Chromosomal Basis Of Inheritance Flashcards
What homogametic and heterogametic mean with regard to sex chromosomes?
The homogametic sex has two identical sex chromosomes (xx or ZZ) the heterogametic has two different chromosomes ( XY and ZW)
What did Tomas hunt Morgan prove?
That chromosomes are basis of inheritance
Describe the XO and ZW system of sex determination in insects and birds?
Insects have XO systems. Males are XO and females XX. XO donate only one type of the X chromosome. Birds have ZW systems. Males are ZZ females are ZW
Explain haploid system of sex determination in bees, wasps, and ants
Females are diploid, males are haploid. Reproductive females( queens) store sperm from their single mating and use to fertilize eggs to produce females offsprings. Queens don’t fertilize eggs which are
What does sex linkage mean?
That a gene’s locus is on a sex chromosome.
What does hemizygous mean ?
The heterogametic sex( XY in mammals) only have one copy of the sex chromosomes. Therefore a male cannot be heterozygous or homozygous for X-link traits he must be hemizygous.
With regard to X- link recessive alleles, why are males are more likely to be affected than females?
Because males are hemizygous and I don’t have that extra X chromosome to mask the x link phenotype
Discuss X inactivation and mosaicism
The homogametic sex ( xx in mammals) only needs one copy of the chromosome. One is inactivated into a super condensed coil of DNA called a bar body. Each cell can inactive one or the other of the X chromosome, leading to different parts of the body having different active X chromosomes.
What is genetic linkage ?
When genes are found in the same chromosome in near enough proximity that they don’t independently assort.
What is recombination ?
When linkage genes are broken apart by crossing over.
What is the difference between parental types and recombine types?
Parental types have the same genotype as one or the other parent. Recombine types have combinations of the parents genotype.
