Genetics of Maize Flashcards
What does it mean that maize is monoecious?
It means male and female flowers are found on the same plant
Male flowers (tassels) produce pollen, while female flowers (ears) develop cobs with ovules.
What are the male and female flower structures in maize?
Male flowers develop in spikelets with stamens; female flowers develop as cobs with ovules protected by silks.
What type of pollination occurs in maize?
Wind pollination.
What is produced during meiosis in male and female maize flowers?
Haploid pollen grains in anthers; haploid egg cells in ovules.
What is the purpose of Lugol’s staining in pollen analysis?
To differentiate between wild-type and mutant pollen.
What does dark purple staining indicate in pollen?
Wild-type pollen (Wx+) contains starch.
What is the appearance of mutant pollen (wx) when stained?
It appears non-stained due to lack of starch.
What is the significance of starch in pollen?
It serves as an energy reserve for pollen tube growth.
What Mendelian inheritance ratio is observed in pollen types?
1:1 ratio of Wx+ (wild-type) to wx (mutant) pollen.
What are the traits of wild-type kernels (Wx+)?
Plump, opaque, starchy.
What are the traits of mutant kernels (wx)?
Shrunken, translucent, sugary.
What is the molecular basis for wild-type kernels?
Functional Wx+ allele enables normal amylopectin synthesis.
What is the impact of the wx mutation in sweetcorn breeding?
It increases sugar content, enhancing sweetness.
What cross-pollination issue can arise in sweetcorn?
Proximity to field maize can lead to starchy kernels if Wx+ pollen fertilizes sweetcorn.
What is the observed ratio for segregation of a single kernel character?
~1:1 for Wx+ (wild-type) and wx (mutant) phenotypes.
What does a heterozygous parent contribute to offspring in kernel segregation?
Equal probabilities of Wx+ and wx alleles.
What gene controls kernel color in maize?
The C gene.
What are the phenotypes associated with the C gene?
- Purple Kernels: Functional C gene (wild-type)
- Yellow Kernels: Lack functional C gene (mutant)
What gene controls kernel shape in maize?
The Sh1 gene.
What are the phenotypes associated with the Sh1 gene?
- Plump Kernels: Functional Sh1 gene (wild-type)
- Shrunken Kernels: Lack functional Sh1 gene (mutant)
What ratio is expected from a cross between a heterozygous plant and a homozygous mutant?
1:1:1:1 ratio.
What does the presence of deviations in observed ratios suggest?
Linkage between genes.
What is the calculated map distance between C and Sh1 loci?
20.8 centiMorgans (cM).
What do deviations from expected Mendelian ratios demonstrate?
Genetic linkage.
