Question 1

What is the difference between dominant and recessive alleles in Mendelian inheritance?

Accepted Answer

Dominant alleles are expressed in the phenotype even when only one copy is present, while recessive alleles are expressed only when two copies are inherited. In Mendel's pea experiments, purple flower color is dominant and requires only one uppercase P allele to appear. White flowers, the recessive trait, only appear when an organism inherits two lowercase p alleles.

Question 2

Why did white flowers reappear in Mendel's second generation of pea plants?

Accepted Answer

First-generation purple flowers were heterozygous, carrying one dominant purple allele and one recessive white allele. When these plants self-crossed, offspring could inherit two recessive alleles, expressing the white phenotype. The Punnett square shows this produces a 3:1 ratio of purple to white flowers in the second generation.

Question 3

How does sex linkage affect inheritance patterns differently than autosomal traits?

Accepted Answer

Sex-linked traits, like hemophilia, are controlled by genes on the X chromosome where males have no corresponding allele on the Y chromosome. Males need only one recessive allele to express the phenotype, while females require two copies. This causes sex-linked recessive disorders to appear more frequently in males than females.

Question 4

What role do chromosomes play in organizing genetic information?

Accepted Answer

Chromosomes are long strands of DNA that typically exist in pairs and contain genes for different traits, similar to recipes in a cookbook. Organisms like Drosophila and humans have autosomes and sex chromosomes. A karyotype is the organized visual representation of an organism's complete chromosome set, revealing chromosome structure and number.

Question 5

Why is the ABC transporter gene important in Drosophila eye color?

Accepted Answer

The ABC transporter gene controls the transport of pigments into eye granules. If this gene is broken, pigments cannot be transported into granules and remain invisible, causing white eyes even when pigment is being produced. This gene's inheritance pattern demonstrates whether traits follow Mendelian or sex-linked inheritance models in the genetics of organisms ref and wef fly genetics procedure.

Question 6

How did Thomas Hunt Morgan use fruit flies to advance our understanding of genetics?

Accepted Answer

Morgan studied Drosophila to investigate inheritance patterns and discovered sex-linked genes, demonstrating that not all traits follow Mendel's simple model. Fruit flies are ideal laboratory organisms because they are easy to maintain, breed, and manipulate. Morgan's work with these organisms revealed that genes are located on chromosomes and helped reconcile Mendelian theory with observed inheritance patterns.

Question 7

What makes heterozygous females carriers of X-linked recessive disorders?

Accepted Answer

Heterozygous females carry one normal allele and one recessive disease allele on their two X chromosomes. The normal allele is typically dominant, so the female does not express the disorder. However, she can pass the recessive allele to offspring. Statistically, half her sons will inherit and express the recessive phenotype, while daughters require two copies to be affected.

生物体遗传学

孟德尔遗传学

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