Term
| What is incomplete dominance? |
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Definition
| Neither allele is completely dominant over the other |
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Term
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Definition
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Term
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Definition
| An intermediate phenotype (mix) |
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Term
| Why is a heterozygote not blending? |
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Definition
| It still has the two original phenotypes, and the offspring of two heterozygotes would be all the same, but this is not the case. The heterozygote offspring has some heterozygote and some parent. |
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Term
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Definition
Occurs when a single gene that has more than two alleles
more than one may be dominant |
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Term
| What is an example of codominance? |
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Definition
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Term
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Definition
Two or more genes affecting the inheritance of the same trait
One gene alters the expression of another |
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Term
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Definition
| They are based on two forms of melanin |
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Term
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Definition
| Melanin that gives you dark pigments |
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Term
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Definition
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Term
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Definition
Tyrosinase related protein 1 stabilizes Tyr (melanin producer), polymerizes eumelanin
B-active TYRP1=black
b-inactive " =brown |
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Term
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Definition
| Melanocyte- stimulating hormone receptor |
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Term
| What is a polygenic inheritance? |
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Definition
| Two or more genes that have an additive effect on the same phenotype |
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Term
| What are quantitative traits? |
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Definition
| Heigh, skin color, intelligence |
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Term
| What is an environmental effect? |
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Definition
phenotypes are not solely determined by genes
genes determine the range within which environment can affect the phenotype
That phenotypic range is called " norm of the reaction"
more common for polygenic traits |
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Term
| What are multifactorial genes? |
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Definition
| Genes that are affected by both genetic and environmental contributions |
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Term
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Definition
One gene affecting multiple phenotypes.
Observed as apparent perfect linkage between traits
Single gene can have multiple effect |
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Term
| What is pedigree analysis? |
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Definition
| Used to analyze inheritance patterns based on extended family information |
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Term
| How can you tell a recessive gene? |
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Definition
| If both parents show the trait, but the child has it |
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Term
| What are recessive inherited disorders? |
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Definition
◦ To have disorder two copies of recessive allele are required
There is no functional copy of a gene for a necessary protein
◦ Heterozygotes have normal phenotype
Make functional protein from one of their copies
Serve as (frequently undetected) carriers of the disorder
◦ Example – albinism
Mutation of Tyr |
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Term
| What is a dominant inherited disorder? |
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Definition
◦ Only one mutated copy is necessary
Heterozygotes have disease phenotype
Make protein that actively creates the problem
No carriers
◦ Dominant disease-causing alleles are rare in population
Tend to reduce reproductive fitness of sufferers, less likely to be
passed on (exception Huntington’s disease – late onset)
Homozygotes tend to be severely affected – fatal early
◦ Example: Achondroplasia
Fibroblast growth factor receptor
3 (FGFR3) inhibits bone growth in
response to FGF.
In achondroplasia FGFR3 is
turned on permanently,
even when FGF is absent. |
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Term
| Describe how sickle cell anemia show incomplete dominance |
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Definition
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Term
| Describe chromosomal basis of inheritance |
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Definition
Mendel’s Laws reflect the
segregation and
assortment of
chromosomes during
Meiosis
◦ Law of Independent
Assortment
Random alignment of
homologous
chromosomes in
Metaphase I
◦ Law of Segregation
Separation of homol.
chromosomes in
Anaphase I
Crossing-over of homol.
