Genetics Final: Midterm #2 Questions Flashcards
Suppose that extra fingers and toes are caused by a recessive trait, but it appears in only 40% of homozygous recessive individuals. Two heterozygotes conceive a child. What is the probability that this child will have extra fingers and toes?
.10
In humans, blood types A and B are codominant to each other and each is dominant to O. What blood types are possible among the offspring of a couple of blood types AB and B?
A, B, and AB only
Refer to question 3
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Hair color is determine in Labrador retrievers by alleles at the B and E loci. A dominant allele B encodes black pigment, whereas a recessive allele b encodes brown pigment.
Alleles at a second locus affect the deposition of the pigment in the shaft of the hair; dominant allele E allows dark pigment (black or brown) to be deposited, whereas recessive allele e prevents the deposition of dark pigment, causing the hair to be yellow.
What type of gene interaction does this represent?
Recessive epistasis
Furthermore, if a black female with the genotype Bb Ee was mated with a yellow male and half of the puppies were yellow, 1/4 were black and 1/4 were brown.
What is the genotype of the yellow male?
bb ee
All recessive
Look up 6-8 on exam.
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Linked genes are _____
on the same chromosome
recombination occurs through:
Crossing over and independent assortment
A testcross includes:
One parent who shows the dominant phenotype for one or more genes and a second parent who is homozygous recessive for these genes.
Review linkage and formulas for linkage.
Also, interference values.
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The image of the complete set of chromosomes possessed by an organism is called a
karyotype.
Know chromosome rearrangement images.
review on 19-21
What is not true about chromosomal inversions?
The inversion mutations will not likely have pronounced phenotypic effects since there is no loss of genetic material.
These are true statements of chromosomal inversions:
- The individual organisms have neither lost nor gained any genetic material.
- An inversion can break a gene into two parts and separate each to different locations.
- The expression of the genes may be altered due to the positional effect.
- Individuals heterozygous for inversions may end up producing abnormal gametes
What form of aneuploidy describes and organism that has an extra copy of a single chromosome?
Trisomy
What form of aneuploidy causes primary down syndrome?
Trisomy
Which type of chromosome mutation is responsible for familial down syndrome?
Robertsonian translocation
A man has a condition where all of his gamete undergo meiosis I normally, but have a nondisjunction of the x chromosome during meiosis II. He mates with a woman who produces all normal gametes. What is the probability that the fertilized egg will develop into a child with Turner syndrome (XO)? Assume that all gametes and zygotes are viable.
1/4
A man has a condition where all of his gametes undergo nondisjunction of the sex chromosomes in meiosis I, but meiosis II proceeds normally. He mates with a woman who produces all normal gametes. What is the probability that the fertilized egg will develop into a child with Klinefelter syndrome (XXY)? Assume that all gametes and zygotes are viable
1/2
What type of organism results from the hybridization of a haploid gamete from one species with a diploid gamete from a different species?
allotriploid
A newly discovered species of dung beetle has 2n=16 chromosomes. It mates with a closely related beetles species that has 2n=12 chromosomes.
How many chromosomes would there be in an allotriploid beetle produced from this cross?
20 or 22
What do nonsense mutations do?
Convert a codon for a particular amino acid within a gene into a stop codon.
Huntington’s disease is an example of a disease caused by what type of mutation?
Expanding nucleotide repeat
Insertion or removal of one or more nucleotide base pairs in DNA within a gene often results in a _____ mutation.
Frameshift
Transposable elements are found:
in practically all organisms
