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Bio 1113 > Chapter 14: Mendel and the Gene > Flashcards

Chapter 14: Mendel and the Gene Flashcards

1
Q

Examples of epistasis

A

Lab coat color - lab will be yellow if pigment deposit gene is homozygous recessive regardless of coat color gene (pigment deposit gene is epistatic to coat color gene)
Gene for widows peak hidden by gene for baldness (baldness gene is epistatic)

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2
Q

Why was hemophilia common among the royal families of Europe?

A

Inbreeding. Small gene pool so a higher chance of members carrying the gene

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3
Q

White dogs and deafness/blindness pleiotropy example

A

White pigmentation gene suppresses melanocytes which leads to the degeneration of cochlear blood supply which leads to deafness

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4
Q

What does gene distance on chromosome predict?

A

The farther they are, the more likely a crossover event will occur

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5
Q

When is the addition rule used?

A

OR. The probability of two or more mutually exclusive events occurring

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6
Q

This determines the phenotype. If this is present, the organism will express the associated phenotype

A

Dominant allele

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7
Q

What causes Huntingtons disease?

A

Expansion of a tri-nucleotide repeat on chromosome 4. Repeats get larger as it is passed down

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8
Q

What are quantitative traits and when are they seen?

A

Traits that vary along a continuum. They are seen in polygenic inheritance

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9
Q

Phenotypic ratio of crossing true breeding parents of different phenotypes

A

3:1 (1 homozygous dominant, 2 heterozygous, and 1 homozygous recessive)

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10
Q

What are multiple alleles?

A

Genes that have more than 2 alleles resulting in more possible combinations (like eye color and ABO blood groups)

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11
Q

Different versions of the same gene

A

Alleles

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12
Q

What are linked genes?

A

Genes close together on the same chromosome that are unlikely to sort independently. Expected to stay together during gamete production

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13
Q

Is polydactyly dominant or recessive?

A

Dominant. Extra digits is actually dominant

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14
Q

Most common lethal genetic disease in US

A

cyclic fibrosis

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15
Q

Why do we know now that the principle of independent assortment can be broken?

A

If the alleles of different traits are on the same chromosome, they could travel together. The closer they are on a chromosome, the less likely they are to travel apart

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16
Q

What is PKU recessive disorder?

A

Lack enzyme to break down phenylalanine, buildup interferes with development and results in severe mental retardation, outcome can be prevented in phenylalanine is removed form diet

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17
Q

Is gender more complex than sex development?

A

Yes, far more complicated

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18
Q

Huntington’s disease death rate and onset

A

Death usually 15-20 years after onset (pneumonia, heart disease, suicide). Late onset around 35-45

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19
Q

What can happen with recessively inherited disorders?

A

Occurrence can skip a generation

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20
Q

Pedigree circle

A

female

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21
Q

Heterozygotes have an intermediate phenotype (in between dominant and recessive)

A

Incomplete dominance

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22
Q

Pedigree half colored in shape

A

carrier

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23
Q

An organism that has two different alleles for a gene

A

Heterozygous

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24
Q

Incomplete dominance vs codominance

A

Incomplete shows fur that would be a blend of the two colors. Codominance is both colors expressed together; individual hairs are one color or the other

