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