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What happens to one of the two X chromosomes in each cell during embryonic development in human and some other female species?
What happens to one of the two X chromosomes in each cell during embryonic development in human and some other female species?
- Both X chromosomes are inactivated
- One of the two X chromosomes is randomly inactivated (correct)
- Both X chromosomes are activated
- The X chromosomes are not affected
What is a good phenotypic example of X inactivation?
What is a good phenotypic example of X inactivation?
A tortoise shell cat
The inactive X chromosome can be seen as a ___________ in the nucleus.
The inactive X chromosome can be seen as a ___________ in the nucleus.
Barr body
A female who is heterozygous for a particular gene located on the X chromosome will always express the dominant trait.
A female who is heterozygous for a particular gene located on the X chromosome will always express the dominant trait.
What is the result of X inactivation in a female mammal?
What is the result of X inactivation in a female mammal?
X inactivation occurs in all cells of a female mammal.
X inactivation occurs in all cells of a female mammal.
Match the following terms with their descriptions:
Match the following terms with their descriptions:
What is the result of X chromosome inactivation in the tortoise shell cat?
What is the result of X chromosome inactivation in the tortoise shell cat?
What is the purpose of pedigree analysis in human genetics?
What is the purpose of pedigree analysis in human genetics?
A recessive allele codes for a malfunctioning protein.
A recessive allele codes for a malfunctioning protein.
What is the significance of pedigree analysis in understanding human inheritance?
What is the significance of pedigree analysis in understanding human inheritance?
If an individual lacks a particular phenotypic trait, but both parents have the trait, then the parents must be _____________ for that gene.
If an individual lacks a particular phenotypic trait, but both parents have the trait, then the parents must be _____________ for that gene.
What is the characteristic of heterozygotes in recessive traits?
What is the characteristic of heterozygotes in recessive traits?
Albinism is a life-threatening genetic disorder.
Albinism is a life-threatening genetic disorder.
Match the following genetic disorders with their characteristics:
Match the following genetic disorders with their characteristics:
What is the significance of identifying the inheritance pattern of a trait as dominant or recessive?
What is the significance of identifying the inheritance pattern of a trait as dominant or recessive?
What is the main characteristic of X-linked genes?
What is the main characteristic of X-linked genes?
A recessive X-linked trait is more common in females than in males.
A recessive X-linked trait is more common in females than in males.
What is the term for genes found on the Y chromosome?
What is the term for genes found on the Y chromosome?
A gene that is located on either sex chromosome is called a _______________ gene.
A gene that is located on either sex chromosome is called a _______________ gene.
Match the following types of genes with their characteristics:
Match the following types of genes with their characteristics:
What is the number of genes identified on the human Y chromosome?
What is the number of genes identified on the human Y chromosome?
X-linked genes are only responsible for sex determination.
X-linked genes are only responsible for sex determination.
For a recessive X-linked trait to be expressed in a female, she needs _______________ copies of the allele.
For a recessive X-linked trait to be expressed in a female, she needs _______________ copies of the allele.
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Study Notes
X-Inactivation in Female Mammals
- In human females, one of the two X chromosomes in each cell is randomly inactivated during embryonic development
- This leads to mosaicism, where a female is heterozygous for a particular gene located on the X chromosome
- Example: tortoise shell cat, which demonstrates X-inactivation
Mendelian Inheritance
- Autosomal dominant or recessive traits: gene loci on autosomes can be dominant or recessive
- X-linked dominant or recessive traits: gene loci on the X chromosome can be dominant or recessive
- Y-linked traits: genes on the Y chromosome, involving hemizygous alleles
- Sex-linked genes: genes located on either sex chromosome
Inheritance of X-Linked Genes
- X chromosomes have genes for many characters unrelated to sex
- Y-linked genes are related to sex determination
- X-linked genes follow a specific pattern of inheritance
- For a recessive X-linked trait to be expressed, a female needs two copies of the allele (homozygous), while a male needs only one copy of the allele (hemizygous)
- X-linked recessive disorders are more common in males than in females
Pedigree Analysis
- Pedigree analysis reveals Mendelian patterns in human inheritance
- Inheritance patterns of particular traits can be traced and described using pedigree analysis
- Information about the presence/absence of a particular phenotypic trait is collected from as many individuals in a family as possible and across generations
- Pedigrees can be used to make predictions about future offspring
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