Concept explainers
Videos
What characteristic of the sex chromosomes allowed Morgan to correlate their behavior with that of the alleles of the eye color gene?
To review: The characteristics of sex chromosomes that helped Morgan to correlate their behavior with that of the alleles of the eye color gene.
Concept introduction: Sex chromosomes are those chromosomes that play a crucial role in determination of Sex of the individual. They have important function in the development of sexual characteristics in the organisms.
Explanation of Solution
The X and Y chromosomes act as sex chromosomes in most of the organisms. The genes which are present on sex chromosome are called sex-linked genes. There are approximately 1,100 X-linked genes. On the other hand, Y chromosome contains relatively very few genes.
The sex-linked genes display a unique pattern of inheritance. The expression of recessive X-linked trait requires two copies of alleles in females (homozygous) and only one copy of the allele in males (hemizygous).
The probability of a male to receive a single mutated X-linked gene from their mother is high as compared to a female receiving both the X-linked mutated genes from the mother (carrier) and father (carrier).
When Morgan crossed red-eyed female (wild-type) with white-eyed male (mutant), all the offspring were red-eyed in the first generation (F1). Then he again crossed the F1red-eyed female to the red-eyed male of F1. The typical ratio of 3:1 (red-eyed flies: white eyed flies) was observed in the F2, but all white-eyed flies were males.
Morgan concluded that this could be due to hemizygous condition (presence of single X-chromosome) of the males. Females required both the mutated alleles to express the phenotype (white eye color) while male needed only one mutated allele to show the phenotype. The probability to inherit both mutated copy is less. Hence, no females displayed the white coloration of eye.
Sex-linked genes exhibit unique inheritance pattern
Want to see more full solutions like this?
Chapter 15 Solutions
IA MODIFIED MASTERING BIOLOGY WITH E TEX
Additional Science Textbook Solutions
Chemistry: The Central Science (14th Edition)
Anatomy & Physiology (6th Edition)
Physics for Scientists and Engineers: A Strategic Approach, Vol. 1 (Chs 1-21) (4th Edition)
Campbell Essential Biology (7th Edition)
Applications and Investigations in Earth Science (9th Edition)
Microbiology: An Introduction
- Human sex chromosomes are XX for females and XY for males. a. With respect to an X-linked gene, how many different types of gametes can a male produce? b. If a female is homozygous for an X-linked allele, how many different types of gametes can she produce with respect to this allele? c. If a female is heterozygous for an X-linked allele, how many different types of gametes can she produce with respect to this allele?arrow_forwardAssume that a meiotic-nondisjunction event causes trisomy 8 in a newborn. If two of the three copies of chromosome 8 are absolutely identical, at what point during meiosis did the nondisjunction event take place?arrow_forwardDuring meiosis in male mammals, sex chromosomes segregate to produce two types of sperm: X‑bearing sperm and Y‑bearing sperm. True or false?arrow_forward
- Which findings support the fact that the presence of the Y- chromosome rather than the lack of a second X-chromosome determines the development of maleness in mammals? A transgenic mouse with two X-chromosomes and the SRY gene from the Y-chromosome develops male sex organs. A human with an XXXY genotype (Klinefelter syndrome) is phenotypically male. A human with an XO genotype (Turner syndrome) is phenotypically female. a and b, but not c a, b, and carrow_forwardButterflies have an X-Y sex-determination system that is different from that of flies or humans. Female butterflies may be either XY or X0, while butterflies with two or more X chromosomes are males. This photograph shows a tiger swallowtail gynandromorph, which is half male (left side) and half female (right side). Given that the first division of the zygote divides the embryo into the future right and left halves of the butterfly, propose a hypothesis that explains how nondisjunction during the first mitosis might have produced this unusual-looking butterfly. Question is also in the picture.arrow_forwardA black female cat (XBXB) and an orange male cat (X0Y) weremated to each other and produced a male cat that was calico.Which sex chromosomes did this male offspring inherit from itsmother and father? Remember that the presence of the Y chromosome determines maleness in mammalsarrow_forward
- Table 8.1 shows that Turner syndrome occurs when an individual inherits one X chromosome but lacks a second sex chromosome. Can Turner syndrome be due to nondisjunction during oogenesis, spermatogenesis, or both? If a phenotypically normal couple has a color-blind child (due to a recessive X-linked allele) with Turner syndrome, did nondisjunction occur duringoogenesis or spermatogenesis in this child’s parents? Explain your answer.arrow_forwardA sexually reproducing organism’s body cells contain which two alleles for every gene?arrow_forwardIn humans, Widow’s peak (W) is dominant over a continuous hairline (w), and short fingers (F) are dominant over long fingers (f). Two individuals with widow’s peaks and short fingers have a child with a continuous hairline and long fingers. Determine the genotype of the parents.arrow_forward
- How does the heterogametic sex differ from the homogametic sex? a. The heterogametic sex is male; the homogametic sex is female.b. Gametes of the heterogametic sex have different sex chromosomes; gametes of the homogametic sex all have the same sex chromosome.c. Gametes of the heterogametic sex all contain a Y chromosome; gametes of the homogametic sex all contain an X chromosome.arrow_forwardA meiotic-nondisjunction causes trisomy 8 in a newborn. If two of the three copies of chromosome 8 are identical, at what point during meiosis did nondisjunction take place? Explain how you arrived at this answer.arrow_forwardin humans brown eyes (B) are dominant over blue (b).A brown eye man marries a blue-eyed woman and they have three children , two of whom are brown eyed and one of whom is blue eyed.Draw the punnett square that illustrate this marrage.what is the man's genotype ? what are the genotype of the children?arrow_forward
Human Heredity: Principles and Issues (MindTap Co...BiologyISBN:9781305251052Author:Michael CummingsPublisher:Cengage Learning
Human Biology (MindTap Course List)BiologyISBN:9781305112100Author:Cecie Starr, Beverly McMillanPublisher:Cengage Learning