Semester 2 Week 2 Flashcards
(28 cards)
Why are X linked disorders more common in males?
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.
Give an example of a gene that is on the Y chromosome.
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.
What is Swyer syndrome?
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.
What is genetic recombination?
Genetic recombination is the exchange of chromosomal fragments BETWEEN homologous chromosomes. This is normal
What is translocation?
Translocation is the exchange of chromosomes between non-homologous chromosomes. This is abnormal.
What is XX male syndrome?
Translocation of part of Y gene containing SRY gene to X chromosome. X chromosome carries male SRY gene, so females have male characteristics.
What happens when one of the 2 X chromosomes is inactivated during embryonic development?
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.
What is gene linkage?
Genes located near each other on the same chromosome tend to be inherited together are called linked genes.
What is offspring that matches one of the parental phenotypes called?
Offspring that matches one of the parental phenotypes is called parental types.
What is offspring with non-parental phenotypes called?
Offspring with non-parental phenotypes are called recombinant phenotypes.
What is genetic recombination?
Genetic recombination is the crossing over of non-sister chromatids of homologous chromosomes during meiosis I.
What is aneuploidy?
Aneuploidy is the presence of an abnormal chromosome number, caused from fertilisation of gametes in which nondisjunction occured.
What is nondisjunction?
Nondisjunction is the abnormal separation of homologous chromosome pairs during meiosis I or sister chromatids during meiosis II.
What is polyploidy?
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.
What are the 4 types of changes that can be caused by breakage of a chromosome?
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
What is Trisomy 21?
Trisomy 21 is Down Syndrome
What is Trisomy 18?
Trisomy 18 is Edwards Syndrome
What is Trisomy 13?
Trisomy 13 is Patau Syndrome
What is Klinefelter syndrome?
Klinefelter is when males have an extra X chromosome (XXY individuals). This causes males to have some female characteristics, such as gynecomastia.
What is Turner Syndrome?
Turner Syndrome is when a female has a missing or incomplete X chromosome.
What is Cri du Chat syndrome?
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.
What is Genomic Imprinting?
Genomic imprinting is the silencing of either maternal or paternal genes (alleles) of certain genes at the beginning of development.
How are genes silenced?
Genes are silenced by “stamping” them with an imprint (methylation - addition of CH3) during gamete production.
What is Igf2?
Igf2 is a growth factor essential for embryonic/fetal development. It’s inactivated by methylation.
