Chromosome Mapping & Meiosis-Genetics Chapter 13

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What would be the expected phenotype of a male with androgen insensitivity syndrome?

Female phenotype without testes (correct)

Male phenotype with normal androgen response

Male phenotype with testes

Female phenotype without ovaries

What is the inheritance pattern of hemophilia in humans?

X-linked recessive (correct)

Autosomal recessive

X-linked dominant

Autosomal dominant

In a mating between a homozygous normal female and a hemophiliac male, what is the expected outcome for their male offspring?

Half of males will be hemophiliac

All males will be carriers

All males will be normal (correct)

All males will inherit hemophilia

What percentage of male offspring results from a cross between a homozygous red-eyed female fruit fly and a white-eyed male, knowing that white eyes are X-linked recessive?

0% Signup and view all the answers

Why are X-linked disorders more commonly expressed in males than in females?

Males have only one X chromosome. Signup and view all the answers

What is the primary genetic mechanism that determines the sex of Drosophila melanogaster?

The number of X chromosomes Signup and view all the answers

In the experiments conducted by T.H. Morgan, what was concluded about the inheritance of eye color in Drosophila?

The eye color gene is located on the X chromosome Signup and view all the answers

What is the sex determination region found on the Y chromosome in humans?

Sex-Determining Region Y (SRY) gene Signup and view all the answers

How does the presence of a functional SRY gene influence sex determination in humans?

It encodes the testis determining factor (TDF) Signup and view all the answers

What phenotype is associated with a non-functional SRY gene in a male genotype (XY)?

Female phenotype with female external genitalia and uterus Signup and view all the answers

What was a significant outcome observed in the F2 generation of the Drosophila crosses conducted by Morgan?

Only males showed the white-eyed trait Signup and view all the answers

In humans, how are females typically characterized genetically?

Having two X chromosomes Signup and view all the answers

What trait did the initial cross between a mutant male and a normal female Drosophila exhibit?

All F1 progeny displayed red eyes Signup and view all the answers

What is the primary purpose of amniocentesis?

To collect fetal cells for genetic examination Signup and view all the answers

During which weeks of pregnancy is chorionic villus sampling (CVS) typically performed?

8-12 weeks Signup and view all the answers

What can happen if crossing over occurs between two genes?

Both parental and recombinant gametes are produced Signup and view all the answers

Which alleles are considered homozygous recessive?

bb Signup and view all the answers

What does 'recombinant gametes' refer to in the context of crossing over?

Gametes with a mixture of alleles from both parents Signup and view all the answers

What are chorionic villi?

Finger-shaped growths in the placenta Signup and view all the answers

If two alleles are located on the same chromosome, what can occur?

They can be inherited together unless crossing over occurs Signup and view all the answers

When is the analysis of gene products and enzymes specifically relevant?

In prenatal genetic testing like amniocentesis Signup and view all the answers

What is the significance of performing karyotyping on cells obtained from CVS?

It assesses chromosomal abnormalities Signup and view all the answers

In genetics, linked genes typically refer to which of the following?

Genes that are inherited together due to proximity on the same chromosome Signup and view all the answers

What is the result of dosage compensation in female cells?

One X chromosome is inactivated. Signup and view all the answers

What genetic mechanism explains the patchy fur coloration in calico cats?

X-inactivation and epistasis. Signup and view all the answers

Which statement correctly describes Turner syndrome?

Occurs due to a missing second sex chromosome. Signup and view all the answers

What is the result of nondisjunction during meiosis?

Chromosome pairs can fail to separate, leading to extra or missing chromosomes. Signup and view all the answers

Which genetic disorder is associated with trisomy 21?

Down syndrome. Signup and view all the answers

In calico cats, the white patch of fur is due to an interaction with which type of gene?

Epistatic gene. Signup and view all the answers

What results from an XXY chromosomal pattern?

Klinefelter syndrome. Signup and view all the answers

What occurs in an individual with Edwards syndrome?

Trisomy 18 results in early mortality. Signup and view all the answers

How can mitochondrial DNA be inherited?

Only from the mother. Signup and view all the answers

What type of chromosome abnormality is characterized by the presence of two Barr bodies?

