Study Genetics Flash Cards

 
Pile Management Card
Genetics

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Linked genes
predicted to always be transmitted together during gamete formation and should violate the principle of independent assortment

-are inherited together unless crossing over occurs

-segregate together unless there is a physical crossover between homologous chromosomes
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What does crossing over do?
It breaks up linkage and makes it appear as if independent assortment is occuring
What determines the frequency of crossing over?
the physical distance between genes
genetic map
diagram that shows the relative positions of genes along a particular chromosome
linkage
the physical association of genes that are found on the same chromosome
autosomes
non-sex chromosomes
Translocations & deletions
portion deleted or transferred to another chromosome
Non-disjunction
failure to separate during meiosis
Genes
Many (most!) genes have multiple alleles
what causes abnormalities of chromosome number ?
It is usually caused by the failure of chromosomes to separate properly in meiosis (“non-disjunction”
Trisomy 21
Down Syndrome
trisomy
extra copy of a chromosome
polyploidy
Complete extra copy of all chromosomes
codominance
both alleles contribute to the phenotype
Incomplete dominance
-phenotype determined by “dominant” allele, but dominance is not complete

e.g. snapdragons and human blood
Polygenetic Inheritance
when two or possibly three genes determine a trait

e.g Parakeet Feather color
X and Y Chromosomes
“Sex” Chromosomes
Chromosomes 1-22
Autosomal” chromosomes
Crossing over
-(during meiosis) recombines genes

-distant genes are more likely to be separated by recombination
ALLELE
is a particular form of a gene
Test Cross
used to determine the genotype of a plant with the dominant phenotype; usually done using a plant with the recessive phenotype.
dipliod
Organisms with 2 genes for each trait
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