Chapter 4 - Sex Determination and Sex-Linked Characteristics Flashcards
T or F: Sex is determined by genotype.
False: sex is based on the phenotype - BUT, it does still involve genes.
How can someone with XX be male?
The Y chromosome is attached to another autosome.
C. elegans can exist as a true ______ meaning that they have both male and female reproductive organs. Additionally, they are _____ – this means they are able to self-fertilize.
hemaprodites; monoecious
Most organisms are _____ meaning they have distinct male and female members of the species.
dioecious
How is sex of sea turtles determined?
Temperature of the nest.
Which sex chromosome was ID first? In what organism? During what time?
X; insects/grasshoppers; late 1800s early 1900s
The presence of one X chromosome in male grasshoppers and XX in females provided proof that genes are associated with _______.
chromosomes.
In grasshoppers, XO zygotes develop into _____. This means that the sperm _____ an ___ chromosome (grasshoppers don’t make ___ ____).
males; lacked; X; Y chromosomes.
The Y chromosome in many species is _____ meaning the centromere is close to the end of the chromosome.
acrocentric
The theory of how the Y chromosome came to be is that it was an X that lost…?
DNA sequences over the eons.
Males of XY species are _______ meaning the produce different gametes whereas females are ______ because their eggs have the same chromosomes.
heterogametic; homogametic
X and Y chromosomes in males pair during meiosis at ______ regions (regions that are homologous between the two sex chromosomes).
pseudoautosomal
Genes that are associated with pseudoautosomal regions on sex chromosomes show:
A. inheritance patterns similar to autosomes
B. sex-linked inheritance patterns
A. inheritance patterns similar to autosomes
Why are pseudoautosomal regions named so?
The chromosomes aren’t autosomes.
In ZZ-ZW sex determination, the females gametes are _______ and the males are ______.
females = heterogametic; males = homogametic
In _____ sex-determination systems, sex is determined genetically, but the genes involved are not associated with a discrete “sex chromosome”.
genic
T or F: in genic systems, the sex can be determined by microscopic observation of the karyotype.
False - there is no observable differences in the chromosomes of males or females.
The master regulator for male development in mammals is the ____ gene located on the Y chromosome; it is critical for determining maleness.
SRY (italicized)
In ______ sex determination, sex is determined by the interaction of genes with the ______ (the example in the book is the slipper limpet).
environmental; environment
For environmental sex determination, the slipper limpet that establishes a colony begins life as a _____, and other larvae that settle on top are _____; but over time, the ____ change their DNA sequence to _____. Bottom line, the upper-most organisms are always _____. This is an example of sequential ________ (can be male and female, but not at the same time).
female; males; male to female.
Male
hermaphroditism
For turtles, warm temps produce _____ and cooler produce ____. What is it for alligators
females; males.
Opposite.
T or F: In Drosophila, Y chromosome is needed to determine maleness.
False: genes on Y are needed for sperm development.
In Drosophila, sex is determined by the ratio of ___ chromosomes to the haploid sets of _____ (normally 2). This is referred to as the genic ____ system and is determined by dividing the number of ___ by the number of haploid sets of _____.
X to haploid sets of autosomes (X:A)
Genic balance system.
X divided by haploid sets of autosomes.
In a normal fly with 2 sets of haploid autosomes, an X:A ratio of 1 yields?
A ratio of 0.5?
2X/2A = 1 = female X/2A = 0.5 = male
In a fly with an abnormal X:A ratio >0.5 but < 1.0, sex is _____ and demonstrates a ____ of male and female characteristics.
intersex; mixture
In a fly with an abnormal X:A ratio > 1.0, the sex is _____ where they are phenotypically female but have severe developmental problems and die before they can produce progeny.
metafemale
In a fly with an abnormal X:A ratio < 0.5, the sex is _____ where they are phenotypically male but are sterile and weak.
metamale
In a normal fly, XXY yields what sex? What about their fertility?
female
The are fertile - the y chromosome doesn’t affect fertility or development.
Flies that are XO yield what sex? What about their fertility?
Male
they are sterile - the Y chromosome is needed for males to develop sperm.
In Drosophila, the tra (Transfomer) gene causes a normal ____ to develop as a _____ (their X:A ratio is 1). Genes like this are said to act ______ of normal processes.
female; male; (1)
Downstream
In Drosophila, the Doublesex (dsx) mutation causes normal males and females to develop as _____ flies.
Genes like this are said to act ______ of normal processes.
intersex
Downstream
Humans that are genetically XO have ______ Syndrome. Their secondary sex characteristics are usually _______; they are short, have a low hairline, normal intelligence, and folds on the skin of the _____.
Turner; underdeveloped; neck
T or F: humans lacking any X chromosomes usually end up developmentally disabled.
False - there aren’t any, so they probably spontaneously abort (one or more genes on X must be needed for development).
Klinefelter Syndrome yields ____ with one or more Y chromosomes, and multiple X chromosomes. They are typically _____, usually tall, and their intelligence is usually ______.
males; underdeveloped; normal.
T or F: Triplo-X is a movie.
False: it is a syndrome of females with 3 or more X chromosomes.
Triplo-X Syndrome is likely not lethal because only ____ X chromosome will be _____.
one; functional
Poly-X / Triplo-X females usually have near normal or slightly below normal _____, and a small percentage are _____. Mental retardation and physical abnormalities increase with ___ or ____ X chromosomes.
intelligence; sterile.
Four or Five
The default pathway for development of sex in humans is ______ because the absence of a ___ chromosome (barring any autosomal hitchhikers) always leads to ____.
female; Y; female
X and Y chromosomes are required for _____.
fertility
How is it possible to have an XX mammalian male?
