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GENETICS FINAL EXAM REVIEW QUESTIONS AND ANSWERS
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GENETICS FINAL EXAM REVIEW QUESTIONS AND ANSWERS
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Name: Score:48 Multiple choice questions
,Term 1 of 48
Define base stacking, major and minor grooves, and identify the 3 forms of DNA and their
properties
X-linked dominant
-affected males (hemizygous): all affected daughters, no affected sons
-affected female (heterozygous): 50% chance the son will be affected
-Heterozygous female + unaffected male: sons and daughters will be equally affected
-seen by 100% incidence of affected daughters from their affected father
X linked recessive
-more males than females are affected
-affected males receive the allele from their mother
-affected daughters can only come from both parents being affected
-seen by 100% incidence of affected sons from an affected mother
Y linked
-Exclusively patrilineal (from father to son)
Autosomal dominant
-males and females have the trait in equal proportions
-almost always appears in every generation
-Individuals with the trait have at least one parent with it ..and if neither parent has it,
none of the offspring will have the trait
-if the trait is rare (<1%), individuals with the trait are most likely heterozygous
-If only one parent has the trait : half of the offspring will have it
-if both parents have the trait: some children may not have it (parents are more likely
heterozygous)
Autosomal recessive
-males and females have the trait in equal proportions
-trait is typically seen in siblings and can skip generations-pedigree looks bare
-individuals with the trait are often from parents that do not show it (parents are
heterozygous)... but if both parents have it all their offspring will have it
-if trait is rare (<1%) and only 1 parent has it, child can only have it if other parent is
heterozygous
Cytoplasmic inheritance and mitochondrial disorders
-cytoplasmic inheritance: the transmission of genes that occur outside the nucleus (in
cytoplasmic organelles, such as mitochondria and chloroplasts)
-Maternal inheritance pattern; ALL offspring are affected if mom is
-Dads and daughters have different mitochondrial DNA since it is passed on from mom
,-Disorder must reflect a deficiency in the bioenergetic function of the organelle; there
must be a specific mutation in mitochondrial DNA
-Incomplete dominance/ partial dominance: when heterozygous individuals display
intermediate phenotypes between wither homozygous type
i.) neither trait is dominant
ii.) ex: red and white parents = pink offspring
iii.) 1:2:1 phenotypic and genotypic ratio
-Codominance: leads to heterozygotes with a different phenotype than that of either
homozygote
i.) detectable expression of both alleles in the heterozygous
ii.) more than one pattern of dominance may exist between different alleles of a gene,
for example: AB or O blood type
-Example: red and white parents = red and white stripped offspring
-1:2:1 phenotypic and genotypic ratio
There are 5 stages of prophase 1
1. Leptonema
2. Zygonema
3. Pachynema: where formation of tetrads occurs and crossing over begins; good for
characterization and mapping
4. Diplonema: contribution of crossing over (tetrads ad chiasmata); non sister chromatids
start to separate but chiasmata keep them still together
-crossing over generates new combinations of parental genetic material, is a source of
genetic variability, and corrects mutations
5. Diakinesis
-Base stacking: the offspring of adjacent base pairs so that their planes are parallel
i.) leads to twist in the double helix
-Creates gaps among the sugar-phosphate backbones that partially expose the
nucleotides-major and minor grooves
i.) the major groove (12A wide) alternates with the minor groove (6A wide)
ii.) these grooves are regions where DNA binding proteins can make direct contact with
nucleotides
-B-DNA:
i.) Watson-Crick model, biologically significant conformation
ii.) aqueous, low-salt conditions
ii.) most common ad has a right-handed twist of the helix (like the A-form)
-A-DNA:
, i.) high-salt or dehydration
ii.) bases tilted in relation to the axis
iii.) modified major/minor grooves
iv.) mainly in vitro conditions
v.) occasionally detected in cell and is common in bacteriophage
-Z-DNA
i.) left-handed double helix, zigzag conformation due to left-handed twist
ii.) no major groove
-commonly found near transcription start sites (Robert wells and colleagues, 1970)
Term 2 of 48
What is the main cellular/biological event on which linkage map depends?
-Crossing over
-the first affected individual who brings a genetic disorder to attention
-not necessarily the first affected one in the predigree
-RNA contains a ribose (A&U, G&C)
-DNA contains a deoxyribose (A&T, G&C)
-Triphosphates are the most significant because:
i.) they are precursor molecules for nucleic acid synthesis in the cell
ii.) adenosine: and guanine triphosphates (ATP and GTP) are essential in cell
bioenergetics
Term 3 of 48
Between the interphase and mitosis, cells can enter a stage called G0, in which they are
quiescent
True
False
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