Genetics of Sex Determination in Mammals

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What is the characteristic of the X and Y chromosomes during meiosis in male mammals?

They are identical and behave like autosomes.

They are fully homologous and undergo crossing-over freely.

They are partially homologous and crossing-over is restricted to pseudoautosomal regions. (correct)

They are completely non-homologous and do not pair during meiosis.

What is the sex determination system in birds and some reptiles?

XY system, where males are XX and females are XY.

XX system, where males are XY and females are XX.

YW system, where males are YY and females are YW.

ZW system, where males are ZZ and females are ZW. (correct)

In mammals, what is the percentage of male gametes that contain an X chromosome?

100%

50% (correct)

25%

75%

What is the behavior of the two X chromosomes in female mammals during meiosis?

They are homologous and behave like autosomes. Signup and view all the answers

What is the term for the regions of the X and Y chromosomes where crossing-over occurs during prophase I of meiosis?

Pseudoautosomal regions Signup and view all the answers

What is the primary function of the testis-determining factor TDF protein?

To signal male development in mammals Signup and view all the answers

Which of the following statements about the X and Y chromosomes in mammals is TRUE?

Short segments at either end of the Y chromosome are homologous with regions on the X chromosome Signup and view all the answers

During meiosis in the ovaries, what is the resulting number of sex chromosomes in each gamete?

One X chromosome Signup and view all the answers

In mammals, which of the following is responsible for determining the sex of an individual?

The presence of the Y chromosome Signup and view all the answers

What is the approximate length of the human X chromosome?

156.0 Mb Signup and view all the answers

What is the primary function of the SRY gene in mammals?

Encoding the testis-determining factor protein for male development Signup and view all the answers

What is the outcome of crossing-over between X and Y chromosomes in humans?

Genetic variation in the offspring through recombination of PARs Signup and view all the answers

What is the significance of the pseudoautosomal regions (PARs) in sex determination?

PARs facilitate synapsis and crossing-over between X and Y chromosomes Signup and view all the answers

What is the chromosomal composition of a zygote formed from a 44+ XY sperm and a 44+ XX ovum?

44+ XY Signup and view all the answers

What is the result of introducing an SRY transgene into a chromosomally female mouse?

A male mouse indistinguishable from a normal XY male Signup and view all the answers

What is the genotype of a male who expresses an X-linked recessive trait?

Xa Signup and view all the answers

A female is a carrier of an X-linked recessive trait. What is the probability that her sons will express the trait?

50% Signup and view all the answers

A male has an X-linked dominant trait. What is the probability that his daughters will inherit the trait?

100% Signup and view all the answers

What is the genotype of a female who expresses an X-linked recessive trait?

Xa Xa Signup and view all the answers

A female is homozygous for an X-linked dominant allele. What is the probability that her sons will inherit the dominant allele?

50% Signup and view all the answers

What is the significance of sister chromatids forming chiasmata in the same homologous chromosome?

It has no genetic consequences Signup and view all the answers

What is the purpose of determining the recombination rate in Drosophila melanogaster crosses?

To produce a genetic map of genes on a chromosome Signup and view all the answers

What is the symbol 'b' representing in the given cross?

A mutant allele for body colour Signup and view all the answers

What is the genetic consequence of recombination between linked genes?

It produces recombinant offspring Signup and view all the answers

What is the relative position of the three genes on the chromosome?

The order of the genes cannot be determined from the given data Signup and view all the answers

What is the fundamental concept underlying the chromosomal basis of inheritance?

Genes are DNA sequence segments located on chromosomes Signup and view all the answers

Who is credited with providing the first solid evidence that genes are located on specific chromosomes?

Thomas Hunt Morgan Signup and view all the answers

What is the relationship between genes and alleles?

Alleles are variations of genes Signup and view all the answers

What is the significance of homologous chromosomes in the context of gene inheritance?

They are involved in the transmission of genetic traits from one generation to the next Signup and view all the answers

What is the primary conclusion that can be drawn from the chromosomal basis of Mendel's laws?

Genes are DNA sequence segments located on chromosomes Signup and view all the answers

What was the species of fruit fly used by Morgan in his experiments?

Drosophila melanogaster Signup and view all the answers

What is the sex chromosome constitution of a male fruit fly?

XY Signup and view all the answers

What is the total number of chromosomes in a fruit fly cell?

8 Signup and view all the answers

Why are fruit flies used as an ideal experimental organism for genetics?

All of the above Signup and view all the answers

What was the title of Morgan's 1915 publication?

The Mechanism of Mendelian Heredity Signup and view all the answers

What was the significance of Morgan's experiments with Drosophila melanogaster?

They showed that genes are located on chromosomes Signup and view all the answers