chapter 15: chromosomal basis of inheritance Flashcards
what is sex-linked gene?
a gene located on either sex chromosome
what is a X linked gene?
a gene located on the X chromosome, showing a distinctive pattern of inheritance
what determines the sex of humans, grasshoppers, chickens, and bees?
humans: XX female and XY male
grasshoppers: XX female and XO male
chickens: ZW female and ZZ male
bees: diploid female and haploid male
what two disabilities are considered X linked traits?
color blindness and hemophilia
what is the disease hemophilia?
is an X-linked recessive disorder defined by the absence of one or more of the proteins required for blood clotting (when a person is injured, bleeding is prolonged because a firm clot is slow to form)
what is genetic recombination?
a new combination of the alleles inherited from parents
alleles of unlinked genes are recombined by what process?
independent assortment
alleles of linked genes are recombined by what process?
crossing over
how is the law of independent assortment and the law of segregation different?
law of segregation: states how alleles of a gene are segregated into two gametes and reunite after fertilization
law of independent assortment: states how alleles of different genes independently segregate from each other during the formation of gametes
what is a genetic map?
an ordered list of genetic loci (genes/ other genetic markers) along a chromosome
what are centimorgans?
a unit of measure for the frequency of genetic recombination
what are map units? how are map units estimated?
a unit of measurement of the distance between genes, one map unit is = to a 1% recombination frequency
when is recombination of linked genes more likely? when the genes are 10 centimorgans apart or 25 centimorgans apart?
25 centimorgans apart
what is the relationship between genes and chromosomes?
genes are located on chromosomes
what is the sex chromosomes of females and males?
female: 2 X chromosomes
male: 1 X and 1 Y chromosome
what is the chromosome theory of inheritance?
principle stating: genes have a specific loci (position) on chromosomes & chromosomes undergo segregation (separation) and independent assortment
what are autosomes?
any chromosome, except sex chromosomes
are genes more likely to be found on the X chromosome of the Y chromosome?
on the X chromosome
what are linked genes?
located on the same chromosome (they tend to be inherited together)
what are unlinked genes?
located on 2 separate homologous chromosomes
what must an organism be to be considered “true-breeding”?
homozygous
when is crossing over most likely to occur?
the further apart genes are
are sex chromosomes homologous?
no
which chromosome is bigger X or Y?
X is much bigger
