Chapter 14/15 Flashcards
Law of segregation
Two alleles for a gene segregate during meiosis into separate gametes
Law of independent assortment
One pair of homologous chromosomes moving to opposite poles does not affect the movement of other homologs
Phenotype
Physical appearance
What gene on the Y chromosome codes for development of testes?
SRY
What are genes on the sex-linked chromosomes called?
Sex-linked genes
Epistasis
1 gene alters phenotypic expression of gene at another locus
Quantitative characters
Genes that vary along a continuum
Polygenic inheritance
Many genes affect one phenotype
Pleiotropy
1 gene gives multiple phenotypic effects
Norm of reaction
Phenotypic possibilities for a certain genotype
Multifactorial
Genetic and environmental factors influence phenotype
What are the 2 fetal testing techniques?
- Amniocentesis
- Chorionic villus sampling (CVS)
Barr body
Because there are 2 X chromosomes in a sex-linked homolog, one X chromosome condenses into a Barr body
Do Barr bodies inactivate independently?
Yes
Either maternal/paternal can condense. Embryo ends up having 1/2 maternal inactivated and 1/2 paternal inactivated
Linked genes
Two or more genes on the same chromosome that are physically connected and sort dependently
How do nonparental phenotypes occur from linked genes?
Crossing over of homologous pairs during meiosis
Genetic map
Ordered list of genetic loci along a chromosome
Linkage map
Genetic map based upon recombination frequencies
Cytogenic map
Gene positions indicated with respect to chromosomal features
What are the three types of chromosomal alterations (2 are abnormal chromosome number)
- Aneuploidy
- Polyploidy
- Breakage of chromosome
Nondisjunction
When homologous pairs do not separate normally during meiosis
Aneuploidy
Fertilization of gametes in which nondisjunction of a homolog has occured in a gamete
Polyploidy
When an organism has more than 2 complete sets of chromosomes
Types of aneuploidy?
Monosomic
Trisomic
Types of Polyploidy?
Triploidy
Tetraploidy
Types of breakages of chromosome
- Deletion
- Duplication
- Inversion
- Translocation
Klinefelter syndrome (XXY) and Turner Syndrome (XO) are the result of what?
Aneuploidic sex chromosomes. In Klinefelter, sex chromosome is trisomic, and in turner syndrome, sex chromosome is monosomic
What are the 2 exceptions to normal mendelian genetics?
- Genomic imprinting intranucleus
2. Defective extranuclear genes
When the phenotype passed down depends on which parent passed down the allele, what is happening?
Genomic imprinting silences the maternal/paternal allele
How does genomic imprinting occur?
Methylation of DNA
