Chromosomal basis of inheritance Flashcards
What is a wild type phenotype?
The normal character phenotype
alternative traits are called mutant phenotypes
What are linked genes?
Genes that are located on the same chromosome that tend to be inherited together due to close proximity to eachother
What is unique about linked genes?
They do not assort independantly
What are incomplete linkages
the result of crossing over in meiosis, which exchanges segments of DNA. Recombinant phenotypes
What are examples of sex determining systems?
X-Y system for humans
X-O system for crickets
Z-W system for chickens
Haplo-diploid system in flies
what is a sex-linked gene?
a gene that is located on a sex chromosome. for humans this gene would be on the X chomosome (shared by both male and female)
fathers pass sex linked alleles to daughters, but not sons
mother pass sex-linked alleles to both sons and daughters
are males or females more likely to inherit sex-linked recessive disorders?
males. because they have only one X chromosome, any recessive allele from the mother will express the trait
What are examples of sex-linked disorders
Duchenne muscular dystrophy ( absense of X-linked gene for a muscle protein called dystrophin)
Hemophilia- (absense of one or more clotting factors)
What is non-disjunction?
When pairs of homologous chromosomes do not separate normally during meiosis.
Gametes then contain two copies or no copies of a particular chromosome
What is aneuploidy?
Occurence of extra or missing chromosomes leading to an unbalanced chromosome complement
What is an example of aneuploidy?
Down syndrome- due to 3 copies of chromosome 21 (autosomal) Klinefelters (XXY Male) Turner syndrome (XO Female) Trisomy X (XXX)
What are structural alterations?
Breakage of a chromosome the lead to changes in chromosome structure and cause human disorders
Deletion, Duplication, inversion, translocation
What is Deletion?
When a chromosome fragment lacjing a centromere is lost during cell division
What is duplication?
When a fragment becomes attached as an extra segment to a siter chromatid
What is inversion?
When a fragment of chromosome reattaches to the origional chromosome but in reverse
What is translocation?
When a chromosomal fragment joins a non homologous chromosome. some are reciprocal, some are not
What is an example of structural alterations?
Cri du Chat
Specific deletion of chromosome 5. undeveloped larynx creates a high pitched cry sounding like a distressed cat.
