40 Questions
What is the characteristic of the X and Y chromosomes during meiosis in male mammals?
They are partially homologous and crossing-over is restricted to pseudoautosomal regions.
What is the sex determination system in birds and some reptiles?
ZW system, where males are ZZ and females are ZW.
In mammals, what is the percentage of male gametes that contain an X chromosome?
50%
What is the behavior of the two X chromosomes in female mammals during meiosis?
They are homologous and behave like autosomes.
What is the term for the regions of the X and Y chromosomes where crossing-over occurs during prophase I of meiosis?
Pseudoautosomal regions
What is the primary function of the testis-determining factor TDF protein?
To signal male development in mammals
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
During meiosis in the ovaries, what is the resulting number of sex chromosomes in each gamete?
One X chromosome
In mammals, which of the following is responsible for determining the sex of an individual?
The presence of the Y chromosome
What is the approximate length of the human X chromosome?
156.0 Mb
What is the primary function of the SRY gene in mammals?
Encoding the testis-determining factor protein for male development
What is the outcome of crossing-over between X and Y chromosomes in humans?
Genetic variation in the offspring through recombination of PARs
What is the significance of the pseudoautosomal regions (PARs) in sex determination?
PARs facilitate synapsis and crossing-over between X and Y chromosomes
What is the chromosomal composition of a zygote formed from a 44+ XY sperm and a 44+ XX ovum?
44+ XY
What is the result of introducing an SRY transgene into a chromosomally female mouse?
A male mouse indistinguishable from a normal XY male
What is the genotype of a male who expresses an X-linked recessive trait?
Xa
A female is a carrier of an X-linked recessive trait. What is the probability that her sons will express the trait?
50%
A male has an X-linked dominant trait. What is the probability that his daughters will inherit the trait?
100%
What is the genotype of a female who expresses an X-linked recessive trait?
Xa Xa
A female is homozygous for an X-linked dominant allele. What is the probability that her sons will inherit the dominant allele?
50%
What is the significance of sister chromatids forming chiasmata in the same homologous chromosome?
It has no genetic consequences
What is the purpose of determining the recombination rate in Drosophila melanogaster crosses?
To produce a genetic map of genes on a chromosome
What is the symbol 'b' representing in the given cross?
A mutant allele for body colour
What is the genetic consequence of recombination between linked genes?
It produces recombinant offspring
What is the relative position of the three genes on the chromosome?
The order of the genes cannot be determined from the given data
What is the fundamental concept underlying the chromosomal basis of inheritance?
Genes are DNA sequence segments located on chromosomes
Who is credited with providing the first solid evidence that genes are located on specific chromosomes?
Thomas Hunt Morgan
What is the relationship between genes and alleles?
Alleles are variations of genes
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
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
What was the species of fruit fly used by Morgan in his experiments?
Drosophila melanogaster
What is the sex chromosome constitution of a male fruit fly?
XY
What is the total number of chromosomes in a fruit fly cell?
8
Why are fruit flies used as an ideal experimental organism for genetics?
All of the above
What was the title of Morgan's 1915 publication?
The Mechanism of Mendelian Heredity
What was the significance of Morgan's experiments with Drosophila melanogaster?
They showed that genes are located on chromosomes
In what year was Morgan awarded the Nobel Prize in Physiology or Medicine?
1933
What is the number of autosome pairs in a fruit fly?
3
What is the sex chromosome constitution of a female fruit fly?
XX
How often can a new generation of fruit flies be bred?
Every two weeks
Understand the genetics behind sex determination in mammals, including the role of X and Y chromosomes in male and female gametes. Learn about the differences between the sex-determination systems in mammals and birds. Test your knowledge of genetics and biotechnology!
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