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25
Pedigree square
male
26
What did the white fly mutants uncover?
Sex linked characteristics
27
Pedigree dot in center of shape
carrier (X linked)
28
An affected father will pass it on to all of his daughter and an affected mother will pass it on to 50% of offspring
X linked dominant pedigrees
29
An organism that has two identical alleles for a gene
Homozygous
30
How was the pivotal role of SRY discovered?
Injecting SRY DNA into an XX embryo and the mouse develops as a phenotypic male
31
What are recombinants?
Offspring that have phenotypes that do not match either parent
32
How can XY be phenotypically female?
Loss of SRY gene or other mutations in other critical genes (like androgen receptors. If cant respond to androgen, then phenotypic female)
33
Examples of X-linked disorders
Color blindness, Duchene muscular dystrophy, hemophilia
34
What is a transcription factor?
Proteins capable of interacting with DNA
35
Determines the organisms appearance
Dominant allele
36
How many genes are on the Y chromosome and what does it lead to?
78 genes that encode 25 proteins. Leads to very few disorders being passed from father to son
37
Examples of polygenic inheritance
Skin color (controlled by at least 3 different genes) and may diseases/disorders (diabetes, cancer, autism)
38
Phenotypic ratio of crossing F1 generation from parents that were homozygous dominant and homozygous recessive for 2 traits
9:3:3:1
39
What does the principle of segregation state?
The two alleles for a gene separate from each other during gamete formation and end up in different gametes (separation of homologous chromosomes in meiosis)
40
When is the multiplication rule used?
AND. The probability of two or more events occurring in a specific combination
41
How we collect info about a family's history for a particular character. Info is assembled into a family tree called this
Pedigree
42
What is the chromosomal theory of inheritance?
Mendelian genes have specific loci along chromosomes. It is the chromosome (not individual genes) that undergo segregation and independent assortment
43
Examples fo dominantly inherited disorders
Achondroplasia, osteogenesis imperfecta, Liebenberg syndrome, and Huntingtons disease
44
What causes genetic recombination?
Crossing over allows for the recombination of linked genes
45
How is a dihybrid produced?
Crossing true breeding plants that differ in both traits
46
What type of dominance is shown by ABO blood groups?
Codominance
47
Heterozygous for 2 traits
Dihybrid
48
How many genes are on the X chromosome and what does this tell us?
About 1100 genes. Tells us most sex linked genes are linked to X
49
Look for an unequal number of males affected and if there is a pattern of mother to son transmission
X linked recessive pedigrees
50
What accounts for Mendels observations?
Meiosis
51
Huntington's disease symptoms
Involuntary movement, behavioral disturbances, dementia
52
How is a test cross performed?
Cross the unknown (test) individual with an individual with a known genotype (homozygous recessive)
53
How can XX be phenotypically male?
Translocation of SRY gene
54
How do number of repeats determine Huntingtons?
More repeats = earlier onset and higher chance of having Huntingtons
55
What is pleiotropy?
Genes with multiple phenotypic effects (most genes). Single genes affect multiple traits/systems in the body
56
What does the SRY gene do?
Codes for a transcription factor and causes gonads to develop into testes
57
Has no noticeable effect (recedes/masked)
Recessive allele
58
Why cant dominantly inherited disorders skip generations?
Cant be a carrier. You either have it and express it or you dont
59
What are pure lines (true breeding plants)
Plants which only produce same variety as parent when self pollinated
60
Are traits transmitted together or inherited independently? (Will GY and gy always stay together?)
Independently. They will not always stay together
61
When do gonads begin to develop as either male or female? What determines which gonads will develop?
After 2 months. Depends on the presence of Y chromosome
62
Pedigree colored in shape
affected
63
Appearance or observable trait
Phenotype
64
What is the F2 generation?
The generation that results from the cross of the F1 generation. The recessive traits can reappear
65
Why is the allele in Huntingtons disease maintained in the population?
Late onset means most have already had children and passed it on
66
2 or more genes have an additive effect on a single phenotypic character (quantitative traits)
Polygenetic inheritance
67
Examples of recessively inherited disorders
PKU, Tay-Sachs, sickle cell anemia
68
What is osteogenesis imperfecta?
Mutation in type 1 collagen that causes "brittle bone disease". No cure. Dominantly inherited disorder
69
When the phenotypic expression of one gene alters that of a different gene
Epistasis
70
What can we do with knowledge from pedigrees?
Genetic testing and counseling. Raises ethical issues on abortion, health insurance, and jobs
71
Examples of pleiotropy
Multiple symptoms associated with most hereditary diseases (PKU - mental retardation, reduced pigmentation and eczema, Marfan syndrome - tall long limbs with abnormally shaped chest and heart problems, white dogs and deafness/blindness)
72
What is achondroplasia?
Point mutation (G to A) in fibroblast growth factor receptor gene. Spontaneously inherited mutations exclusively from father. Homozygous = lethal. Dominantly inherited disorder
73
Neither allele is dominant and both are expressed with no blending (two sets of capital letters)
Codominance
74
What often happens in cystic fibrosis?
Bacteria get into the mucus and are hard to get rid of which causes bad infections that lead to more issues. Avg lifespan is only 37 years
75
Actual genetic makeup (the letters)
Genotype
76
How can environment impact phenotype?
Many traits of a phenotype can be altered/influenced by the environment. Like PKU if phenylalanine is eliminated from diet, development would be normal as long as caught early
77
What did Mendel not account for?
Linked genes, not all alleles are completely dominant or recessive, some genes have more than 2 possible alleles, some genes produce multiple phenotypes, some phenotypes determined by multiple genes
78
Why are X-linked recessive disorders far more common in males than females?
Females have 2 copies of the X chromosome so both must contain the defective allele. Males only have 1 X chromosome so if they inherit a bad copy from their mother, they will express it
79
What does the principle of independent assortment state?
Each pair of alleles separates independently of every other pair of alleles during gamete formation
80
What causes cystic fibrosis?
Missing/defective channels cause a buildup of mucus. Normal allele codes for a membrane protein that transports chloride ions
81
What causes different alleles?
Differences in nucleotide sequences
82
Used to determine genotype when an organism expresses a dominant phenotype (heterozygous or homozygous?)
Test cross
83
What is particulate inheritance?
Mendels proposed model of inheritance that said there are discrete, unchanging particles (genes) that are passed to offspring
84
Heterozygous for the one trait being followed that is produced by crossing true breeding plants (P)
Monohybrid
85
What is the F1 generation?
The generation that results when cross pollinating two contrasting pure lines
86
Pedigree diamond
sex unspecified
87
What happens when a X bearing sperm fertilizes an egg? A Y bearing one?
``` X = female Y = male ```
88
What did Medels numbers show?
Almost perfect results. Less than 1% statistical chance to obtain the results but he had to know the right numbers without any proof if he did fudge them
89
What causes gonads to develop into testes?
SRY gene (sex determining region of Y)

Bio 1113 (22 decks)

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