Semester 2 Week 2 Flashcards

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1
Q

Why are X linked disorders more common in males?

A

X linked disorders are more common in males because for a recessive trait to be expressed, a female needs 2 copies of allele but males only need 1.

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2
Q

Give an example of a gene that is on the Y chromosome.

A

One gene that’s on the Y chromosome is the SRY gene, which codes for the development of testes.

Absence of SRY gene leads to development of gonads into ovaries.

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3
Q

What is Swyer syndrome?

A

Mutations in the SRY gene leads to XY females with gonadal dysgenesis. SRY gene is responsible for maleness, so if it’s inactivated then XY individuals will have female characteristics.

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4
Q

What is genetic recombination?

A

Genetic recombination is the exchange of chromosomal fragments BETWEEN homologous chromosomes. This is normal

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5
Q

What is translocation?

A

Translocation is the exchange of chromosomes between non-homologous chromosomes. This is abnormal.

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6
Q

What is XX male syndrome?

A

Translocation of part of Y gene containing SRY gene to X chromosome. X chromosome carries male SRY gene, so females have male characteristics.

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7
Q

What happens when one of the 2 X chromosomes is inactivated during embryonic development?

A

When 1 of the 2 X chromosomes is inactivated during embryonic development, the inactive X chromosome condenses into a Barr body, which lies in nuclear envelope.

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8
Q

What is gene linkage?

A

Genes located near each other on the same chromosome tend to be inherited together are called linked genes.

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9
Q

What is offspring that matches one of the parental phenotypes called?

A

Offspring that matches one of the parental phenotypes is called parental types.

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10
Q

What is offspring with non-parental phenotypes called?

A

Offspring with non-parental phenotypes are called recombinant phenotypes.

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11
Q

What is genetic recombination?

A

Genetic recombination is the crossing over of non-sister chromatids of homologous chromosomes during meiosis I.

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12
Q

What is aneuploidy?

A

Aneuploidy is the presence of an abnormal chromosome number, caused from fertilisation of gametes in which nondisjunction occured.

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13
Q

What is nondisjunction?

A

Nondisjunction is the abnormal separation of homologous chromosome pairs during meiosis I or sister chromatids during meiosis II.

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14
Q

What is polyploidy?

A

Polyploidy is when an organism has more than 2 complete sets of chromosomes.

Triploidy (3n) is three sets of chromosomes

Tetraploidy (4n) is four sets of chromosomes.

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15
Q

What are the 4 types of changes that can be caused by breakage of a chromosome?

A

The 4 types of changes caused by breakage of a chromosome are:
Deletion - removal of chromosome segment
Duplication - repetition of a segment
Inversion - reversal of a segment within a chromosome.
Translocation - exchange of segments between non-homologous chromosomes

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16
Q

What is Trisomy 21?

A

Trisomy 21 is Down Syndrome

17
Q

What is Trisomy 18?

A

Trisomy 18 is Edwards Syndrome

18
Q

What is Trisomy 13?

A

Trisomy 13 is Patau Syndrome

19
Q

What is Klinefelter syndrome?

A

Klinefelter is when males have an extra X chromosome (XXY individuals). This causes males to have some female characteristics, such as gynecomastia.

20
Q

What is Turner Syndrome?

A

Turner Syndrome is when a female has a missing or incomplete X chromosome.

21
Q

What is Cri du Chat syndrome?

A

Cri du chat syndrome is when part of chromosome 5 is deleted. Children born with this syndrome are mentally retarded and have a cat-like cry. They usually die in early childhood.

22
Q

What is Genomic Imprinting?

A

Genomic imprinting is the silencing of either maternal or paternal genes (alleles) of certain genes at the beginning of development.

23
Q

How are genes silenced?

A

Genes are silenced by “stamping” them with an imprint (methylation - addition of CH3) during gamete production.

24
Q

What is Igf2?

A

Igf2 is a growth factor essential for embryonic/fetal development. It’s inactivated by methylation.

25
Q

What is Beckwith-Wiedemann Syndrome?

A

Beckwith-Wiedemann Syndrome is abnormal activation of the maternal Igf2 allele during egg formation/ early development. This increases risk of childhood cancer.

26
Q

What are extranuclear genes and why are they inherited maternally?

A

Extranuclear genes are genes found in organelles in the cytoplasm, such as mitochondria.

These genes come maternally because zygote’s cytoplasm comes from the egg.

27
Q

What do defects in mitochondrial genes cause?

A

Defects in mitochondrial genes prevent cells from making enough ATP and cause serious neuromuscular disorders such as mitochondrial myopathy (muscle deterioration) and Leber’s hereditary optic neuropathy (nerve deterioration).

28
Q

How can defects in mitochondrial genes be prevented?

A

Defects in mitochondrial genes can be prevented by ‘Three person IVF’. 2 eggs allow women with mitochondrial DNA disorders to have healthy children.