What does this suggest?
The Y chromosome - or a critical portion of it - was attached to an autosome.
This suggests that there is gene(s) required for male development - not necessarily the whole gene.
SRY gene gets its name from ___-_____ Region ____ gene
sex-determining region Y gene.
Transgenic (laboratory transfer of genes) XX mice having an engineered copy of the ____ gene develop into males, but without the Y gene, they are ____.
SRY; sterile
Individuals with _____ Insensitivity Syndrome are externally female, so the condition isn’t discovered until ____ (due to amenorrhea); and upon pelvic examination, the vagina terminates at the cervix (no uterus) and ____ are located in the abdomen.
Androgen; puberty; testes
Women with Androgen Insensitivity Syndrome have the __and__ sex chromosomes, but they develop as women because they have a genetic defect in the ____ chromosome responsible for making receptors for ________. This demonstrates that sex development depends on the ____ of gene ____.
XY; X; testosterone.
regulation; expression
The product of the SRY gene is a protein called ___- ___ factor (TFD).
TFD stimulates fetal ____ to develop into ____; but someone with a mutation on their X chromosome for receptors will develop ______ _____ syndrome and be phenotypically _______. This defect is always inherited from the ______.
Testes-determining factor (the acronym’s kinda fucked up).
gonads; testes; androgen insensitivity syndrome; female.
Mother.
Since XX-XY males and females differ in their sex chromosomes, inheritance of genes on the ____ chromosome will also be different between the 2 sexes.
X
To discern between autosomal recessive and sex-linked traits, perform a ______ cross by first mating a wild-type male/female to a mutant of the opposite sex, then vice versa. If the results are the same, the trait is ______ _____; if the results are different, the trait is ____ _____.
reciprocal; autosomal recessive; sex-linked.
When there is only one gene present due to sex chromosomes, males are said to be _____ because they only have one. As a consequence, sex-linked recessive alleles will always appear in the _____ of males who’s mothers are carriers.
hemizygous; phenotypes
_______ is a condition where homologous chromosomes or sister chromatids don’t disjoin (separate).
Nondisjunction
When crossing white-eyed female Drosophila to red-eyed males, Calvin Bridges expected to get red-eyed females and white-eyed males, but the opposite was seen in about 2.5% of the progeny due to _________. Why? Include # and type of sex chromosomes the female had.
This was due to nondisjunction. The white-eyed female had X^wX^wY, so her possible gametes were (X^wY), (X^w), (X^wX^w), and Y. The (X^wX^w) was the nondisjoined gamete and led to either (X^wX^wY) females or (X^+X^wX^w) males (lethal).
Advantages of using Drosophila are short _____ time of progeny every 10 - 14 days; _____ number of progeny, and easy to _____, small ______ of only 175 Mbp; and giant polytene ______ in the salivary glands that facilitated ID of loci.
generation; large; maintain; genome; chromosomes
Colorblindness is due to a mutation of the genes that code for _____ and _____ wavelengths - these two genes lie _____ to each other on the ____ chromosome.
green and red; close; X
Colorblindness is an X-linked recessive trait that alternates between sexes from one generation to the next, which is called _____ inheritance.
crisscross
If a normal color vision female (homozygous WT) has kids with a color blind male, the daughters will be genetically ______ with _____ vision, and the sons will be genetically ______ with ______ vision. A reciprocal cross between a homozygous recessive female and WT male will yield?
heterozygous; normal; hemizygous/WT with normal vision.
Colorblind sons and heterozygous daughters.
What is heterochromatin?
Densely packed chromatin with little or fully suppressed functionality.
Changes in DNA sequence don’t have to affect functional genes in order to be useful for genetic studies as evidenced by the case of proving what?
That Thomas Jefferson was a rapist.
Suppose the locus of Your Favorite Gene (YFG) lies within the pseuodoautosomal region of the X-chromosome. A woman who is homozygous recessive for a mutation in YFG has a mutant phenotype. However, a man who also has the same recessive mutation in YFG on his X-chromosome has a wild-type phenotype. What are their children?
Sons are heterozygous - one WT allele form their dad on the pseudoautosomal region of the Y chromosome and one mutant from the mom; and they will have the WT phenotype.
Daughters will inherit the mutant allele from both mom and dad (from the pseudoautosomal regions of their X chromosomes since mom’s homo and dad had it on his X).
You discover a new amphibian and name the sex chromosomes A and B. If the female is heterogametic and the male is homogametic, then what could be the chromosome arrangement of sex chromosomes in the adult? (A) female AA and male BB
(B) female AB and male AB
(C) female AB and male BB
(D) female BB and male AB
(C) female AB and male BB
Jr. Scientist found a fruit fly that had three sex chromosomes (XXY) and three copies of each autosome. The sex of this fruit fly was _________ .
2X/3A = 0.667 = intersex
A human with two X chromosomes and one Y chromosome will develop as a ______ while a fruit fly with the same chromosome composition will develop
as a _______.
male; female
A female with a single X-chromosome will develop _________ syndrome
Turner
In which scenario with all daughters be colorblind?
Both the mother and father would be colorblind (which would make all children colorblind).
Hemophilia is associated with a sex-linked recessive genetic mutation. Assume that a man with hemophilia marries a women with no blood disorder whose father had hemophilia. What % of the sons will have hemophilia?
50%
______ is possession of a single allele at a locus. Males of XX-XY organisms are _____ for X-linked loci because they’ve got only one copy. The opposite is true in ZZ-ZY organisms
Hemizygosity; hemizygous
The ___ gene is a gene on the X chromosome that codes for ___. The ___ binds to, and causes inactive X chromosomes to condense.
Xist; RNA; RNA
