BIOL230 Final QUESTIONS AND VERIFIED SOLUTIONS 2
How does the selfish X chromosome work? - ✔✔Gene on X chromosome breaks down
gametes (sperm) with Y chromosomes How do selfish X genes affect female fecundity? -
✔✔X^D X^D females have much fewer offspring than XX or XX^D females What is a
transcriptome? - ✔✔Sequence of RNA instead of DNA What was found in the
transcriptome for the selfish X individuals - ✔✔Divergent protamine-like gene What do
protamines do? - ✔✔package, compact, and stabilise sperm DNA How can selfish X
populations survive? - ✔✔Gene flow, epigenetic regulation, females passing on regular X
to males Where is the suppressor for X^D found? What are its effects? - ✔✔Found on an
autosome, not a sex chromosome. Makes sex ratio of offspring apprx. 50/50 Are selfish X
chromosomes common? - ✔✔Yes, very! How do dominant and recessive allele expression
work? - ✔✔Recessive alleles do not meet the threshold for gene expression, but even just
one dominant allele does meet the threshold and will be expressed What are the
definitions of wildtype and mutant? - ✔✔Wildtype: most common, assumed to be
functional Mutant: uncommon, often defective How else can genes be classified? -
✔✔Compare to a standard or compare to evolutionary history (among other things, I
presume) What does the reference and the alternate refer to? - ✔✔reference: found in the
standard sample alternate: not found in the standard sample What is a caveat of
comparing a gene to a standard? - ✔✔It makes assumptions about the reference used to
set the standard (e.g. using white males to make BMI) What is a caveat of comparing a
gene to its evolutionary history? - ✔✔Some information needs to be known to infer which
gene is ancestral and which is derived, especially since there can be multiple of each.
What is incomplete dominance? - ✔✔Heterozygote is intermediate between dominant and
recessive traits What is an example of multiple alleles for a gene? Is this sort of inheritance
common? - ✔✔Blood type. Yes, very common What is overdominance? - ✔✔Heterozygote
has traits outside the range of the homozygotes ex: sickle cell anemia and malaria
resistance How common is overdominance? Why is it not stably maintained over
generations? - ✔✔Very rare. Not maintained because the selected-for heterozygotes can
produce homozygotes of both the dominant and recessive genes What is pleiotropy? How
does this happen? - ✔✔Multiple effects of one gene: product can affect cell function in
more than one way, may be expressed in different cell types, may be expressed at different
life stages What is an example of pleiotropy? - ✔✔CFTR gene causes: increased mucus in
lungs, saltier sweat, poor nutrient absorption How are most traits controlled? -
✔✔Controlled at many loci by small effects from many genes What did Clausen, Heisey,
and Keck find about about Yarrow in California? - ✔✔It grows to different heights at
, different altitudes and different soil conditions due to a combination of genetics and
environment What is complementation? How is it different from epistasis? - ✔✔Two
different genes (often two different mutations) cause a certain phenotype (often a normal
phenotype), whereas in epistasis a phenotype requires alleles at multiple loci to interact If
there is no complementation, where is the mutation? - ✔✔On the same gene How do XX
males and XY females exist? - ✔✔XX male: SRY gene translocated to be on the X
chromosome XY female: SRY gene is mutated or missing Describe X linked genes -
✔✔Males more likely to be affected (hemizygous) Describe Y linked genes - ✔✔Very rare in
humans, only transmitted from father to son What is pseudo-autosomal inheritance? -
✔✔Not sex-linked inheritance that still occurs on X and Y chromosomes because X and Y
still pair up in meiosis, but there are very few genes that do this What is sex-influenced
inheritance? - ✔✔Allele dominance depends on sex What is sex-limited inheritance? -
✔✔Trait only occurs in one sex because the gene is controlled by sex hormones/sexual
development Why do lethal alleles sometimes seem like they are non-Mendelian? -
✔✔They produce atypical ratios because a certain proportion dies What are the rules of
Mendelian inheritance? - ✔✔1. gene expression in offspring influences traits directly 2.
genes are passed on unaltered (except for mutations) 3. genes obey law of segregation 4.
gene obey law of independent assortment What happens when maternal effects affect
offspring phenotype? - ✔✔The genotype of the mother affects the phenotype of the
offspring. In snails, the cells around the egg (from the mother) input chemicals into the egg
to influence the phenotype How do different systems compensate for dosage of
chromosomes? - ✔✔Placental mammals: one X chromosome is inactivated Marsupial
mammals: paternal X is always inactivated Drosophila melanogaster: expression of X is
doubled in males C. elegans: expression of X decreased by 50% in hermaphrodites What
happens in genomic imprinting? How? - ✔✔Only the allele from one parent is expressed.
