Final- 15 Flashcards
Chromosome theory of inheritance
Mendellian genes have specific loci on chromosomes
Chromosome undergo segregation and independent assortment
Why did Thomas Hunt Morgan use fruit flies
They produce a lot of offspring
They reproduce quickly
They only have four pairs of chromosomes
Wild type
Most typical phenotype (only one)
Mutant
All other phenotypes that are not the wild type
Where is the sex linked gene located
On the sex chromosome, unrelated to sex
Most sex linked traits are on the ___ chromosome
X
Who is affected more by X linked traits, male or female
Male. Only one X needed (hemizygous)
X always comes from the mother
How many copies of the allele do females need to be affected
2 (homozygous)
Examples of sex linked genes
Color blindness, Duchenne muscular dysthrophy, hemophilia
What is a Barr body
When one X chromosome is innactivated in females (Calico cats)
How do offspring get a unqiue combination of traits different from each of the parents
Genetic recombination events
What drives natural selection
new combinations of alleles
What produces genetic recombination of unlinked genes
Independent assortment of chromosomes
What can damage the chromosomes in major ways or alter their number in the cell
Physical and chemical disturbances, as well as errors in meiosis
What can tolerate genetic defects well
Plants
What leads to abnormal chromosome number
Nondisjunction
Nondisjunction
may occur if members of a pair of homologous chromosomes do not separate properly during meiosis I or sister chromatids fail to separate during meiosis II (one gamete receives 2 of the same type of chromosome, other receives none)
Aneuploidy (types)
Trisomic
Monosomic
Aneuploidy deinition
Fertilization of gametes where nondisjunction occurred
Trisomic
cells have three copies of a particular chromosome type and have 2n+1 chromosomes
Monosomic
cells have only one copy of a particular chromosome type and have 2n-1 chromosomes
Polyploid
Organisms with more than two complete sets of chromosomes
Common in plants
What can lead to changes in the chromosome sturcture
Breakage of the chromosome
Four types of changes in the chromosome structure
- Deletion
- Duplication
- Inversion
- Translocation
Deletion
Occurs when a chromosome fragment is lost. The chromosome is missing certain genes
Duplication
Occurs when a fragment become attached as an extra segment to a sister chromatid
- Alternatively a detached fragment may attach to a nonsister chromatid of a homologous chromosome
- In this case, the dupicated segments will not be identical if the homologs carry different alleles
Inversion
Occurs when a chromosomal fragment reattaches to the original chromosome, but in reverse orientation
Translocation
A chromosomal fragment joins a homologous chromosome
Moves a segment from one chromosome to another
What disorder is due to a chromosome alteration
Downs syndrome- aneuploid condition, 3 copies of 21
Cri du chat results from ____
specific deletion in chromosome 5
What can cause leukemia (CML)
chromosomal translocations
