Indifferent Fetal Gonad 1) (11 point question)The genetic signaling pathway in t
ID: 267211 • Letter: I
Question
Indifferent Fetal Gonad 1) (11 point question)The genetic signaling pathway in the diagram to the right contains some of the chemical hormones, organs and proteins that act together as a signaling pathway to control sex determination in humans e) (2 points) Some men do not have a Y chromosome and yet they still form testes. How is this possible and SRY why are they sterile? Ovary Testis a) (2 points) Where is the primary defcct in this 2) (4 point question) Consider a hairy pea plant that was grown from yellow seed (an Fl hybrid). This hybrid had one parent (P1) that was an inbred variety with no hairs and was grown from a green seed. P2 was also an inbred variety, but grown from a yellow seed and had hairy leaves. y for individuals who have Androgen sitivity Syndrome (AIS)? MIS Testosterone Testosterone receptor After a backcross of the F1 hybrid to the P1 parent the following progeny are obscrved b) (3 points) People with AIS have either a partial (PAIS) or a complete phenotype (CAIS) 29 82 Ycllow sccd Smooth a functional (molecular level) what is Yellow sccd /Hairy Green sced Smooth PHENOTYPE the difference between the two? e in function Green seed Hairy 30 rie Scri caused by the mutation e in function a) (1 point) What is the null hypothesis for the ratio of progenies based on the backcross described above. Partial AIS b) (3 point) Using a Chi square statistical test, do you reject or fail to reject the null hypothesis. Show your calculations. Complete AIS c) (2 points) Some women can have a mutant version of the SRY gene (SRY-). Is it e for SRY- or CAIS women to appear to be men in a sex test that uses a e karyotype'? Explain your reasoning. c) (1 points) Is there an casy explanation for your conclusion? d) (2 points) Is it possible for SRY- gr CAIS women to appear to be men in a sex test that measures the "level of male hormone? Explain your reasoningExplanation / Answer
(1) (a)The primary defect in the signalling pathway for individuals with Androgen insensitivity syndrome (AIS) lies in the mutated or defective androgen receptor (AR), a type of nuclear receptor that is activated by binding to either of the androgenic hormones (testosterone or dihydrotestosterone) in the cytoplasm, and then translocates into the nucleus where it binds to DNA, provided androgen response elements and coactivators are present. The combination functions as a transcription complex to turn on androgen gene expression in the human body affecting the development and maintenance of the male sexual phenotype.
(b)
Briefly describe the change in function caused by the mutation
Morph that describes the change in function
Partial AIS
Mutation is X-linked recessive, and functions in partial cell insensitivity to androgens is clinically significant only when it occurs in genetic males (i.e. individuals with a Y chromosome, or more specifically, an SRY gene)
The partial unresponsiveness of the cell to the presence of androgenic hormones impairs the masculinization of male genitalia in the developing fetus, as well as the development of male secondary sexual characteristics at puberty.
Complete AIS
Function of mutation in the complete inability of the cell to respond to androgens. As such, the insensitivity to androgens is only clinically significant when it occurs in genetic males (i.e. individuals with a Y chromosome, or more specifically, an SRY gene).
(c) In case of a chromosome karyotype test for complete androgen insensitivity syndrome (CAIS) women, they are genotypically males with a Y chromosome (46,XY). Therefore, karyotyping study can be used to confirm the presence of Y chromosome in CAIS affected females, as the studies will show the presence of a Y chromosome in such females and thus they will appear as men in such a test, and SRY locus could also be checke dfor using PCR analysis which will show the presence of SRY in such females.
(d) Endocrinological tests to measure the level of male hormones such as testosterone can be used for diagnosis of CAIS affected females since, their total serum testosterone values are extremely high in comparison with reference values. Elevated levels of serum testosterone, FSH and LH result from imperfect feedback mechanism of testosterone at pituitary and hypothalamus due to defective androgen receptor.THerefore, such females do appear to be men in a sex test measuring the level of male hormone.
(e) Some males without Y chromosome develop testes in cases of XX male syndrome where an individual with a female genotype has phenotypically male characteristics that can vary between cases. It results from unequal crossing over when the X chromosome in the father harbours the SRY gene. When the X with the SRY gene combines with a normal X from the mother during fertilization, the result is an XX male.
As a result, most XX males have small testes, are sterile, and have an increase in maldescended testicles compared to normal XY males.
* Since the specific questions to be answered has not been specified, I have tried to answer all the five parts of the first question. ( as our policy points enables us to answer a maximum of 4 questions in such cases).
Briefly describe the change in function caused by the mutation
Morph that describes the change in function
Partial AIS
Mutation is X-linked recessive, and functions in partial cell insensitivity to androgens is clinically significant only when it occurs in genetic males (i.e. individuals with a Y chromosome, or more specifically, an SRY gene)
The partial unresponsiveness of the cell to the presence of androgenic hormones impairs the masculinization of male genitalia in the developing fetus, as well as the development of male secondary sexual characteristics at puberty.
- Failure of one or both testes to descend into the scro tum after birth
- Hypospadias, a condition in which the opening of the urethra is on the underside of the penis, instead of at the tip
- Reifenstein syndrome (also known as Gilbert-Dreyfus syndrome or Lubs syndrome)
- Infertile male syndrome is also considered to be part of incomplete AIS.
Complete AIS
Function of mutation in the complete inability of the cell to respond to androgens. As such, the insensitivity to androgens is only clinically significant when it occurs in genetic males (i.e. individuals with a Y chromosome, or more specifically, an SRY gene).
- have the external sex characteristics of females, but do not have a uterus and do not menstruate or conceive a child (infertile).
- are typically raised as females and have a female gender identity.
- have male internal sex organs (testes) that are undescended, abnormally located in the pelvis or abdomen.
- Undescended testes have a small chance of becoming cancerous later in life.
- also have sparse or absent hair in the pubic area and under the arms.