Which one is active is established in gametogenesis by an epigenetic marker that is
maintained throughout development (erased and reestablished in the germ line) How does
methylation cause genomic imprinting? - ✔✔Used to repress one parent's allele How does
chloroplast and mitochondrial DNA differ from nuclear DNA? - ✔✔Doesn't obey law of
segregation, inheritance in independent of nucleus, only 100-200k bp (compared to 100M-
100B bp), one cell can have many chloroplasts/mitochondria and therefore have many
different variations in genomes What is the 3-parent technique? - ✔✔Nucleus from one
parent is transferred into oocyte from healthy donor. Gets rid of negative mitochondrial
mutation from the original mother What are orthologs? - ✔✔Homologous genes in different
species What are paralogs? - ✔✔Homologous genes duplicated within the same genome
What prezygotic conditions lead to speciation? - ✔✔Habitat isolation, temporal isolation,
How does the selfish X chromosome work? - ✔✔Gene on X chromosome breaks down
gametes (sperm) with Y chromosomes How do selfish X genes affect female fecundity? -
✔✔X^D X^D females have much fewer offspring than XX or XX^D females What is a
transcriptome? - ✔✔Sequence of RNA instead of DNA What was found in the
transcriptome for the selfish X individuals - ✔✔Divergent protamine-like gene What do
protamines do? - ✔✔package, compact, and stabilise sperm DNA How can selfish X
populations survive? - ✔✔Gene flow, epigenetic regulation, females passing on regular X
to males Where is the suppressor for X^D found? What are its effects? - ✔✔Found on an
autosome, not a sex chromosome. Makes sex ratio of offspring apprx. 50/50 Are selfish X
chromosomes common? - ✔✔Yes, very! How do dominant and recessive allele expression
work? - ✔✔Recessive alleles do not meet the threshold for gene expression, but even just
one dominant allele does meet the threshold and will be expressed What are the
definitions of wildtype and mutant? - ✔✔Wildtype: most common, assumed to be
functional Mutant: uncommon, often defective How else can genes be classified? -
✔✔Compare to a standard or compare to evolutionary history (among other things, I
presume) What does the reference and the alternate refer to? - ✔✔reference: found in the
standard sample alternate: not found in the standard sample What is a caveat of
comparing a gene to a standard? - ✔✔It makes assumptions about the reference used to
set the standard (e.g. using white males to make BMI) What is a caveat of comparing a
gene to its evolutionary history? - ✔✔Some information needs to be known to infer which
gene is ancestral and which is derived, especially since there can be multiple of each.
What is incomplete dominance? - ✔✔Heterozygote is intermediate between dominant and
recessive traits What is an example of multiple alleles for a gene? Is this sort of inheritance
common? - ✔✔Blood type. Yes, very common What is overdominance? - ✔✔Heterozygote
has traits outside the range of the homozygotes ex: sickle cell anemia and malaria
resistance How common is overdominance? Why is it not stably maintained over
generations? - ✔✔Very rare. Not maintained because the selected-for heterozygotes can
produce homozygotes of both the dominant and recessive genes What is pleiotropy? How
does this happen? - ✔✔Multiple effects of one gene: product can affect cell function in
more than one way, may be expressed in different cell types, may be expressed at different
life stages What is an example of pleiotropy? - ✔✔CFTR gene causes: increased mucus in
lungs, saltier sweat, poor nutrient absorption How are most traits controlled? -
✔✔Controlled at many loci by small effects from many genes What did Clausen, Heisey,
and Keck find about about Yarrow in California? - ✔✔It grows to different heights at
, different altitudes and different soil conditions due to a combination of genetics and
environment What is complementation? How is it different from epistasis? - ✔✔Two
different genes (often two different mutations) cause a certain phenotype (often a normal
phenotype), whereas in epistasis a phenotype requires alleles at multiple loci to interact If
there is no complementation, where is the mutation? - ✔✔On the same gene How do XX
males and XY females exist? - ✔✔XX male: SRY gene translocated to be on the X
chromosome XY female: SRY gene is mutated or missing Describe X linked genes -
✔✔Males more likely to be affected (hemizygous) Describe Y linked genes - ✔✔Very rare in
humans, only transmitted from father to son What is pseudo-autosomal inheritance? -
✔✔Not sex-linked inheritance that still occurs on X and Y chromosomes because X and Y
still pair up in meiosis, but there are very few genes that do this What is sex-influenced
inheritance? - ✔✔Allele dominance depends on sex What is sex-limited inheritance? -
✔✔Trait only occurs in one sex because the gene is controlled by sex hormones/sexual
development Why do lethal alleles sometimes seem like they are non-Mendelian? -
✔✔They produce atypical ratios because a certain proportion dies What are the rules of
Mendelian inheritance? - ✔✔1. gene expression in offspring influences traits directly 2.
genes are passed on unaltered (except for mutations) 3. genes obey law of segregation 4.
gene obey law of independent assortment What happens when maternal effects affect
offspring phenotype? - ✔✔The genotype of the mother affects the phenotype of the
offspring. In snails, the cells around the egg (from the mother) input chemicals into the egg
to influence the phenotype How do different systems compensate for dosage of
chromosomes? - ✔✔Placental mammals: one X chromosome is inactivated Marsupial
mammals: paternal X is always inactivated Drosophila melanogaster: expression of X is
doubled in males C. elegans: expression of X decreased by 50% in hermaphrodites What
happens in genomic imprinting? How? - ✔✔Only the allele from one parent is expressed.
Which one is active is established in gametogenesis by an epigenetic marker that is
maintained throughout development (erased and reestablished in the germ line) How does
methylation cause genomic imprinting? - ✔✔Used to repress one parent's allele How does
chloroplast and mitochondrial DNA differ from nuclear DNA? - ✔✔Doesn't obey law of
segregation, inheritance in independent of nucleus, only 100-200k bp (compared to 100M-
100B bp), one cell can have many chloroplasts/mitochondria and therefore have many
different variations in genomes What is the 3-parent technique? - ✔✔Nucleus from one
parent is transferred into oocyte from healthy donor. Gets rid of negative mitochondrial
mutation from the original mother What are orthologs? - ✔✔Homologous genes in different
species What are paralogs? - ✔✔Homologous genes duplicated within the same genome
What prezygotic conditions lead to speciation? - ✔✔Habitat isolation, temporal isolation,
