Chapter 5 flashcards
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45 Terms
What are the major reproductive modes found in organisms?
Asexual reproduction and sexual reproduction.
Give an example of an organism that reproduces entirely asexually.
Bacteria
Give an example of an organism that reproduces entirely asexually.
Bacteria
What is sexual reproduction?
Reproduction involving meiosis, gamete formation, fertilization, and sexual differentiation.
What is the main natural mechanism for producing new members of a species in most diploid eukaryotes?
Sexual reproduction
What processes are involved in sexual reproduction?
Meiosis, gamete formation, fertilization, and sexual differentiation.
What is phenotypic dimorphism?
Physical differences in appearance between males and females of a species.
What are sex chromosomes?
Chromosomes that differ between the sexes and are involved in determining sex.
Are sex chromosomes always the basis of sex determination?
No. In some organisms, specific genes rather than sex chromosomes determine sex.
Who first linked X chromosomes to sex determination in insects?
Edmund B. Wilson.
What did Edmund B. Wilson discover in Protenor butterflies in 1906?
Females had two X chromosomes, while males had only one X chromosome.
What is the chromosome system in Protenor?
XX females and X0 males.
In Protenor, what determines the sex of the offspring?
Whether the sperm carries an X chromosome or no X chromosome.
In Protenor, what happens when an X-bearing sperm fertilizes an egg?
A female (XX) offspring results.
In Protenor, what happens when an X-deficient sperm fertilizes an egg?
A male (X0) offspring results.
In Protenor, what happens when an X-deficient sperm fertilizes an egg?
A male (X0) offspring results.
What is the chromosome system in Lygaeus?
XX females and XY males.
What is the chromosome system in Lygaeus?
XX females and XY males.
What is a heterogametic sex?
The sex that produces two different types of gametes with respect to sex chromosomes.
What is a homogametic sex?
The sex that produces only one type of gamete with respect to sex chromosomes
In the XY system, which sex is heterogametic?
Males
In the XY system, which sex is homogametic?
Female
What is the ZZ/ZW sex-determination system?
A system in which males are ZZ and females are ZW.
In the ZZ/ZW system, which sex is heterogametic?
Females (ZW)
In the ZZ/ZW system, which sex is homogametic?
Males (ZZ)
Give an example of an organism with a ZZ/ZW system.
Chickens
How many pairs of chromosomes do humans normally have?
23 pairs
Which pair of human chromosomes differs between males and females?
The sex chromosomes
What are the normal female sex chromosomes in humans?
XX
What are the normal male sex chromosomes in humans?
XY
Which human sex chromosome determines male differentiation?
The Y chromosome
What happens to sex development in humans when there is no Y chromosome?
Female differentiation occurs.
What is Klinefelter syndrome?
A condition in which a person has an XXY chromosome complement (47,XXY) and develops male characteristics.
What is the karyotype for Klinefelter syndrome?
47,XXY
What happens to the testes in Klinefelter syndrome?
They are typically underdeveloped and may fail to produce sperm.
What is Turner syndrome?
A condition in which a person has only one X chromosome (45,X) and develops female characteristics.
What is the karyotype for Turner syndrome?
45,X.
What happens to the ovaries in Turner syndrome?
They are typically underdeveloped.
What causes both Klinefelter and Turner syndromes?
Nondisjunction during meiosis
What is nondisjunction?
Failure of chromosomes to separate properly during meiosis or mitosis.
What is the Lyon Hypothesis
Random inactivation of the X chromosomes in the somatic cells during early embryonic development that causes all descendants to have the same inactivation
What what stage does Lyon Hypothesis happen?
Early embryonic development
What happens as a result of Lyon Hypothesis?
All descdants have the same inactivation
What is Calico?
The name for the yellow/orange-yellow patches seen in female cats
Which genotyping cat shows calico fur?
Heterozygous