XXX syndrome. Signup and view all the answers

Study Notes

Chromosome Mapping & Meiosis-Inheritance Connection

Chapter 13 covers the relationship between chromosomes, mapping, and inheritance during meiosis.

X-Linked Genes in Drosophila

T.H. Morgan's experiments with fruit flies (Drosophila melanogaster) demonstrated X-linked inheritance.
Crossing a mutant white-eyed male with a normal red-eyed female produced all red-eyed F1 offspring.
Crossing F1 females with F1 males, the F2 generation had both red and white-eyed flies, but all white-eyed flies were male.
A testcross confirmed that the eye color gene resides on the X chromosome.

Sex Determination

Sex determination varies across species.
- Humans: presence of a Y chromosome determines maleness (XY), absence of Y results in femaleness (XX).
- Drosophila: number of X chromosomes determines sex. 2X's = female, 1X = male
- Birds and some other species use different chromosome combinations
- Grasshoppers and Honeybees have other methods

SRY Gene and Male Development

In humans, the SRY gene on the Y chromosome encodes the testis-determining factor (TDF), which initiates male development.
Swyer syndrome is associated with a nonfunctional SRY gene, leading to a male genotype (XY) but a female phenotype.

Androgen Insensitivity Syndrome

Androgen insensitivity syndrome results from mutations in the androgen receptor gene on the X chromosome. This leads to a male genotype(XY) but a female phenotype.

Sex-Linked Disorders

X-linked disorders, like hemophilia, are more prevalent in males because they only have one X chromosome.
Hemophilia (a blood clotting disorder) is caused by an X-linked recessive allele.
X-linked disorders can appear in both males and females, but males are more often affected.

Mating Results: Hemophilia

A mating between a normal (non-carrier) female and a hemophiliac male results in carriers but no affected daughters, and a chance of the sons being affected with hemophilia.

White-Eyed Fruit Fly Cross

A cross between a homozygous red-eyed female and a white-eyed male will result in all male offspring having white eyes.

Dosage Compensation and Barr Bodies

In females, one X chromosome is inactivated in each cell to prevent a doubling of gene products compared to males (one X).
The inactivated X chromosome condenses into a Barr body.

Calico Cats

Calico cats are females whose heterozygous alleles are responsible for the patches of different colors. The difference in color are in relation to the inactivation of one of the X chromosomes's alleles.

Mitochondrial DNA Inheritance

Mitochondrial DNA is only inherited from the mother.

Nondisjunction and Aneuploidy

Nondisjunction is the failure of homologous chromosomes to separate properly during meiosis.
Aneuploidy is the result of nondisjunction; it refers to having an abnormal number of chromosomes (missing one less, one extra).
Conditions like Klinefelter syndrome (XXY) and Turner syndrome (XO) are examples of sex chromosome abnormalities caused by nondisjunction.

Autosomal Chromosome Abnormalities

Edwards syndrome (trisomy 18) and Down syndrome (trisomy 21) are examples of autosomal trisomies, which often result in significant health problems and may cause death. Both are related to the mother's age at time of pregnancy

Genetic Disorder Testing

Amniocentesis and chorionic villus sampling (CVS) are prenatal testing procedures for diagnosing genetic disorders. These methods obtain fetal cells from amniotic fluid or chorionic villi, respectively, facilitating karyotyping and biochemical tests.. Both methods may potentially have risks of causing damage/miscarriage to the fetus

Linked Genes and Recombination

Linked genes are on the same chromosome and tend to be inherited together.
Crossing over during meiosis can result in recombination, producing gametes with new combinations of alleles.
Recombination frequency is used to estimate the distance between genes on a chromosome, map units or centimorgans (cM) are used to measure this.

Gene Distance Determination

The frequency of recombination between genes provides an estimation of the relative distance between them on a chromosome, or how far apart they are on a chromosome. Genes far apart are more likely to be separated during meiosis

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Explore the essential concepts of chromosome mapping and the meiosis-inheritance connection as outlined in Chapter 13. Delve into the fascinating experiments of T.H. Morgan with Drosophila, revealing X-linked inheritance. Learn about sex determination mechanisms across various species.