chromosomes in
Prophase I |
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Term
| Why is Thomas Hunt Morgan important? |
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Definition
◦ Pioneered fruit fly as a model
◦ Discovered sex-linked genes
Correlated inheritance of sex-linked
genes with sex chromosomes
Suggested all inherited traits resided on
chromosomes
Proposed chromosome crossing-over
◦ Presented early synthesis of Darwinian
evolution and Mendelian genetics,
forerunner of modern neo-Darwinism
(genetic/biochemical understanding of
Darwinian evolution) |
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Term
| Why use a fly as a genetic model? |
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Definition
◦ Easy to breed
◦ Produce many offspring
◦ Short generation time
◦ Easy to induce and visibly identify mutations
◦ Small number of easily visible and distinguishable
chromosomes |
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Term
| Describe drosophila chromosomes |
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Definition
(Fly)
◦ Chromosome number = 8
◦ Diploid – 4 pair
3 invariant
1 sex-specific
◦ Polytene chromosomes
Salivary glands make 1000+
copies of chromosomes
These self-associate,
produce LARGE
ordered aggregates with
visible distinct banding
Gene deletions can be
directly observed by
changes in banding
Individual genes ‘puff’
when making RNA |
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Term
| What are drosophila characteristics? |
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Definition
◦ Wild type
Phenotype commonly observed in the ‘wild’
◦ Mutant phenotype
Phenotype not commonly seen in the wild |
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Term
| Describe drosophila eye color genetics in the P, F1, And F2 generation |
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Definition
◦ P generation
Crossed red-eyed female with white-eyed male
◦ F1 generation
All red-eyed
◦ F2 generation
All red-eyed females
Males half red-eyed, half white-eyed
Seeming violation of Mendelian inheritance (eye color
and sex should segregate independently) |
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Term
| What are sex linked traits? |
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Definition
◦ Sex-linked traits are not
inherited with classical
Mendelian patterns
◦ This is because they are
physically located on X or
Y chromosomes and their
inheritance is inextricably
linked to the inheritance
of those chromosomes |
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Term
| What are the different systems for chromosomal sex determination? (5) |
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Definition
XY – females have 2 homologous
chromosomes, males heterologous
ZW – males have 2 homologous
chromosomes, females heterologous
X0 – females have 2 homologous
chromosomes, males 1 chromosome
Haplo-diploid - females diploid
males haploid
XXXXXYYYYY – don’t ask – the platypus
is just plain weird – duck in the front,
beaver in back, venomous, egg-laying
mammal . . . . and 10 sex chromosomes! |
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Term
| how is sex determination in placental mammals and flies? |
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Definition
◦ XX – female
◦ XY – male
◦ Sex determined by sperm
◦ Female must get their father’s only X
◦ Males must get their only X from their mother |
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Term
| Describe sex chromosomes in humans |
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Definition
◦ Most chromosomes exist as homologous pairs, independent of
sex
Called ‘Autosomal’
◦ X
Includes hundreds of genes (800+), unrelated to sex
◦ Y
Includes dozens of genes (40-80 depending on what you count)
Y has ‘pseudoautosomal’ region homologous to region of X, with
which it pairs and crosses over during meiosis
Two genes that have homologs on the X, but
do not pair/cross over
A dozen genes that are unique, related to
male differentiation and development
SRY – male-determining gene |
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Term
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Definition
◦ Only one X chromosome is left active in
mammals
(usually one X is inactivated in females,
after initial rounds of mitosis)
Results in patchy mosaicism
Tight compaction and inactivation
of all but pseudoautosomal region
Forms Barr body |
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Term
| What are most cases of sex linked genes due to? |
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Definition
◦ Most cases are due to recessive genes
on the X (X-linked)
(Y has so few unique genes, all related to
sex-determination and sexual development) |
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Term
| What is an example of sex-linked chromosome? |
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Definition
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Term
| What is a typical x-linked recessive pedigree? |
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Definition
• Only seen in males (No affected females because of relative rarity)
• Affected males are never sons of other affected males
• Inherited by maternal nephews (sister’s sons) of affected individuals
• The descendants of a non-affected male are disease-free
Unaffected males can have affected sons/descendants, but only
if they inherit it from their mother. No one can inherit the
disease through an unaffected father. |
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Term
| Give the example of how hemophilia is a sex linked chromosome related illness |
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Definition
◦ Genes for blood clotting factor 8 and 9
are both on X chromosome
◦ Hemophilia among Queen Victoria’s
descendants shows X-linked pattern
◦ Alexei son of Tsar Nicolas II of Russia, was
a descendant and hemophilia sufferer |
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