Question 19

heritability-

Answer 19

the proportion of the observed variation in a progeny that is inherited.

Question 20

Additive component

Answer 20

contributed by genes having linear additive effects.(most important)

Question 21

Dominance component-

Answer 21

represents deviation of heterozygote form mid-parent or average of homozygous parents.

Question 22

Nonallelic interaction variance-

Answer 22

deviations caused by epistatic effects.

Question 23

broad sense and narrow sense heritability-

Answer 23

– (H)estimates heritability on basis of all genetic effects

-(h2)estimates heritability on basis of only additive genetic effects

Question 24

• Why is plant breeding both an art and a science?

Answer 24

art in observing unique and valuable characteristics, and science of molecular genetics.

Question 25

Discuss:
maturity-
temperature response-
standability-

Answer 25

1. earliness or lateness
2. Low or high temperature,Cold hardiness
3. Reduces photosynthetic area,Increases potential for disease,Reduces harvest efficiency

Question 26

Discuss:
Resistance to Shattering-
Pest resistance-
Numerous Other stresses

Answer 26

1. Ability to hold fruit/seed until harvest
2. Immunity or tolerance of pests during some critical period of development
3. Drought tolerance, herbicide tolerance.

Question 27

What quality traits are important?

Answer 27

Grower
processing traits
Consumer desirable traits

Question 28

hybridization-

introduction-

Answer 28

– bringing together dissimilar genotypes to produce desired offspring
-bringing new types into an area and using them for selection or hybridization.

Question 29

the two essential characteristics of a cultivar? Be able to briefly describe each.

Answer 29

being Identifiable-recognized and distinguished from other cultivars
and reproducible- maintained from year to year.

Question 30

how are cultivars different from strains?

Answer 30

A cultivar further differs from a strain in that it has been proven superior and has been named and released commercially for use

Question 31

What is the pure-line theory?

Answer 31

once a pure line (homozygous genotype) is established, further selection within that pure line is ineffective due to all genotypes being identical.

Question 32

What are the objectives of mass selection?

Answer 32

Purify a mixed cultivar or plant population through selecting and multiplying visibly similar plants (similar phenotypes)
Develop a new cultivar that will have improved average performance over the parent population.

Question 33

Describe the procedure used in mass selection.

Answer 33

plants chosen by phenotype,harvested, and seeds bulked.

New cultivar is comprised of selected phenotypes.

Question 34

What is pure-line selection?

Does this method create new genotypes?

Answer 34

a method of isolating pure lines from a mixed population. No

Question 35

What factors affect the effectiveness of pure line selection?

Answer 35

limited to isolating the best genotype from a mixture of genotypes

Question 36

Describe the procedure used in pure-line selection, broken down by years within the procedure.

Answer 36

year 1- select 200-1000 plants from mixed population of self-pollinating plants
year 2- grow prodgeny of each plant in single row,harvest and composit seed,
year 3- grow strains in replicated observation plots, harvest superior strains.
year 4-7 - conduct yield tests and choose best strains for distribution.