68 Questions
What is the process by which chromosomes and genes are paired in diploid cells and then separated during meiosis?
Meiosis
What did Gregor Mendel propose in 1860?
The laws of inheritance
What is the consequence of fertilization on chromosomes and genes?
They are restored to a paired condition
What is the technique used to visualize the location of a particular gene?
Staining with a fluorescent dye
When was the process of mitosis worked out by cytologists?
1875
What is the name of the biologist who published a drawing of mitosis in 1882?
Walther Flemming
What is the term used to describe traits that are alternatives to the wild type?
Mutant phenotypes
What is the notation used to symbolize the allele for the wild-type trait in Drosophila?
w+
How are human genes typically written?
In all uppercase letters
What is the origin of the symbol for a gene in Drosophila?
From the first mutant discovered
What is the symbol for the allele for white eyes in Drosophila?
w
What is the concept that suggests that Mendelian genes have specific loci along chromosomes?
Chromosome theory of inheritance
What is the process that accounts for the segregation of alleles of a gene into separate gametes?
Anaphase I
Who first demonstrated that Mendelian inheritance has its physical basis in the behavior of chromosomes?
Thomas Hunt Morgan
What is the name of the common insect used by Morgan for his genetic studies?
Drosophila melanogaster
What is the term for the phenotype most commonly observed in natural populations?
Wild type
How many pairs of chromosomes do fruit flies have?
Four
What is the period of time required to breed a new generation of fruit flies?
Two weeks
What was the characteristic of the single male fly discovered by Morgan?
White eyes
What was the task that Morgan had to do to find naturally occurring variant individuals?
Both A and B
What is the term for the location of a gene on a chromosome?
Locus
What is the term for the random arrangement of chromosome pairs during metaphase I?
Independent assortment
What was the unexpected result observed by Morgan in the F2 offspring?
All the F2 females had red eyes, while half the males had red eyes and half had white eyes
Why did Morgan conclude that the gene for white eyes is located on the X chromosome?
Because the correlation between the trait of white eye color and the male sex of the affected F2 flies suggested a linkage to the X chromosome
Why is it necessary for a female to have two copies of the recessive allele to express the white-eyed trait?
Because females have two X chromosomes, and one of them must carry the recessive allele
What can be inferred about the presence of the wild-type allele in a male fly?
A male fly can have only one copy of the wild-type allele, and it will always be expressed
What is the reason for the 3:1 phenotypic ratio observed in the F2 offspring?
Because the gene for white eyes is recessive
What is the genotype of a male fly that expresses the white-eyed trait?
XwY
What is the primary reason Morgan's finding of the correlation between a particular trait and an individual's sex provided support for the chromosome theory of inheritance?
It showed that genes are located on specific chromosomes.
What is the role of the SRY gene in sex determination in humans?
It is required for the development of testes.
What is the term for a gene located on either sex chromosome?
Sex-linked gene
What is the consequence of fertilization by a sperm cell containing a Y chromosome?
The zygote develops as a male.
What is the difference between the X and Y chromosomes in terms of size?
The Y chromosome is smaller than the X chromosome.
How do the X and Y chromosomes in males pair and behave during meiosis?
They pair and behave like homologs during meiosis.
What is the probability of a male or female offspring being produced in mammals?
50% chance of male, 50% chance of female.
What is the term for the classification of an individual into a group with a shared set of anatomical and physiological traits?
Sex
How many genes are located on the human X chromosome?
Approximately 1,100 genes.
What is the term for the genes located on the Y chromosome?
Y-linked genes
What percentage of genes on the human Y chromosome are expressed only in the testis?
About 50%
What is the function of the WNT4 gene in the development of female gonads?
It promotes ovary development
How are the Y-linked genes typically passed on from one generation to the next?
From father to son
What is the result of an embryo having extra copies of the WNT4 gene?
It develops rudimentary female gonads
What is the current understanding of sex determination?
It is a complex process involving multiple genes
What is the term used to describe individuals born with anatomical features that do not match their sense of gender?
Transgender
What is the main difference in the pattern of inheritance between autosomal genes and X-linked genes?
The number of chromosomes involved
Why do males have a higher incidence of X-linked recessive disorders?
Because they have only one X chromosome
What is the term used to describe the genetic makeup of a male with respect to an X-linked gene?
Hemizygous
Who observed the pattern of inheritance of X-linked genes in Drosophila?
Morgan
What is the condition of red-green color blindness inherited as?
An X-linked recessive trait
Why do females need to inherit two copies of the recessive allele to express the phenotype?
Because they have two X chromosomes
What is the typical life expectancy of an individual with Duchenne muscular dystrophy?
Early 20s
What is the main cause of bleeding in individuals with hemophilia?
Absence of a key protein for blood clotting
Why was Queen Victoria of England significant in the spread of hemophilia?
She was a carrier of the hemophilia allele
What is the current treatment for individuals with hemophilia?
Intravenous injections of the missing blood-clotting protein
What is the role of dystrophin in muscle function?
It is a key protein required for muscle strength
What is the mode of inheritance of Duchenne muscular dystrophy?
X-linked recessive
What is the purpose of X inactivation in female mammals?
To maintain a balance of X-linked gene expression between males and females
What is the compact object formed by the inactivated X chromosome in each cell of a female?
Barr body
What happens to the inactive X chromosome in the ovaries?
It is reactivated
How is the selection of which X chromosome will form the Barr body determined?
Randomly and independently in each embryonic cell
What is the result of X inactivation in terms of cell types in females?
Females have a mosaic of two types of cells
What happens to the inactive X chromosome in subsequent cell divisions?
It remains inactive
What happens in a female who is heterozygous for a sex-linked trait?
About half of her cells will express one allele, while the others will express the alternate allele.
What is involved in the inactivation of an X chromosome?
Modification of DNA and proteins, including the attachment of methyl groups.
What is the role of the XIST gene in X inactivation?
It becomes active only on the chromosome that will become the Barr body.
What is the result of the interaction between the XIST RNA product and the X chromosome?
The X chromosome is inactivated.
Why do females who are heterozygous for a recessive X-linked mutation have patches of normal skin and patches of skin lacking sweat glands?
Because they are heterozygous for the mutation and the X chromosome is inactivated.
What is the significance of the association of the two regions, one on each X chromosome, during embryonic development?
It initiates X inactivation.
Learn about the location of genes along chromosomes, how they are identified using fluorescent dyes, and how this concept relates to Mendel's 'hereditary factors'. Explore the connection between genes and chromosomes in this quiz.
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